What is welding mode

Studying welding modes

Almost every building construction, construction and installation of structures requires welding work. Depending on the type of workpieces to be joined, their thickness and other parameters, it is necessary to use different methods.

Welding modes mean adjustable parameters based on which the welding process occurs. The more accurately the master adheres to the selected mode, the stronger the connection will be. Let's look at the basic welding modes and clarify how to calculate them for certain types of work.

Welding parameters

Before choosing the desired welding mode, it is necessary to accurately determine the composition of the metals, thickness and type of structure. After receiving the data, the appropriate mode is set. There are many factors on which the quality of welding depends, so they are divided into two groups: primary and secondary.

Basic

The amount of energy, as well as the method of its transfer to the metal surface, depends on these parameters. The main parameters of the welding mode include:

• current magnitude, polarity and type;
• electrode diameter;
• welding arc length and voltage;
• speed of movement along the seam;
• number of passes.

The formation of the seam depends on each of the parameters. By changing one or another indicator, you can get a more reliable connection. Let's briefly look at some points.

1. The intensity of the current determines how intensively the material melts. The higher the indicator, the more productive the welding. If you set too much current without using a sufficient electrode diameter, then the quality will decrease. And vice versa: at low current levels, the welded arc may break, causing lack of penetration.
2. Current polarity refers to the direction of energy movement - from the cathode to the anode or vice versa. Along with the direction, the type of current is chosen - either direct or alternating. Thus, when welding parts with direct current with reverse polarity, the seam will be 40% deeper.
3. It is important that the melted material has time to fill the seam and does so evenly. Otherwise, the strength will decrease.

Additional

Secondary parameters include:

• electrode protrusion;
• material and thickness of electrode coating;
• temperature of the parts being welded;
• position of workpieces;
• edge shape;
• quality of surface preparation.

Selecting the appropriate mode

Having seen what mode parameters there are in general, let’s move on to the settings of each individually.

Ratio of current to electrode thickness

The diameter of the electrode is selected based on the thickness of the seam being welded and the welding method. So, for metal 3-4 mm thick, a 3 mm electrode is suitable. Multi-profile parts are welded in several passes, first using a 4 mm electrode.

Having selected an electrode, refer to the tables to determine the required current strength. For the same diameter of 3 mm, the working indicator is 65-100 A. In addition, if you have to carry out vertical welding or a seam overhead, the diameter of the electrode should not be less than 4 mm. When horizontal welding, the current strength is reduced by 15-20%.

Arc length

This parameter means the distance from the end of the electrode to the object. The indicator depends on the size of the selected electrode and is given in the tables. For high-quality penetration, it is necessary to achieve a uniform value along the entire length of the seam. It is difficult for a person to monitor the uniformity of the indicator; experience is needed. So, for a 4 mm electrode, the arc length is 4.5 mm, and it is difficult to maintain this distance. To automate the process, welding carriages are used.

Penetration rate

When carrying out welding work, it is important that the molten metal fills the bath. There should be a uniform transition, edge coverage, and a seam without undercuts or sagging. In this case, the recommended seam width is 1.5-2 times larger than the diameter of the electrode used. If the welding speed is too high, the metal will not heat up sufficiently and strength will be lost.

Polarity and type of current

Many models of welding machines convert household alternating current into direct current. It is important not to make a mistake with the polarity, the direction of flow of electricity. Basic polarity involves connecting the part to “+” and the electrode to “-”. Depending on the properties, the selected mode parameter is applied.

• Straight polarity is suitable for welding cast iron, low and medium carbon steel with a thickness of more than 5 mm.
• Reverse polarity is selected when joining mild steel and thin sheet structures.

Electrode inclination and length

The position of the electrode affects the quality of weld welding. In most cases, the electrode is held perpendicular to the workpiece and moved at an angle forward. This method makes it possible to increase the width of the seam. If the angle is more than 90°, then the direction is changed. This position helps to completely fill the deep bathtub.

The stick out of the electrode depends on its diameter and the strength of the supplied current. The longer the length, the slower the heating occurs.

Tilt of workpieces

For normal filling of the seam, it is recommended to tilt the parts at an angle of 8-10°. Otherwise, either lack of penetration may result, or the molten metal will drain. When connecting pipes, it is impossible to change the angle of the seam, so welding is done from top to bottom.

Source: https://electrod.biz/tehnologii/izuchaem-rezhimyi-svarki.html

Welding modes: main parameters and features

Welding is often used during any construction and industrial work. Using it, you can weld various metal structures, repair equipment and other products.

There are different types of welding technologies that are used depending on the type of metal, its thickness, strength and other important parameters. But the quality of the connection also depends on the correct settings on the welding equipment. It is worth first considering the main welding modes, their features and correct settings.

How to choose a welding current

Calculation of manual arc welding modes is carried out taking into account the setting of the main current parameters, namely type, polarity and strength. Depending on the type of current, it can be alternating or constant. Polarity is divided into forward and reverse.

When considering the main parameters of the welding mode, it is worth paying attention to the magnitude of the current. It is selected using certain tables. The current indicator is determined in accordance with the thickness of the welded steel products and welding wire. But the exact adjustment indicators are determined depending on the type of arc and connection. It is worth considering that the stronger the current, the higher the temperature readings under the base of the arc will be. This will all affect the speed of welding work.

Carrying out welding technology using high current and very thin welding wire can cause overheating and splashing of molten metal. If elements that are too thin are used, this mode can lead to their burning.

When using a weak current, the arc may break and become unstable. As a result, the connection is of poor quality, and many zones with lack of penetration are formed. For this reason, many welders do not recommend using this mode.

Important! The depth of the weld pool depends on the type of current used. If the equipment is used on alternating current, then the penetration depth will be 15% higher than that of alternating current.

