What is cold welding of cast iron

Welding cast iron at home - electrodes, welding methods

Welding cast iron at home - electrodes, welding methods

Cast iron is an alloy of iron and carbon containing a large number of various impurities. Cast iron products are in great demand both in industry and in everyday life. It is the active use of cast iron over the past 50 years that has led to the need to repair something more and more often. At the same time, welding cast iron remains one of the most practical ways to bring a product into working condition.

To cook cast iron at home you will need an inverter and special electrodes for cast iron. Previously, the website mmasvarka.ru already described how to make them using a homemade method using ordinary copper wire. Therefore, this article will cover questions regarding the various nuances of welding cast iron, since this work is very different from the work associated with welding steel.

The main difficulties when welding cast iron

Cast iron has much greater fluidity than steel, so it is recommended to cook various cast iron products at home only in the lower position. If cast iron is overheated during welding, this will lead to the formation of large pores and stress in the weld. Therefore, it is not recommended to overheat cast iron and subject it to rapid cooling.

The main defects when welding cast iron are associated precisely with uneven heating and cooling of the welded products. The appearance of cracks in this case is the most difficult defect, which is very difficult to get rid of in the future. In addition, when welding cast iron, it is very important to properly prepare the materials.

Preparing cast iron for welding

To obtain a high-quality welded joint, the surface of the cast iron is properly prepared before welding. Firstly, it must be cleaned of any contaminants, and then degreased, for example, with acetone or solvent.

If it is necessary to cook thin cast iron, then it is imperative to provide special heat-dissipating pads for welding points. A prerequisite for welding cast iron is the cutting of product edges. For these purposes, even before welding, their edges are processed with a file or an angle grinder with a metal disc.

In the case when it is necessary to weld a crack in cast iron, it must be drilled along the edges, after which, as with the edges, it is cut along its entire length. Some welders cut out the cracks first and then drill out the edges to prevent them from spreading further.

Depending on the chosen method of welding cast iron, and there are only three of them (hot, semi-hot and cold method), heating of the product is required. Let's take a closer look at the technological process of welding cast iron products at home.

Methods of welding cast iron

There are three ways to weld cast iron:

Hot method - requires heating cast iron products before joining to a temperature of at least 600°C.

The semi-hot method is not much different from the hot method of welding cast iron, with the exception of the temperature, which is almost half lower (300-350°C).

Cold method - carried out using a piece electrode without preheating the cast iron workpieces. Welding cast iron at home is carried out using this joining method.

Welding cast iron with an electrode

To weld cast iron at home, you will need an inverter and electrodes with a special rod. Electrodes for cast iron contain copper and nickel. Well, how to make homemade electrodes for cast iron has already been discussed in previous issues of the site.

The most popular factory electrodes for welding cast iron are:

• Electrodes OZZHN-1, OZCH-2, as well as OZCH-3, OZCH-4, OZCH-6;
• Electrodes MNC-2;
• Electrodes TsCh-4.

It is very important to choose the correct welding mode for all of the above brands of electrodes. For TsCh-4 electrodes (3 mm), the current strength should be set on the inverter within 70A. For OZCh-2 electrodes, about 90A. For OZZHN-1 electrodes with a diameter of 3 mm, approximately 100A, and for MNCh-2 electrodes of the same diameter, the current strength on the inverter should be set to around 90A.

The technological features of cast iron welding are as follows:

• You need to cook cast iron with short seams, no more than 5 cm long;
• Severe overheating of cast iron products during welding should be avoided. Therefore, in addition to welding with a short seam, the workpieces should be given a sufficient amount of time to cool;
• When welding cast iron with an electrode, the inverter should be switched to reverse polarity.

If you adhere to all the above rules, you will be able to cook cast iron at home without any particular difficulties.

Source: https://mmasvarka.ru/svarka-chuguna.html

Welding cast iron

Often the joining of metals is carried out using welding equipment. Welding can be done at home, for which it is enough to follow the recommendations of professionals.

Welding cast iron in comparison with other metals is much more difficult, which is due to the special properties of the material. Often, welding cast iron at home results in the formation of a low-quality weld.

Heat treatment causes an increase in the fragility of the metal; cracks and other defects may appear at the welding site. Let's consider all the features of this process in more detail.

Welding cast iron

Features of cast iron welding

Cast iron is characterized by a high concentration of carbon in its composition (from 2 to 6%), which determines increased fragility. In addition, the composition contains a fairly large amount of harmful impurities, for example, phosphorus, sulfur and manganese. Recently, cast iron has also been alloyed: chromium, nickel, molybdenum, and so on are added.

When considering the weldability of cast iron, it should be borne in mind that this indicator largely depends on the chemical composition of the metal. The type of impurities used determines what properties the cast iron will have.

The low cost of the material, ease of production and its high machinability determine the features of cast iron welding. Considering the features of welding, we note the following points:

1. The poor degree of weldability is associated with the unusual structure of the material in question.
2. Metal with finely dispersed fracture is distinguished. It has increased weldability.
3. Industrial cast iron is practically impossible to weld, which can also be associated with the structural features of the material.

Weld seam on a cast iron product

The resulting cast iron parts can be highly brittle. When welding, the following process features should be taken into account:

1. Cast iron has increased fluidity when heated, so welding is recommended to be carried out in the lower position.
2. Due to the high concentration of carbon, pores are formed when it is heated and burned out. That is why the resulting seam is highly brittle.
3. Reduced ductility causes internal stresses. They lead to the appearance of a large number of cracks, as a result of which the connection does not have the required strength.
4. In the molten state, the metal begins to oxidize. The resulting oxide has a higher melting point than the material being processed.

When manual arc welding, defects in the form of cracks quite often form. Before working with the material in question, its composition and structure are studied in detail.

You can improve the quality of the resulting seam by:

1. eliminating the possibility of overheating of cast iron at the time of welding;
2. reducing the likelihood of stress occurrence leading to structural deformation.

There are quite a large number of welding methods for the metal in question, each with its own specific advantages and disadvantages.

Welding methods

Considering methods of welding cast iron, we note that a wide variety of equipment can be used for this. Semi-automatic electric welding in a carbon dioxide environment has become widespread.

The work being carried out can be classified as follows:

1. Welding during production.
2. Connecting metal when repairing or restoring a product.
3. Welding during the assembly of cast iron products.

