How to solve the problem of weld cracking when welding carburizing heat treated steel parts with 45

In this way, since it is a crack in the weld, you can choose a low-alloy high-strength steel alkaline wire and add elements of deterioration treatment to reduce the heat input. In terms of stress, try to improve the structure, pay attention to the welding sequence, and tell me about the on-site welding situation, which can be followed up.

The steel that has been carburized and heat treated is generally low-alloy steel, while 45 steel is medium-carbon steel, so the weld belongs to the welding of dissimilar steel, and the weldability is poor, and it is easy to produce cracks during welding, especially cold cracks. Main measures: use J507 electrode or J506 electrode, preheating measures are used before welding, the preheating temperature is greater than 250°, and the fusion ratio is reduced during welding, that is, short-track, multi-layer and multi-pass welding are used.

It is best to place the weldment in a vertical or semi-vertical welding position, with the electrode swinging horizontally slightly. The weld is subjected to repeated heating for a short period of time from start to finish. Achieve the effect of preheating or heat preservation.

After welding, 600-650° stress relief heat treatment is carried out.

Sandwich cracks appeared in the steel plate during welding19935

Sandwich cracks in the steel plate during welding 19935: the interlayer cracks in the steel plate during welding are because the steel plate material has high carbon content, the welding rod is not selected in the wrong grade, there is no preheating treatment before welding, and there are many reasons for the cracking of the steel plate after welding, mainly because the steel plate material has high carbon content, the welding rod is not selected in the right grade, there is no preheating treatment before welding, and there is no insulation after welding, which are the reasons for the cracking of the steel plate. Before the steel plate is welded, the material must be inspected, and when the material is determined, the welding plan can be formulated.

Gas cutting heating can reduce the influence of moisture inside the steel on the welding quality, and at the same time, it can avoid cracks in the welding part caused by rapid cooling, and the method is correct. What is the way of heat treatment before welding, it is estimated that it has little impact on the welding performance, and the C content has a great impact on the welding performance of the steel.

One. 40cr weldability:

It is easy to segregate during crystallization, and is sensitive to crystallization cracks (a kind of hot cracking), and it is easy to crack the concave part of the arc pit and weld during welding.

The carbon content is high, and it is easy to obtain a hardened structure (martensitic structure) that is sensitive to cold cracks when it is cooled quickly.

When the cooling rate of the superheating zone is large, it is easy to form a hard and brittle high-carbon martensite and make the superheating zone embrittle.

Two. Key points of steel welding process:

1. Welding is generally carried out in the annealed (normalized) state.

2. The welding method is not restricted.

3. Use a large line energy to appropriately increase the preheating temperature, and the general preheating temperature and interlayer temperature can be controlled between 250 and 300.

4. The welding material should ensure that the composition of the deposited metal is basically the same as that of the base metal, such as J107 CR

5. Quenching and tempering heat treatment should be carried out in time after welding. If it is difficult to quench and temper in time, intermediate annealing or holding at a temperature higher than preheating for a period of time can be performed to exclude diffused hydrogen and soften the tissue.

For products with complex structure and many welds, an intermediate annealing can be carried out after a certain number of welds have been welded.

The heating temperature is too high, and the heating with gas cutting is a sudden heat, and it is easy to produce water vapor and cause pores, and the current air temperature should be cooled slowly.

The cooling method is wrong, isn't it getting cold fast?

Cracking after heat treatment is a very complex thing, and there are many reasons that cannot be described one by one, and the following possibilities are provided according to your description:

1. First of all, see if the material of your workpiece is the same as the material of the welding rod, if the material is not the same, the thermal expansion coefficient of the material during the heat treatment process is not the same, which will lead to cracks.

2. If the material is the same, how about the welding process? The level of welding process is not high, and there will be pores, inclusions, and microcracks during the welding process, which will also lead to cracks in the heat treatment process.

3. See if the welded structure is the same as the matrix structure, if not, it will lead to cracks.

4. Is annealing carried out after welding? If there is no annealing, the thermal stress and microstructure stress of the weld heating part will lead to the formation of cracks in the heat treatment.

5. Is the temperature increase too fast during the heating process of heat treatment? If it is too fast, it will lead to the formation of cracks.

6. The most troublesome question is what do you mean by "heat treatment"? Normalizing? Spheroidized annealing?

Fully annealed? Stress relief annealing? Recrystallization annealing?

Dehydrogenated annealing? Diffusion annealing? Single-media quenching?

Dual-media quenching? Grading quenching? Isothermal quenching?