With straight polarity, strong heating of the metal product is observed. For this reason, this polarity is recommended for welding thick elements, because more melting of the metal is required to form a high-quality joint. If straight polarity is used for thin parts, they will quickly burn out and the seam will be of poor quality. For thin products it is worth using current with reverse polarity.

Relationship between current strength and electrode thickness

When considering welding parameters, it is worth paying attention to the relationship between current strength and electrode thickness. The size of the rod should be selected in accordance with the thickness of the welded seam and the welding technology used. For example, for a product with a thickness of 3-4 mm, it is recommended to use 3 mm rods. Welding of multi-profile elements is carried out in several passes; at the initial stage, an electrode with a size of 4 mm is used.

After selecting the rods, you should use special tables that indicate the required current strength indicators; they allow you to correctly calculate the welding modes. For example, for 3 mm rods the figure corresponds to 65-100 A. For vertical and ceiling welding, an electrode with a diameter of at least 4 mm is suitable. When welding horizontally, the current strength is reduced by 15-20%.

Features of arc length

The choice and calculation of welding modes is influenced by the length of the arc, namely the distance from the end of the rod to the workpiece. This criterion depends on the selected rods; it is usually indicated in special tables.

It is worth noting! To obtain a strong welded joint and high-quality welding, it is necessary to achieve a uniform arc length throughout the entire weld area. This requires experience and certain skills.

For rods with a diameter of 4 mm, the arc length should be 4.5 mm. Maintaining this state during the welding process is quite difficult. Typically, welding carriages are used for these purposes.

Electrode diameter

The selection of welding mode parameters is carried out taking into account the type of electrode. The diameter depends on the thickness of the metal product and the position of the connection. Regardless of the thickness, the seams in different positions are welded using rods with a diameter of 4 mm.

If the seam has a multi-layer structure, then 3 or 4 mm rods should be used to weld the first joint. The remaining seams are processed using electrodes with a large diameter. Below there is a table of welding modes, which indicates the thickness of the metal, the diameter of the electrode and the current strength.

Electrode angle

When calculating semi-automatic welding modes, it is necessary to take into account the criteria for the angle of inclination of the electrode. When welding, the rod in relation to the seam should have a slight deviation from the norm by 10 degrees. The depth and width of the connection depends on the location of the rods to the joint.

If welding is carried out at an angle forward, the depth indicators will decrease and the connection will expand. This happens because the arc drives a wave of melt in front of itself, through which the metal is melted.

If a mode with a backward tilt angle is selected, the melt will move to the end of the welding zone. The electric arc has a direct effect on the products being connected. As a result, there will be an increase in the penetration depth of the joint and a decrease in the width of the seam.

Interesting video

Source: https://osvarka.com/obuchenie-svarke/osnovnye-rezhimy-i-parametry-svarki

Welding modes - selection and parameters

When the conversation turns to such a concept as welding modes, it is necessary to realize that this is a fairly large set of various parameters, which in turn determine the conditions of the welding process. And in order for the quality of the final result to be only positive, you need to choose these same parameters correctly. And although experts conditionally divide them into primary and secondary, all of them, without exception, affect the quality of the weld.

The main parameters of the welding mode include:

• The amount of current installed on the welding machine.
• Its gender (fixed or variable) and polarity (direct or reverse).
• Welding arc voltage.
• Diameter of the electrode used.
• Speed ​​of the welding process.
• Number of passes to fill the weld.

The secondary ones include:

• The quality of cleaning of welded workpieces.
• The shape of the joined edges.
• Type of electrode: its brand, type of coating, coating thickness.
• The angle of inclination of the electrode relative to the welding surface.
• Its position (top, bottom or side).
• How the joint is located (horizontally, vertically, at an angle).

Welding mode parameters

It should be noted that most often welders pay attention to the main parameters and their mutual relationship, but at the same time they do not lose sight of the secondary ones.

For example, the diameter of the electrodes is selected depending on the thickness of the metal parts being welded, the position of the joint, as well as the shape of the prepared edges.

And although there are tables that determine the diameter of the consumable relative to the thickness of the workpieces, it is very important to take into account the position of the electrode itself during the welding process.

Electrodes with a diameter larger than 4 mm cannot be used for ceiling welding. The same applies to the multi-pass process, because it is in this case that the root weld may not penetrate properly.

Welding current

As for the current strength, here too there are several provisions regarding the choice of welding parameters. The thing is that the more intense the current, the higher the temperature inside the weld pool. And this affects the rate of metal melting and the productivity of the welding process itself. And this is correct, but with some reservations.

• With increased current and a small diameter of the electrode, overheating occurs in the welding zone of the workpieces. This is already a decrease in the quality of the seam. Plus intense splashing of metal inside the bathtub. Often this mode leads to burnout.
• If the current strength is reduced, then this is a guarantee of lack of penetration, because at low current the arc becomes unstable. And with such an arc, the welding process often breaks down. This is the reduction in connection quality.
• If an electrode with a large diameter is selected without taking into account the thickness of the workpieces, the current density deteriorates. The reason is low cooling of the metal in the welding zone.

Not the last word in such a concept as the choice of welding mode is the polarity of direct current. With reverse polarity of the current, the penetration depth is 40% greater than with direct polarity. When using alternating current for welding, it must be taken into account that the penetration depth when using it is 15% less than when using constant current. And this is at the same current value.

Welders themselves with extensive experience set the welding current experimentally. They simply pay attention to the stable state of the arc, to its stable combustion. Beginners can use various tables or formulas. For example, one of the formulas that determines the current strength depending on the diameter of the consumable. It can be used if welding uses an electrode with a diameter of less than 3 mm.

I=30d

Welding process speed

The choice of arc welding mode also depends on the speed of movement of the electrode. This parameter is directly related to the thickness of the parts and the thickness of the seam. Its ideal value can only be considered when the area where the molten metal joins the edges of the parts is free of undercuts, burns and lack of penetration. The seam itself is a transition of a uniform shape without sagging or undercuts.

