What is checked when inspecting welding materials?

Quality control of welding materials and materials for flaw detection

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The quality of welded joints largely depends on the welding materials, so each batch of electrodes, welding wire, fluxes, and shielding gas cylinders is carefully checked before starting welding. Welding materials must have certificates that fully contain data in accordance with the requirements of GOSTs, technical specifications and passports.

Packaging boxes, boxes, cylinders, and packs must have tags or labels indicating basic passport data.

If these conditions are not met, the batch of welding materials is not allowed for use and is subject to full inspection for all indicators established for this type of welding materials.

The issue of the possibility of using welding materials that have a quality discrepancy or damage to the packaging is decided by the service of the chief welder of the enterprise (organization).

Electrode monitoring

The quality of electrodes is checked during their manufacture in factories and before welding work begins in workshops or on construction sites.

The coating must be dense and durable, adhere well to the electrode rod and not be destroyed (according to GOST 9466-60) when the electrode freely falls flat on a smooth steel plate from a height of 1 m for electrodes with a diameter of 3 mm or less and from a height of 0.5 m for electrodes with a diameter of more than 3 mm. Partial chipping of the coating with a total length of no more than 20 mm is allowed.         

The coating of the electrodes must be moisture-resistant and not deteriorate after being in water at a temperature of 15-25 ° C for 24 hours. The following defects on the surface of the electrodes are allowed:

surface roughness, longitudinal scratches and individual scuffs - no more than 1/4 of the coating thickness;

local dents - no more than three in number, with a depth of 1/2 the thickness of the coating and a length of up to 12 mm each;

pores - no more than three per length of 100 mm, with a diameter of up to 2 mm, and a depth of up to 1/2 of the thickness;

hairline cracks - no more than two, each up to 12 mm long.

Quality control of electrodes in factory and installation conditions before welding structures operating in difficult conditions (vibration load, high temperature and pressure, transportation of toxic gases) consists of checking the availability of certificates and selective monitoring of the condition of the external surface.

In addition, the mechanical and technological properties of the deposited metal are checked, and, if necessary, metallographic analysis is performed.

Such a check is also necessary in cases where the electrodes used produce an unstable arc, have uneven melting, or if cracks and pores appear in the weld.

For external examination, 10-15 electrodes are selected from different packs. If there are unacceptable defects, double the amount is taken, and if defects are detected again, the entire batch of electrodes is rejected, drawing up a complaint report.

The electrode coating should be concentric with the rod. To check concentricity in different sections along the length of the electrode, cuts are made and the thickness of the coating is measured.

The thickness difference should not exceed:

with an electrode diameter of 2 mm. 0.08 mm with an electrode diameter of 2.5 mm ..0.1 mm with an electrode diameter of 3 mm ..0.15 mm with an electrode diameter of 4 mm ..0.2 mm with an electrode diameter of 5 mm ..0.25 mm

with an electrode diameter of 6 mm or more. 0.3 mm

Electrodes are checked for weldability and mechanical properties periodically for different batches. In this case, surfacing is carried out on plates made of carbon or low-alloy steel with a thickness of 10-14 mm (pipes with a wall thickness of at least 8 mm can also be welded).

For electrodes that produce austenitic deposited metal, the presence of a ferrite phase in it is checked, for which five to six layers are deposited onto an austenitic steel plate or pipe. The surfacing mode is selected in accordance with those recommended for electrodes of this type and diameter.

Ferrite is determined by the volumetric magnetic method using a ferritometer or by the metallographic method on samples with a diameter of 5 mm and a length of 60 mm, cut from the two upper layers of surfacing. Samples are etched for 2-2.5 minutes with a reagent consisting of red blood salt (10 g), sodium hydroxide (10 g) and water (100 g).

Testing of metal, seam or welded joint for intergranular corrosion is carried out in accordance with GOST 6032-58*.

For all electrodes and filler wires for welding austenitic steels, the tendency to form hot cracks is checked on a rigid T-test sample or on a sample with a six-layer surfacing.

The sample is made from the same grade of steel as the structure being welded, and the electrodes are taken from the batch intended for welding.

Six-layer surfacing is carried out in the lower position, and each layer is deposited in the same direction. Each subsequent layer is placed after the previous one has completely cooled to room temperature.

After complete cooling and removal of slag from the seam, the sample is inspected, broken along a controlled seam and checked for cracks.

Next, the sample is cut into three parts to make macrosections, which are etched in hydrochloric acid, washed, dried and examined under a magnifying glass with 4-7x magnification.

If cracks are present, the electrodes are rejected.

The tested electrodes are stored in a dry room, avoiding their moisture. Before welding, the electrodes are dried at a temperature of 150-180 ° C for 1.5-3 hours in drying ovens. It is strictly forbidden to dry electrodes using gas torches or short circuits, as this leads to a deterioration in the protective properties of the coating and may cause defective welded joints.

Flux control

The quality of the flux received from the manufacturer and having a certificate indicating its chemical composition and granulation is determined in accordance with GOST 9087-59 or TU by welding plates or pipe joints in conditions determined by the technological process.

If there are pores or cracks in the welds deposited under a layer of flux, then carefully check the particle size distribution, uniformity, bulk density, humidity and contamination of the flux (if the humidity exceeds 0.1%, the flux is dried).

After such a check, the weld is deposited under a layer of flux on a T-type sample and the deposited metal is examined for carbon and sulfur content by chemical analysis of a sample taken from the top layer of the welded joint.

If the control results are unsatisfactory, the tested batch of flux is rejected or subjected to re-calcination, followed by a complete recheck, including determination of the chemical composition of the flux.

In the same way, the quality of flux intended for welding structures operating in difficult conditions is checked.

Shielding gas monitoring

Shielding gases (carbon dioxide, argon, helium) are supplied in cylinders, which must have a certificate from the supplying plant indicating GOST, the name of the gas, the percentage of impurities, humidity and date of issue. The use of protective gas cylinders that do not have certificates is prohibited.

If certificates are available, the quality of shielding gases is checked only in cases where pores, cracks and other unacceptable defects are found in the welds.

Inspection of welding and surfacing wire

The wire is supplied in coils with metal tags, which indicate the manufacturer, heat number and wire grade according to the standard. Steel welding wire is manufactured in accordance with GOST 2246-70, steel surfacing wire - in accordance with GOST 10543-63, welding wire made of aluminum and its alloys - in accordance with GOST 7871-63.

