What is a welded joint?

T-weld joints

A T-joint is a connection of two parts located at an angle to each other, i.e. the end of one part is adjacent to the side surface of the other at an angle of 90 degrees.

In simple words, a vertical part is welded to a horizontally lying part, forming the letter “T”. Such connections can be without edge cutting, with one-sided or double-sided groove.

T-joints are used in arc welding; they are welded very conveniently in horizontal and vertical positions, most conveniently in an inclined position (in a boat).

Where is it used?

Double-sided with cutting edges

The use of T-joints is very wide: in the automotive industry, in building structures (trusses, supports, columns, racks), metal furniture (benches, tables, shelves), bridges and overpasses, gas pipelines, oil pipelines, water supply systems, heat supply systems for buildings and structures.

Advantages and disadvantages

The T-joint is the most common and one of the strongest. This connection makes it possible to obtain products and structures of complex shapes. The arrangement of parts in the letter “T” provides additional rigidity to the structure. Quality work guarantees practicality and reliability.

The disadvantage of such a connection may be defects:

• Welding defect - crater - is a depression in the weld that occurs when the arc breaks;
• pores are a consequence of the accumulation of gases in the seam; the cause of such a defect lies in poor quality of metal preparation;
• lack of fusion is a local lack of fusion of the base metal with the electrode metal, the reason: high welding speed, as well as burns, cracks, etc.

Such defects depend on the quality of the work. Low qualifications of the worker will directly cause defects, but equipment and consumables (welding machines, wire, electrodes, shielding gas) are also equally important. The process itself is dangerous, you must follow all safety regulations without exception.

Technique, features

For all welded joints, the technique will be standard; it is important to take into account the welding method. The T-joint is convenient, it is easy to form a seam, control the size of the leg and the appearance of the seam.

Before starting work, technological preparation of the surface is carried out, otherwise the presence of dirt and rust will reduce the productivity of the welding process and lead to defects. When welding a T-seam, the electrode is placed in a plane at an angle of 30-40 degrees relative to the bottom plate, having assembled the parts and grabbed it - this way the connection will not move.

Single-sided with seam groove in the lower position

It is necessary to check the angle between the parts and the correct location; if everything is done correctly, then you can proceed directly to welding.

We excite an electric arc and tilt the electrode slightly towards ourselves and hold it in one position; we should move carefully backwards, making oscillatory movements along the axis of the seam to melt the edges. This is necessary in order to avoid lack of penetration of the corner and one of the sides of the part.

You can apply a mark above the corner on the top plate beyond the boundaries of which the electrode should not extend, this will result in a more even seam.

The techniques for welding a T-joint in different positions are somewhat different from each other.

For your information! Considering the welding technique, you can immediately note that it is easiest to perform welding in the lower position, or the “boat” position. Therefore, if there is such a possibility, it is recommended to rotate the welded structure so that the welds are made in the lower position.

After welding, the slag is cleaned off and the surface is treated with a metal brush or other devices.

Recommendations

If you weld a thin and thick plate with a T-joint, the angle of inclination of the electrode relative to the thick plate will be approximately 60 degrees. To “pull” more metal from the thick part to the thin part.

It is also advisable to dry the surfaces to be welded for better quality of the weld.
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Pipe welding

Based on GOST 16037-80, which applies to welded joints of pipelines made of steel and establishes the main types, structural elements and dimensions of welded joints of pipes with pipes and fittings, it would be correct to say that there is no T-joint in it. All seams that are called T-joints are referred to as corner seams .

However, when a plate plug or flange is welded to the end of the pipe, it will be a T-joint.

By and large, in order not to argue about this, it is necessary to understand that the T-joint of pipe parts or any other rolled metal is performed using a fillet weld and the technique of welding pipelines comes down to the technique of welding fillet welds .

First of all, you need to focus on preparing the pipes before welding the T-joint. The pipes must meet all requirements and be free from defects, contamination and rust, after which welding can be performed.

Tacks should be made; for pipes with a diameter of up to 300 mm, 4 evenly spaced tacks are sufficient. For wider pipes, tacking is done at equal intervals throughout the entire diameter.

The end of one pipe must be cut in a certain way so that it fits tightly to the side surface of the other pipe. For pipes with a small diameter, this is not very difficult to do with the help of a few manipulations with a grinder.