Welding cast iron with argon

The technology of welding cast iron with argon has also recently become widespread. Argon welding of cast iron is used to repair steel studs or perform other similar work.

Cold way

Welding cast iron with an electrode at home can be carried out to connect various parts. OZCH-2 with a copper rod is used as an electrode. There are also other versions of electrodes on sale, which today are considered scarce due to the difficulties encountered in their manufacture.

Cold welding of cast iron

The technology of cold welding of cast iron is characterized as follows:

1. Metal processed in this way has better cutting machinability.
2. The electrodes in question are expensive and are a scarce material.
3. In everyday life, a copper-steel type electrode can be used.

Cold welding of cast iron with electrodes is carried out at low current, since heating the metal can deteriorate the quality of the resulting weld. In addition, the work must be carried out with periodic breaks, since time is required for the metal to cool.

You can make electrodes yourself. The features of their manufacturing process include the following points:

1. Copper wire can be used as a base.
2. The rod is cleaned of contaminants with an organic solvent.
3. The coating is a combination of crumbs from iron electrodes, as well as powder from fine iron filings.
4. The resulting mixture is combined with watery glass.
5. The rod is covered with a layer at least 2 millimeters thick.
6. Drying is carried out in the open air, after which the applied composition is baked. A conventional oven can be used to heat the medium, since the baking temperature is relatively low.

When using homemade electrodes, a short arc is created, as well as a constant current. Do not forget that you should leave the metal to cool. The recommended temperature is 50 degrees Celsius. To ensure high quality of the resulting seam, it should be applied in small parts, the length of which is 30-50 millimeters. This eliminates the possibility of cracks occurring.

Hot way

Hot welding of cast iron is much more complex than cold technology. Despite the difficulties that arise, it has recently been used extremely often, since this method allows one to avoid cracks in the transition areas of the seam. It is recommended to heat the metal evenly, which helps avoid the appearance of breaks and cracks.

Hot welding of cast iron

The features of this technology include the following points:

1. Before heating, the material should be secured in the prepared frame. This reduces the likelihood of stress occurring. It is tension that causes cracks to appear.
2. It is imperative to use a rigid frame if local heating of the material in question is carried out.
3. In most cases, heating is carried out using an inductor using industrial frequency currents. In addition, flame torches, blowtorches, and forges can be used.
4. Graphite molds are used to weld through cracks. In their manufacture, it is customary to use graphite plates, which are connected to the molding sand.
5. Before carrying out welding work, the weld area should be prepared. Preparation involves removing dust and dirt, which can cause deterioration in the quality of the resulting seam.

There are also several recommendations related to the features of the technology in question:

1. It is necessary to control the volume of molten material during work. To do this, during welding, the molten composition is mixed with the end of the filler rod or electrode.
2. Cooling should be carried out evenly. In order to prevent the metal from cooling too quickly, the workpiece is covered with charcoal or hot sand. As practice shows, it takes from 3 to 40 hours to cool small parts; larger ones can cool within 5 days.
3. When heated, the metal may oxidize. Due to this, the melting temperature increases significantly, which complicates the welding process. To eliminate the possibility of metal oxidation, boron-based fluxes are used.

Gas welding of cast iron has a fairly large number of features that determine the popularity of the technology. The features of this technology include the following points:

1. Gas welding allows you to obtain a high-quality connection. To do this, you can use a burner that runs on different types of fuel.
2. This technology allows for the restoration of parts. An example is the case when a damaged part needs to be attached to a product.
3. When using this technology, it is possible to heat the workpiece more uniformly. Due to this, the resulting seam will be of high quality and less fragile.

This information determines that when using manual gas arc welding technology, the surface being processed is heated. Cast iron rods are used as filler material.

Gas welding technology using brass rods is highly efficient. This alloy has a much lower melting point than the cast iron being processed.

The features of the technology include the following points:

1. The procedure involves the use of various fluxes, which prevent the formation of oxides.
2. The edges of the cracks being processed should be heated to a temperature of about 900 degrees Celsius, after which the surface is coated with flux.
3. The next step is to finish the edges with brass.

All of the above information determines that welding cast iron is difficult. Only following all the recommendations allows you to get a high-quality connection that will last longer.

In conclusion, we note that less refractory cast iron should be selected for welding. An example is ductile cast iron, which is less susceptible to the formation of internal defects.

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

Cold welding on cast iron

page » About welding » How to cook correctly » How to cook cast iron » Welding cast iron with electrodes

Cast iron is an alloy of iron and carbon (content exceeds 2.11-2.14%), which contains impurities: silicon (no more than 3%), manganese (up to 1%), sulfur, phosphorus and alloying additives: chromium, nickel , vanadium, aluminum, magnesium and others. Without special additives and heat treatment, cast iron has low strength, hardness and ductility .

Carbon may be present in the alloy in the form of cementite and graphite. Depending on the proportion of these substances in the composition, several types of cast iron can be distinguished.

Some of them can be processed by welding, others cannot. For each type of alloy there are certain brands of electrodes. Next, we will look at which cast iron is welded with electrodes in various situations.

White cast iron is characterized by the fact that all carbon is present in the alloy in the form of cementite. This type has high hardness and cannot be processed with cutting tools.

Most or all of the carbon is present in gray cast iron in the form of graphite. This type lends itself well to processing; has high casting properties, thanks to which it is actively used as a material for casting. Welding of gray cast iron with an OZCH-2 electrode is performed with direct current with reverse polarity.

Also for this type are the brands OZCh-4 and OZCH-6, OZZHN-2, MNCh-2.

Malleable iron is the result of casting and heat treating white iron to form flake graphite; used in the production of cars, tractors and agricultural machinery. Electrodes designed for working with malleable alloy: OZCh-2 and 6, MNCh-2, TsCh-4.

Welding is carried out with direct current; the polarity when welding cast iron is reversed.

In half cast iron, carbon is present in two forms: graphite and cementite; used in the manufacture of parts operating under conditions of increased wear resistance.

Ductile iron contains nodular graphite, which is formed during the crystallization process; used for the production of critical parts in mechanical engineering, as well as for oil and gas pipelines, water supply pipes.

In the article we will look at how to weld cast iron with electrodes, depending on the connection method used.

Difficulties in welding cast iron

Before starting work, the contractor must take into account the features of welding cast iron with electrodes. These specific features are due to the unique properties of cast iron.

