Post-welding Heat Treatment Tips (FAQ)

author: YITECH

2025-01-19

Heat treatments are commonly used to improve the strength, ductility, and other mechanical properties of metals by altering their microstructure through heating and cooling processes. Today we will learn something about post-welding heat treatment tips:

1. The pressure vessel is segmented for post-welding heat treatment, and what is the length of repeated heating?

Pressure vessel after welding heat treatment, when the stage heat treatment is taken, the repeated heating length is not less than 1500mm, and the external vessel part of the furnace should be insulated to avoid excessive temperature gradient.

2. Under what conditions to use local heat treatment?

Local post-welding heat treatment can be used in the following cases:
(1) Class B welds, Class A welds with spherical head connected to the cylinder, and defect repair welds;
(2) Annular welds of high-pressure ultra-thick seamless steel pipes;
(3) Girth weld of 10MoWVNb high pressure hydrogen resistant seamless steel pipe.

3. What is the width of the local heat treatment heating of the ring joint?

The width of the heating belt is the smallest on each side of the widest weld, which is twice the nominal thickness of the base material. The shell close to the heating belt should be equipped with a heating belt to reduce the temperature gradient without affecting the organization and performance of the material.

4. Why normalize after electroslag welding?

Because the electroslag welding is a one-time welding, the required heat is large, the weld forms a coarse columnar crystal, and the mechanical properties are poor, especially the impact work is significantly reduced, so the normalization treatment should be carried out after welding to achieve the purpose of restoring mechanical properties and eliminating residual stress.

5. What is the maximum temperature difference of the whole container during post-welding heat treatment?

When the container is subjected to post-welding heat treatment in the furnace, the flame should not be directly radiated to the container to avoid local overheating of the container. During the treatment process, the container should be evenly heated, during the heat preservation period, the temperature of the whole container and the specified temperature deviation shall not exceed 25°C, the thermometer should be connected to the workpiece, the thermometer is distributed in the container top, middle, bottom and the structure of the discontinuous and rigid place or the temperature is prone to change.

6. Whether to heat treatment after surfacing the pressure elements of the container?

The thickness of the heat treatment after welding should be the thickness of the base layer.

7. How much deformation rate of cold formed pipe should be heat treated?

After cold bending, the deformation rate of the steel pipe should be heat treated when it exceeds the following range:
(1) The deformation rate of the outer fiber after bending of the steel pipe of carbon steel and low alloy steel should not be greater than half of the elongation of the steel pipe standard, or the remaining elongation of the outer material should not be less than 10%;
(2) For steel pipes with impact toughness requirements, the maximum deformation rate should not be greater than 5%.

8. Pressure vessel forgings after repair welding must be heat treatment?

What are the regulations? Post-welding heat treatment should be done if the forgings meet any of the following after repair welding:
(1) The forging material of any thickness must be subjected to post-welding heat treatment;
(2) The welding depth is greater than 6mm or the area of a single welding area is greater than 3750mm.

9. What are the requirements for post-welding heat treatment of containers made of quenched and tempered steel plates?

According to the engineering standards of foreign engineering companies, the temperature of post-welding heat treatment of quenched and tempered steel containers should be 28 ° C lower than the tempering temperature, mainly to avoid strength reduction.

DongGuan YiTai Electronic Technologies Co.,Ltd

DongGuan YiTai Electronic Technologies Co.,Ltd is a manufacturing service provider located in Dongguan, China.

YiTai specialized in CNC turning machining and sheet metal fabrication mainly. As a member of Hung Mou Group, we focus on the overseas marketing development. And based on our parent company’s manufacturing capability and resources, YiTai also expended machining services such as die casting, injection molding, aluminum profile extrusion, 3D printing, which are committed to providing customers with one-stop purchasing services and experience.

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