The certificate for welding wire indicates the diameter and grade of the wire, the manufacturer, the smelting number of the metal from which the wire is made, the weight of the wire, the chemical composition and the standard number.

The wire should be free of oxides, traces of grease and dirt. If necessary, it is cleaned mechanically or chemically.

If pores or cracks appear in the deposited metal, the wire is tested for weldability by welding plates with a thickness of 9-10 mm or pipes with a wall thickness of at least 8 mm. Six samples are cut from the welded plates or pipes for mechanical testing (three for tensile testing and three for bending angle).

Welding wire that does not have a certificate is subject to careful control, which consists mainly of determining the chemical composition and grade of the wire, as well as testing for weldability.

Inspection of materials for flaw detection

Each batch of materials for flaw detection (reagents, X-ray film, intensifying screens, ferromagnetic tape) upon arrival to the laboratory and before use is controlled by the quality control department or laboratory personnel. On the packaging sheets (pack, container, box), it is necessary to check the presence of a label with characteristics of materials in accordance with the requirements of the relevant GOST, TU (technical conditions) and instructions.

Materials and packaging must not be damaged.

In case of any deviation from the standards, this batch of materials is tested in accordance with GOST or TU. If the inspection results are unsatisfactory, the batch of materials is rejected and is not allowed for flaw detection.

Source: https://www.autowelding.ru/publ/1/1/kontrol_kachestva_svarochnykh_materialov_i_materialov_dlja_defektoskopii/7-1-0-405

Welding materials: what electrode parameters should be controlled, what is checked in the equipment

Welding equipment and welding materials – everything related to the welding process.

Welding materials include everything that is used during welding work. Generally speaking, these are mostly consumables.

Types of welding materials

The functions performed by welding materials are as follows:

• Protecting metal with gas or slag from the harmful effects of air.
• Increased stability of the flame and the entire welding process.
• Measuring the dimensions of the weld being formed.
• Formation of the required metal composition of the weld according to the specified properties.
• Cleaning the seam from impurities after welding.

Types of welding consumables can be classified in different ways. Based on their composition, they can be divided into two large groups: those directly related to welding as a chemical process and so-called gadgets that facilitate the welder’s work at one stage or another.

By function, welding materials are divided as follows:

Electrodes and rods

Electrodes are either consumable or non-consumable. Fusible, in turn, differ in the type of coating: mixed, acidic, basic, rutile, etc. Filler rods are placed inside the weld. The electrodes are designed to efficiently supply electrical current to the melting zone.

Welding wire

Available in three versions: powder, activated, solid.

Flux mixtures

Marking of welding wire.

They are divided into heat-conducting and protective. Designed to protect the arc welding process. They contain chemical components that protect the welded metal from exposure to air.

Inert protective and flammable gases

Used to protect the arc and support the flame. Inert gases include argon, helium and their mixtures in various concentrations. Carbon dioxide and its mixtures are among the active types of gases that interact with metal or dissolve in it.

Combustible gases are used in gas cutting and gas welding, these are acetylene, hydrogen, oxygen and various mixtures.

Linings, triangles, etc.

Ceramic pads come in different shapes: round, all-position, for specific types of seams, etc. They facilitate the work process and contribute to the formation of a reverse bead in a high-quality seam.

Quality control of welding materials

The quality of the seam depends on many factors. But the highest dependence is always on the same factor: the quality of consumables. This quality must be constantly monitored by complying with standards and rules for control and, most importantly, storage and use of all welding components.

The very first and simplest requirement is compliance with the labeling of packaging products in the form of boxes, packs, cylinders or pallets, on which the main passport data must be indicated.

Without this type of data, the entire batch of consumables must be checked for all established indicators and the packaging must be opened, until the end of which the use of these products is prohibited.

The question of how and to what extent consumables that do not conform or whose packaging is damaged can be used is decided by management on a case-by-case basis.

Electrode quality control

Electrodes are the most “tested” consumables. Their quality begins to be controlled at the factory. Repeated inspection is carried out in areas with welding; sometimes it is called incoming inspection of welding materials.

Coverage check

First of all, we check the coating, which should be dense. The electrode should not crumble or collapse if thrown flat onto a steel surface from a height of one meter. One meter is for thin electrodes with a diameter of 3 mm or less.

Types of electrodes for welding various metals.

An important requirement for electrode coating is its moisture resistance and resistance to being in water for 24 hours.

Defects on the surface of electrodes that are allowed during quality control:

• roughness with a depth of no more than a quarter of the thickness of the coating itself;
• dents with a depth not exceeding half the thickness of the coating and a length of no more than 12 mm, the total number of dents should not be more than three;
• Pores with a depth of no more than half the thickness of the coating, no more than three in number in a section of the electrode 100 mm long.
• Cracks no longer than 12 mm and no more than two in number.

If the welding process takes place under extreme conditions such as high pressure or powerful vibration, quality control of the electrodes can be limited to checking certificates and randomly checking the condition of the external coating of the electrodes.

In addition to these parameters, the chemical and technological qualities of the deposited metal are checked. An advanced version of such control is special metallographic analysis. It is carried out in cases of defects in the seams or during the melting process.

When conducting a selective external examination, about 10–15 electrodes are taken from different packages. If any defect is detected, the number of copies inspected doubles. Well, if a defect is discovered a second time, a report is drawn up to reject the entire batch of products.

The quality of the coating is checked through its concentricity, which must be maintained around the rod. For such control, special cuts are made along the entire length of the consumable, after which the thickness of the coating is measured.

There are special tables with the values ​​of the permissible difference between different coating thicknesses depending on the diameter of the electrode.

Weldability and mechanical properties

The following electrode control parameters are weldability and mechanical properties. They are tested using periodic samples from different batches.

Technically, this is done like this: test surfacing is performed on steel plates with a thickness of 10 mm, and the steel must be carbon or low-alloy.

Ferrite control

The plate should also be made of a high-alloy alloy. Ferrite is determined by a magnetic ferritometer or in surfacing samples by metallography.

Intergranular corrosion

Intercrystalline corrosion is another parameter for monitoring the quality of electrodes. These actions fall under the rules of GOST 6032-58.

Hot cracks

GOST for welding electrodes.