It’s a different matter when you have to work with large diameter pipes. In this case, as a rule, various patterns and patterns are used when marking.

Useful video about how to cut pipes to weld them end to side.

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Next, the parts are assembled using tacks or in an assembly and welding fixture. Welding of pipe joints can be performed both in a rotary position (it is possible to rotate the joint around its axis) and in a fixed position (there is no possibility of rotating the joint around its axis). When welding pipes, the weld has to be made along a curved surface, which somewhat complicates the process. It is necessary to divide the joint into sections and perform welding in several steps.

IMPORTANT! In this case, it is necessary to ensure remelting of the previously deposited weld.

Depending on the thickness of the pipe wall, the weld is performed in one or several passes. You should pay attention to the composition of the pipes and select suitable electrodes. The weld on the pipes must be perfect, and the presence of defects must be checked. If there are defects, they are corrected.

https://www.youtube.com/watch?v=qBf24cIxYuU

Profile pipes are used for fences, frames, and various metal structures.

Advice! When connecting, it is advisable to make sure that the cut is even, otherwise a gap will appear that will have to be welded abruptly.

When making T-joints of profile pipes, tack welding is also performed. The electrode is moved at an angle with oscillatory movements from bottom to top. After welding, the slag is cleaned off.

Upright

With a T-joint in a vertical position, the welding current is set higher for good penetration; welding must be performed from the bottom up with arc separation.

For your information! Vertical seams are made both with arc separation and through passage. This depends on various factors: metal thickness, welding method, electrode brand.

The movement of the electrode is carried out by loops, corners, arc vibrations, etc., the position of the electrode should be 45 degrees, sometimes welding is performed from top to bottom. When igniting the arc, we hold the electrode perpendicular to the surface to be welded; this welding technique is not convenient and you need to carefully control the weld pool .

To control the pool, it is necessary to reduce the welding current so as not to overheat the metal, the electrode must be set to the correct position so that the arc pressure maintains the liquid metal, and does not contribute to its flow to the bottom.

Welding is performed with a short arc so that the distance between the end of the electrode and the workpiece is minimal.

Source: https://WeldElec.com/svarka/nauchitsya/soedineniya/tavrovoe/

Fusion welding

It is not always possible to completely manufacture various iron structures. In some cases, it is not advisable to manufacture them from a single workpiece due to the large amount of unwanted waste; in other cases, the dimensions of the parts will not allow for normal mechanical processing. Therefore, various methods of connecting workpieces to each other were invented.

These are all kinds of threaded connections, gluing parts, soldering, and also, well known to everyone, welding. It is applicable not only to parts and workpieces made from various metals and their alloys, but in general to any materials that can be melted. There are several types of welding: one where only heat is required to melt the material, where only pressure is required, and combined.

Below we will consider the option of fusion welding.

Fusion welding

The welding process is a method of joining two or more metal parts by thermally melting the edges of the joined workpieces. Being in a molten state, the metal from which the workpieces are made is mixed and a strong permanent connection is formed at this point.

After cooling, a so-called weld seam is formed in place of the molten metal. This process is somewhat similar to casting, but on a limited scale. Nowadays, welding has found wide application for joining two or more workpieces both on an industrial scale and in the artisanal production of metal products.

It is also used in the process of repairing various components, since it allows the metal to be fused where it has been worn away.

Weld

Depending on which method of heating the workpiece material to the melting point is chosen, there are several types of welding, which we will discuss below.

Classification of types of fusion welding

Depending on the source of thermal energy, which is capable of heating the edges of parts to the melting temperature, fusion welding is divided into electric, gas and other types of welding. Electrical technology can again be divided into electric arc and induction. Let's consider the types most used both in everyday life and in industry. The most widely used types of welding are electric arc and gas welding.

In the case of electric arc, metal melting occurs due to the high temperature of the electric arc (about 5000 degrees), which occurs between the workpiece and the electrode. When using gas welding, the heat source capable of bringing steel to the melting point is a burning gas or a mixture of gases (for example, propane and oxygen with a combustion temperature of up to 2050 degrees).

The filler material for the seam in this type of welding is most often either a separate special filler, or its role is played by metal from the body of the workpiece.

