How to weld thick metal correctly

Welding thick metal and thick-walled pipes

Welding thick metal, of course, differs from the technology used when joining thin-walled workpieces. After all, the process of welded installation of thick-walled workpieces is based on the formation of a multi-layer seam, the elements of which are applied to the joining edges using special technological techniques.

And in this article we will look at the mentioned technological methods with the help of which thick metal is welded, as well as the technology for preparing joined edges and other nuances of joining parts with a wall thickness of 2 centimeters or more. We hope that this information will help you understand the rather complex process of welding thick-walled and thick-plate parts.

Edge preparation

The term “thick-walled workpiece” or “thick-sheet workpiece” in welding refers to products with a joining edge thickness of 20 millimeters or more.

Of course, before welding the workpieces, such edges are prepared in a special way, namely:

• First, grind the first edge under the U-shaped profile.
• Secondly, grind the second edge under the stepped profile.

Without such preliminary preparation, welding thick sheet metal with an electrode of any thickness is practically impossible. Moreover, on the outer plane (in the upper part, from the side of the electrode insertion) of the joined parts, a gap of 10-15 millimeters or more should form between the edges, and on the inner plane (in the lower part) the gap should be practically zero.

If you do not make a mistake with the dimensions of the edges, then you can count on a double increase in the welder’s labor productivity (the speed of welding will increase) and a 25 percent saving in filler material (electrodes or wire).

Welding of thick-walled pipes and thick-sheet blanks

When joining thick-walled workpieces, the following technologies for welding the gap between parts are used:

• Technique for sequential suturing
• Technique of sequential cascade sutures.
• Technique of sequential or parallel block sutures.

And further in the text we will consider all three processes.

Welding "slide"

The first technology – forming a seam “slide” – is based on the following welding scheme:

• The first seam is placed at the bottom of the gap between the parts, using a 5 mm electrode for this purpose. The thickness of the seam in this case should be equal to one third of the thickness of the metal being welded.
• After the scale has broken down and the spatter has been removed, a second one is applied from one wall of the gap to the other, on top of the first seam. The total height of the joining seam (first and second) in this case is equal to two-thirds of the metal thickness.
• Guided by a similar principle, the welder applies a third layer of molten metal to the “hill” of the second seam, cleared of scale and splashes. The thickness of the seam in this case is equal to the thickness of the metal.
• The last, fourth seam is used to weld the space between the mound and the edges of the ends of the workpieces.

Cascade welding

In this case, the suture pattern looks slightly different:

• At the very beginning, a root suture is applied, the length of which will be no more than 20 centimeters.
• Next, a second suture is applied, 40 centimeters long, creeping onto the first. Moreover, 20 centimeters of the second seam will be root, and the next 20 cm will creep onto the first seam.
• The next one is the third seam, has a length of 60 centimeters. Of which 20 centimeters will be root, another 20 will lie on the root part of the second seam and the next 20 will be located on top of the first and second seams, filling the 20-centimeter area to the full thickness of the joint.
• The fourth seam has a similar length - 60 centimeters. It covers the third seam and extends to the thickness of the metal above the root of the second seam.

Simply put: the seams are applied in steps, forming cascades. And the outermost 20 centimeters of the third and subsequent seams extend to the thickness of the workpiece being welded.

Moreover, semi-automatic cascade welding of thick metal or a thick-walled pipe turns out much better than the manual version of this process.

After all, measured 60-centimeter welds are best obtained with a continuous supply of filler metal to the weld pool area.

Block welding

If you don’t have a semi-automatic welding machine at hand, then the cascade technology can be converted into a block suture option.

And in this case, the technological process of welding a thick-walled workpiece will look like this:

• First of all, the root weld area is welded.
• Next, a second, intermediate seam is welded above the root seam, the length of which will be slightly less than the dimensions of the first seam.
• A third seam is placed on top of the second (intermediate) seam, extending to the outer surface of the metal at a length only slightly behind the dimensions of the root seam.

Next, welding is continued with the fourth root seam, the fifth intermediate seam, creeping onto the first, and the sixth, applied end-to-end with the second. In short, the technology is very similar to a cascade. Only the “neighboring” seams do not creep, but are joined to each other.

As a result, it is possible to use block technology even when a short rod electrode is used instead of a filler wire.

Source: https://steelguide.ru/svarka/svarka-konstrukcij/svarka-tolstolistovogo-metalla.html

How to weld thin metal to thick metal - Metalworker's Guide

Welding thin metal is a challenge even for some experienced welders. Beginners in welding generally have a hard time.

The rules that apply here are completely different from those when welding thick products: there are many features and difficulties, which makes it more difficult to select modes and electrodes.

It’s easier to do this with semi-automatic welding machines, but they are quite rare in everyday life; inverters are much more common. We will talk about welding thin metal with an inverter.  

And the first difficulty when welding metal of small thickness is that you cannot heat it too much: it will burn out and holes will form.

Therefore, they work according to the principle “the faster, the better” and there is no talk of any trajectories of electrode movement at all.

Thin sheet metal is welded by passing the electrode in one direction - along the seam without any deviations.

When welding thin metals, the sheets overheat and bend

The second difficulty is that you need to work at low currents, and this leads to the fact that the arc has to be short. With a slight separation, it simply goes out.

There may also be problems with arc ignition, so use devices with a good current-voltage characteristic (no-load voltage above 70 V) and smooth adjustment of the welding current, which starts from 10 A.

Another trouble: with strong heating, the geometry of thin sheets changes: they bend in waves. It is very difficult to get rid of this shortcoming. The only option is to try not to overheat or remove heat (read about the method with heat-dissipating pads below).

When butt welding thin sheets of metal, their edges are carefully processed and cleaned. The presence of dirt and rust will make welding even more problematic. Therefore, carefully align and clean everything.

The sheets are placed very close to one another - without a gap. The parts are fixed with clamps, clamps and other devices. Then the parts are tacked every 7-10 cm with short seams - tacks.

They will prevent the parts from shifting and are less likely to bend.

If you clean the edges well, you can get a good seam

How to weld thin metal with an inverter

Welding machines that produce direct current are good because we can weld with reverse polarity. To do this, we connect the cable with the electrode holder to “+”, and connect “-” to the part. With this connection, the electrode heats up more, and the metal heats up minimally.