One of the main disadvantages of cast iron is poor weldability, which is due to the following factors:

• poor connection of cast iron by welding is explained by its chemical structure and properties; In the photo: time in the welding bead
• Various elements, in particular silicon, are oxidized in the weld pool, resulting in the formation of oxides. The refractoriness of these oxides leads to the appearance of uncooked areas ;
• rapid cooling of the joint and heat-affected zone leads to the formation of areas of cementite characterized by increased hardness. These areas are difficult to machine ;
• cast iron is characterized by high fluidity , which makes it difficult to retain the molten metal in the bath and complicates the formation of a seam;
• uneven heating and cooling of brittle cast iron can most likely lead to cracks ;
• molten cast iron tends to release gases, which can cause pores .

Despite these difficulties and features, a performer of any level can obtain a high-quality and reliable connection. To do this, you need to select the right consumables. We will discuss below which electrodes to choose for welding cast iron.

How to choose cold welding glue – types, features

Cold welding is a special glue that is used to connect various elements made of one material or another. The peculiarity of such fastening is that it is produced in the absence of temperature influence.

Application of cold welding

Cold welding

Typically this adhesive is used to join the following materials:

Cold welding glue is divided into several types:

1. Liquid formulations that include two components. Immediately before starting to work with the adhesive mass, it should be mixed with a special hardener.
2. Plasticine-like substances, which are made in the form of single-layer or two-layer bars. If the latter option is used, then before
3. When used, the existing layers must be mixed with each other.
4. Universal compounds used for gluing materials such as metal, PVC, wood, etc.
5. Special masses that contain a metal component.
6. Compositions intended exclusively for working with vehicle parts.
7. Substances used in cases where it becomes necessary to perform welding work under water.

Metal

Cold welding, which is intended specifically for metal, includes the following components:

• Epoxy resins. These components give the composition plasticity and uniformity of structure;
• A metal component that is a filler;
• Certain additives that perform auxiliary functions;

Thus, welding for metal is a polymer substance that has excellent adhesive properties, which require some deformation of the adhesive mass, causing its partial penetration into the surface being treated.

The cold welding composition provides significant joint strength, provided that the composition is used correctly, as well as optimal preparation of the material for the specified operation. However, it is most advisable to use this adhesive mass for metal only if it is necessary to carry out minor repair manipulations.

Linoleum

The cold welding composition, designed for working with linoleum, consists of the following components:

• - tetrahydrofuran;
• — plasticizers;
• - polyvinyl chloride.

This composition makes it possible to somewhat straighten the edges of the glued material using the glue itself. The main feature of this type of welding is the difference in its behavior when in contact with one or another type of linoleum. This characteristic determined the fact that this composition was divided into three main types:

Type “A” glue

This type is used in cases with fairly hard material. The consistency of this composition for linoleum is characterized by significant fluidity, so it leaves a rather thin seam.

Type “C” glue

This cold welding is intended for linoleum, which remains in operation for a relatively long time and is subject to repair. The consistency of this substance is thicker, which determines the specifics of its use.

As a result of filling the seam, which has somewhat diverged under the influence of time, a new strip of material is formed at the site of the defect.

Type “T” glue

This type is also intended for linoleum made of PVC, but using polyester. The composition for linoleum of the specified modification is usually used by professional builders.

Cast iron

For cast iron, the cold welding composition is also applicable. Quite often it is used in domestic conditions when correcting some defects that appear in heating radiators.

For cast iron, a universal composition or an adhesive mass containing a metal component will do. It is worth noting that welding of these types can be used for cast iron only in cases where it is necessary to repair a minor hole or connect oversized parts. This situation is explained by the relatively low strength of welding seams.

Choice

Nowadays there is a fairly large selection of adhesive substances for various types of materials on the market. The most popular is Almaz glue. Its technical and operational characteristics comply with all established standards, which determines the high quality of work with the specified composition.

“Diamond” is suitable for all surfaces that can be joined using cold welding adhesive. However, when buying a substance called “Diamond” you must follow some rules.

The most important of these rules is that you should not think that Almaz glue is universal, just like the composition of any other brand, it is an ideal means with which you can fasten anything.

Of course, universal cold welding is capable of joining a fairly large number of types of materials, but this same characteristic contributes to a decrease in the quality of the seams made.

That is why, no matter what cold welding glue is called, you must choose only the option that is suitable for the job in a particular case.

Source: http://kleiexpert.ru/klej-holodnaya-svarka

Cold gas welding of cast iron

Cold gas welding of cast iron is used if, when heated and cooled, the parts freely compress and expand without causing large residual stresses, in this case the power of the burner flame should be as high as possible.

The technological process of gas welding without preheating is almost similar to the process of hot gas welding, but it also has its own characteristics. Before welding a defect, it is necessary to heat the areas adjacent to the defect with a burner flame. After filling the defect, the burner is slowly withdrawn for 2-3 minutes, directing the flame to areas adjacent to the defect.

The part or part of the part on which the welded area is located is covered with sand or covered with asbestos for slow cooling.

The method of cold gas welding of cast iron differs from conventional methods in that the base metal is not brought to the melting temperature, but is heated only to a temperature of 820-860 ° C, i.e., to the “wettability” temperature. This method is based on the use of special cast iron rods and fluxes.

Drops of molten filler metal under the action of a welding flame easily spread over the surface of the metal being welded, ensuring a tight connection of the parts being welded. Low-temperature gas welding of cast iron is used when welding casting defects in parts made of gray cast iron, as well as when welding cast iron parts in finished products in cases of their breakage, cracks and other defects.

LF-2 cast iron rods are used as an additive for welding thin-walled castings, and UNCH-2 cast iron rods are used for thick-walled castings. For low-temperature soldering and welding of cast iron, special fluxes FSC-2 and MAF-1 are used.

The fluxes used chemically clean the heated surface to be welded from oxides, fats and other contaminants, increase the adhesion strength of the deposited metal to the base metal, increase the fluidity of the molten metal and protect the heated surface and molten metal from oxygen and nitrogen in the air. The composition of fluxes for low-temperature soldering and welding of cast iron is given in the table.