All electrodes and filler wires intended for use with high-alloy iron alloys are tested for hot cracking. Such control is carried out on special samples with six layers of surfacing.

Such samples are made from the same material as the consumables from the batch being tested.

Surfacing in six layers is carried out in the lower position, each layer is added only after the previous layers have cooled to a temperature of 20 - 25°C. When all layers are ready and cooled, the slag is removed.

The sample is broken along the weld seam, and possible cracks are checked visually. Then the sample is cut into pieces and macrosections are prepared for etching in hydrochloric acid. After washing and drying, they are checked through a magnifying glass.

Consumables that have passed the test are placed in a dry room. Before work, they must be calcined at a temperature of 180°C for 2 - 3 hours. Drying should be carried out in a drying oven and under no circumstances on gas burners.

Flux quality control

The requirements and technology for testing flux mixtures are set out in GOST 9087-59. The overall quality is checked in accordance with the factory certificate, which sets out data on the chemical composition of the mixture. The test is simple in principle: it is welding with the flux being tested.

If defects in the form of cracks or pores are found in welds produced using this flux, a more in-depth check of the mixture is carried out: homogeneity of granules, weight, percentage of moisture, contamination, etc. Humidity should not be higher than 0.1%.

The next stage is surfacing the weld on the sample under submerged arc followed by testing for the presence of sulfur and carbon. To do this, a sample is taken from the top layer of the surfacing for chemical analysis.

If there are significant defects, the flux is sent for calcination with subsequent rechecking or is completely rejected and a report is drawn up.

Quality control of protective gases

The main thing in gas control is to check the condition of the cylinders in which it is supplied.

Cylinders must have factory certificates with GOST, which indicate the following parameters:

• gas name;
• composition of chemical impurities in percentages;
• humidity;
• Date of issue.

If certificates are available and they meet all requirements, then gas testing is not carried out. Special inspection with in-depth inspection can be carried out if there are serious defects in the welds.

Tack welding

Tacks in welding can be classified as temporary auxiliary devices. These are special short seams that are located according to their own rules and regulations.

Rules for performing tacks.

the function of tack welds is to keep parts from moving by means of fixation, reducing gaps between welded workpieces, reducing possible deformations and increasing the strength of the entire welded structure.

Most often, tack welding is performed using the spot method with special clamps. Clamps are excellent assistants in assembling the structure. This can be done either manually or automatically. The more complex the welding unit, the higher the automation of its assembly should be.

Requirements for tacks:

• The length of the tacks should be no more than 20 mm, as for the thickness, they should be exactly half as much as the weld seam itself.
• The composition of the tack electrodes must fully correspond to the brand of electrodes used for further welding.
• The parameters of the welding current for complete penetration of the gripping areas must comply with the standards and be 20% higher than its value during further welding.
• Localization of tack welds always takes place where there is a risk of deformation and where there will be maximum stress. They are never placed at the intersection of major seams.
• By the time of the main welding, the tacks should be free of slag and drops of metal, so that the area with their location is as even as possible.

Source: https://tutsvarka.ru/oborudovanie/svarochnye-materialy

Visual and measuring inspection of welds and joints

When performing welding work, from the very beginning to the end, an inspection is necessary to confirm the quality of the result.

Over time, the structure on which the weld was applied may need to be re-examined to ensure that the connection is intact and the product is safe to use.

For this purpose, visual and measuring inspection of welded joints is used. Its parameters are determined by GOST 23479-79. What is the essence of the method? What defects can they identify? When and how is it carried out?

Definition

Visual quality control is a procedure for examining the joint both before and after making a seam. The purpose of the inspection is to ensure that all stages of the work are carried out in accordance with the rules.

Failure to comply with standards can result in structural failure, injury and death. Technological violations due to ignoring standards are prosecuted by law.

In this regard, GOST has been developed, which regulates the procedure and method of conducting an inspection, as well as maintaining relevant documentation.

Measuring seams and joints using optical tools and templates is a non-destructive test that allows you to maintain the integrity of the structure and its joints, but gives a certain understanding of their condition. If hidden defects are suspected, an examination by other methods (ultrasound, spectroscopy) is prescribed.

visual measuring control of welded joints

A specialist inspector is invited to carry out the examination, who must undergo appropriate training and have a certificate. Control is carried out visually, using an optical instrument, measuring devices and tactile sensations (relates to determining the roughness of a seam). The assessment and all comments are recorded in the inspection report and stored.

What does the method reveal?

Visual inspection of welded joints, carried out with the naked eye, helps to identify a number of defects:

• incorrect seam leg;
• incorrect proportions regarding the width and height of the deposited metal;
• burns;
• rare scaliness;
• open craters of the weld pool;
• metal deposits;
• high current undercuts;
• change in metal color (due to overheating or incorrect additive material);
• uncooked areas.

If you use additional magnifying equipment, non-destructive testing can detect:

• cracks (longitudinal and transverse);
• delaminations in the metal structure;
• corrosion damage;
• pores due to escaping carbon;
• risks from solid inclusions in the alloy;
• shells;
• nicks;
• nadirs;
• displacement of the seam relative to the connection line;
• Defects in protective coatings made of polymer or paint.

At the preparatory stages, non-destructive testing allows you to evaluate how well the edges are beveled for the joint, and how thoroughly the surface is cleaned of rust, paint and debris. This method also controls the application of markings or stamps on finished seams, as well as the correspondence of the type of stamp to a specific joint.

Advantages and disadvantages

Measuring inspection of welds, according to GOST 23479-79, refers to the primary methods of inspection, after which a decision is made on subsequent inspection by other methods. Its advantage is as follows:

• simplicity of the procedure;
• small amount of time spent;
• lack of complex and expensive equipment;
• gives enough information (only what is outside) regarding the quality of the connection;
• it's easy to double-check the result.

Quality control of welds should be carried out both at the stage before work and during all manipulations, and even after the end of the work process, for comprehensive diagnostics and evaluation of the result. But this method is imperfect because it has a number of disadvantages:

• during examination, conclusions can be drawn only on the visible part of the seam, while the internal condition remains unknown;
• the result depends on the subjective assessment and professionalism of the controller;
• Only suitable for detecting large defects up to 0.1 mm in size.

When is it carried out?

Visual measurement control can be carried out at various stages of work. This applies to the inspection of incoming parts for welding. The compliance of the markings with the material itself is checked, as well as the integrity of the metal (no defects during casting and rolling).

