Features gas welding ferrous metals

The process gas welding iron has a number of features. That will be rasskazno below. Gas welding alloy steels
Possibility of gas welding for joining alloy steels, which are composed of chromium, nickel, molybdenum, titanium, and other elements, depending on the characteristics of the chemical composition of a particular type of steel.

High-chromium steel
Expose this steel gas welding is not recommended at all, since prolonged heat exposure during welding will be the emergence of numerous grains due to high content of chromium - more than 15%.

Chrome steel
It is clear that during the gas welding of grain growth will not be as specified steel contains in its composition is much less chromium than high-chromium. However, chromium steel-welded rapidly quenched in air, and that always leads to cracking. To prevent this negative process can only be this: make slow cooling suture connection. To do this, at the end of weld metal should continue to heat the burner flame near the weld zone of 30-40 mm from it.
Thus, gas welding is applicable in principle to join chromium steel, but only with careful observance of the thermal regime.
Nickel steel can be subjected to welding, acetylene, but be sure to use the special fluxes. In addition, the thickness of the weld metal shall not be more than 1 - 2 mm, and a subsequent heat treatment it is essential.
Note that in strict compliance with the above conditions the mechanical characteristics of the suture connections will be much worse than that of the base metal. To ensure a high quality weld, welding electrodes should be performed only with special coatings.
To remember that the use of gas substitutes for acetylene gas welding the steel out of the question.
For high-quality connection to use chromium-nickel steel TIG welding, as results are robust and reliable joints.
Molybdenum steel, like chrome steel, tends to quenching in air at temperatures below 0 ° C. Therefore, at the end of gas welding is necessary to heat treatment in order to slow the cooling weld. In addition, the said steel welding should be done only after the metal has to be heated to a temperature of 250-300 ° C.
Specified condition is particularly important when welding metal thickness over 10 mm, and welding in freezing temperatures.

Chromium-molybdenum steel
It can be put in gas welding, subject to certain conditions.

Gas welding of carbon steels
Must hasten to note that when working with high-carbon steel should only be surfacing or soldering; gas welding can be used.
For low and medium carbon steel is possible to use gas welding, the effectiveness of which in terms of the strength of the seam will be higher, the lower the carbon content of the steel. Thus, a very good weldability is a mild steel welding characteristics of which are described below.
Mild steel is exposed without using gas welding fluxes, this results in the joints with good mechanical parameters. The working gas, use a mixture of acetylene and oxygen. Immediately after welding to produce forging seam at a cherry-red glow.
Then, slowly cooked cool design. When welding of mild steel can be used additives with less carbon than in the base metal. This is in order to prevent the appearance of porosity. The above technological features are assigned to work with sheets or details of up to 5 mm thick.
When working with metal thickness greater than 5 mm are best used arc welding using a consumable electrode, which can operate in an environment of carbon dioxide.
It should be noted that the mechanical weld quality will be worse in the case instead of acetylene-oxygen mixture will be used as fuel gas propane, butane or natural gas.
Medium carbon steel is characterized by the fact that after welding may appear a strong possibility of cracking, as specified steel as well as chromium and molybdenum, has a tendency to air-quenched.
So after welding necessarily need to spend a slow cooling of the joint. Receive a quality weld can only be used as a fuel gas
oxyacetylene, the use of substitute gases is possible.
However, the use of oxyacetylene does not allow you to perform high-quality seam welding steels with a carbon content of more than 0.4%. To improve the quality of suture connections should use arc welding.
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