Composition Brand of flux

FSC-2	MAF-1
Fused borax	23	33
Soda ash	—	12
Sodium nitrate	50	—
Sodium nitrate	—	27
Lithium carbonate	0,5	—
Sodium carbonate	26,5	—
Sodium fluoride	—	12,5
Potassium fluorozirconium	—	8,5
Cobalt oxide	—	7

The cutting of the defective area for cold gas welding of cast iron is performed by milling, drilling or planing. The welding site is pre-cleaned to a metallic shine.

The cutting profile of the edges of through and non-through defects is shown in Figure 1. The cutting angle is 70-90°. Shallow pores and slag inclusions are cut out with a chisel or removed with a grinding wheel.

Before welding, the product is heated with a torch to a temperature of 300-400°C. Products of complex shapes are heated in an oven.

a - cutting a non-through defect, b - through a defect using a lining made of refractory material

Figure 1 — Profile of defect cutting for cold gas welding of cast iron

The scheme for eliminating through defects (cracks) is shown in Figure 2. When eliminating drilled defects (porosity, cavities), the filler metal is applied along a helical ascending line. A layer of flux is evenly applied to the heated surface to be deposited. The welding site is heated with a torch to a temperature of 820-860°C, the flame must be strictly normal.

At this temperature, the flux paste melts, covering the welding site with a thin film. The filler rod is also coated with flux. When melted, the filler metal flows onto the welded surface and spreads over it. Welding is carried out in the left way.

The distance between the flame core and the end of the rod should be 2-3 mm, the angle between the burner axis and the plane of the part should be 20-30°.

Figure 2 - Scheme for eliminating through cracks (a) and drilled defects (b)

After gas welding, the product is slowly cooled under a layer of asbestos or in sand. Since with this method the base metal is not brought to melting, there are no areas of bleached cast iron and the weld metal is dense, soft and can be easily processed by mechanical methods.

When cold gas welding of cast iron, substitute gases can be used instead of acetylene. When using propane-butane as a flammable gas, the power of the welding flame is selected at the rate of propane-butane 60-70 dm3/h per 1 mm of the thickness of the metal being welded. The flame appears normal. With a metal thickness of up to 6 mm, welding is performed in one pass, with a thickness of 9-12 mm - in two passes.

When using FSC-2 as a flux, the operating temperature is 900-950°C. At this temperature, the appearance of hardening structures in the heat-affected zone cannot be ruled out, so this flux has limited use. It is used in cases where increased hardness of the deposited metal is allowed.

MAF-1 flux allows the process of cold gas welding of cast iron to be carried out at an operating temperature of 750-800°C.

In some cases, it is advisable to use cold gas welding of cast iron with brass solders. This method is used for repair welding.

The advantage of cold welding cast iron with brass compared to fusion welding is that heating cast iron to the melting point of brass (850-900°C) does not significantly change the structure of the metal, which eliminates the danger of cast iron chilling and does not cause significant thermal stress.

The edges of parts up to 25 mm thick are beveled at an angle of 45°, and for larger thicknesses, stepwise cutting is recommended; When cold gas welding cast iron with brass, it is better when the surfaces of the joined edges are rough.

Carbon is burned from the surface of the edges being joined to a depth of 0.12-0.15 mm in two ways:

• the joined edges of the part are coated with a paste of iron filings and boric acid and heated with a burner flame to 750-900°C;
• the edges of the part are heated with a burner flame adjusted with excess oxygen to the same temperature.

The second method has found the greatest application. The technique for cold gas welding of cast iron is as follows. The edges are heated to red, sprinkled with flux and tinned in sections.

The welding flame should be normal or with a slight excess of oxygen. The part must be in an inclined position, soldering and welding is performed from the bottom up. The position of the torch and filler metal is the same as with the right-hand method.

The power of the welding flame is selected at the rate of 60-75 dm3/h of acetylene per 1 mm of thickness.

For cold gas welding of cast iron, special fluxes FPSN-1 and FPSN-2 have been developed, which neutralize the effect of free graphite, the particles of which protrude on the surface being welded and interfere with its wetting. Silicon wire LOK 59-1-03 is used as solder; it contained on average up to 0.3% Si.

For soldering and welding of products whose mechanical properties are subject to increased requirements, use LOMNA 49-25-10-4-0.4 solder, containing copper (Cu), tin (Sn), manganese (Mn), nickel (Ni) and up to 0.6% aluminum (Al).

When cold gas welding with this solder, the metal of the solder weld has the color of cast iron, hardness HB 180-200 and tensile strength 280-340 MN/m2.

For cold gas welding of cast iron, surface-active flux of the FPSN-2 brand is used. It contains 45% boric acid, 22.5% lithium carbonate, 22.5% soda ash and 10% salt alloy. It is used in powder or paste form. Flux melts at a temperature of 600-650°C. Cold gas welding of cast iron is performed with a conventional welding torch running on acetylene or substitute gases.

First, the welding area is heated to 450-500°C with a slightly oxidized flame, and then flux is introduced into the groove. Soldering and welding begins at the moment the flux melts, directing the flame to the areas adjacent to the cutting. The molten flux is distributed evenly over the entire surface of the welded area using a solder rod, then the flame is directed to the end of the rod, melts it and fills the groove with solder metal.

The deposited metal is hammered with a hand-held copper hammer immediately after welding.

Source: https://weldering.com/holodnaya-gazovaya-svarka-chuguna

Cast iron welding technology

So, there are a number of reasons for the poor weldability of cast iron.

This includes heterogeneity of composition (inclusions of graphite, like carbon, make cast iron brittle and non-plastic), and uneven heating and cooling with high brittleness, which contribute to the formation of cracks in the weld or nearby metal, and gases leaving the bath, which contribute to the formation of pores, and silicon with other elements that oxidize, and then their oxides cover the weld pool, which leads to lack of penetration. Moreover, at temperatures above 750°C, cast iron becomes fluid, which makes it difficult to form a weld pool and seam due to the banal reason of leakage.

There are three technologies for welding cast iron:

1. Cast iron is supplied to the weld metal
2. high-carbon steel is supplied to the weld metal, and low-carbon steel is supplied to the last layers
3. the seam is filled with alloys of non-ferrous metals

Cast iron can be welded using electrodes, flux-cored wire and gas welding. Another technological subtlety is that the parts being welded can be “cold” or heated.

“Cold welding” is technologically simpler, however, in order for the seam to be of high quality, the electrode must be special, and its composition must be similar to the composition of the cast iron being welded. If heating is used during welding, then it should be slow (increase by 150° per hour), as well as subsequent cooling. Then, during hot welding, structural changes will not occur in cast iron, and cracks will not form during cooling.