At the next stage, the assembly of parts for welding and the correct cleaning of the surface from debris, corrosion and oil are monitored. Attention is paid to the preparation of edges, which must correspond to the thickness of the metal and the welding current, as well as the type of connection.

After completing the welding work, the seams are examined for all types of defects that can be identified visually: cavities, undercuts, lack of penetration, pores, cracks, etc. If the work involves surfacing several layers on a worn-out structure, then the inspection is carried out after each layer is completed. After all work is completed, the product is finally handed over with an inspection report.

The visual measuring method can also be applied to a structure that has already been put into operation if the service life of the welds is coming to an end. If there is any suspicion of deterioration in the quality of connections, in order to avoid breakdowns or injuries, an examination by a controller is ordered.

Tools used

GOST 23479-79 also indicates the use of specific equipment and tools for qualitative visual research. It is divided into workshop devices that can operate at temperatures from +5 to +20, and field devices that operate from -55 to +55 degrees. These tools include:

• measuring magnifiers;
• welding templates for checking weld geometry parameters;
• squares for checking 90 degrees;
• bore gauges;
• protractors with vernier;
• probes for monitoring gap maintenance;
• micrometers;
• thickness gauges for determining pipeline walls;
• calibers;
• calipers;
• rulers and tape measures.

Good lighting is necessary for proper inspection and control, so the inspector should always have a flashlight and additional lighting equipment. In some cases, microscopes and borescopes are used. This allows you to more accurately determine the nature of the defect and its severity. If the product is located at a high altitude, and it is not possible to deliver a specialist there, then binoculars of various powers are used.

It happens that the need for visual inspection arises on structures where it is impossible to deliver an inspector and with which there is no direct visual contact. This can be underground in specialized tunnels, or in an environment with high temperatures and dangerous background radiation.

Then, to search and analyze defects, remote platforms with video surveillance and television installations are used, through which the inspector can monitor the area being inspected. In addition to robotic systems, lighting equipment is installed.

But these automated means are used extremely rarely with the visual method of monitoring welded joints.

Visual inspection is carried out in several stages, each of which is aimed at identifying certain defects. The first thing every inspector does is inspect the seam with the naked eye. This way you can detect pores, cracks, undercuts that weaken the joint.

Uncooked areas and shells are easily found. If the welder did not complete the “lock” and left a crater from the weld pool, then this is also not difficult to notice. Rough scales, metal deposits, and too narrowed seams will indicate a violation of the technology.

If a connection that is already in use is examined, then corrosion is easily visible visually.

After such an examination, the second stage of control is performed - studying the seam with optical instruments. This helps to detail the area and clarify the parameters of the defect. Magnifying glasses, microscopes, and borescopes are used. For example, if a visual inspection reveals risks, but their depth is unclear, examining the area under a microscope will help determine the severity of the defect and the need for other inspection methods.

The third stage of control is measuring the parameters of the welded joint using instruments. The length of the seam is measured and compared with the required standard for a given area with its loads. The leg of the deposited metal is removed. The seam height and width are determined using a caliper. All this is compared with the wall thickness of the base metal. The square measures the correct installation of the sides and the absence of displacement during operation.

After all stages of the inspection, a report is drawn up, where all found defects are entered, the condition of the connection is described, and recommendations for using other control methods are described.

Visually examining the quality of a seam allows you to quickly obtain information about its condition. The use of simple equipment makes the method accessible in many conditions. And timely implementation of this control method will allow welding structures to function for a long time.

Source: https://svarkalegko.com/tehonology/vizualnok-izmeritelnyj-kontrol-vik.html

Quality control of welded joints. State standard, control methods, their characteristics

Requirements for checking the conformity of quality indicators of welded joints are regulated by GOST 3242-79 “Welded joints. Quality control methods".

The document includes a list of non-destructive methods for quality control of welded joints:

• technical inspection;
• capillary;
• radiation;
• acoustic;
• magnetic;
• leak detection.

The characteristics of each method, scope of application, and standard designations are given.

Characteristics of some methods for quality control of welded joints

Inspection of finished welded joints is carried out after welding or after heat treatment of the finished part.

Quality control methods are divided into groups:

• non-destructive (the integrity of the connection is not compromised);
• destructive (destruction of the control sample is performed).

Checking the quality of welding of the finished product of both groups may include:

• visual inspection;
• connection measurements;
• density test;
• transillumination by radiating rays;
• magnetic control;
• ultrasonic flaw detection;
• luminescent control;
• metallographic studies;
• mechanical tests.

Visual inspection

It is mandatory and the simplest type of control. External inspection is carried out with the naked eye or using a magnifying glass of 5-10x magnification.

Preparation for inspection consists of cleaning the weld and adjacent surfaces from scale, metal splashes, and slag. Etching is performed if necessary.

The purpose of a visual inspection is to identify:

• external defects (lack of penetration, sagging, undercuts, external cracks, burns);
• part displacements;
• discrepancies between dimensions and technical specifications and drawings.

To compare the appearance of welds, it is practiced to use special standards. Measuring tools and templates are used to check geometric parameters.

After a visual inspection, they begin to identify internal defects using physical methods.

Capillary

Refers to non-destructive testing methods and is based on capillary penetration of an indicator liquid into the capillaries of the surface layer of the test object material in order to identify it.

Target:

• detection of surface and through defects;
• determination of the length of cracks , location of defects, orientation along the surface of the sample.

The capillary method allows you to control products of any shape and size made of metals and their alloys, plastics, ceramics, and glass. There are:

• basic control methods based on the use of capillary phenomena;
• combined , including a combination of several non-destructive testing methods, different in their physical nature, one of which is capillary.

Equipment used:

• capillary flaw detector;
• control device;
• aids;
• flaw detection ultraviolet irradiator;
• flaw detection materials.

Before conducting the study, preliminary cleaning of the surfaces and cavities of the control sample is carried out.

Checking seams for leaks

The method is used for welded products intended for storage and transportation of liquids and gases. Verification methods:

• ammonia;
• kerosene;
• pneumatic and hydraulic tests;
• vacuuming.

The essence of the ammonia test is based on the change in color of indicators (certain chemical compounds) as a result of exposure to liquefied ammonia. If there are cracks and pores in the seams, the indicator tape will turn silver-black.