Read about how to choose a welding inverter for your home or cottage here. 

It is necessary to cook using the thinnest electrodes: from 1.5 mm to 2 mm.

In this case, you need to choose one with a high melting coefficient: then even at low currents the seam will be of high quality. The current is set to small.

For electrodes measuring 1.5 mm it should be about 30-45 amperes, for a “two” - 40-60 amperes. In fact, sometimes they put it lower: it is important that you can work.

Metal thickness, mm0.5 mm1.0 mm1.5 mm2.0 mm2.5 mm

Electrode diameter, mm	1.0 mm	1.6 mm - 2 mm	2 mm	2.0 mm - 2.5 mm	3 mm
Current strength, A	10-20 amps	30-35 amps	35-45 mm	50-65 mm	65-100 mm

To ensure that the metal heats up less, the parts are placed in a vertical or at least inclined direction.

Then they cook from top to bottom, moving the tip of the electrode strictly in this direction (without deflecting or returning). The tilt angle is forward, and its value is 30-40°.

This way, the heating of the metal will be minimal, and this is one of the most important tasks for welding thin metals.

Electrode positions for welding and their use

General recommendation for choosing electrodes for welding thin metals: buy high-quality imported electrodes for such work. There will be many fewer problems.

Read about making a shed on a metal frame here. 

Techniques and methods for welding thin sheet metals

Sometimes thin sheets need to be welded at an angle. In this case, it is more convenient to use the flanging method: the edges of the sheet are bent to the required angle, fastened with short transverse seams every 5-10 cm. Then they are welded as mentioned above: with a continuous seam from top to bottom.

The video shows how to weld thin sheet metal with an electrode using a welding inverter. The flanging method is used: the edges of the parts are bent, then secured in several places with short seams. This is followed by welding with a thin electrode 2 mm thick.

It is not always possible to avoid burn-through when welding without separation. Then you can try tearing off the arc for a few moments, and then lower the electrode again to the same place and move it a few more millimeters.

Source: https://ssk2121.com/kak-privarit-tonkiy-metall-k-tolstomu/

How to properly cook thick pieces using a semi-automatic machine? Technological features

The connection of massive parts using semi-automatic welding is carried out in accordance with GOST 14771-76. To ensure the strength of the joints, it is necessary to follow the general rules: correctly prepare the edges of the parts, set the welding current in certain ranges, and ensure the supply of the required amount of carbon dioxide to the welding zone.

Technological features of semi-automatic welding of thick metal

In order for welded metal structures to withstand loads, it is necessary to create reliable connections:

• seams must firmly connect all elements of the product;
• it is necessary to relieve the stresses that arise after welding inside the alloys . You can use preheating for this. After welding, it is recommended to ensure slow cooling;
• It is important to obtain a weld leg determined by technology ; this also strengthens the metal structure.

It should be taken into account that when working at high currents there is a risk of deformation, this means that the control dimensions of the part will change, and the shape of the structure will differ from that which was planned.

Necessary equipment and materials

To work you will need:

1. Powerful welding machine . The maximum value of welding current is not less than 250 A.
2. Cylinder for storing and transporting carbon dioxide . There are containers with a volume of 5, 10 and 40 liters. The cylinders are painted black.
3. Reducer for reducing gas pressure . A special CO2 device is required. It is desirable to have a heating element.
4. Hose and clamps - for connecting the cylinder.

For semi-automatic welding of steels, use wire type Sv-08G2s or similar for welding carbon steels 08x18n9t, as well as an equivalent for welding corrosion-resistant steels. Diameter – 1 to 1.6 mm. Common reels weigh 5, 15 and 18 kg.

Approximate cost of wire for welding carbon steels on Yandex.market

Some devices operating on a 220-volt network can only accommodate small coils of wire.

Setting up the device and gas equipment

Semi-automatic welding machines from different manufacturers are designed differently. There are at least two or three regulators on the front panel:

• setting the wire feed speed – the rotation speed of the electric motor that moves the wire is adjusted;
• change in current strength - the parameter affects the melting rate of the additive in the weld pool;
• inductance adjustment - the change concerns the current characteristics. At minimum values, the depth of metal penetration is less and the seam is more convex. For welding thick workpieces, it is recommended to increase it to medium or even higher.

Tip: you can set up the device by ear. During welding, the melting of the wire occurs very smoothly, the semi-automatic machine produces an even rustling sound.

After connecting the reducer to a carbon dioxide cylinder, you need to set the outlet pressure. For indoor work, 1-1.5 kg/sq.m. is sufficient. cm. If a flow meter is installed on the gearbox, then it should be set to 10-12 liters per minute.

Preparation for work. Edge processing

Welding work using a semi-automatic machine should be carried out only with clean workpieces. The surface should be free of rust, oil and dirt. Otherwise, pores will appear.

Proper cutting of edges is an important stage in preparing parts for welding. To ensure the formation of high-quality seams, chamfers should be removed in accordance with GOST 14771-76 - depending on the type of connection. If everything is done correctly, the connection will be strong. It is important to ensure that the metal is fused throughout its entire thickness.

Welding process

Thick pieces should not be cooked in one pass. Sequence of actions after preparatory work:

1. Assembling elements on tacks.
2. Checking the dimensions of the future part.
3. Boiling the root of the seam.
4. Filling the groove between the edges in several passes.
5. Creating a facing seam.
6. Processing joints using a grinder with a grinding wheel.

The tack is a full-fledged short seam about 15-25 mm long with a pitch of 45-50 cm. It is welded at the same current as the entire product. The tacks should be positioned so that the future product becomes rigid and does not “lead” during welding.

If you want to eliminate (or minimize) deformation from heating, it is recommended to fix the part on the assembly table using clamps or clamps. You can temporarily grab it to a workbench or steel plate.

First pass. Root of seam

The root seam is the first and most important welded connection between the edges, which is as far as possible from the front part of the parts. It is important to ensure that a roller is formed on the reverse side, smoothly connecting both elements.

If the root weld is welded with defects, cracks may appear during operation of the part, which can lead to destruction of the entire structure.

During operation, you must ensure that the part does not heat up too much. If the cascade welding method is used, a root weld is not required.