Do not forget that cast iron begins to melt at 750°C, so the heating temperature should not exceed 650°C.

Cold welding of cast iron using electrodes with non-ferrous metals

In order to obtain seams that have high ductility even in a cold state, special electrodes made of nickel or copper are used in practice. These non-ferrous metals do not form compounds with carbon, but their presence in alloys is very effective in reducing the solubility of carbon in iron, and as a result, promotes graphitization.

Thus, when entering the zone of incomplete melting, which is adjacent to the seam, the likelihood of bleaching is reduced. Among other things, the plasticity that occurs in the weld metal helps to partially absorb welding stresses, and therefore the risk of cracks and pores appearing is significantly reduced. When welding cast iron, as a rule, both copper-iron and copper-nickel electrodes are used. There are several types of copper-iron electrodes.

Thus, there are electrodes with a copper rod, the braid of which is made of tin (with a thickness of 0.2-0.3 mm), which is wound onto the rod in the form of a tape (width 5-6 mm) in the helical direction. Also, ionizing coatings are applied to the electrode and pressed into a copper tube if these are electrodes with a combined wire. In addition, there is another version of such electrodes - they contain a copper core along with a steel shell.

There are other electrodes that consist of a bundle of electrodes with one or two copper rods and a steel core. The bundle is tied in 4-5 places using copper wire, and tacked at the end for reliable contact between the rods. The most advanced copper-iron electrodes are electrodes of the OZCh-1 brand. They are a copper rod (diameter about 3.5-5 mm), on which a special coating is applied.

This coating consists of a dry mixture of substances such as SSSI and iron powder. Welding with copper-iron electrodes is performed in such a way as to prevent severe overheating of the parts being welded. To do this, at low (as soon as possible) currents, they provide a stable arc and make short sections of it randomly, with some breaks, so that the parts being welded can cool.

The main advantage of such electrodes is the ability to forge metal that has been welded in a hot state in order to reduce the level of welding voltage . Therefore, forging is a mandatory step, since it reduces the risk of cracks.

Electrodes that are necessary for cold and semi-hot welding

During cold welding of cast iron, the use of simple electrodes is unacceptable, since in this process there is a high cooling rate of the product, as a result of which white cast iron is formed on the surface of the seam and in the heat-affected zone, and in addition, a sharp hardening of the cast iron and metal base occurs, which also detrimental to cast iron products.

Among other things, due to all of the above factors, significant surface deformation can occur, which in 99.9% of cases will lead to the formation of cracks. Therefore, in order to prevent cast iron from bleaching, it is necessary to make a weld composition that, under different conditions, will form a gray cast iron structure that is most favorable for welding.

This can be achieved by introducing a large number of graphitizers into the welding process, as well as through the influence of alloying elements that contribute to the spheroidization of carbide. For example, electrodes marked EMC, in which the rod is cast iron with a high silicon content (up to 5.3%) and also in which there is a two-layer coating, are ideal as such elements. One layer is an alloying layer, and the second provides gas protection.

The first layer consists of 40% graphite, 41% silicon-magnesium; it contains 14% iron scale and 5% aluminum powder. The second layer consists of 50% marble and 50% fluorspar. When welding cast iron using such electrodes, you do not have to heat the surface of the product if its thickness is up to 12 mm. This way it will not be subject to bleaching or hardening.

The use of such electrodes also helps to slow down the cooling rate somewhat due to the reaction that occurs between iron scale and aluminum powder. When using this type of welding, it is recommended to use heating at a temperature of 400°C. This welding method will already be called semi-hot .
However, if there is no heat source at hand, you can also use cold welding .

In order to improve and facilitate the processing of a ductile metal seam after welding, special electrodes are used, made of so-called nickel cast iron, which are niresist or nicrosilal. Thus, cold and semi-hot welding involves the use of special types of electrodes, since the use of conventional ones will simply make the welding process impossible.

Hot cast iron welding technology

Let's consider the technological process of hot welding, which is not as simple as it might seem at first glance. In fact, it consists of several stages, which include preparation and heating of products for welding, the immediate welding process and subsequent cooling of the product. So, let's take a closer look at all the processes.

Preparing a product for the welding process largely depends on what type of defect to be corrected is provided. But in any case, preparation is necessary to thoroughly clean the surface of contaminants and mark the cuts where cavities will form, which provide access and manipulation of the electrode and the effects of the welding arc.

To prevent leakage of liquid metal during welding, molding is often used at the welding site. It is performed depending on the size and location of the work area in which welding will be carried out. After molding, it is necessary to dry the mold at a low temperature - about 60 - 120 ° C, after which further heating is performed at a temperature of 120 - 150 ° C.

This can occur through the action of a burner or in special ovens or heating devices.

Looking ahead, we note that slow cooling after welding occurs due to covering the cast iron part with heat-insulating materials - using asbestos sheets or filling with sand, for example. Hot welding of cast iron is also possible using a carbon electrode. Carbon electrode welding is somewhat intermediate, between gas welding and welding with consumable electrodes.

Thus, when using carbon welding, the process takes place at a direct sequence current, and the diameter of the electrodes is 8‑20 mm. The diameter itself is selected depending on the value of the welding current and the thickness of the metal with which the welding will take place. Rods are used as filler materials.

Thus, hot welding of cast iron is by no means an easy job, but it is quite progressive and facilitates productivity, unlike other types of cast iron welding.

Source: https://kovkapro.com/svarka/osobennosti-holodnoy-polugoryachey-i-goryachey-svarki-chuguna/

Cold welding adhesive for cast iron

Cold welding glue will help connect metal surfaces without exposing them to high temperatures. Bonding occurs due to plastic deformation of the welding composition and its penetration deep into the surfaces.

Technical characteristics and composition

Cold welding adhesive can be one-component or two-component; in essence, it is an adhesive composition intended for metals.

Cold welding consists of several components:

• the base is epoxy resins, they give the composition the necessary plasticity and homogeneity;
• a metal component is used as a filler;
• Welding also includes sulfur and other substances.

It is the composition that determines what temperature conditions cold welding can withstand. Typically, all parameters are indicated on the packaging.