And also, depending on the type of electrode used, the following types of welding can be distinguished:

• Using a consumable electrode. The seam is formed during the melting process of an electrode coated with a special coating. It is selected individually, depending on the types of steels being connected. Not used when joining thin sheet metals due to excessive overheating and frequent burns.
• Using a non-consumable electrode. It is made of a refractory metal, most often a tungsten alloy, and is intended only for igniting and maintaining the arc. Welding is often carried out in an inert gas shielding environment, which isolates the seam from the nitrogen contained in the surrounding air. Most often used in the case of sheet products.

Gas welding

Other types of fusion welding, such as induction, laser, plasma, etc., have not yet found widespread use due to the high cost of the equipment, so they will not be considered.

Welding principle

Source: https://stankiexpert.ru/spravochnik/svarka/svarka-plavleniem.html

GOST for welded joints: parameters of welded joints specified in the standard tables - Machine

If you say that GOST is your favorite word, hardly anyone will believe you. But if you are engaged in welding and claim to be a high-class professional, you will have to treat this word with all respect, if not love it.

You need to not only respect him, but also have a good understanding of the required state standards regarding the typology of welding methods. Why? Because if you are working with something more serious than an old basin at the dacha, you will definitely come across working drawings with huge quantities of icons, letters and abbreviations.

That's right, without technical specifications and standard designations - nowhere. Modern welding technologies are a wide range of very different methods with their own requirements and technical nuances. All of them fit into several standards, which we will now go through and consider in the most careful manner.

Welding designations on GOST drawings look intimidating at first glance. But if you figure it out and stock up on the original versions of the three main GOSTs on the types and designations of welding technologies, the designations will become clear and informative, and your work will be accurate and professional.

Types of welding seams

First, ESKD is the Unified System of Design Documentation, or, to put it simply, a set of various standards according to which all modern technical drawings, including documentation for welding work, must be carried out.

This system contains several standards that interest us:

1. GOST 2.312-72 entitled “Conventional images and designations of seams of welded joints”.
2. GOST 5264-80 “Manual arc welding. Welded joints”, which comprehensively describes all possible types and designations of welds.
3. GOST 14771-76 “Seams of welded joints, welding in shielding gases.”

To understand the symbols of welding methods in engineering drawings, you need to understand their types. We suggest looking at an example of a weld designation in the drawing:

It looks bulky and intimidating. But we won’t be nervous and will slowly figure it out. There is a clear logic in this long abbreviation, let's start moving step by step. Let's break this monster down into nine parts:

Now these same components in squares:

• Square 1 – auxiliary signs to indicate: a closed line or an installation connection.
• Square 2 is the standard by which the symbols are given.
• Square 3 – designation by letter and number of the type of connection with its structural elements.
• Square 4 – welding method according to the standard.
• Square 5 – type and dimensions of structural elements according to the standard.
• Square 6 – characteristic in the form of the length of a continuous section.
• Square 7 – characteristics of the connection, auxiliary sign.
• Square 8 is an auxiliary sign for describing a connection or its elements.

In square No. 1 there is a circle - one of the additional characteristics, a symbol of a circular connection. An alternative symbol is a flag, indicating a mounting option instead of a circular one.

A special one-way arrow shows the suture line. Another specific feature of welding drawings is associated with this arrow. This single-faced arrow has a nice feature called a shelf. The shelf plays the role of a real shelf - all symbols can be located on the shelf if a visible connection is indicated.

Or under the shelf, if the seam is invisible and located on the reverse side, i.e. from the inside out.

What is considered the front side and what is the back side? The front side of a one-way connection is always the one that is being worked on, it's simple.

But in the double-sided version with asymmetrical edges, the front side will be the one where the main joint is welded. And if the edges are symmetrical front and back, any side can be used.

Here are the most popular auxiliary signs used in welding drawings:

We disassemble squares No. 2 and 3, types of seams according to GOST standards

Two standards closely deal with connection options: the already familiar GOST 14771-76 and the famous GOST 5264-80 on manual arc welding.

An example of a drawing of welds according to GOST.

The types of welding joints are as follows:

C – butt seam. The metal surfaces to be welded are connected by adjacent ends, located on the same surface or in the same plane. This is one of the most common options, since the mechanical parameters of butt structures are very high. At the same time, this method is quite complex from a technical point of view; experienced craftsmen can do it.