The phenomenon of capillarity (the rise of liquid under certain conditions through capillary tubes) underlies the kerosene test. Capillary tubes in welds refer to pores and cracks. The presence of defects is determined by yellow spots appearing on the chalk or kaolin coating of the weld.

Pneumatic tests

This method is used to check pipelines and pressure vessels.

Plugs are used to seal small vessels. An inert gas or nitrogen is supplied into the vessel under pressure 10-20% higher than the working pressure. The vessel is immersed in a container of water. Defective areas are detected by escaping air bubbles .

Large vessels are sealed and filled with high pressure gas. A soap solution is applied to the welds. The appearance of bubbles on the surface of the seam indicates the presence of defects.

Hydraulic studies

It is used to test the strength and density of welds in water pipes, gas pipelines, boilers and welded products operating under pressure.

Before testing, the control container is sealed with a plug and filled with water using a pump under excess control pressure, one and a half to two times higher than the operating figures. During the period specified by the technical conditions, an exposure is made, then the pressure is reduced to working pressure. The heat-affected zone (15-20 mm from the seam) is tapped with a special hammer.

Areas with detected leaks are marked and sealed after draining the water. Repeated inspection is carried out.

Vacuuming is used when pneumatic or hydraulic control is not possible . The essence of the method is to create a vacuum and detect the penetration of air through defects. A vacuum chamber is used for control. The area of ​​the sample being tested is lubricated with a soap solution. Soap bubbles form in leaks in the welded joint.

Ultrasonic

The essence of the method is the reflection of ultrasonic waves from the interface between two layers with different acoustic properties. Ultrasonic vibrations are produced by a method based on the piezoelectric effect of certain artificial materials or crystals. When opposite charges are applied to opposite faces of a crystalline plate, its dimensions will change as the signs of the charges change, according to the transmitted frequency.

Ultrasonic vibrations are introduced into the weld using a device - a piezoelectric transducer. The same device receives vibrations reflected from the defect, recorded using a signal on the screen of the flaw detector.

The ultrasonic method allows you to detect in welds:

• pores;
• slag inclusions;
• lack of penetration;
• cracks;
• bundles.

The disadvantage is the difficulty of deciphering and assessing defects.

Radiation

The radiation flaw detection method is based on the property of radiation penetration through opaque bodies and its effect on various indicators. X-rays and gamma radiation are used - short-wave electromagnetic waves.

The goal is to identify defects (external and internal) and their location without compromising the integrity of the elements being tested.

Types of radiation monitoring:

• radiographic;
• radioscopic;
• radiometric.

Magnetic

The essence of the method is to use the effect of magnetic scattering, which manifests itself above a defect in a magnetized control sample.

If there is no defect in the weld, the magnetic force lines spread evenly over its cross section. If there is a defect, the power magnetic flux bends around the problem area, creating a magnetic leakage flux.

Depending on the method of recording scattering fluxes, the following methods are distinguished:

• magnetic powder;
• induction;
• magnetographic.

Source: https://elsvarkin.ru/texnologiya/kontrol/kachestva/

Control of welding materials: what is checked, norms and requirements (GOSTs), assessment methods

The manufacture and installation of various metal structures is not complete without the use of electric arc welding. The process is approved by some GOSTs and SNiPs, depending on the nature of the work performed.

Incoming control or verification of the quality of welding materials is determined by their routine inspection, verification of actual certificates for the newly purchased batch.

These are electrodes, tapes, cored and solid wires, rods, fluxes, and protective regulated gases.

The former are used to supply high-frequency current to the workpiece, while the welding wire is a filler material that fills the area between the workpieces. The composition of the latter must correspond to the material of the structures being connected.

Fluxes dissolve oxides on a metal surface, which improves the wetting of parts with molten metal and prevents oxidation by limiting the access of oxygen.

Welding threads and rods act as filler substances. Shielding gases prevent the entry of the surrounding atmosphere into the weld pool.

Material control

All welding elements and materials supplied to the enterprise must be supplied with certificates that stipulate the data of GOSTs, SNiPs, technical factors and passports.

Packaging boxes, crates, packs and pressure containers must have tags or labels indicating the passport information of the welding material.

Failure to comply with this condition does not allow the use of a specialized substance for the work, which is the reason for a complete check of the welding material in all quality parameters. They must correspond to the given type of welding elements.

Electrodes

The compliance of the electrodes with the passport data is checked at the manufacturer and before carrying out work at the production site or construction site. Inspection of rods made of electrically conductive material begins with an external inspection.

From each batch, 10-20 welding units or 0.5% of the batch are selected for quality control. If testing reveals an increased number of electrodes with a flaw, the entire group is rejected.

The mechanical properties of electrically conductive rods with a diameter of up to 3.0 mm are checked by bending them and dropping them onto a steel plane from a height of 100 cm; if the thickness of the electrode exceeds the specified size, the height is halved.

The quality control rules for welding materials provide for partial spalling of the coating, but its total length should not exceed 20 mm, which is stipulated by State Standard 9466-60.

The technical conditions also allow for minor defects in the area of ​​the rods:

• some roughness of the coating, insignificant longitudinal notches, burrs that have a depth not exceeding a quarter of the coating;
• no more than three local depressions per half the thickness of the lining, no longer than 1.2 cm each;
• voids - up to 3 by 10 cm in length, and their diameter should be less than 2.0 mm, no more than half the depth of the layer;
• no more than 2 hairline cracks, each up to 1.2 cm long.

The homogenized mass—coating—must be applied concentrically relative to the rod. Its compliance is checked over the entire section by making cuts and measuring the thickness of the coating.

The thickness difference cannot exceed the following indicator:

electrode Ø 2.0 mm - 0.080 mm;

• 2,50 — 0,10;
• 3,0 — 0,150;
• 4,0 — 0,20;
• 5,0 — 0,250;
• 6.0 and above - 0.30 mm.

The layer must be waterproof and not crumble after immersing the electrode in liquid for 24 hours, and the heating of the water should be +15-25° C. After a trial welding operation, the coated rod is evaluated according to the following factors:

1. Ease of ignition of the electric arc.
2. The stability of its combustion.
3. Metal spatter indicator.
4. Proportions of melting homogenized mass.
5. Soot separability.

Based on the data obtained, an assessment of the quality of welding materials is made.