Types and manufacturers

There is a wide range of cold welding products available on the market. Depending on the consistency, the following types are distinguished:

1. Cold welding, reminiscent of ordinary plasticine. It looks like a two-layer or single-layer bar. Double layers are mixed before use.
2. Liquid cold welding is a two-component composition that is combined with a hardener before use. For example, epoxy contact glue.

Which glue to choose depends on its composition, so when choosing, you should take into account the manufacturer and purpose. A line of one brand may contain adhesives for different purposes:

• universal - suitable for gluing wooden and metal surfaces, polymer materials, are not durable;
• for metal products - include a metal filler and perfectly welds metals, often transparent in color;
• underwater welding;
• for car repairs - designed for gluing metal car parts.

Tip
Do not use glue intended for another material. The connection between the surfaces will not be strong, since this property is provided by the filler.

Cold welding adhesive from domestic manufacturers has a low price, but is not of high quality. The best Russian products are Almaz and Polymet. It is better to purchase foreign-made compounds, for example, WEICON, Hi-Gear, Poxipol, ABRO, Permatex, which are more expensive, but have proven themselves.

The higher the temperature indicated on the packaging, the better the glue. High-temperature compounds have increased strength compared to conventional ones for absolutely any use of products.

Methods of use

The popularity of cold welding is explained by the fact that its use does not involve working with special equipment and does not require special skills. To firmly glue two surfaces, just follow the instructions.

Before starting work you should prepare:

• acetone;
• clamps (may not be needed);
• cold welding adhesive;
• sandpaper.

The glue usually comes with instructions that describe how to apply the composition. If you do not follow the manufacturer's recommendations, the seam will be very fragile.

Tip
Before starting to work with glue, wet your hands with water. This will prevent it from sticking to your hands and disturbing the proportions of the components of the composition.

Cold welding application:

1. Clean the surfaces to be welded with sandpaper and degrease with acetone. The strength of the connection depends on how well the pre-treatment was carried out.
2. Apply glue to a perfectly dry surface; the rougher it is, the stronger the resulting seam.
3. Mix the solid two-component composition by kneading, like plasticine, and the liquid one - in accordance with the instructions indicated on the package. When mixing, the mixture warms up slightly, which is normal.
4. The working state of cold welding after mixing the components is maintained for a maximum of three minutes. For this reason, it should be applied as quickly as possible and mixed in small portions.
5. Secure the surfaces to be glued with clamps.

Manufacturers indicate in the instructions how long it will take for complete hardening. The seam can be puttied and painted. The drying time of cold welding depends on its composition and ranges from 60 minutes to eight hours.

Useful tips

Following the recommendations will help to connect surfaces as firmly and efficiently as possible:

1. Before starting work, ensure free access to the area to be repaired; this will make the task much easier.
2. Most often, cold welding is used to repair damage to radiators or heating batteries and to repair cars. A gas tank repaired in this way will still serve, but it will still have to be replaced.
3. To repair damage to radiators, choose only high-quality compounds that can withstand high temperatures and are designed for continuous contact with water (for example, epoxy “Contact”).
4. Cold welding will allow you to efficiently repair minor damage. Holes of significant size can only be sealed for a while. To eliminate large gaps, use a semi-automatic or inverter.
5. Such an adhesive composition is not suitable for repairing components that carry a large load.

Source: https://vi-pole.ru/klej-holodnaja-svarka-dlja-chuguna.html

Cold welding adhesive

“Cold welding” is called glue, the composition of which is characterized by high adhesion to any building materials undergoing repair. The glue can be putty if you add special steel powder to the usual traditional mixture.

The gluing mixture becomes so strong that it is compared to metal (steel) in strength. The mixture does not react to aggressive environments or elevated temperatures. Withstands up to 270ºС. The gluing procedure and the use of dry cold welding are easy and simple to work with. The mixture leaves no waste from production.

It can be used for repairing and restoring furniture, gluing mirrors, and plumbing fixtures.

If urgent repairs of water pipes are required, cold welding can be used. When working with glue, it creates a voluminous plug that gives an excellent result and closes all possible holes and cracks in water pipes. The plug and connection made by the cold welding method do not differ in quality from the cold welding method. The resulting item can be painted, threaded, or processed on a lathe.

The scope of use has practically no boundaries: repair of equipment, cars, restoration of furniture, repairing chips and cracks in plumbing items. Can be used as sealing containers, tanks, leveling defects on the surfaces of various objects.

Brands of popular adhesive mixtures: Almaz, Mastix, Poxipol. The production of glue involves compositions depending on the purpose of gluing. For plumbing repairs - one, metal - another, woodworking - a third. Universal mixtures have been created and offered by manufacturers. The following options can be offered:

• Mastix . Affordable and easy to use. It is recommended for use in repairs and sealing of joints. It makes it possible to work in rainy weather and low temperatures. Neither rain nor frost interfere with work. The composition is used for 30 minutes, it holds the parts together in 45 minutes. The optimal result is achieved at a temperature of +20ºС. After 2.5 hours, the seam can be subjected to additional processing. Before starting work, the surface is cleaned with sandpaper. Adhesive plasticine is easily removed from the work surface and does not stick to your hands. It is applied to both parts of the parts to be glued and is securely and firmly fixed to the bars.
• This composition is produced in Argentina. It is recognized as super durable. Two-component glue. The consistency is pasty. Does not require solvents. They are recommended to fill cracks and other voids. After preparing the mixture, the chemical bonding process begins within 10 minutes. The Argentine mixture is used under the influence of water; it glues complex, practically incompatible alloys: bronze, steel, copper, ceramics, steel (galvanized). Before starting work, the surface is degreased, cleaned and dried. This improves the adhesion of two surfaces, resulting in a strong, reliable seam that is almost invisible.
• Diamond. Manufacturers prepare it from polymers and add a discrete filler to the matrix. Glue connects ferrous and non-ferrous metals, wood, ceramics, marble, glass, granite, even concrete. The mixture has a high level of adhesion. It works even on oily and wet surfaces. They can eliminate radiator leaks, holes and cracks in radiators, pipes, and gasoline tanks. Even leaks that appear in inconvenient, hard-to-reach places can be easily closed with diamond. It can be used for home repairs.

Two-component “Cold Welding” adhesive is offered to the consumer in two small tubes:

• The first contains epoxy resin combined with a plasticizer and additional individual filler;
• The second is with a material that performs the task of a hardener.