T – T-seam. The surface of one metal workpiece is connected to the end of another workpiece. This is the most rigid design of all possible, but due to this, the T-bar method does not like and is not intended for bending loads.

N – lap seam. The surfaces to be welded are parallel offset and slightly overlap each other. The method is quite durable. But it carries less load than the butt options.

U – fillet weld. Melting occurs at the ends of the workpieces; the surfaces of the parts are kept at an angle to each other.

O – special types. If the method is not in GOST, a special type of welding is indicated in the drawing.

Both standards within the framework of the ECSD resonate well with each other and fairly divide responsibilities by type:

Options for depicting welds in drawings.

Manual arc connections according to GOST 5264-80:

• C1 – C40 butt
• T1 – T9 T-bar
• H1 – H2 overlap
• U1 – U10 corner

Gas shielded welding connections according to GOST 14771-76:

• C1 – C27 butt
• T1 – T10 tee
• H1 – H4 overlap
• U1 – U10 corner

In our abbreviation, in the second square, GOST 14771-76 is indicated, and in the third T3 - the double-sided T-bevel method without beveled edges, which is precisely indicated in this standard.

Square No. 4, welding methods

How are the different types of seams designated?

The standards also contain designations for welding methods; here are examples of the most common ones:

• A – automatic submerged without cushions and linings;
• Af – automatic submerged arc on a pad;
• ИH – in an inert gas with a tungsten electrode without additives;
• IHP – method in inert gas with a tungsten electrode, but with an additive;
• IP – method in inert gas with a consumable electrode;
• UP is the same thing, but in carbon dioxide.

In square No. 4 we have the welding designation UP - this is a method in carbon dioxide with a consumable electrode.

Square No. 5, seam dimensions

These are the required seam dimensions. It is most convenient to indicate the length of the leg, since we are talking about a T-type version with a perpendicular connection at a right angle. The leg is determined depending on the yield strength.

It should be noted that if the drawing shows a connection of standard sizes, the length of the leg is not indicated. In our drawing designation, the leg is equal to 6 mm.

Classification of welds.

Additional connections are:

• SS one-sided, for which the arc or electrode moves on one side.
• BS double-sided, the melting source moves on both sides.

The third participant in our drawing and welding party comes into play - GOST 2.312-72, which is dedicated to images and symbols.

According to this standard, seams are divided into:

• Visible, which are depicted as a solid line.
• Invisible, indicated in the drawings by a dotted line.

• Now let's go back to our original seam. We are able to translate this welding symbol into simple text that is understandable to the human ear:
• Double-sided T-seam by manual arc welding in protective carbon dioxide with edges without bevels, intermittent with a staggered arrangement, weld leg 6 mm, length of the welded area 50 mm, pitch 100 mm, remove the convexities of the seam after welding.

Source: https://regionvtormet.ru/metally/gost-na-svarnye-soedineniya-parametry-svarnyh-shvov-ukazannye-v-tablitsah-standarta.html

Fittings for metal pipes: connecting parts in different ways

Fittings for metal-polymer pipes, as well as parts for assembling communications made only from metal elements, can be very different. However, the differences lie both in the material from which the connectors are made and in their design.

A small part of the total variety of products used in pipeline laying

Below we will look at the main types of parts, paying attention to their strengths and weaknesses.

What are they made of?

Let's start our review of the range of fittings with an analysis of the materials used for their production. As a rule, the metal of the connecting part coincides with the metal of the pipes used for laying communications, but there are exceptions.

Most often used for the manufacture of pipe connectors:

• Cast iron . The material is resistant to stress and chemical influences, and can withstand high pressure. Most cast iron models provide a threaded connection, but you can also find couplings that require additional sealing with cement mortar, sealants, or even lead. The disadvantage of cast iron fittings is their large mass and high price.

Cast iron crosspiece

• Steel. It is used in the same place as cast iron; it is less brittle due to its greater elasticity. Unlike cast iron, steel fittings fail earlier because they are more susceptible to corrosion (including electrochemical corrosion).
• Brass . A good option in terms of connection reliability, durability and performance. Brass fittings can be used both for arranging metal pipelines and for installing plastic communications.
• Copper . Such parts will be the most expensive, but at the same time they provide the most reliable and durable pipe connection. They are most often used in heating systems, but can also be used in the assembly of water pipes in private homes and commercial organizations.

