When stainless steel is welded in multiple layers, how to choose the temperature between the layers,

The preheating of stainless steel multi-layer before welding and the control of interlayer temperature have a certain impact on reducing the formation of cracks. If the preheating temperature is too high, the cooling rate of the stainless steel multi-layer weld will be slowed down, which may cause the precipitation of carbides at the grain boundary of the welded joint and the formation of ferrite structure, which will greatly reduce the impact toughness of the joint. If the preheating temperature is too low, it will not play the role of preheating and cannot prevent the formation of cracks.

The preheating temperature and interlayer temperature of stainless steel multilayer welding with carbon steel should be controlled at 150 300.

The pre-welding preparation of stainless steel composite plate, the cutting of stainless steel multi-layer and the bevel processing should be made as much as possible by mechanical processing methods, the cutting surface should be smooth, and the composite layer should be facing upward when cutting with a shearing machine. Plasma cutting can also be used, and the lamination is facing upwards when cutting, and it is strictly forbidden to drop the cut slag on the lamination.

Stainless steel multi-layer processing and inspection, groove form and size according to the drawing design provisions, if the design is not clearly specified, can refer to the drawing for other options. The principle of groove selection: to ensure the welding quality with less filler metal, small fusion ratio, and easy to operate.

Beveling is generally made by mechanical methods. If plasma cutting, gas cutting and other methods are used to open the groove, the oxide layer on the surface of the composite must be removed. The finished groove should be visually inspected, and there should be no cracks and delamination, otherwise it should be repaired.

Before welding cleaning of stainless steel composite plate, mechanical methods and organic solvents should be applied to clean the surface within 20mm of the groove and its sides, and the oil, rust, metal scraps, oxide film and other dirt on the surface should be removed, and the anti-splash coating should be coated within 100mm of the groove from the groove.

The assembly of stainless steel composite plate should be based on the layer, and the amount of misalignment shall not be greater than one-half of the thickness of the layer, and not more than 2mm. Positioning welding should be welded to the base metal and use the same welding material as the welded base metal.

In order to prevent the crystal on one side of the stainless steel clad plate from being coarse, causing embrittlement and cracking, the following process measures should be taken: Small heat input, small welding current, and fast welding speed should be selected. Short arc welding is adopted, and the arc is slightly biased to the side of the carbon steel base metal, so that the heating of the two base metals is uniform and consistent.

Due to the need for multi-layer welding, the previous weld is cooled to 200 300 and the next weld is welded. Slow cooling is carried out after welding.

The difference between the preheating temperature and the temperature between the layers of the stainless steel composite plate needs to be treated separately.

What is the welding method? And what kind of material. It stands to reason that welding process qualification should be done.

The temperature between the weld layers depends on the welding method, the steel grade, and the maximum thickness of the steel at the weld. You can refer to the table of AWS: 2008 "Steel Structure Welding Code" to exempt the minimum preheating and inter-channel temperature assessment", the steel grades listed in this table are in the United States, and for domestic steel grades, you only need to find the corresponding or similar steel grades listed in the table to use this table.

It depends on the material of the base metal you are welding, and the thickness of the base metal. For example, the electrode is welded with 8mm thick stainless steel, V-shaped groove, two-layer welding, and the temperature between the layers should be controlled between 60 and 70, that is, you can approach it with your hands without feeling hot; The welding of heat-resistant steel 15crmo, the interlayer temperature is about 200 350.

You refer to the "Welder Handbook" and the "Welding Engineer's Handbook", and you will gain something.

Generally speaking, the interlayer temperature of the weld is controlled below 200-250.

The interlayer temperature of high-nickel alloy is 60 degrees, and austenitic stainless steel is generally controlled at about 150 degrees, or even lower, which mainly depends on the mass fraction of alloy steel.

Interlayer temperature is another name for inter-channel temperature. The inter-channel temperature is the instantaneous temperature of multiple welds and base metal before the next weld is applied, and is generally expressed as the highest value. The determination of the interlayer temperature value shall be subject to the qualified welding process.

When setting the interlayer temperature parameters in the welding process, it is necessary to fully consider the base metal material, wall thickness, heat input and other factors, you can refer to AWS and other standards, and set a reasonable temperature value in combination with the actual situation to ensure that the physical and chemical testing can pass the evaluation requirements. Finally, the qualified process is used to guide the product welding.