The higher the speed, less metal will get into the bath, the edges will not heat up to the required temperature, hence the lack of fusion of the seam, which will quickly crack. If the speed is lower, nodules are formed that interfere with penetration. The optimal mode is when the width of the seam is twice the diameter of the consumable.

What is welding mode

» Articles » What is a welding mode

• December 05
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• Characteristics of the main welding ranges used
• Description of the influence of the main welding parameters

Welding modes are the main physical indicators that determine the entire course of the metal welding process and are established based on the initial data. Moreover, these indicators must be met in full in order to obtain the required quality of the weld, its dimensions and shapes, which were established by the engineering design.

The influence of welding mode on the shape of the seam.

When welding, several stages of changing the physical component of the metal occur successively, namely:

• heat;
• melting;
• crystallization.

For example, when performing spot welding, the structure of the formed welded products is most often columnar, coarse-grained dendritic. And it is precisely this structure that is most characteristic of ferrous metals. But aluminum and its alloys in the vast majority of cases form an equilibrium structure in the very central casting zone. The most preferred welding modes depend on these indicators

There is a conventional system according to which welding work is divided into basic and additional parameters.

Table of arc welding modes.

The main parameters include:

1. Direction of current relative to the poles.
2. Welding current voltage.
3. Increase in current power.
4. The cross-sectional size of the conductor used.
5. Processing speed.
6. Indicators of oscillatory movements of the electrode.

But additional parameters that characterize the welding mode include:

• initial temperature of the metal;
• chemical composition of the conductor coating;
• conductor location: vertical or inclined;
• the position of the welded product itself.

Return

Having figured out what types of argon arc welding modes there are, now you need to understand what and how they affect, and perform the necessary calculations for the work. We will try to briefly describe the influence of each factor on the welding process and the final result.

Modes for welding aluminum tires with a non-consumable electrode in argon.

When the welding current increases, it increases the depth of metal penetration, which, in turn, changes the amount of heat that falls on the length of the welding joint, and partly the variability of pressure on the top layer of the weld pool itself. The type of current and its direction greatly influence the shape of the seam and its size.

Moreover, when cooked with direct current with reverse direction, the penetration becomes 40-50% greater than in the case of treatment with current with constant direct polarity. But when treated with intermittent current, the penetration of iron will be 15-20% less.

Depending on the thickness of the material to be welded, an electrode with appropriate indicators is selected. In this case, the thickness of the conductor will also depend on its position when performing welding work, as well as on the thickness of the metal being processed. The width of the welded simplex and the depth of penetration are affected by tension. The current strength will be directly affected by the cross-section of the electrode and its length as the main parameters.

It is impossible not to mention that the amount of heat released by the product when performing welding work directly depends on the polarity and type of current.

The width and depth of the seam can be changed by the angle of the electrode.

Return

In our text, we described only some of the main parameters and modes of gas welding that must be taken into account when welding metal. Thanks to this, you will be able to correctly select the welding mode in a particular case.

expertsvarki.ru

Welding modes - selection and parameters

When the conversation turns to such a concept as welding modes, it is necessary to realize that this is a fairly large set of various parameters, which in turn determine the conditions of the welding process. And in order for the quality of the final result to be only positive, you need to choose these same parameters correctly. And although experts conditionally divide them into primary and secondary, all of them, without exception, affect the quality of the weld.

The main parameters of the welding mode include:

• The amount of current installed on the welding machine.
• Its gender (fixed or variable) and polarity (direct or reverse).
• Welding arc voltage.
• Diameter of the electrode used.
• Speed ​​of the welding process.
• Number of passes to fill the weld.

The secondary ones include:

• The quality of cleaning of welded workpieces.
• The shape of the joined edges.
• Type of electrode: its brand, type of coating, coating thickness.
• The angle of inclination of the electrode relative to the welding surface.
• Its position (top, bottom or side).
• How the joint is located (horizontally, vertically, at an angle).

What influences the choice of welding mode

The operating mode of a welding machine is a set of primary and secondary welding characteristics that make it possible to obtain a high-quality weld of a particular alloy.

Since there are many grades of steel and non-ferrous metal alloys, and they have their own specifics, choosing a welding mode becomes a difficult task. But there are basic parameters that need to be taken into account regardless of the type of alloy.

Important parameters

Before starting work, you need to understand what quantities you have to deal with. Main parameters influencing the welding mode:

• strength, type and polarity in the case of direct current;
• electric arc voltage;
• welding wire thickness;
• number of passes;
• welding speed.

Secondary factors influencing the characteristics of the connection include the condition of the parts being welded, the shape of the edges, the brand, type and thickness of the electrode coating. The choice of welding seam type has a certain influence.

The most important thing is to calculate the modes for automatic welding. Some characteristics are set using ready-made tables, while others have to be determined using formulas contained in the instructions for the equipment. Each equipment has its own tables, worked out empirically.

Effect of current

When setting the mode, the current strength is selected according to the tables. The current depends on the thickness of the products being welded and the welding wire.

Precise adjustment is made according to the type of arc and seam. It is necessary to understand that the stronger the current, the higher the temperature under the base of the arc will be and this will affect the speed of welding.

Welding mode with high current and an excessively thin welding wire will cause overheating and spattering of the metal. If the workpieces are thin, then they are often burned out in this mode.

With a weak current, the arc becomes unstable or breaks off completely. The seam is of poor quality, uncooked areas appear. This mode should not be chosen.

It must be taken into account that the depth of the weld pool depends on the type of current. If a device is used on direct current, then its penetration depth will be 15% greater than that of alternating current.

Welding in DC mode also has its own characteristics. Thus, with direct polarity, the crater depth is 40% less than when using reverse polarity.

Direct polarity is when the electrode is connected to the inverter terminal with the “-” sign, and the connected products are connected to the terminal with the “+” sign. With reverse polarity, everything is connected in reverse.