It is recommended that before starting welding processes, the first ones should be dried in special ovens up to +180° C, but not with gas devices. The operation worsens the performance parameters of welding rods.

For stainless steels

Electrodes and welding threads - wire, for high-temperature face-centered modification of iron and its alloys have increased requirements, which explains their special control.

The latter is carried out on a rigid T-shaped beam or a sample having six layers of surfacing. The sample used must be similar to the type of steel from which the structure being welded is made.

The electrically conductive rod is taken from the batch selected for work and quality control is carried out on it.

Six-layer deposition is carried out in the lower extreme position, and each layer is deposited in a unidirectional position. After the previous layer has cooled to +18-20° C, the next one is applied to it.

After the process is completed and the sample reaches room temperature, the slag is removed, and the sample is inspected for the presence of hot cracks - casting defects in the form of a rupture or tear in the body. In this case, the prototype is broken along the line of the controlled seam.

Then the first one is divided into three equal bars for the production of materials with a ground surface - macrosections. Their flat surface is intended for etching parts with hydrochloric acid or alkali.

After treatment with an aggressive environment, the prototypes are dried, then examined for defects under a magnifying glass. The presence of cracks along the crystal boundaries indicates defective electrodes. However, control welding allows for some defects.

These are individual gas inclusions or fumes up to one and a half millimeters in size and three pieces per 0.15 m of the length of the brand break. Inclusions cannot exceed one third of the seam height.

Upon completion of the control study of these welding materials, a special report is drawn up.

Fluxes

Multi-composite materials for dissolving oxides on welded surfaces - fluxes - are also required to undergo quality control.

The latter must comply with the attached certificate, which indicates their chemical composition and granulation, defined by technical specifications or standard 9087-59.

GOST specifies the conditions for welding flat joints and pipe joints of the corresponding modes.

If pores or cracks are detected in seams made under a layer of flux, the granulometric composition of the composite material, homogeneity, volumetric weight, and its blackening are checked. If the moisture content of the composite is exceeded by 0.10%, it is dried.

After drying, the weld is made under a protective layer on the brand, after which the deposited metal is examined for the presence of carbon and sulfur through chemical analysis. The quality test is taken from the side of the top layer of combined parts.

Statement of an unsatisfactory result results in rejection of the flux. However, the situation can be corrected by repeated calcination of the latter, including a subsequent more thorough check.

It is also characterized by identifying the chemical composition of the multicomposite material. The uniformity of the crushed composition is checked using high magnification of 10 g of the substance. Foreign particles should be no more than 0.5 g in the test weight.

Granulometric - by sifting 100 g of composite through a fine sieve, which corresponds to GOST No. 9087-81. Residues on the sieve should be from 0.250 to 4 mm, depending on the type of media.

Shielding gases

Modern welding uses various welding mixtures—shielding gases—to protect against ambient air. The latter are divided into dynamic, inert and conglomerate.

Cylinders with a controlled protective environment are equipped with tags that indicate the brand, chemical composition of the substance, and the name of the manufacturer. The artificial atmosphere is examined for the presence of various impurities and moisture.

The latter is detected by passing a gas stream through a condensation hygrometer or filter paper.

If it is moistened, the protective medium is driven through a desiccant filled with silica gel. To remove moisture from argon, dryers with titanium shavings are used, which are preheated to +450° C.

If a large number of defective connected seams are detected, the quality of the gas is checked. To do this, 5% of cylinders from each batch are randomly selected, and the minimum number of the first must be three units.

Containers equipped with certificates are usually not subject to quality control of welding materials. It occurs when various defects are detected in the seams.

Wire

Welding wire is supplied to production structures rolled into coils, coils, or on spools and cassettes, which corresponds to standard 2246-70. Upon receipt, it is checked against the certificate, inspected, and the coils and coils are measured.

If the product is not provided with a certificate, use is assumed only after a chemical study of the composition to confirm carbon, manganese and sulfur.

Similar content is verified for low-carbon threads, while alloyed ones undergo control of chromium, vanadium, nickel and other elements. The product must comply with the following standard:

• welding - 2246-70;
• surfacing - No. 10543-63;
• aluminum - No. 7871-63.

The diameter of the thread is measured with a precision of up to 0.010 mm in two places located five meters from one another.

An external inspection allows you to make sure that the entire skein or reel is one piece, there are no tangled strands, and they are tightly tied to avoid unraveling or accidental unwinding.

The ends of the fabric should be easily distinguishable. There should be no traces of oxide, grease or dirt on the wire, there should be no delamination, cracks, sunsets or holes.

The presence of clogging is removed mechanically or chemically. GOST allows for the presence of small scratches, some rippling, individual dents, and traces of soap lubricant that does not contain graphite and sulfur.

For chemical analysis, 0.5% of the skein is selected from each group. The depth of defects is regulated by the maximum deviation in diameter, and is determined by the following parameters:

• diameter 0.80 mm - deviation 0.070 mm;
• 1,0 — -0,090;
• 1.20 - previous value;
• 1.40 – previous figure;
• 1,60 — -0,120;
• 2.0 - previous;
• 2.50 - -0.120 mm;
• 3.0 - the above;
• 4,0 — -0,160;
• 5.0 - previous.

If pores or cracks are detected in the deposited welding material, the wire is tested for weldability by joining two 10 mm plates or pipes with a body thickness of 8 mm.

The processed samples are divided into six parts, which are tested for tensile strength and bending angle strength. The lack of a positive result allows the wire to be rejected.

For work of increased responsibility and in the presence of a large number of defects, corrosion resistance, continuity of the completed weld, and ferrite content in the working metal are examined.

Flux-cored wire is controlled by external inspection and measurement, checking the filling of the sheath, mechanical and chemical tests. The entire arriving group of cassettes is subject to inspection.

If dents, cracks, or breaks are detected in more than five areas, the batch is rejected and quality control is considered failed.

Flaw detection

In addition to mechanical tests and examination of the chemical content of elements, welding materials undergo flaw detection.

The latter consists of the use of chemical reagents, X-ray control, ferromagnetic strip, intensifying metal or fluorescent screens.

Their action is based on enhancing the release of secondary electrons during ionizing radiation. When information is received, it is checked against the labels on the packaging lists, which must have good visual readability.

Any deviation from the norms is formalized by a special act, however, products that have passed preliminary control are allowed for the type of research described.