Filling the space between welded edges

Thick metal must be welded in several passes, filling the space between the edges. The cascade welding method or the “slide” method is often used:

• “cascade” - this option involves the simultaneous formation of the root of the seam and filling the space between the edges. First, a section of the root connection about 20-25 cm long is welded. Next, a second seam 40-50 cm long is applied, half of which lies on the root. The third - 60-65 cm long - partially (by two thirds) overlaps the previous ones, and ⅓ will become root. The fourth seam (also about 60-65 cm) should overlap the third and reach the thickness of the metal above the root part of the second. This method is similar to step welding;
• “slide” - after welding the root, a second seam is welded, connecting the edges and overlapping the first. After it, the third and fourth (facing) are applied.

Due to the fact that the semi-automatic machine allows you to continuously feed wire into the weld pool, you can form long seams at high speed.

Welding in vertical and overhead positions

The peculiarities of working in positions other than horizontal are that the metal is difficult to hold; under the influence of gravity, it tends to flow out of the weld pool. To avoid this, two methods are used.

1. Reducing the welding current by 15-20% . The metal heats up less intensely and crystallizes faster.
2. Welding with separation . Short sutures are applied one after another. In a vertical position, you should go from bottom to top. Welding from top to bottom is not allowed due to possible lack of penetration.

Whenever possible, avoid working in positions other than horizontal. Welding vertical and ceiling seams requires more careful preparation of the edges and is considered less productive and more labor-intensive.

Features of flux-cored wire welding

If shielding gas is required when working with copper-plated wire, then the use of powdered wire does not require it. The process is reminiscent of electrode welding - with the formation of a slag crust that must be removed. The wire coating contains elements (flux) that, when heated, protect the weld pool from exposure to air. Distinctive features:

• high mobility - no need to move cylinders around the work site;
• Many varieties of wire grades allow you to choose the one that is needed in specific conditions;
• flux-cored wire is often used during outdoor work ; in this case, gusts of wind do not interfere with the process, unlike welding with gas.

The main disadvantage is the high cost. On average, flux-cored wire is 50% more expensive than regular copper-plated wire.

Defects that occur when welding massive parts. How to avoid problems

During work, problems may arise that affect the quality of connections.

Description of the defect	Causes and remedies
Pores appear during welding	Insufficient gas pressure. Feed needs to be increased. The wind blows away the gas. It is necessary to use protective screens or carry out welding indoors. There is dirt, paint or oil on the metal surface. Any foreign particles or liquids should be removed from the edges. Low quality of welded alloys, gas mixture or wire. It is recommended to use proven materials. The welding current voltage is too high. Reduce tension.
The seam is too convex	It is necessary to configure the semi-automatic machine correctly. Adjust wire feed speed and current value. Test on unnecessary scraps of metal. The wire should flow smoothly into the welding zone and melt in a timely manner without cracking or clicking.
Spattering of metal during welding	Excessive gas pressure has been established at the outlet of the reducer; a strong flow blows away the molten metal. Reduce pressure. The device is not configured correctly. The current and wire feed speed should be adjusted.

If a metal structure has a complex shape and there is concern that it will deform during welding, assemblers often grab additional temporary reinforcements from corners, channels or reinforcement in critical places. They allow you to keep the dimensions of the product within specified limits. When the part has cooled, they can be cut off.

Welding massive parts with a semi-automatic machine is considered the most productive method. With a minimum of effort you can get beautiful and reliable connections.

Source: https://elsvarkin.ru/texnologiya/tolstye-zagotovki/

Features of welding thick metal

For products made of thick metal, electric arc and electroslag welding are mainly used. They have high performance, have a small heating area, therefore create small internal stresses, and do not require expensive consumables.

Electroslag

In electroslag welding, slag is heated by electric current, which melts nearby metal and protects the weld from oxidation and saturation with hydrogen. The technology allows making only vertical seams from bottom to top. Deviation from the vertical is allowed within 30 degrees.

Copper slide plates are installed on both sides of the thick metal sheets being welded, which are cooled with water. A gap is left between the sheets being welded. No joint processing is required.

The joints and sliders form a weld pool. When an electrode is introduced into it, the slag heats up, the metal begins to melt, and welding occurs without creating an arc.

As the seam is formed, the sliders move upward. Everything happens in one pass. You can weld thick metal up to 60 cm. The seam must be formed in one pass, otherwise irreparable defects will occur. The technology allows the use of electrodes of various shapes.

Electric arc

Welding metal of large thickness (20 mm or more), due to the impossibility of welding the entire thickness of the product in one pass, has its own specifics. The edges of the surfaces to be welded must be prepared.

To do this, the edges are ground at an angle. When connecting the parts, the cross-section should form the letter V. Sometimes, one edge is ground at an angle, and the other in steps. A gap is left between the parts to be welded; in the upper part there should be a groove 10-15 mm wide or more.

The width of the groove depends on the thickness of the metal. When welding metal of different thicknesses, the edge of the thicker one is ground down to the thinner section.

When butt welding and the presence of intersecting seams, stresses arise, leading to deformation and even destruction of the product. This is especially pronounced at low temperatures, when the metal loses its plastic properties.

Rigid fastening of parts in the tooling also causes excessive stress. Long seams with a large cross-section also lead to this.

It is necessary to weld a thick metal sheet so that the time between applying subsequent layers is minimal . To avoid stress, it is necessary to lay the next seam on a hot layer. The thickness of the layers should be within 4-5 mm, this will ensure sufficient heating.

When welding thick metal, due to the large depth of the weld pool, the likelihood of pore formation increases. To prevent this from happening, a cascade welding method or the “slide” method is used.

During welding, transverse shrinkage occurs, which can reach 4 mm with a metal thickness of 40-50 mm. When welding thick sheets, it is necessary to make tacks 2-3 cm long every 30-50 cm.

To reduce stress, work can be performed by two welders at the same time. Heating thick metal to 150-200 ⁰C also reduces internal stresses and slows down crystallization, which leads to a longer time for gas release and, accordingly, a decrease in the number of pores.

Types of sutures and methods of applying them

According to the position and type of connection, seams are divided into several types, which determine the welding settings.

According to their position in space they are divided into:

1. horizontal;
2. vertical;
3. ceiling;
4. lower ones.