With direct polarity, an electrode with calcium-fluorine coating can be used; it allows you to weld low and medium carbon steel and cast iron.

Inverter mode (reverse polarity) is used when it is necessary to weld low-carbon and low-alloy steels and thin-sheet parts.

The current also changes depending on the position of the welded joint in space. So, with a horizontal seam, it is recommended to reduce the table values ​​by 15-20%.

Electrode characteristics

The dimensions of the electrode are interrelated with the dimensions of the products and the type of edges. If the thickness of the alloy being welded is 3-5 mm, then the welding wire should be 3-4 mm.

When welding thick-walled workpieces, many passes are required. For the first time they pass with an electrode with a diameter of no more than 4 mm. When making ceiling seams, it is also recommended to use wire no thicker than 4 mm.

Usually there is a table on the packaging of the electrodes, which indicates the most preferred modes. With a diameter of 1.5-2 mm, the recommended welding current is 3045 A, for 3 mm - 65100 A, for 3-4 mm - 100160 A, and so on. The variation is related to the type of welding and the thickness of the alloy.

With a thickness of the alloy being welded of 1-2 mm, it is recommended to use a welding wire with a diameter of 2-3 mm, with a thickness of 3-5 mm - 3-4 mm, a thickness of 4-10 mm - diameter 4-5 mm, if the thickness is 12-24 mm, then use a 5-6 mm electrode. When choosing a mode, it is necessary to take into account the position of the part or seam in space; the number of passes also influences the choice.

Arc length and seam quality

The length of the arc affects the quality of the connection. It is important that it be the same throughout the entire seam; the distance between the end of the welding wire and the edge of the part should be equal to its thickness.

Welding mode with too short an arc leads to burning or sticking of the electrode. The mode with a long arc causes its extinguishing and lack of penetration. The length of the arc can be controlled by the sound it makes.

The optimal weld width is considered to be 1.5-2 wire diameters. In this case, a small bead should form along the connection line without sagging from the molten electrode. The optimal seam depends on the welding speed, the thickness of the product and the width of the seam.

The welding mode, in which the holder with the electrode moves very slowly, leads to excessive accumulation of liquid metal in the weld pool, which will splash and prevent normal penetration of the joint.

Moving the holder too quickly along the seam will lead to lack of penetration, and it may crack or become deformed after cooling.

If a pool is formed with a width of 1.5-2 wire diameters, a depth of up to 6 mm and a length of 10-30 mm, then this indicates the optimal welding speed for this particular material and type of connection.

Selecting welding mode: current, arc length, polarity

Selecting welding mode: current, arc length, polarity

To get a high-quality and reliable welding seam, you need to understand which electrodes are best to use and which mode of manual arc welding to choose. In addition, it is important to take into account other equally significant factors, such as: the composition and thickness of the metal, the dimensions of the workpiece being welded, and for what purposes it will be used in the future.

In general, the welding mode is selected according to many factors and after analyzing the data obtained. In this article from the website mmasvarka.ru we will consider the main factors that, to one degree or another, can influence the choice of mode.

Welding mode selection

So, what factors influence the choice of one or another mode of manual arc welding. First of all, this is:

The main criteria when choosing a mode for MMA welding, of course, is determined by the burning nature of the welding arc, the stability of which depends on how correctly the current strength is selected for some specific electrodes. The higher the current, the larger the diameter of the electrodes you can weld thick metal. In simple words, high currents ensure better arc burning and good heating of the metal.

You should know that when a seam is applied vertically, the current strength changes less than when applied horizontally, by about 15%. For ceiling seams, the value of the welding current will be even less, by about 20%. Very often, values ​​​​regarding the current strength are on the packaging with electrodes. In addition, you can determine what current strength to set on the welding machine from the table below with the values.

Average welding current (A):

• Electrode diameter (1.6 mm) - electrode with rutile and basic coating (30-55 A) and (50-75 A);
• Electrode diameter (2 mm) - electrode with rutile and basic coating (40-70 A) and (60-100 A);
• Electrode diameter (2.5 mm) - electrode with rutile and basic coating (50-100 A) and (70-120 A);
• Electrode diameter (3 mm) - electrode with rutile and basic coating (80-130 A) and (110-150 A);
• Electrode diameter (4 mm) - electrode with rutile and basic coating (120-170 A) and (140-200 A);

In turn, in order to correctly determine the diameter of the electrode, it is necessary to take into account the thickness of the metal, the welding method and the geometric location of the seam. So, for example, for each electrode its own “own” current value is selected. If you greatly increase its performance, you can easily burn through the metal or, conversely, not achieve a high-quality and reliable weld.

Selecting current depending on the diameter of the electrodes

Thin metal, no more than 1 mm thick, is welded with 1 mm electrodes, and the current strength is set to the minimum possible values, in the range of 10-30 A. When welding thicker metal, up to 2 mm, electrodes of a slightly larger diameter are used, 1. 5 or 2 mm. The current strength for welding with these electrodes is set in the range of 30-50 A.

A 3 mm electrode is used to weld metal up to 4 mm, and the current on the inverter is set to 60-120 A. For welding metals over 10 mm thick, much thicker electrodes are already used - 4 and 5 mm. For their normal use, the welding machine must be set to a current of more than 120 A.

Welding arc length

To achieve a good connection, it is important to correctly determine not only the diameter of the welding electrodes, but also the length of the welding arc. There is a common belief among welders that the length of the arc should correspond to the diameter of the electrode used. However, it is very difficult for novice electric welders to maintain such a short arc without it being pulled to the side.

Therefore, when selecting this value, you should proceed from the current strength and diameter of the electrodes used for welding:

• For electrodes up to 2 mm - the arc length is 2-2.5 mm;
• For 3 mm electrodes, the arc length is 3.5 mm;
• For 4 mm electrodes, the arc length is 4.5 mm;
• For 5 mm electrodes, the arc length is maintained within 5.5 mm.