Thin-walled copper adapters, corners and elbows

Note! Copper and brass are extremely rarely used for laying main communications.

In addition, when installing water supply systems based on metal-plastic pipes, connectors made of technopolymers with metal (steel or brass) inserts are also used.

For welding or soldering

Photo of a welded joint using an elbow

If everything is more or less clear with the materials, let’s try to figure out the configurations.

The simplest are connectors that use welding or (in the case of copper/brass parts) soldering.

• A welded fitting is a fragment of a pipe of a certain configuration. As a rule, its diameter corresponds to the diameter of the pipelines being connected, which makes it possible to butt weld the edges of products.
• The vast majority of welded fittings are made from “black” steel. In this case, the weld is reliable enough to withstand the highest possible pressure.

Soldering process of copper products

• Copper and brass are used to produce parts for which soldering is used. Their configuration provides for the presence of a socket for installing a pipe, while a minimum gap for filling with solder must remain.

Note! Welding and soldering of pipes are quite complex technologies that require long-term mastering. So the text instructions and explanatory video should be studied thoroughly, and best of all, under the guidance of an experienced master.

Threaded

Threaded parts are among the most common. They can be made from any of the above-mentioned materials, but steel and brass confidently hold the lead in this segment.

Brass products

The following is typical for a threaded connection:

• Most often, such parts are used for joining pipes with a diameter of 50 mm or less. With a larger circumference, the thread cannot provide the required tightness.
• To install an elbow, tee or cross, it is necessary to have a thread not only on the fitting, but also on the pipe. In some cases, cutting has to be done independently using special tools - dies.
• Sometimes the connection requires additional sealing. To do this, at the junction, a winding is made of synthetic (polymer tape) or natural (linen tow and analogues) material.

Sealing winding

Advice! Beginning craftsmen often make the mistake of thinking that the tighter the thread is tightened, the tighter the joint will be. In fact, if you apply too much force, there is a risk of “over-tightening,” breaking the thread and causing a guaranteed leak.

For flange

For mounting parts with a diameter of more than 50 mm, pipe flanges are used.

An example of such a fitting is shown in the image in this section.

• As a rule, these products are selected for the cross-section of the pipeline. Also, sometimes the flange parts for joining are welded directly to the pipes, but in this case the reliability of the unit is greatly reduced.
• To seal, a gasket made of elastic material can be installed at the contact point. In this case, the junction of two pipes requires periodic maintenance to replace the worn part.

• The advantage of flange fittings is the fact that with their help, shut-off valves, various sensors, valves, etc. can be installed on large-diameter pipelines.

For crimping

Relatively recently, so-called compression fittings began to be used to connect metal pipes.

Their operating principle is almost identical to that used when using a compression fitting for a plastic pipe:

• A union nut made of metal (steel or brass) is installed on the thread.
• When screwed on, the nut presses a special gasket made of elastic material or thin metal to the joint.

Note! The use of a rubber or polymer gasket imposes a limitation on the temperature regime in which the system can be used: the maximum heating is 950C.

Device diagram (sectional view)

• At the same time, due to the pressure, a tightness sufficient for the functioning of the system is ensured.
• Some companies produce universal models of such devices that are equally suitable for both steel and polymer pipes.

Products of this type are usually used in the construction of water supply systems. The main advantage in this case is a significant saving in time: the pipe is inserted into the fitting without threading, which makes our work much easier.

On the other hand, this installation scheme also has disadvantages. For example, by applying serious force, the pipe can simply be pulled out, especially if the gasket has shrunk somewhat and lost its elasticity. Of course, such a force vector is atypical for pipelines, but it is imperative to remember this feature!

Conclusion

When installing metal communications with our own hands, we need to choose not only the pipes themselves, but also the parts that will be used to connect them. That is why it is important to familiarize yourself with the entire available range of fittings before starting work, and choose those that will best suit your tasks, our requirements and financial capabilities.

You can find a more detailed overview of the products described above in the video in this article.

Source: https://remstroymast.ru/fitingi-dlia-metallicheskih-tryb-soediniaem-detali-raznymi-sposobami.html