They can be overlapped, end-to-end, and there are also T-joints and corner joints. There are several methods for placing seams when welding thick metal.

Overlay methods

The method of welding thick metal in a cascade is as follows: the entire section is divided into 20 cm sections. First, the lowest section, called the root section, is welded. Its length is approximately 20 cm. A new layer is made over the root overlap, without interrupting the arc. Its total length will be 20 +20=40 cm.

The welding method is best understood in the diagram. It is applied to thick metals when the sheet thickness is more than 20mm. With this welding method, layers are applied to uncooled metal, which reduces deformations and internal stresses.

Welding thick metal with a slide is similar to a cascade, only two welders work from the middle to the edges of the seam.

They cascade along the length and width. The goal is to ensure that the contact area is hot when applying the next layer.

Length

Seams are divided into short ones up to 25 cm long, medium ones up to 1 m, and long ones over 1 m. Short ones are laid in one pass.

When welding thick metal, it is necessary to make several layers - one for each pass, since each subsequent layer becomes wider, the welder makes zigzag or spiral movements across the seam. Thus, the edges of the welded parts are melted.

This technology is usually used for butt joints of thick metal. Medium and long sutures are applied using the cascade and slide methods.

When welding corner and T-joints, a multi-layer, multi-pass double-sided weld is used. First, the root seam is formed. Then a second layer is laid on top of it with an offset to one of the joints, then a third with an offset to the second joint with its melting.

The fourth goes on top of the second layer, melting the edge of the part. The fifth passes next to the fourth, and the sixth layer on top of the third, melting the edge of the second part. The seventh layer is applied on top of the fourth, fifth and sixth layers.

On the back side of the seam, the eighth finishing layer is applied to the first layer and the edges of the product.

Welding machine parameters

Reducing the welding current reduces the depth of the weld pool and vice versa. Its width practically does not change. The required current depends on the thickness of the metal and the diameter of the welding electrode. An increase in voltage leads to an increase in the width of the seam, while the penetration depth decreases.

The penetration depth depends on the speed of movement of the electrode, all other things being equal. It increases at speeds up to 40 m/hour, and then decreases. The seam width decreases continuously with increasing speed.

Working with thick metal requires more training for the welder. The seam always turns out to be multi-layered. Before taking on such welding, it is necessary to master the basic technological techniques.

Source: https://svaring.com/welding/soedinenie/svarka-tolstogo-metalla

Welding thick metal with an electrode

For products made of thick metal, electric arc and electroslag welding are mainly used. They have high performance, have a small heating area, therefore create small internal stresses, and do not require expensive consumables.

High-quality welding of thick metal

Welding of thick metal is based on the multi-layer weld method, in which elements must be applied to the edges of the joints using special technological processes. There are several techniques for welding metal with thick walls, which provide for technological preparation of the edges and some subtleties when connecting products with a wall of 20 mm and above.

At the junction of the two parts, it is necessary to leave a gap where the electrode will pass.

How to prepare an edge: features

Before starting welding of workpieces, no matter what cross-section the material has, the edges must be prepared, carefully approaching this issue:

• the first edge needs to be ground to a U-shape;
• another edge is ground under the stepped profile.

Preliminary preparation before welding thick metal is necessary, since without it the connection is impossible.

In the upper part of the joined parts, at the point of insertion of the electrode, a gap of 1-1.5 cm or more is required, but there should not be any inside the plane.

Welding thick-walled metal

When welding metal with thick walls, there are several technologies:

• sequential suture placement with a slide;
• cascade overlay;
• serial or parallel block overlay.

Heap welding method

Scheme of welding thin metal with thick one.

The initial seam is applied to the gap between the parts, using an electrode with a cross-section of 5 mm. The applied element must be 1/3 of the thickness of the metal being processed.

After removing scale and splashes, a second element is applied to the primary element. The total height of both seams will be equal to 2/3 of the thickness.

Following the first two principles, creating a “slide”, a third layer is applied. In this case, the thickness of the welded component is the same as the cross-section of the metal.

By applying the fourth element, the space that has formed between the edge and the slide is leveled.

Cascade welding method: nuances

Using this method, the applied seam will have a slightly different appearance:

Options for welded joints.

• before starting the main joint, apply a root suture about 20 cm long;
• the next joint, having a length of 40 cm, seems to creep onto the first one, while 20 cm will be the root for the third seam, and the remaining 20 will creep onto the first;
• 20 cm of the third seam will also be root seams, 20 will lie on the root seam of the second, and the remaining 20 will be located on top of the first and second seams;
• the third closes with the fourth, which has the same length of 60 cm and goes to the root section of the second seam.

If you use a semi-automatic machine for cascade welding, the quality is much better than with the manual method.

Using block welding

If it is not possible to use a semi-automatic welding machine, then the cascade welding method can easily be changed to the block method of laying seams.

When using the block version, metal welding looks like this:

• metal welding begins with the root weld;
• On top of the root seam, the next one is welded, which is intermediate. Its length is less than that of the first seam.
• On top of the intermediate seam, a subsequent one is laid, which goes to the surface of the thick metal, its length is almost equal to the length of the root seam.

Arc welding of joints

Arc welding diagram.

Welding of thick metal products can also be done using the arc method. An arc occurs when the electrode touches the area being welded. Experience and practice are needed here, since if you delay in separating the electrode from the metal, its end will “freeze” due to the fact that it has the ability to melt under the influence of a strong current supply.

During the occurrence of an arc, the master must constantly maintain the required arc length; the arc must also not be allowed to break, and as the electrode melts, it must be lowered.

It happens that welding suddenly stops and the arc breaks. It needs to be lit again, but in front of the place where the break occurred on the unmelted metal, and then they are only transferred to the seam and the place where the arc broke is melted again, since a crater has formed there. This way a continuous weld can be achieved.

To fill a seam with molten metal, the electrode must be moved along the seam, and to ensure the resulting seam has the required width, and to melt the edges of the product, the electrode must be moved across.

If you need to fuse a joint in the form of a bead, movements are made lengthwise, without deviating from the seam. When surfacing the bead, the width of the joint will be 2 mm wider than the electrode itself. During operation, the electrode is moved along the seam, maintaining uniformity and a certain current voltage.