Two tubes are needed to complement each other's action. Resin in its natural form is fragile in composition and does not withstand vibration, shock, physical and force stress. Supplementing it with a plasticizer is necessary to increase elasticity. The filler gives the composition special properties: thermal conductivity, heat resistance, abrasion resistance.

Depending on the tasks assigned to the glue, various metal powders are chosen as filler. This can be aluminum, steel, cast iron, minerals and artificial compounds. For the hardener , polyethylene polyamine or an amine component is most often used. The hardener reacts with the epoxy resin, based on its chemical properties, and a hardening process occurs. The technical characteristics of the glue depend on the composition of the components:

• Mechanical properties;
• Solidification period;
• Working temperature.

There are detailed instructions for the consumer for both glue and putty. It varies and depends on the brand and production features. Instructions for working with glue:

• The surface required for welding is cleaned, degreased, dirt, dust, oil, grease and other traces of impurities are removed.
• The mixture is prepared, and work is carried out in a room with ventilation and a working ventilation system. Eliminates the possibility of irritation to the eyes and nose.
• All proposed components are mixed in a pre-prepared container. The instructions explain the mixing volumes, most often they are equal parts, but there are also features. The ingredients are mixed until a homogeneous mass is obtained (equal in color and viscosity). The period of application depends on the temperature of the room where the work will be carried out and the manufacturer’s brand. Basically it is in the corridor between 10 minutes and an hour.
• Glue is applied to both surfaces to be joined. Then they are connected to each other.
• Excess composition, which is released after pressing, is removed with a dry cloth or a damp one (in a solvent).
• Strong pressure is not required; it is not recommended to use a press or other devices for pressure and pressure.
• The item is left at rest for the period prescribed in the instructions (from 5 minutes to 1 hour).
• After the initial hardening and checking the quality of the composition, the item is left until completely hardened. This period varies for different brands and manufacturers, lasting from 12 to 24 hours.
• Store the glue in a dry, ventilated working area, the optimal storage temperature is 25±10°C.

Quick Steel Rod or Putty

  The manufacturer produces them in the form of bars: a homogeneous or single-layer bar. Instructions for working with putty

• Before welding, the surface of the parts is thoroughly cleaned and degreased. It must be perfectly clean and dry. There should be no traces of oil or grease.
• Cut off the required amount from the glue stick.
• Wet your hands in water or wear protective gloves.
• The glue is stirred until a homogeneous and plastic mass is obtained. It will take approximately 3-5 minutes. When mixed, the glue heats up slightly. The time for using the composition ranges from 4 minutes to an hour. This is directly related to the temperature of the room and environment where the work is carried out, the thickness of the metal, the brand and manufacturer of the glue.
• Glue is applied to the surfaces of those parts that need to be connected. You can use a spatula to spread the glue over the entire surface, but it must first be moistened in clean water.
• The parts are left for the putty to harden. The parts must be in a static state, without the possibility of movement.
• The hardening time required for a particular metal is maintained.
• The seam is being sanded.
• If required, the product is painted.
• The item is stored in a dry place, the recommended temperature is 25+-10ºС.

  Recommendations for using welding:

1. You can only weld materials specified in the instructions for the product being offered;
2. Observe all conditions specified in the instructions: room temperature, environmental humidity, oil resistance, etc.
3. 3. Precisely use the required composition: it is recommended to use glue for joints and overlaps of flat parts; for T- and corner welding, putty is recommended for sealing gaps and cracks.  
4. To fill cracks that appear in a horizontal or vertical position, putty is preferred. But it is also possible to use an adhesive mixture. Then you will need a mesh of reinforcing steel or other metal and glass patches. When filling cracks, the ends of the parts are subject to mandatory drilling.

  To repair and correct impact marks (dents), regardless of their position, putty is preferred. Traces on horizontal surfaces can simply be filled with adhesive.

List of materials

Typically, glue is chosen for working with materials such as metal, cast iron, linoleum. Glue is divided into types:

• Liquids containing two ingredients. To prepare the glue, it is mixed with a special hardener.
• Plasticine. They look and have properties similar to a bar. Externally single-layer or double-layer. If there are two layers, then the existing layers are mixed before use.
• Universal adhesive masses. They are used for working with metal products, PVC, and wood.
• Special compositions that contain metal additives for strength.
• Compounds intended only for working with automotive parts.
• Compositions that allow you to work when there is a need to carry out welding work under water.

Working with metal

"Fast steel", which is used only for metal, consists of the following components:

• Epoxy resins. They make the mass plastic and homogeneous in structure;
• Metal filler;
• Special additives. They perform the necessary additional tasks and support functions;

We can conclude that welding for metal is a polymer with excellent adhesive properties. They easily make it possible to obtain a slight deformation of the adhesive composition, allowing partial penetration into the surface of the parts. The “Cold Welding” composition provides the required joint strength . But there are basic conditions for an excellent result:

•  compliance with the instructions for the correct use of the composition;
•  optimal and thorough preparation of material for welding.

However, it is most advisable to use the described adhesive mass for metal products when carrying out small work, rather than large parts.  

Welding with linoleum

"Cold welding" or "Fast steel" are allowed for welding with linoleum. They consist of the following substances: tetrahydrofuran; plasticizers; polyvinyl chloride The composition allows you to somewhat straighten the edges of the glued linoleum using the prepared mass. The main feature of this type of welding is the difference in its behavior during the work and in contact with different types and brands of linoleum. Manufacturers recommend three main types of adhesive components:

Type A glue

It is used when it is necessary to join the seams of a fairly hard material. The consistency of linoleum glue is characterized by significant fluidity. When working, you get a fairly thin, neat seam.

Type "C"

This cold steel is suitable for linoleum, which has been in use for a relatively long time, has a high degree of wear and is subject to cosmetic repairs. The consistency of the adhesive mixture is thicker than “A”. This determines the specifics and scope of its use. As a result of the work, the seam is filled. It fills the gap between the old strips of linoleum. A visible new strip of adhesive will form at the bonding site.  

Type "T" glue

This type is designed for cold welding of linoleum. The building material is made of PVC. Polyester is used. The composition of type T adhesive for linoleum is specified in the product modification. It is used more often by professionals and builders.

Working with cast iron

The “Cold Welding” adhesive composition is also suitable for repairing cast iron products. It is often used to solve everyday problems. It will help in the restoration of some defects that appear in the radiators of the heating system.