Control of welding materials before their use is carried out at the enterprise that uses them in its activities. For this purpose, there are special methods and devices that make it possible to detect defects in any type of welding product.

Source: https://prosvarku.info/rashodnye-materialy/kontrol-svarochnyh-materialov

Metal table for welder

The welding table is useful for amateurs and professionals. It is not profitable to buy such a table in a specialized store. Therefore, you can make a welding table with your own hands at home.

When assembling the table yourself, you can make it the size you want. Also, to save space, the welding table can be used not only for welding, but also for other work.

What type of welding table should it be?

Working with a welding mechanism is dangerous, so the table must be comfortable and safe for work. There are many types of welding tables, but for comfortable use, any type must meet certain requirements:

The workplace must have a hood. When welding, a lot of harmful dust and gases are released, so the air must be cleaned through an exhaust hood so as not to harm your health.

At the workplace, there must be a fan at the end of the table. It is better to place it at a height of 150 cm.

The edges of the welding table should be covered with copper material.

For lighting, a homemade system is made, with a power of no more than 36V.

The welding table must have a built-in place for storing electrodes and another place for other necessary tools.

One lockable compartment where tools that are rarely used will be stored.

An integral part of the welding table is grounding.

It is important to remember that a table for welding at home must be made of a material that does not melt, does not burn, and does not emit toxic substances at high temperatures. The recommended table height for welding is 0.7-0.9 meters, area – 1.0 by 0.8 meters.

Next, you need to make a drawing of the welding table with dimensions and prepare all the necessary tools.

Required tools for assembly

• Welding machine and elements necessary for its operation.
• Squares, rulers and marker for notes.
• Tape measure or measuring tape about 3 meters.
• 4 clamps, in the shape of the letter “C”.
• Wire cutters.
• Metal hacksaw or grinding machine.
• Tap.
• Drill and elements necessary for its operation.
• Metal sheets, pipes, wire.
• Bolts, nuts, etc.
• Jigsaw, vice.
• Bulgarian.

Instructions for making a welding table with your own hands

The top cover will be made for the welding table from a profile pipe, with a section of 0.5 by 0.5 cm at the edge and 0.3 by 0.3 cm on the outside. It is better to cut the pipe with a grinder. The prepared parts are fastened using a welding machine. The edging of the lid will be made of a 0.5 by 0.5 cm rectangular profile

The inner part is laid with a profile 0.3 by 0.3 cm. The pipes are attached by welding in such a way that a lattice is formed, the seams are cleaned.

Next we make the legs, they can be made from a pipe 0.25 by 0.25 cm. In total, you need to cut 4 pieces, then weld them to the base of the table. To make it easier to understand what and how to do, for clarity, look at the photo of the welding table.

For additional rigidity, we make a belt around the perimeter of the table, at a height of 30-40 cm from the floor. This is necessary so that when working the table stands firmly and does not wobble.

For convenience, you can make handles to move the table to any place. It is better to make them from metal fittings with a diameter of 0.8-1.0 cm.

Wheels for more convenient transportation of the welding table. Just 2 wheels, which can be taken from an old cart, will be enough.

Storage space for tools. It is recommended to make the niche from chipboard or plywood. If desired, you can use a metal sheet. A niche is attached at the bottom of the table.

The garbage casing is made of metal sheets of any thickness.

The finished welding table can be painted with special paint for metal if desired.

There must be a container of water next to the workbench, because welding work is flammable. Also, the floor surface next to the welding table, at a distance of 1.5 meters, must be covered with non-flammable material.

If you follow the instructions on how to make a welding table and apply these tips in practice, then you will succeed.

Photo of the welding table

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Inspection of welds and joints

The quality of the weld directly affects the reliability of the entire element, this is especially important for parts experiencing increased or load-bearing loads. Therefore, for quality control, after the main work, an inspection is carried out in order to identify defects. There are many diagnostic methods, which are divided into

• destructive
• non-destructive.

The first involves mechanical or other impact on the weld in order to identify its errors. In this case, part or all of the welded section loses its structural properties.

For this reason, non-destructive methods of weld inspection, which we will discuss below, are considered more popular and appropriate.

Non-destructive testing methods

At the moment, the following non-destructive methods are distinguished:

• visual inspection;
• radiation method;
• magnetic research;
• ultrasonic method;
• capillary method;
• permeability control.

Visual inspection

Any quality control of welded joints begins with a simple external inspection. This is often enough to identify both external and internal gaps, plus there is no need to use non-destructive testing equipment. For example, different seam heights may indicate lack of penetration in different areas. Before inspection, the seams are cleaned of process contaminants, namely slag, scale and metal splashes.

Visual inspection of the weld

To make minor defects more visible, the surface is treated with an alcohol solution, and then with a 10% solution of nitric acid. After this procedure, the surface will become dull and show pores and cracks.

The main thing is not to forget to clean the acid with alcohol after troubleshooting the seam.

Inspection is the main way to identify geometric deviations, such as pores, cracks, sagging, undercuts. This test point can be carried out more efficiently using additional instruments.

To do this, it is best to use a magnifying glass, as well as better lighting, preferably with a mobile light source. A magnifying glass will allow you to detect cracks and pores that are hidden to the eye, as well as trace their path. To control the width of the rollers, you can use measuring instruments such as a ruler or caliper.

Tools for visual inspection

Radiation flaw detection

The radiographic method of testing welded joints exists in two variations:

• x-ray radiation;
• gamma radiation.

The simplest way to identify weld errors is to illuminate the product with X-rays. They have the property of penetrating through metal objects, while acting on photographic film. Thus, the resulting image is a direct map of most of the defects. Using penetrating rays, slag inclusions, gas pores, edge displacements, burns and other gaps are identified.

Slag inclusions on x-ray

Before starting work, the area under study and the adjacent plane must be properly cleaned. To do this, remove slag, splashes, scale and other defects. Also, before x-raying, an inspection is mandatory and if low-quality areas are identified, they must be eliminated.

It is prohibited to start candling in the presence of external defects, since the procedure is intended to diagnose and identify hidden defects.

If errors are detected, the decision to accept or rework a specific part lies with the regulatory documentation. It is the established rules and instructions that make it possible to determine whether errors fall within the standards established for a given product.

