How to weld low carbon steel?
Low carbon steel has low carbon content and good plasticity. It can be prepared into various forms of joints and components.
In the welding process, it is not easy to produce hardened structure.
The tendency to produce cracks is also very small, and it is not easy to produce pores. It is the best welding material.
Good welding joints can be obtained by using gas welding, manual arc welding, submerged arc automatic welding, gas shielded welding and other methods to weld low carbon steel.
When using gas welding, do not heat for a long time, otherwise the grains in the heat affected zone are easy to become larger.
When the joint stiffness is large and the surrounding temperature is low, the workpiece shall be preheated to 100 ~ 150 ℃ to avoid cracks.
How to weld medium carbon steel?
Due to the high carbon content of medium carbon steel, the weld and its heat affected zone are easy to produce hardened structure and cause cracks, so it should be preheated to about 300 ℃ before welding and slow cooling after welding.
It can be welded by gas welding, manual arc welding and gas shielded welding.
Welding materials shall be welding rods with good crack resistance such as junction 506 and junction 507.
How to weld aluminum and aluminum alloy?
Aluminum and aluminum alloys are particularly prone to produce oxide films with large and high melting point in welding.
This oxide film can also absorb a large amount of water.
Therefore, defects such as slag inclusion, poor fusion and pores are easy to occur in welding.
In addition, aluminum alloys are also prone to thermal cracks.
Gas welding or manual arc welding can be used for welding aluminum and aluminum alloy.
However, the heat of gas welding is not concentrated and the aluminum heat transfer is fast, so the production efficiency is low and the workpiece deformation is large.
It is rarely used except for thin plate.
At present, AC argon arc welding is widely used to weld aluminum and aluminum alloy, because it has concentrated heat, beautiful weld, small deformation, argon protection and can prevent slag inclusion and pores.
If aluminum is welded by manual arc welding, it is suitable for plates with a thickness of more than 4mm.
The grades of welding rods used are aluminum 109, aluminum 209 and aluminum 309.
They are all salt based electrodes with poor arc stabilization performance, so DC reverse power supply is required.
How to weld titanium and titanium alloys?
Titanium is a very active element. In liquid state and solid state above 600 ℃, it is very easy to interact with gases such as oxygen, nitrogen and hydrogen to generate harmful impurities and embrittle titanium.
Therefore, oxygen acetylene gas welding, manual arc welding or other gas shielded welding can not be used for titanium and titanium alloys, but argon arc welding, vacuum electron beam welding and contact welding can only be used.
Argon arc welding is used to weld the thin plate below 3mm.
The power supply is directly connected, and the purity of argon is not less than 99.98%.
The nozzle should be close to the workpiece as much as possible, the welding current should be small, and the welding speed should be fast.
Generally, low-temperature annealing treatment should be carried out after welding to improve the crystalline structure and eliminate the welding stress.
How to weld copper and copper alloys?
There are many difficulties in the welding of copper and copper alloys.
Because of their excellent thermal conductivity, they are easy to cause defects such as poor penetration and fusion.
After welding, the workpiece will produce large deformation, and cracks and a large number of pores are easy to occur in the weld and fusion area.
The mechanical properties of the joint, especially the plasticity and toughness, are lower than those of the base metal.
Gas welding can be used to weld red copper, but the efficiency is too low, the deformation is large, and it needs to be preheated to more than 400 ℃, and the working conditions are not good.
Manual arc welding can use copper 107 or copper 227 electrodes, the power supply is connected reversely with DC, the arc is kept as low as possible, and the straight-line round-trip strip transportation method is adopted to improve the weld formation.
Hammer the weld after welding to improve the weld quality.
If tungsten argon arc welding is adopted, high-quality welded joints can be obtained and the deformation of weldments can be reduced.
Wire 201 is used for welding wire. If purple copper wire T2 is used, flux 301 is also used.
The power supply adopts DC positive connection.
During welding, the workpiece and welding wire shall be carefully cleaned to reduce pores and slag inclusion.
Large current and high speed shall be adopted during welding.
Gas welding is commonly used to weld brass. Wire 221, wire 222 or wire 224 can be used as welding wire.
These welding wires contain silicon, tin, iron and other elements, which can reduce the burning loss of zinc in the molten pool.
Due to the low temperature of gas welding, the burning loss of zinc in brass can be reduced;
Using a slight oxidation flame to cover the surface of the molten pool with a layer of zinc oxide film can reduce the evaporation of zinc.
In addition, brass can also be welded by manual arc welding and argon tungsten arc welding.
What are the characteristics of ordinary low alloy steel welding?
Ordinary low alloy steel is commonly used in reproduction.
The main characteristic of this kind of steel welding is that the heat affected zone of the joint has a large tendency to harden, and the hydrogen content will lead to the cold crack of the joint.
With the increase of the strength grade of ordinary low alloy steel, the tendency of hardening and cold crack is greater.
What is the welding method of 16 manganese steel?
Alkaline electrodes such as junction 506 or junction 507 shall be selected for 16 manganese steel welding, and DC reverse connection shall be adopted.
When the structural crack tendency is small, acidic electrodes such as junction 502 or junction 503 can also be used, and the welding process is similar to that of low carbon steel;
When the weldment is rigid and the ambient temperature is lower than – 10 ℃, it needs to be heated before welding.
Satisfactory results can be obtained by manual arc welding, submerged arc welding or electroslag welding.
What is the welding method of No. 15 manganese vanadium and No. 15 manganese titanium steel?
Both 15 manganese vanadium and 15 manganese titanium belong to 40 kg ordinary low alloy steel.
The strength grade of the steel is improved due to the addition of some vanadium or titanium;
However, their weldability, welding materials and welding process are not much different from those of welded 16 manganese steel.
When automatic submerged arc welding is adopted, the welding wire can be used to weld 08 manganese high and 08 manganese 2 silicon, and satisfactory results can be obtained by cooperating with flux 431, flux 350 or flux 250.
How about the welding method of No. 18 Mn Mo Nb steel?
No. 18 manganese molybdenum niobium steel is a 50kg high-strength ordinary low-alloy steel, which is often used to manufacture important welding products such as high-pressure vessels and boiler drums.
Due to its high strength and high hardening tendency, local heating measures should be taken during spot welding.
Pay attention to drying the welding rod and cleaning the groove to prevent cold cracks caused by hydrogen.
Welding rods such as 607 are used for manual arc welding;
Automatic submerged arc welding adopts 08 manganese 2 molybdenum high welding wire, which can be welded with flux 250 or flux 350.