In addition, it is important to take into account the optimal welding speed, which also largely depends on the current strength and other features. Here you can follow one proven path, and with the correct selection of welding speed, the welding seam should be approximately twice the diameter of the electrode used.

Reverse or straight polarity?

To select the welding mode with a coated stick electrode, it is equally important to determine which operating mode to switch the welding inverter to. There are two of them, reverse and direct polarity.

In order to weld thin metal with an inverter and not burn it later, it is recommended to switch the welding machine to reverse polarity, when the flow of electrodes is directed not at the workpiece, but at the electrode. Conversely, if you connect the inverter in direct polarity, you can improve the quality of welding, for example, when you need to weld thick metal.

To connect the inverter in reverse polarity (for welding thin metal):

• A positive terminal is connected to the holder with the electrode, and a negative terminal is connected to the workpiece.

To connect the inverter in direct polarity (for welding thick metals):

• A negative terminal is connected to the holder with the electrode, and a positive terminal is connected to the workpiece.

To choose the right welding mode with an inverter, you need to take into account many different nuances. Only in this way will it be possible to achieve a high-quality and reliable welding joint that will withstand heavy loads.

Source: https://mmasvarka.ru/vybor-rezhima-svarki.html

Manual arc welding mode: what it is, how it is performed, application features and equipment

The manual arc welding mode is a set of operations and parameters due to which the welding of metals occurs correctly under various operating conditions.

The choice of welding mode occurs in accordance with the parameters of the parts being processed; the environment in which the work will be carried out; necessary connection characteristics.

The classification of manual arc welding indicators is conditional. She divides them into two types:

The first type of RDS parameters includes the diameters of the filler rods used, the properties of the welding current, its power, and the voltage level of the welding arc.

Additional characteristics of manual arc welding are the position of the joint, the composition of the metal, the thickness of the part, the speed at which the joint is joined, and the type of coating of the weld wire.

These indicators will be discussed in more detail below.

Determination of welding current

Welding current has its own indicators. These include gender, polarity, and strength. They are divided into more precise characteristics. Current is divided into direct and alternating types. Polarity can be positive or negative.

Most welding equipment is designed to work with direct current. The variable type is characterized by changes in direction and magnitude.

The permanent type is not subject to these changes. Therefore, the arc working on it burns without interruptions or jerks.

However, it does have its drawback. When using a permanent type during arc welding of metals, a “magnetic blowing effect” occurs. This problem can arise when working with complex, large-sized structures.

From the effects, the metal acquires its own magnetic field, which changes the magnetic characteristics of the welded arc. In such cases, the arc can be attracted and jump out beyond the boundaries of the working area, disrupting the evenness of the seam. This also affects the quality of combustion.

There are three ways to combat this problem. The manual arc welding work area can be protected with protective shields that neutralize unwanted magnetic influences.

You can protect the metal from magnetization by grounding the structure. You can also consider the admissibility of welding with equipment operating with alternating current.

The advantages of direct current equipment are the stability of arc combustion and options for choosing parameters such as polarity.

Features of proper operation

The direct type is created by oriented the magnetic field minus to the rod, and therefore is called negative. The operating principle of the inverse type, based on the opposite position of the values, is called positive.

The action of negative and positive polarities is based on physical laws. Our physics is designed in such a way that where there is plus there is more heating. In accordance with this, exposure to negative polarity leads to greater heating of the metal.

In this mode, thick-walled parts are welded well. To obtain a high-quality connection when processing them, a higher level of melting is required, which direct polarity can provide.

This mode can burn thin metal sheets, which will simply ruin the part. Therefore, thin-walled metals are processed by arc welding with reverse polarity.

The current strength depends on the model of welding equipment. Now you can select an arc device with the correct strength by studying its instructions.

In the absence of technical documentation for the device, the force is selected in accordance with the diameter of the electrode. The current intensity should not exceed that recommended for the type of electrode selected.

Exceeding the permissible level may compromise the integrity of the coating of the filler rod, which will reduce the stability of the welded arc. However, the diameter of the electrode should not exceed values ​​suitable for the size of the joint of the part.

Welding with the wrong type of electrode will reduce the current density. This will disrupt the stability of the arc and its length, resulting in unevenness and breaks in the connection.

How to choose the correct electrode diameter

It is very important to choose the right electrode for arc welding

The filler wire size for manual arc welding is selected according to the thickness, size of the workpiece and the position of the weld. For vertical, horizontal or ceiling seams, a rod with a diameter of four millimeters is used.

This does not depend on the thickness of the metal part. When creating a multilayer connection, the first level is welded with electrodes of 2-4 millimeters, the subsequent ones are finished with larger rod diameters.

You can see the ratio of the current strength to the thickness of the metal of the part and the electrode used in the table above.

Determination of welding arc voltage

The voltage level of the welding arc depends on its length. The standard voltage indicator is 20-36V. Its increase occurs with increasing length of the welded arc. The length is characterized as short, medium or long.

It is measured by the distance from the working end of the rod to the surface during welding. The weld arc length must be stable throughout the entire cycle.

For novice welders, the average length of the welding arc is most typical. With minimum length values ​​using manual arc welding technology, welders with extensive experience work.

Working speed for manual arc welding

One of the indicators of the welding mode is the speed of operation. This parameter is responsible for the width of the weld seam. Narrow seams are created at high speed, wider ones at slow speed.

The width and depth of the weld depend on the lateral movements of the filler rod.

Violation of the speed characteristics of manual arc welding leads to defects. Do not process the metal too quickly. This will create gaps in the seam and lead to its heterogeneity, which is dangerous due to the appearance of cracks.

Slowing down the process overheats the metal. It melts and begins to flow.

The movements of the end of the filler rod during welding are divided into 4 types, the pattern of which depends on which joint location requires increased heating.