Electrode movement diagram.

Recently, manual high-speed welding using the support method has become widely used. The principle of this method is that the thickly coated electrode melts faster than the coating, and this leads to the formation of a cap of the coating.

After the visor is formed, the electrode is placed on the place to be welded and without hesitation, it is guided along the entire seam, which results in an excellent seam. In this way, deeper welding is carried out, in contrast to conventional welding, which gives higher productivity.

Advantages and disadvantages of arc welding

The advantages of manual arc welding, which is performed with an electrode at temperatures up to 60,000°C and concentrated heating, in contrast to gas and hydrogen welding, are that it has high speed, a small temperature zone, and small deformation.

The disadvantages include:

• it is impossible to adjust the depth of metal penetration, there is no way to control the speed of melting of the electrode, which leads to deterioration in the quality of the joint when welding thin metals;
• a lot of time is spent on training qualified welders (about 2 years);
• formation of slag on the back side of the joint when using one-sided welding.

Correct welding of corner joints

When carrying out welding work, it happens that the thick metal products being welded are located at an angle. When welding products located at an angle, the molten metal flows down.

To prevent this from happening, it is recommended to weld in the lower position in a “boat” position, and the material to be welded is placed in such a position that the slag does not flow down in front of the arc, but you need to take into account the fact that it is not always possible to install the part in the desired location.

If the bottom plane is positioned horizontally during fillet welding, then lack of penetration of the top of the corner or edge may occur. If you start welding from a vertical sheet, the bottom sheet will not be welded. Due to the fact that the melt flows down, the surface of the bottom sheet will not be properly heated. For these reasons, welding of these joints begins with ignition of the arc on the plane located below.

The angle of the electrode should be 45° relative to the plane of the sheet; it should be slightly tilted when welding to one side or the other alternately.

The corners are joined not in a “boat” manner using a single-layer seam up to 8 mm, and with a larger joint thickness, two layers or more are applied.

When making a fillet weld consisting of many layers, first apply a bead with a cross-section of about 4 mm, which will ensure deep penetration of the root. Taking into account the cross-section of the seam, you need to decide on the number of passes. This value is calculated separately for each layer and is equal to 30-40 mm square.

Source: https://moyakovka.ru/process/svarka-tolstogo-metalla.html

How to weld thick metal using electric welding

The invention of the welding machine greatly simplified the process of joining metal objects. When working with thin workpieces, beginners may experience certain difficulties.

Welding thin metal with an electrode must be performed using welding machines that
allow this operation to be carried out without deformation or burning of the thin sheet.

Welding technology

To prevent metal burning, welding should be carried out as quickly as possible. The electrode is passed once along the seam, without delay. In order to weld thin metal sheet without problems, it is necessary to reduce the operating current as much as possible.

The inverter device used for this purpose must have smooth adjustment of the output power. To avoid problems with arc ignition, devices are used that have an open circuit voltage of at least 70 V.

When performing work, you should pay attention to the geometry of the thin sheet, which can change during strong heating. For a reliable butt joint, it is necessary to clean the edges of the material from rust. The workpieces should also be leveled, if necessary, and secured. Only a clean and smooth metal sheet will allow you to obtain the required quality of welded surfaces.

When the preparatory work is completed, the products to be welded are grabbed every 7 - 10 cm, and only then the final connection of the material is made.

If you need to overlap two thin sheets, then this welding option allows you to use more current, while the negative effects of high temperature on the surfaces being welded are significantly reduced. The probability of burning through the material is reduced several times, and a change in geometry is practically not observed.

To minimize the effect of high temperature on the metal being butted or overlapped, sheet copper should be placed under it. This material perfectly removes excess heat from the surface being welded, thereby preventing the appearance of warping and other negative manifestations of thermal expansion of the surfaces being welded. Sometimes, for the same purpose, wire is used, which is laid at the junction of two metals.

Working as an inverter

Welding thin metal with an inverter allows you to perform this operation using reverse polarity. In this case, "-" is connected to the metal being welded, and "+" is connected to the electrode holder.

This electrode welding technique allows us to minimize the likelihood of deformation and burnout of the metal product. With reverse polarity, the electrode heats up significantly more than the metal being connected, so it is possible to complete the connection work as efficiently as possible.

To obtain a high-quality seam, it is necessary to use thin electrodes with a diameter of no more than 2 mm. Products that have a high melting coefficient should be used. This quality makes it possible to weld thin structures at low current, which will have a positive effect on the quality of the weld.

Welding thin sheets with an inverter should be carried out with a smooth movement of the electrode. In order not to burn the product and to ensure an even seam, it is necessary to position the electrode within 45 - 90 degrees to the surface to be welded. It is better to make the connection at an angle forward.

The level of connection depends on the quality of the electrodes used. Electrodes for welding thin metal with an inverter must be of good quality and, preferably, imported.

simple techniques for overlap and butt are shown.

Advantages of welding thin workpieces with an inverter

This method allows you to make a high-quality connection of thin metal. If welding work is carried out by a professional, then temperature deformation does not occur and the product will have an aesthetic appearance. With direct current, thin products can be cooked with less current, so the likelihood of burnout is significantly reduced.

Source: https://MyTooling.ru/instrumenty/kak-varit-tolstyj-metall-jelektrosvarkoj

Technological features of metal welding depending on the material

Welding of metals was invented by people a little later than metalworking itself. Already the ancient blacksmiths knew how to create a single whole from individual iron products. Today welding is an integral part of modern civilization.

It is used in production, in everyday life, in the manufacture of building structures and cars, mechanical parts, and jewelry. Performed underwater and in outer space.

Modern technologies make it possible to achieve such strength in the resulting product as if it was originally solid.

The weldability of metals is studied by specialized institutes around the world, and welding is one of the most in-demand working professions today.

Basic Process Concepts

The task of welding is to create a permanent connection of parts . To obtain it, it is necessary to move the atoms that form the metal so close that interatomic cohesive forces begin to act. Why this happens, what physical processes occur in this case, has been studied rather poorly, but the property itself has been used for a long time.