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To carry out the procedure, the X-ray tube is positioned so that the beam hits the suture at a right angle. On the other side of the product there is a cassette with X-ray film.

Since existing defects have less impact on X-ray transmission, they will be visible as darker areas on the film. The radiographic test lasts depending on – film quality, thickness and focus.

Afterwards the film is developed and you can see the result of welding.

Radiographic monitoring does not reveal:

• any discontinuities and inclusions with a size in the direction of transmission less than twice the control sensitivity;
• lack of penetration and cracks, the opening plane of which does not coincide with the direction of transmission;
• any discontinuities and inclusions, if their images in the photographs coincide with the images of foreign parts, sharp corners or sharp changes in cracks of the metal being scanned.

Gamma radiation is practically no different in operating principle from X-rays. These are radioactive rays that can penetrate metal and react to its unevenness. Using this method, I inspect from 10 to 25% of all seams; if the structure is critical, then all seams.

Various chemical elements suitable for certain metals are used as a radiation source:

• Cobalt – 60 (steel, cast iron, copper, bronze and brass up to 25 cm thick), thanks to its rigid penetration, the element is suitable for most steels and large thicknesses;
• Cesium – 137 (steel up to 10 cm);
• Iridium-192 (steel up to 5 cm, aluminum up to 10 cm);
• Thulium-170 (steel and aluminum up to 20 cm).

With a decrease in penetration, the type of alloys and their thickness decrease, but at the same time the average image quality remains and makes it possible to determine the main defects.

Portable X-ray machine MART-250

Unlike X-rays, gamma rays have a number of advantages:

• isotopes remain functional for a long time;
• lighter equipment;
• possibility of troubleshooting complex components;
• increased ray permeability;

Important! Both types of radiation are extremely dangerous for humans. That is why only specially trained employees wearing a full set of protective equipment can be allowed to work. The location and operation of penetrating equipment must also be protected; lead plates, screens and other means are used for these purposes.

Magnetic flaw detection

This control of welded joints is based on the property of magnetic lines of force to respond to changes in the thickness of the metal. By recording such deviations with special instruments, it is possible to accurately detect errors in the thickness and on the upper part of the alloys.

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There are currently three variations of the method:

• magnetic powder;
• magnetic induction;
• magnetic-graphic.

Powder testing consists of applying dry powder or emulsion to the surface, going beyond the seam joint, then magnetizing the alloy and determining inaccuracies. If the “dry method” is taken, then iron scale or oxides act as powder. The product is magnetized using an electromagnet, solenoid, or by applying current to the product. Then, lightly tapping with a hammer, give the powder

opportunity to take your position. The excess is removed with a jet of air and then the flaws are fixed. The last step is demagnetization.

In the wet method, magnetic powder is mixed with kerosene or special oil. The resulting suspension is applied to the seam, and its mobility, dispersion or accumulation of powder are direct identifiers of errors.

With the induction method, all data is recorded by an induction coil. Special devices - flaw detectors - record magnetic scattering in metals up to 25 mm thick.

Graphic consists of fixing magnetic fluxes on a special tape. It is attached along the seam, and then the deviations are determined on the screen of the cathode ray tube.

Magnetic methods are only suitable for ferromagnetic alloys; other metals cannot be studied in this way.

Ultrasonic testing method

Along with the previous method, ultrasonic flaw detection makes it possible to record deviations formed when waves are reflected from the boundaries of media with different properties.

The ultrasonic source sends out a signal that is reflected when it reaches the end of the alloy. If a signal encounters a defect along its path, this is reflected on the wave, which in turn is recorded by the device. Different defects have their own reflections, so determining the nature of the defect is quite simple.

Ultrasonic flaw detector

Of the methods already described, this one is considered the most convenient to use. This is due to the ability to identify flaws both on the surface and in the depths of the metal. Also, the method does not have such strict restrictions as magnetic. There are a number of coarse-grain metals, such as cast iron, that are not amenable to ultrasonic examination, but for all other alloys it is possible to easily control the quality of welding work.

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There is another drawback - the difficulty of deciphering the received data. Unfortunately, flaw detectors provide the user with very specific data that must be deciphered. It is almost impossible to do this without preliminary preparation, so a trained specialist is needed for the work.

Penetrant flaw detection

This method is based on the properties of liquids with low surface tension. Such liquids do not form large drops in one place and tend to drain, but at the same time they are able to fill the smallest grooves and holes. Surface defects and, in rare cases, through channels are determined in a similar way.

Penetrant flaw detection

A special solution is applied to the seam, which instantly fills all grooves, pores and other small defects. Then, examining the seam, you can find large flaws. For greater convenience, liquids are tinted with dye, luminescent and other coloring additives are added.

Welding quality control for permeability

The method is a logical continuation of the capillary method. The main idea is that by using fluids with deep penetration properties, it is possible to identify through-grooves in the weld.

To do this, take simple kerosene, apply it to one side of the seam, and fix wet spots on the other, signaling through channels. Among the disadvantages, it is worth noting the need to thoroughly clean the surface and maintain precision at all stages to avoid accidental contamination of the opposite side of the weld.

Conclusion

Welding and quality control of welded joints of metal structures are inseparable parts of one process. It doesn’t matter whether the work is carried out at home or in production, without proper strength testing, the product cannot continue to exist. The methods described above will allow you to check the quality of welded joints without destroying the seam.

Source: https://svarkagid.ru/tehnologii/metody-kontrolya-svarnyh-shvov.html

What is checked when inspecting welding materials?

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When should each batch of welding and soldering materials be inspected? This question can often be heard at enterprises of various sizes: from small-scale production to large-scale factories. By default, all welding materials must have their own certificate, which will confirm their compliance with GOSTs and quality standards. Also, the packaging of welding materials must contain all the basic data about the product.

These are the basic conditions that must be met. But what about individual inspection of individual welding consumables? They, of course, need to be checked before releasing a whole batch. Incoming inspection is a must if you want to produce products in accordance with laws and regulations. In this article we will describe in detail what is checked when inspecting welding materials and how the inspection is carried out.

Control of welding materials

When we hear “quality control of welding materials,” we first of all think of welding electrodes, since this is the most numerous type of welding materials. The quality of electrodes can be checked several times: during their production, in laboratory conditions and before welding. The larger the enterprise, the more often inspections are carried out, since the batches are very large and it is not always possible to recognize the defect the first time.