Bottom line

Manual arc welding is a set of actions to create a high-quality weld. It includes the selection of the necessary parameters of the device, electrodes, voltage, and movements during welding.

Choosing the right welding mode for a beginner can be a difficult task. However, instructions and certificates available at factories can help with this.

And also practice, gaining your own experience, which will tell you which welding mode should be used to work with a specific part.

Source: https://prosvarku.info/tehnika-svarki/dugovaya-svarka-ruchnogo-tipa

Manual arc welding mode parameters: current, electrode diameter, welding speed, etc.

The set of factors that influence the quality of the resulting seam and ensure stable progress of the welding process are called welding mode parameters.

When performing manual arc welding, the following welding mode parameters are distinguished:

• electrode diameter;
• welding current strength;
• type and brand of electrode;
• arc voltage;
• type of current and polarity;
• welding speed;
• location of the seam in space;
• heating and heat treatment;
• ambient temperature.

The last three parameters are considered additional, the rest are basic for this type of welding.

Current strength

The current strength is set after selecting the electrode depending on its diameter. To calculate the welding current when welding in the lower position, there is a formula:

Ist = delK

where Ist is the current strength, A; K - proportionality coefficient (changes its value depending on the type and diameter of the electrode).

Table 2. The value of the proportionality coefficient depending on the diameter of the electrode

Electrode diameter, mm	1-2	3-4	5-6
Proportionality coefficient (K), A/mm	25-30	30-45	45-60

You can use a simplified formula for selecting welding current for manual arc welding:

Ist = (20 + 6 div)div

In order to avoid waste when welding in the lower position of metal with a thickness of less than 1.5 divisions, the welding current is reduced by 10-15% of the calculated one. If the metal thickness is more than 3 div, the current is set to 10-15% more.

When welding seams in a vertical position, the current is reduced by 10-15%, and in the ceiling by 15-20% of that selected for welding in the lower position.

If welding work is performed with high-quality, certified electrodes, the current strength should be set in accordance with that recommended on the packaging with the electrodes. The calculations above can be used in the absence of recommendations from the manufacturer as an alternative method.

Once the amperage is selected, the welder must place several beads on a separate plate of metal. In this case, the width of the seam and the depth of penetration are assessed. If necessary, the current strength is additionally adjusted.

Too small current modes lead to unstable combustion of the welding arc. Lack of penetration appears in the welded joint, and labor productivity decreases.

Increased current values ​​are accompanied by its overheating, high combustion rate, lack of fusion, intense metal spattering and deterioration in the appearance of the seam.

A balanced current strength is characterized by a moderate melting rate of the electrode, stable arc burning with insignificant metal spattering.

Electrode type and brand

First of all, it is necessary to select electrodes that ensure uniformity of the chemical composition of the base metal and the metal rod of the electrode. Also, the type and brand are selected depending on the spatial position of the seam, the required density of the seam, ambient temperature, strength of the product and operating conditions of the structure. Using an electrode, you can give the seam the necessary properties.

Arc voltage

The welder can adjust the arc voltage by changing the length of the welding arc. Depending on the arc length in manual arc welding, the voltage is in the range of 16-40 V.

According to welding technology, the voltage should be kept at 16-20 V. For this, welding is usually performed with a short arc measuring 0.5 -1 thickness of the electrode diameter. This value may vary depending on the brand of electrode and the position of the seam in space.

Type and polarity of current

AC welding is used to join low-carbon and low-alloy steels (type 09GS) in construction and installation conditions with rutile-coated electrodes. For welding thick structures made of low-carbon steels. If magnetic blast occurs during welding with direct current sources.

DC welding can be divided into two processes - manual arc welding with direct and reverse polarity.

On straight polarity

Direct polarity is used for welding cast iron and deep penetration of the base metal. For welding low-, medium-carbon and low-alloy steels with a thickness of 5 mm or more using electrodes with calcium fluoride coating: UONI-13/45, UONI-13/55, etc.

On reverse polarity

Reverse polarity is used for welding sheet metal of low thickness and welding with an increased melting rate of the electrode. For welding low-carbon steels (type 16G2AF), low-, medium- and high-alloy steels and alloys.

To indicate a certain type of current, the designations AC and DC are often used today.
The abbreviations AC and DC (short for alternative current and direct current) mean alternating and direct current, respectively.

The welding speed is selected by the welder depending on the properties of the base metal, the characteristics of the electrode, the position of the seam, etc.

The welding speed should be such that the liquid metal of the weld pool rises slightly above the surface of the base metal with a smooth transition to it without undercuts or sagging.

To prevent overheating of the metal, high-alloy steels are welded at a higher speed.

Seam location in space

The location of the seam in space affects the choice of the main parameters of the manual arc welding mode. Manual welding is used for joints in all spatial positions, but the bottom position is considered the most convenient. It is worth considering the position of the seam in space when calculating the main parameters and choosing an electrode.

Preheating and post-heat treatment

Preheating of the base metal and subsequent processing are used for welding steels prone to the formation of hardening structures - medium and high carbon steels. For welding cast iron, non-ferrous metals and their alloys. The temperature and method of heating and processing depends on the thickness of the base metal, chemical composition and size of the structure.

Ambient temperature

All steels can be divided into four groups according to the degree of their weldability. Steels of groups II, III and IV cannot be welded at temperatures below -5 °C.

Source: http://osvarke.net/mma/rezhimy-ruchnoj-dugovoj-svarki/

Spot welding modes, parameters

Spot welding in production

The spot welding mode is set by the following basic parameters: current strength or density, heating time, pressure, diameter of the working part of the electrode. In addition, the pre-compression time of the electrodes tсж, the forging time tnp, the shape of the working part of the electrode and the material for its manufacture are often specified . Modes of special types of spot welding have some additional parameters.