Connections are achieved using three methods:

1.  Thermal , melting the metal of the parts themselves, or an additional additive. An example is the widespread arc and gas, laser, plasma jet. This includes soldering.
2.  Thermomechanical , in which products are heated and then compressed or forged. This is the most ancient method, which was used by blacksmiths already in the fifth millennium BC. In addition to forging, these are diffusion welding, contact welding, and induction-press welding.
3.  Using the mechanical method, products are welded, subjected to various influences without special heating. Example - ultrasonic techniques, connections by explosion, friction, pressure.

The first type is most common at construction sites and in everyday life. It is used to connect steel, cast iron, and to weld non-ferrous metals and alloys.

https://www.youtube.com/watch?v=PKs5mph0kkg

The second and third methods are used on industrial lines, for serial production, and also for the manufacture of unique products.

Regardless of the technique used, there are only two types of process:

1. Seamless , when the metal of the parts themselves is connected directly.
2. With the formation of a seam . In this case, auxiliary additives are used. They can either exactly match the base metal or differ. Example - joining steel with a copper electrode, soldering with tin, all types of welding using a fusible electrode.

Story

Until the second half of the 19th century, the only method of welded joints was forging, as well as soldering . The blacksmiths heated and placed the workpieces on top of each other, after which they beat them with hammers. Of course, there was no need to talk about reliability and accuracy.

The real revolution in welding processes began with the discovery of the electric arc process. Russian engineers were able to use it to connect parts. The method of arc welding with carbon electrodes was invented by N.N. Benardos, and literally a few months later, N. G. Slavyanov managed to perform the first connection of metals with a consumable electrode.

The 20th century was marked by a real welding boom. French engineers invented gas welding; in 1956, turner A.I. Chudikov managed to connect parts rotating on a lathe by friction. By the late 60s, people learned how to laser weld metal. Around the same time, industrial plasma spraying devices, induction and diffusion welding, etc. appeared.

Basic methods

Today there are more than 150 different welding methods. Although they differ in detail, they all fall into several main categories, which we will briefly consider.

Automatic submerged

Welding flux is a powder made from various substances . Its task is twofold:

1.  Protect the molten metal from oxidation.
2.  Add substances to the joint to enhance the strength of the joint.

The process goes as follows.

Pre-prepared parts are fixed on a special stand. After this, a layer of flux is applied to the joint using a special tube, forming a long mound. Behind it comes the welding head, which forms an arc. This may be followed by another tube that sucks in unused flux powder.

The work is carried out with a non-consumable or consumable electrode. The flux partially melts. How to distinguish metal from slag during welding is not a task: after completing the work, it is enough to tap the seam so that the slag crust formed by the flux melt bounces off.

Electron beam and plasma, diffusion and contact

While the methods and principles of connecting products differ, all these types are united by the absence of a voltaic arc (or a special type of it, as in plasma welding). Moreover, with contact technology, an arc is undesirable.

Electron beam joining of parts was first achieved back in the 50s. The process is similar to laser joining, but instead of a beam of photons, there is a directed beam of electrons. In this way, it is possible to connect tiny parts, the dimensions of which are measured in fractions of a millimeter, or to weld sheet metal measuring tens of square meters.

Plasma welding is suitable for working with refractory metals. Unlike an electric arc, whose temperature is 6-7 thousand degrees Celsius, in a plasma flow the heat reaches 30,000ºC. In addition to joining, the process allows for sputtering of dissimilar metals.

Diffuse welding is based on the interpenetration of metal atoms of tightly compressed, preheated parts. This process, called diffusion, gives the method its name. The method is effective in difficult cases, for example, it is used to weld non-ferrous metals.

Contact welding also refers to pressure joining. When parts are compressed, an electrical impulse passes through the contact point. current that provides communication.

Cold welding of parts and induction method

The basis of cold welding: deformation of the parts being joined . Otherwise - cold forging. Despite the attractiveness of the method (no electric current), it can be used to connect only non-oxidizing parts.

The induction method is the exact opposite of the cold method . The parts are heated, not with a flame or arc, but with a high-frequency electromagnetic field. In this case, welded metal products are heated to a significant depth.

The method is technologically advanced, so it is used, for example, on automated ones. pipe rolling lines.

How are different metals and alloys welded?

A special quality of metals is the concept of weldability, that is, the ability to be joined by welding using one or another method . It can depend on many reasons: chemical composition, specific properties of the metal or alloy, methods for preparing parts for welding, and much more.

GOST divides this property into the following weldable groups:

• Fine;
• satisfactorily;
• limited;
• Badly.

Cast iron, aluminum, and high-alloy steels have poor weldability. There are two main obstacles:

• oxide film preventing contact;
• the presence of alloying additives, in particular carbon, making the seam brittle and weak.

Weldability is improved by preliminary specific preparation of the metal for welding.

Non-ferrous metals are especially difficult to weld, each with its own specific characteristics..

Procedure

Although the technology for creating welded joints is different, in all cases the process begins with preparatory operations. For arc methods, this is preparing edges for welding, or, as they say, cutting them. For cold forging - thorough cleaning (even polishing) of parts to be joined, etc. Preparation may include cleaning from dirt and degreasing.

Another negative phenomenon that unites all types of welding contacts is temperature deformation and stress.

They deal with this in different ways. In some cases, products are fixed in advance with clamps. Another common method is heat treatment of the finished product: heating followed by slow cooling (tempering).

Finally

We have not considered all types and methods of welding. In addition, existing technologies are constantly being developed and new ones are being invented.

At the same time, technological solutions are dictated by tasks. In one case, the question is how to properly weld a metal bypass for an apartment heating system using the simplest manual method, in another - to create an ultra-precise product for the aircraft industry. Accordingly, a different approach is required.

The existing ones will inevitably be replaced by new methods, faster and more reliable.

Source: https://svarka.guru/tehnika/opredelennih-metallov/osobennosti.html

How to cook thick metal with an inverter

Among the search queries, the same question very often appears - “how to cook with inverter welding?” It is not difficult to understand the intricacies of working with a welding inverter; operating instructions for this device are available even to novice welders.

Thanks to the advent of welding inverters, the welding process has become much easier for both professionals in this matter and beginners. These devices made it possible to make the transition to higher quality and faster welding of metal structures. At the moment, the technology of metal welding with an inverter has managed to spread so much that it has already managed to relegate welding work using classic transformers, rectifiers and generators to the background.