For cast iron, a universal composition or adhesive mass is suitable. It must have a metal component. Welding of cast iron products is used when it is necessary to repair small cracks and holes, and when oversized parts are successfully connected.

This approach is explained by the low strength of welding seams.

Source: https://svarkagid.com/klej-holodnaja-svarka/

Features and problems of welding cast iron: how to avoid cracks when the seam cools and achieve joint strength

Welding cast iron alloys is done using several methods. Each of them is chosen as a balance between the cost and complexity of the work and the strength required from the seam. This is caused by the physical characteristics of cast iron materials, which differ sharply from the vast majority of other alloys and metals.

Cast iron welding options and their brief characteristics

Depending on the strength requirements and the nature of damage to cast iron parts, one of several welding methods is used.

Hot welding

Hot welding is used in cases where it is necessary to obtain high machinability of the seam and the proximity of its composition and structure to the rest of the cast iron. The parts to be welded are prepared as described above and heated to a temperature of 700°C. If necessary, before heating, a mold is made from materials used in foundry. This is required for through and edge (chip) damage. Sanded surfaces and threads should be protected with clay.

Hot welding is used for products of large mass in cases where increased strength is required . Heat for the bath is obtained either from an electric arc or from a gas burner. Hot welding differs from other types in the largest volume of the bath (up to 0.5-1 cubic inch). This requires the workpieces to be installed only in the lower position.

Filler material for hot welding - cast iron electrodes of increased diameter (from 8 mm or more) or flux-cored wire.

Semi-hot welding

Semi-hot welding of cast iron is carried out similarly to the hot welding described above, but the preheating temperature here is lower, about 300-350°C. This helps to reduce the cooling rate of the metal after welding.

With semi-hot welding, the degree of “bleaching” of cast iron is less compared to the hot method, which also contributes to a lower risk of cracks. In addition, less energy is required to heat the parts.

Semi-hot welding is done with low-carbon steel electrodes with alloying additives or autogen, adding a cast iron rod for additive.

Basic methods of welding cast iron

Gray cast iron can be cooked in several ways. Most often this is arc welding with steel or special electrodes. These methods belong to the cold welding method.

Manual arc welding with consumable electrodes

The smallest damage to cast iron parts can be repaired with ordinary 3 mm steel electrodes with a thin coating. Before welding, the seams are cleaned and cracks are cut out or cut out. Welding is carried out with a small current of 80-120 amperes.

Damage	Electrodes	Additionally
Small	Steel	Forging a seam with a hammer
Average	Copper
Large	Copper and nickel	Reinforcement with studs

If it is necessary to improve the quality of the weld using the arc method, then an inverter is used instead of a transformer, since it allows operation on direct current. This gives you some additional features, listed in the table below.

Polarity	Detail	Electrode	Peculiarities
Straight	Plus	Minus	Increased heating of the part. Low consumption of electrodes
Reverse	Minus	Plus	Moderate heating of the part. High consumption of electrodes

The reason for this difference is in the physics of the process: the positive electrode is heavily bombarded with heavy negative ions, which provides additional energy in the overall balance of heat release. The difference in temperature can reach 700°C. In general, for the ability to avoid overheating of cast iron during electric arc welding, you have to pay a certain price: wasting extra electrodes.

The use of a transformer deprives the welder of the opportunity to warm up the electrodes in different ways, since with alternating current there is no such difference - heat is released equally at each end of the arc. In addition, the stability of the arc decreases - on alternating current it does not burn all the time.

To reduce overheating of the seam, move the electrode in a zigzag or in a circle, as is more convenient for the welder. The heat is distributed more evenly. It is also useful to divide large seams into smaller sections, and in between sections, allow the metal to cool to 80-50°C.

To improve the quality of the weld on cast iron, electrodes with the addition of copper, nickel or monel metal (an alloy of copper and nickel) are used. The simplest and cheapest option: steel wire Sv-08 (Sv-08A) is wrapped with copper wire and dipped into a solution of sodium silicate (liquid glass). After the coating has dried, you can cook it.

Gas welding

Gas or electricity for welding is just a method of heating and supplying energy to the weld pool. But due to the difference in the physics and chemistry of these processes, technological differences may appear.

When welding cast iron with gas, you can use acetylene or a propane-butane mixture, but both options use oxygen . Instead of an electrode, a nickel filler wire or a cast iron rod is used.

To avoid oxidation, you can coat the filler material with fluxes (borax-based), but often it is sufficient to use heating of the metal with the reducing part of the burner torch.

Use a torch to gradually heat the area around the weld. Only the experience of the welder will help determine the appropriate temperature in the weld area (200-350°C). Having achieved this, the area is welded. Then gradually remove the burner, avoiding sudden cooling. Of course, much more gas is consumed here than when welding steel, but this is inevitable when gas welding cast iron, otherwise cracks will develop.

Argon-arc

Argon arc welding of cast iron is possible, but it is too expensive an option and does not provide any particular advantages over other types of welding. Cast iron does not need as much protection from oxidation as, for example, aluminum. If you still have to cook cast iron with argon, then the same rules should be followed:

• avoid overheating the metal;
• gradually warm up the seam area;
• cool gradually after welding.

All this leads to a large consumption of argon. Therefore, it is better to use other methods for heating. Usually this is the same acetylene torch, which makes it pointless to cook with argon at all. When welding with argon, non-consumable electrodes or a semi-automatic machine are usually used. In the latter case, it will need to be charged with the desired type of wire, for example, nickel.

Other options

Among other options, you can supplement the section on hot welding. This method requires the highest energy consumption and preparation of molds for a large-volume weld pool.

After cleaning the place for the seam, partitions are made from refractory clay around this place (and if necessary) from below. Graphite plates are also used for molds. The outside of the mold is protected by a box made of sheet iron: this ensures that the bath will not spill.

Ovens are used to preheat and slowly cool parts (in the old days a fire was used for large parts).

When cold welding large parts, the metal is cut at an angle of 90 degrees, and short-length studs made of low-carbon steel are screwed into the cutting chamfers. The upper ends of the pins of both halves of the seam are also welded together with steel with a low carbon content. They give the seam significant strength. The seam on top is welded with copper or copper-nickel alloy.

Source: https://elsvarkin.ru/texnologiya/svarka-chuguna/