Soft modes are characterized by low current strength and long heating time; for hard modes, the current strength is high and heating time - the mode option must be made taking into account the specific production conditions and requirements for the welding joint.

Spot welding

Welding in soft modes is accompanied by the formation of a wide heating zone, which facilitates the deformation of the metal and allows us to limit ourselves to not very high requirements for the accuracy of straightening workpieces, as in hard modes.

Exact. welding

Hard modes provide higher performance and less power consumption. Due to the fact that the surface of the parts under the electrodes heats up relatively less under harsh conditions, the electrodes heat up less and, despite the increase in pressure, their consumption decreases.

The depth2 of indentation at the welding site and warping of the product are noticeably reduced.

In general, hard modes are advisable, first of all, in mass production, where the gain in productivity and energy consumption will fully compensate for the additional costs associated with the acquisition, operation and power supply of more powerful equipment.

Current strength and density

As the thickness of the sheets being welded increases, the current strength should increase. For welding low-carbon steels of medium thickness on serial machines, the approximate selection of current strength l can be carried out according to the following relationship:

l=6500qa,

Where q is the thickness of the sheets being welded in mm.

When welding sheets of different thicknesses, the choice of parameters is made under the condition that there is sufficient heating and deformation of the thinner sheet. Therefore, in the given relationship and in subsequent ones, the value of q is related to a thinner sheet.

Current density I for hard modes is selected within the range of 120 - 360 d/Lm*, for soft modes 80 - 160 A mm2.

With increasing sheet thickness, the density is then/? decreases. When the metal of the parts being welded has increased thermal and electrical conductivity, the current density should increase. Thus, when welding aluminum or its alloys, the current density sometimes reaches 1000 A/mm2 and higher. As mentioned earlier, the current density should be selected higher when, for some reason, the pressure is assumed to be increased.

Resistance spot welding

Heating time

Like current, heating time (tcs) increases with increasing part thickness. Approximately for welding low-carbon steel at hard conditions, the heating time can be selected according to the ratio

tce — (0.1 -f-0.2) q sec.,

where q is the thickness of the thinner sheet in mm.

It is not recommended to take a shorter heating time, since random, even minor errors in the operation of the time regulator can cause serious deviations from the required heating and welding quality.

For welding sheets up to 3 mm thick in soft modes, the heating time can be selected according to the ratio.

I = (0.8×1) q sec.

Heating for too long can cause overheating of the metal in the welding zone.

For welding metals with high thermal conductivity, the welding time is assumed to be short (at high current strength); when welding hardening steels, on the contrary, in order to avoid the formation of hardening cracks during rapid cooling, the heating time often has to be increased (with a corresponding decrease in current).

Spot welding progress

Pressure

The choice of pressure (P) is made depending on the thickness, condition and material of the workpieces, as well as on the nature of the adopted heating mode.

For welding low-carbon steel, the pressure depending on the thickness is selected according to the formula

P=(60×200)q kg.

where q is the thickness in mm.

The specific pressure has a limit of 3x10 kg/mm2.

Mild hot-rolled steel can be coupled at lower pressures. Cold-rolled steel, which has received increased work hardening, requires a slight increase in pressure (by 20-30%). When the workpieces are poorly straightened and have warping, then before tightly squeezing the sheets in the Siamese area, it is necessary to straighten them under the electrodes.

The total force required in this case must be increased, especially for larger thicknesses. So, for sheets with a thickness of 3-6 mm, this additional force alone is 100-400 ke.

For the same reason, the force should also increase when the points are located in those places of the welded unit where squeezing the sheets is difficult (near the ribs and other stiffeners, and at the places where the parts meet at a radius, etc.).

The specific pressure increases with the strength of the metal being welded. When welding low-alloy steels, it can be 120-160% of the specific pressure for low-carbon steel; when welding austenitic and heat-resistant steels and alloys, it increases by 2-3 times.

• Electrode diameter. The electrode diameter (d) determines the current density, specific pressure and degree of cooling intensity of the surface of the part.
• The diameter of the electrode has a relatively small effect on the electrical resistance of the welding zone, only at the final stage of heating, when complete contact of the surfaces of the electrode and the part is achieved.
• Therefore, during prolonged heating, the influence of the electrode diameter is more pronounced. The diameter of the electrode increases with the thickness of the parts.
• For thicknesses up to 3 mm, the diameter of the electrode is calculated using the following formula:

D=2q+3mm,

where q is the thickness of the thinner sheet.

For parts with greater thickness, the calculation is carried out using the formula

Changing the diameter of the electrode is often used to equalize the heat when welding parts that are unequal in thickness or type of metal.

During the welding process, under the influence of strong heat and heavy mechanical load, the working part of the electrode changes with the formation of a mushroom-shaped thickening, and the surface becomes contaminated with metal oxides. An increase in the actual diameter of the electrode at constant current and compression force means a decrease in current density and specific pressure.

As a result, the heating intensity in the welding contact is greatly reduced, and metal compaction becomes more difficult and welding may be of poor quality. In addition, contamination of the surface of the electrodes can cause an increase in contact resistance, overheating and even melting of the surface of the sheets. It is generally believed that wear-related increases in diameter by more than 10% are no longer acceptable.

Such electrodes must be cleaned with a file, a special device, or sharpened.

Pre-compression time

The pre-compression time is understood from the start of applying pressure to the start of heating. It must be sufficient so that the compression mechanism has time to bring the electrodes together and develop pressure to a given value. This parameter does not have a direct effect on thermal processes during welding. To improve performance, this parameter should be reduced as much as the speed of the compression mechanism allows.

Forging time

The forging time (tnp) is determined by the duration of the already welded point being under the compressive influence of the electrodes. This parameter affects the cooling rate of the metal after welding, since after heating, under conditions of close contact between the electrodes and the part, heat from the welding zone is transferred especially quickly to the electrodes.

When welding hardening steels, accelerated cooling can cause cracks and forging time should therefore be reduced.