If the interlayer temperature is too high, the grain will be coarse in the heat-affected zone, which will reduce the strength of the weld and the low-temperature impact toughness. If it is below the preheating temperature, cracks may develop during the welding process. Therefore, it is stipulated that the temperature between the roads shall not be lower than the preheating temperature, and the maximum temperature shall not be greater than the temperature of a certain boundary.

For austenitic stainless steels, too high interlayer temperatures can cause the weld to overheat, resulting in a black weld bead.

For ordinary carbon steel, the interlayer temperature is required to be less than 250, and for ordinary austenitic stainless steel, it is less than 150 (some are even lower than 100, and generally required to be less than 120).

When manual welding: for materials that require preheating welding, when multi-layer welding is required, the interlayer temperature should be equal to or slightly higher than the preheating temperature, if the interlayer temperature is lower than the preheating temperature, the preheating should be reheated. Second, for austenitic stainless steel, a faster cooling rate is required, so it is necessary to control the lower interlayer temperature, that is, the welding of the subsequent weld is carried out when the front weld is cooled to a lower temperature.

The interlayer temperature generally refers to the maximum temperature of the weld bead during welding, and the interlayer temperature of different base metals is different, see what material you want to know.

There are upper and lower limits for interlayer temperature, and the lower limit is generally not lower than the preheating temperature of 3 N; y* k7 ^8 t1 s2 w

Low temperature will cause temperature internal stress in the weld, and at the same time, the cooling rate of the weld is large, which affects the microstructure transformation of the weld.

N8 a( K0 t- i i% high temperature will make the weld metal temperature in the molten pool larger, and at the same time, the base metal temperature in the heat-affected zone will be larger, and the weld metal grains will increase, which is easy to produce Wechsler structure. If the temperature of the heat-affected zone is too high, the coarse grain zone will become larger and the mechanical properties will deteriorate.

Abstract: When multi-layer multi-pass welding is carried out on weldments, when welding the rear weld, the lowest temperature of the front weld is called the interlayer temperature. 1. For materials that require preheating and welding, when multi-layer welding is required, the interlayer temperature should be equal to or slightly higher than the preheating temperature, and if the interlayer temperature is lower than the preheating temperature, the preheating should be reheated.

The intergranular corrosion of stainless steel is related to the heating temperature and heating time of the steel. The heating temperature of 1Cr18Ni9Ti stainless steel is 450 850, and this temperature range is called the "danger zone" or "sensitized temperature zone" for intergranular corrosion.

When stainless steel is welded, we generally control the temperature between layers below 150 degrees.

When welding, why should we control the interlayer temperature, mainly to control the generation of intergranular corrosion.

The interlayer temperature is mainly related to the steel grade, wall thickness, and heat input, and the welding method does not play a major role in this. To carry out a welding, it is necessary to have a qualified welding process, and the setting of the interlayer temperature value in the process should refer to the implemented standards and the actual production situation to ensure that the final physical and chemical testing meets the requirements. Generally, a numerical value will be given in the welding process card provided in the standard, and we can quote it directly; If not given, refer to the following values:

Carbon steel is generally required to be controlled at 200 250, if preheating is required, it is appropriate to be slightly higher than the preheating temperature, and stainless steel is generally required to be controlled below 100, or even below 60.

The interlayer temperature is not a fixed value, but is determined according to the different materials and the use and working environment of the final product, and whether there is post-weld heat treatment. The temperature between the SAW layers is 700-800°, and it is not easy to make the SAW reach this temperature in production, so some insulation measures should be taken. In addition, the same welding method adopts different processes, and the temperature between the layers is also different.

This requirement will only appear in the product technical documentation (e.g. WPS, etc.), and this requirement is only for this product.

What others say must be verified before being believed, and sometimes even what the teacher says is not necessarily right. But sometimes the teacher doesn't know if it's wrong, it's just because others say the same.

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308L welding wire should be used, so the use of 308 may cause the corrosion resistance of the weld to decrease, especially when the workpiece is corroded environment. If the environment is not very bad, then there is nothing wrong with He Zuolu.