Tempering? Carburizing? Nitriding treatment?

……You don't know what's going on, it's really hard to answer, it's like asking, "I fell on my heel and got a headache?" "The same, you first have to tell the doctor if you fell on the head, fell to that part, fell on the head, whether there is a history of headache, what kind of pain method is, except for the headache ** shouting pain ......and so on, the doctor takes a photograph, does CT, B-ultrasound, and then can make a correct judgment.

For 20crmo forgings, it is recommended to use wewelding600 alloy steel electrode welding with good crack resistance for welding, and if it is wewelding600tig argon arc welding wire for argon arc welding.

Characteristics of wewelding600 alloy steel electrode.

Wewelding 600 alloy steel electrode (referred to as Weodin 600 electrode) is a kind of low heat output, suitable for all-round welding of special nickel-chromium alloy steel electrode, extremely versatile, high-strength general base metal strength design, with excellent welding process performance, arc stability, uniform and beautiful weld, in the presence of oil, water and rust conditions can also be excellent welding effect, can weld different steels.

Application of WeWelding600 alloy steel electrode.

It is suitable for welding tools and molds, high-speed tool steels, hot work tool steels, manganese steels, cast steels, T-1 steels, seismic steels, vanadium-molybdenum steels, spring steels, martensitic stainless steels, austenitic stainless steels, ferritic stainless steels, unknown steels, and welding between various types of steels. For example, it is used for high-pressure valves, the removal of broken bolts, the modification of shafts, etc., and the effect is very ideal.

Technical parameters of WeWelding600 alloy steel electrode.

Tensile strength: 125,000 psi (862MPa).

Yield Strength: 90,000 psi (620MPa).

Elongation: 35%.

Hardness after welding: HRC23 (HRC47 after work hardening).

Power selection: AC and DC dual-purpose, DC reverse connection when DC.

Process parameters of wewelding600 alloy steel electrode.

Diameter (mm).

Current (amps): 40-80, 65-120, 90-150

Package Weight (lbs) 2 2 2

The applicable process of wewelding600 alloy steel electrode.

1. Wewelding 600 alloy steel electrode (referred to as Weodin 600 electrode) has a very favorable thermal expansion and cold contraction rate, which can minimize cracks and distortion.

2. When welding crack-sensitive case-hardened metals, low-layer welds are an ideal choice.

3. Bevel cut heavy parts to form a 90-degree V-shaped groove.

4. Preheat 200 before welding high-carbon steel; When welding spring steel, the welding temperature should be controlled to prevent the spring from softening.

5. Maintain a short arc length and use a narrow weld bead to prevent overheating.

6. Before removing the slag, let the welding part cool.

Cracks that occur in sharp concave and convex corners, edges of holes, markings, stamping, and surface defects caused by machining are mostly quenching cracks.

If the crack section is white or dark white or light red (water rust caused by water quenching), it can be judged as a quenching crack, if the crack section is dark brown, or even oxygen scale, it is not a quenching crack, it is a crack that exists before quenching, and it is a crack formed when the parts are forged or calendered, and these cracks will be expanded due to quenching.

Because quenching cracks are basically formed below the ms point, their cross-sections will not be oxidized.

If the forging is medium carbon steel or high carbon steel, it may be a cold crack caused by a large hardening tendency; If the heat treatment is quenching, it may be a thermal stress crack caused by large shrinkage stress. Welding rods with good plasticity, such as stainless steel electrodes, should be selected.

Specific measures to avoid microcracks in welded welds of medium carbon alloy steel:

1. Determine a reasonable welding process and weld by skilled welders.

2. The welding of medium carbon alloy steel should be preheated before welding, and the wind barrier should be built during open-air welding, and the temperature between the welding layers should be kept stable, and the asbestos should be wrapped for thermal insulation treatment after welding.

3. Select the welding rod corresponding to the weldment material, generally use the low-hydrogen electrode with good welding performance, and the welding power supply adopts DC reverse connection.

4. Select the appropriate welding current and welding speed.

In general, if you do all of the above, there will be no weld cracks.

In general, the key to the welding of medium carbon alloy steels is to clean up and preheat before welding, as well as to maintain the temperature between the layers and post-heat treatment. This depends on the grade of your material. After the crack appears, all the cracks must be removed before repair welding, and it is generally necessary to confirm with the help of PT or MT The removal of cracks should be carried out by grinding, and the use of carbon arc gouging should be avoided as much as possible.

Preheating is also required before repair welding.