However, in all cases, the pressure should not be released before some time necessary for complete hardening and strengthening of the core. Otherwise, the sheets deformed during welding, trying to elastically return to the initial position, can destroy the core that has not yet cooled. With increasing thickness, the forging time increases, since the volume of heated metal and the cooling time increase.

We also recommend that you familiarize yourself with:

Flash butt welding mode parameters.

Source: http://svarak.ru/kontaktnaya-svarka/rezhimyi-tochechnoy-svarki-parametryi/

Welding mode on a welding machine - Welder's Handbook

The quality of a welded joint is the result of a successful combination of the correct choice of electrode, compliance with the conditions, skill and abilities of the welder, as well as the selection of the correct welding mode on the welding machine. By the way, in this article we will dwell on the last component of this chain in more detail.

The fact is that almost 50% of the total result depends on the choice of welding mode on the welding machine, so every welder needs to know how to choose it correctly, regardless of whether once every 5 years you decide to weld pipes in the country, or you are faced with this daily.

Arc welding is controlled by a number of parameters, and to be more specific, by such values ​​as: welding current and arc voltage, speed of the welding process, as well as the type and polarity of the current, the spatial position of the seam and the type of electrode (including its diameter). Therefore, before you start welding, pay attention to these parameters, and in the end, you will get a high-quality weld.

Welding current value

One of the main parameters during manual arc welding is the value of the welding current. It is this that determines the quality of the resulting weld, as well as the speed and productivity of the entire welding process.

As a rule, all recommendations regarding the choice of welding current are given in the user manuals that come with the machine. But, if this instruction was lost or was not there initially, the value of the welding current can be determined based on the diameter of the electrode.

Thus, the diameter of the electrode and the magnitude of the welding current are interdependent. In turn, the diameter also depends on the thickness of the product that will be welded. Therefore, the value of the welding current will depend on the thickness of the product.

It must be remembered that an increase in the diameter of the electrode leads to a decrease in the welding current density. This, in turn, causes the welding arc to wander, oscillate and change the arc length. In this case, the width of the weld seam increases, and the depth of penetration decreases, in other words, the quality of welding noticeably deteriorates.

Also, the welding current depends on the spatial position of the weld. If during welding the machine is in a ceiling or vertical position, it is recommended to use electrodes with a diameter of at least 4 mm, and at the same time reduce the welding current by 10-20% of the standard values ​​​​accepted for a horizontal position.

The magnitude of the arc voltage (including the length of the welding arc)

Once you determine the strength of the welding current, you should begin to calculate the length of the welding arc. In this case, the length between the end of the electrode and the surface of the material being welded is called the welding arc length. The stability of the arc length during welding is a very important indicator, which ultimately seriously affects the quality of the seam.

It is best to work on a short arc, the length of which is no more than the length of the electrode. However, in practice these conditions are difficult to achieve, even with extensive experience. Therefore, it is customary to consider the length of the arc to be the one that is midway between the minimum value of the short arc and the maximum long arc. For clarity, refer to the table below.

Determining the welding speed

The welding speed depends on the thickness of the part being welded, as well as on the thickness of the welding seam. The speed should be determined in such a way that the weld pool is filled with molten metal from the electrode and can rise above the surface of the edge, with a smooth transition to the part being welded, with minimal sagging or undercuts. The ideal speed would be a value at which the width of the welding seam was 1.5-2 times greater than the diameter of the electrode.

If the electrode moves too slowly, a large amount of liquid metal will form along the joint, which, in turn, will begin to spread before the welding arc, thus preventing its action on the edges. As a result, you will end up with a lack of penetration or a poorly made seam.

In fact, moving too quickly also causes lack of fusion, due to insufficient heat in the welding zone. This is also fraught with deformation of post-cooling seams, as well as the formation of cracks.

To quickly determine the optimal welding speed, the easiest way is to approximate the size of the weld pool. Typically, it is 8 to 15 mm wide, 6 mm deep, and 10 to 30 mm long. It is very important that during the welding process, the bath is filled evenly, which indicates that the depth of penetration does not change, which means everything is fine.

From the above figure you can see a pattern in which the width of the seam noticeably decreases if the welding speed is increased, but the depth in this case remains constant. Therefore, the best quality seams will be obtained at a speed of 30 to 40 m/h.

Parameters of current type and polarity

Most household arc welding machines operate with direct current. In this case, perhaps there are only 2 options for connecting the electrode to the part being welded, these are:

- current of direct polarity, in which the part is connected to the “+” terminal and the electrode to the “-”;

- reverse polarity current, in which, on the contrary, the part is connected to the “-” terminal, and the electrode to the “+” terminal.

Please note that the “+” terminal always generates more heat than the “-” terminal. Accordingly, when welding thin-sheet metal parts, they use reverse polarity, connecting the “+” terminal to the electrode, and not to the part.

This will prevent you from burning the part, thus preventing you from “messing up” the welding. Also, reverse polarity is used when welding high-alloy steels to prevent overheating.

Straight polarity is most often used for welding massive and thick parts.

For those who didn’t know, low-alloy steel is structural steel in which the content of alloying elements does not exceed a threshold of 2.5%. Such steels are widely used in construction, shipbuilding, and pipe rolling. Welding of low-alloy steels is carried out both manually and automatically, regardless of polarity.

Ignition of the welding arc

As a rule, in domestic and professional welding, the most common methods of igniting the arc are “chickening” and “touching”.

We also recommend paying attention to the inclination and length of the electrode. Typically, the electrode is held in a vertical position, tilting in relation to the direction of the wiring. Therefore, by adhering to these rules, you can install and select the optimal welding mode on the welding machine.

Source: http://www.vse-o-svarke.org/publ/analiz_i_reshenie_svarochnykh_problem/rezhim_svarki_na_svarochnom_apparate/20-1-0-263