How does a welding inverter work?

The inverter welding machine operates on alternating current. Its frequency must be 50 hertz. Alternating current enters the inverter from the consumer network and is supplied to the rectifier.

The resulting electric current is converted inside the inverter. This occurs due to the operation of special transistors. They increase the frequency of current switching, which is then used for welding. After conversion, its frequency level reaches 20-50 kilohertz.

The increased frequency of the electric current is the main technical feature of the welding inverter. It allows you to achieve high productivity in the operation of the device and reduce the time spent on welding metals. This feature gives the inverter an advantage when compared to other types of welding machines.

After converting the frequency of the current in the device, its voltage is changed. It decreases until it reaches levels between 70-90 volts. At the same time, the current rises to 100-200 amperes. Despite the high power of generated current, the dimensions of the inverter are small. This is achieved due to the fact that there are no bulky induction coils in its design.

Welding thin metal with an inverter: a guide for beginners

The first recommendation for beginners in welding thin metal with an inverter is the correct polarity setting. It switches on the device itself. This parameter determines the direction of electron movement and depends on the connection of the cables to the hardware connectors.

When welding thin metal with an inverter, the polarity must be reversed. In this case, electrons will move from the metal structure to the electrodes. With reverse polarity, the electrode elements will heat up significantly more. Thanks to this, the risk of burning through the metal is significantly reduced.

There are also three more tips for beginners in inverter metal welding.

TIP 1: watch several videos on how to properly perform inverter metal welding. They contain useful tips from welding professionals. The videos will also help you see the correct welding technology.

TIP 2: Learn proper ignition technique. There are two ways to light an arc in a welding machine - by tapping or striking the metal being processed.

TIP 3: Learn how to properly hold a welding machine. It is best to hold the inverter above the metal being welded at an angle of 90 degrees. In this case, the welding seam will be of better quality.

How to properly weld thin metal using inverter welding

The technique of welding thin metal with an inverter involves careful selection of operating parameters and individual components of the welding device. First of all, it is necessary to establish the current generated by the device. The thicker the structure being processed, the stronger the electric current should be.

Next, select electrodes suitable for welding. Their diameter should be the same as that of the structures being welded. For example, if welding needs to be carried out on a sheet of metal 2 millimeters thick, then the same parameter for the electrodes should be identical. In this case, the current should be set within 35 amperes.

Before welding thin metal using inverter welding, you need to check the operation of the welding machine on any unnecessary part. It is recommended to ensure that the metal does not burn through and leaves a smooth seam. If the welding goes well, this means that the current strength and thickness of the electrodes were selected correctly.

After checking, you can begin welding thin metal. The inverter must be moved intermittently. This will help create a denser seam that will reliably withstand external mechanical stress and possible deformations.

Welding thick and thin metal structures with an inverter

The main problem when welding thin metal to thick metal with an inverter is that parts of different thicknesses require different polarities when welding. If thinner parts are welded with reverse polarity set, then other parameters are required with products thicker than 3 millimeters.

The thing is that thick metals must be welded at high temperatures. Otherwise, the parts will not warm up to the required level and the welding seam will not be of sufficient quality. Direct polarization helps solve the heating problem. It directs electrons from the electrode to the metal, which helps heat it to an acceptable temperature. This makes thick metals ready for welding.

For this reason, before welding structures of different thicknesses, it is recommended to warm up thicker parts. This will allow them to be processed efficiently and tightly welded to thin metals. For welding metal products of different thicknesses, it is best to set the inverter to reverse polarity. The current strength should fluctuate between 30-50 amperes.

How to cut metal parts using inverter welding?

Using inverter welding, you can cut metal of any thickness. To do this, it is necessary to increase the current generated by the device. For high-quality cutting of metal products, an electric current is suitable, whose power rating will be 140-160 amperes. It is also necessary to correctly set the polarization of the device. When cutting metal, you will need to activate the straight polarity of the inverter.

The technique of inverter cutting of metal parts is that the electrode is pressed into the surface being processed until it forms a through hole in it. After it appears, the inverter moves, and the process of creating new gaps proceeds in the same way. It is recommended to warm up the metal before cutting. It is better to cut it in a vertical position - this way drops of molten material will flow onto the work surface.

Pros and cons of using an inverter

In conclusion to all of the above, it is necessary to note the advantages and disadvantages of a welding inverter. The main positive aspect of using this device is its light weight. This helps to significantly increase welding productivity.

The other most important advantage of an inverter is the ability to widely adjust the welding current. This allows the use of argon as an inert gas and non-consumable electrodes for welding. Inverters also have the option of stopping the current supply if a short circuit occurs.

The most significant disadvantage of inverters is their high cost. These devices cost two to three times more than conventional welding machines. However, they do not have more serious protection against dust and dirt particles.

Very often, novice welders wonder how to weld metal using inverter welding at sub-zero temperatures. Alas, this method of welding is not suitable for use in cold weather. Often, metal processing with an inverter is carried out at a temperature of at least 15 degrees Celsius. In extreme cold, the device will not be able to provide high-quality welding.

Despite these disadvantages, the inverter can be called a reliable and high-performance device. The welding work carried out by him gives high-quality and durable results. For this reason, inverter welding is suitable for high-quality processing of metal structures. Despite this, beginners are still advised to familiarize themselves in advance with how to weld metal using inverter welding.

Welding of thick metal is based on the multi-layer weld method, in which elements must be applied to the edges of the joints using special technological processes. There are several techniques for welding metal with thick walls, which provide for technological preparation of the edges and some subtleties when connecting products with a wall of 20 mm and above.

At the junction of the two parts, it is necessary to leave a gap where the electrode will pass.

Source: https://vi-pole.ru/kak-varit-tolstyj-metall-invertorom.html

Welding thick metal with a thin electrode

Although an inverter welder is a piece of equipment that can be operated by even a non-professional with little experience, welding thin metal with an inverter can be a challenging task. The difficulty is to correctly select the strength of the current and the impact on the metal so that it does not end up being burned through.

Welding thin metal with an inverter: video, features

Unlike welding thick metal, a 1mm thick metal sheet cannot be subjected to high heat. If overheating occurs, the sheets become deformed and burn through. The electrodes are carried strictly along the seam in one direction, without deviating to the sides.

The second feature of welding thin sheet metal with an inverter is that it is necessary to use a short arc, because the work is carried out at low currents. The difficulty with this is that when separated from the metal, it can go out, and insufficient current strength will lead to lack of penetration.

If the edges of the product are butt welded, they must be carefully cleaned and processed, because contamination will make the welding process even more problematic.

Taking these features into account, as well as relying on detailed instructions, welding 1 mm thin metal with an inverter for beginners will not be a difficult process with a high-quality result.

Electrodes for welding thin metal with an inverter

The electrical conductor is of utmost importance in the welding process. To weld 1 mm metal, it is necessary to use electrodes with a small diameter. Welding thick metal with an inverter is done using electrodes 3-4 mm thick, and to weld 1 mm metal you need to use a diameter of 0.5-2 mm with a current value of up to 60 amperes. If the sheet thickness is 1.5-2 mm, an electrode with a diameter of 2-2.5 mm is used.

Electrodes for welding thin metal with an inverter

In addition to their small diameter, electrodes for thin sheet metal have a special coating that ensures normal arc burning and forms a fluid metal, since the electrode melts very slowly.

The result is a neat, shallow weld. An example of a suitable electrode is "OMA-2", the composition of which includes titanium concentrate, ferromanganese ore, flour, and additives. Thanks to this composition, arc burning stability is ensured.

In addition to OMA-2, the MT-2 type of electrodes is often used.

The brand of electrodes is selected based on the composition of the material. For low and medium carbon steel, carbon electrodes are used. The same principle works for alloy steel.

Depending on the type of connection of the sheets, the position of the electrode is set in a certain way to avoid overheating of the metal:

• For welding vertical, horizontal, and ceiling seams, the electrode is set at an angle forward of 30-60 degrees.
• For welding in hard-to-reach places, the electrode position is set vertically at an angle of 90 degrees.
• For welding corner and butt joints, the position of the holder with the electrode is set at an angle back at an angle of 110-120 degrees.

The tip of the electrode is moved strictly in one direction without deviation.

Welding metal with a 1mm inverter: existing methods

There are several methods by which metal welding with an inverter is carried out on sheets 1 mm thick:

This method is used when it is necessary to weld sheets of thin metal 1 mm at an angle. In this case, the edges of the sheets are bent at the required angle, fastened with transverse short seams with an interval of 5-10 cm. Then the seam is welded with a continuous movement from top to bottom.

When using this method, the metal product has time to cool down somewhat, which avoids overheating. The intermittent method involves lifting the electric arc from the surface of the sheet for a few seconds, after which the electrode is again lowered to the same place and advanced a few millimeters. The main thing is that the metal sheet does not cool down too much.

1. With heat-dissipating pads.

This method is used using heat sink wire or copper plates. Typically this method is used when butt welding thin sheet metal parts.

In the first case, a wire of small diameter (2.5-3.0 mm) is laid between the sheets so that on the front side it is flush with the surface of the sheet, and on the back side it protrudes slightly beyond its edges. The welding arc passes through the location of the wire, which takes on the main thermal load.

The edges of the parts being welded are heated by peripheral current. As a result, the seam is smooth, the metal does not overheat and does not deform. After welding, the wire is removed without visible traces of its presence.

When using a copper plate under the joint as a heat sink, it absorbs most of the heat, preventing the metal from overheating.

There are the following types of welds:

1. Most often, a weld is made when joining sheets with an overlap, because This is a simpler method in which one sheet overlaps the other by 1-3 cm.
2. A spot weld is obtained when welding parts with a continuous seam is not required. In this case, spot intermittent welding is carried out at a certain distance of the seams from each other.
3. Butt seam. A more complex type in which two sheets are welded to each other end-to-end without overlapping. As a rule, it is obtained using the welding method with heat-dissipating pads.

Technological process

Welding thin metal with an inverter

Step-by-step instructions for the welding process will allow you to cope with the work without much difficulty. To begin with, it is necessary to ensure safety measures when carrying out work, which include the use of protective clothing - a welding mask, gloves, clothing made of thick, coarse fabric. Do not use rubber gloves.

You can then follow the following instructions:

1. First, the current is adjusted and an electrical conductor is selected to work with the inverter. The current indicator is taken based on the characteristics of metal parts. The required diameter of the electrode is selected and inserted into the holder. The ground terminal is connected to the part; the electrical conductor should not be brought too sharply to avoid sticking.
2. Ignition of the electric arc starts the operation of the inverter apparatus. To activate the arc, point the electrode at a slight angle to the welding line. The electrode should be held until a small red spot appears on the surface - this means that a drop of hot metal is located underneath it, which will facilitate further welding along the entire length of the seam.

The electrode is held from the welding site at a distance corresponding to its diameter.

1. By following these steps and choosing a specific welding method, there is a great chance of getting a high-quality and even seam. Scale and scale formed at the welding site are removed with a small hammer.

Practical advice

During operation, it is necessary to maintain a constant distance between the electrode and the metal surface. The arc gap must correspond to the diameter of the electrode. If the distance is too small, the seam joint will have convex formations. If it is too large, there is a risk of undercooking.

When obtaining an overlap seam, it is necessary to press one sheet onto the other with a weight so that there is no empty space between them.

It should be remembered that the shorter the spot welding step, the less the thin metal is deformed.

If you move the electrode too quickly, the result may be an uneven seam. To avoid the appearance of a defective weld, you need to understand what a weld pool is: it is liquid metal formed during the welding process into which filler material enters. If a weld pool is formed, then the welding process is successful.

The bath is located under the surface of the metal product. If the electric arc penetrates evenly and to a great depth into the product, an even seam is formed in the weld pool. In this case, you need to ensure that the seam is level with the surface of the metal. A high-quality connection is formed by making circular movements with the electrode.

In this case, the bath is distributed in a circle.

The most optimal angle of inclination of the electrode is the range from 45 to 90 degrees.

The electrodes should be connected to the positive terminal. This will avoid excessive thermal load on the surface of the product and obtain an even seam with shallow penetration.

Source: https://respect-kovka.com/svarka-tolstogo-metalla-tonkim-elektrodom/