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Method used for local postweld heat treatment of large-size steel casting after rewelding

A post-heat treatment and partial welding technology, which is applied in heat treatment furnaces, heat treatment equipment, furnace types, etc., can solve problems such as unsafety, limited application range, and limited shape and specification of sheet resistance heating blankets, and achieves simple operation and unique process methods Effect

Inactive Publication Date: 2012-11-28
KOCEL GROUP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, its application range is limited. The resistance heating wire is energized and heated, and then the heat is transferred to the casting. The electric heating loss is very large, so the thermal efficiency is also low, the power factor is low, the heating speed is slow, and the heating treatment time is long; In order to make the small The temperature of the welding defect part meets the process requirements, the area of ​​the electric blanket laid is large, and the heating area of ​​the casting is large, especially for the casting with a thick wall, which wastes electricity; in addition, the shape and specification of the sheet resistance heating blanket is limited, and it cannot be bent significantly , the resistance wire is fragile, easy to connect to electricity, unsafe
[0006] There is currently no way to overcome the above drawbacks

Method used

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Examples

Experimental program
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Effect test

Embodiment 1

[0015] Embodiment 1: For the material of low carbon steel, the hardness of the third welding zone after the final heat treatment is required to reach 160-200HB. After the defects are repaired by welding, the hardness is controlled at 180-240HB, and local induction post-weld heat treatment can be carried out if this requirement is met. The specific process parameters of induction heat treatment are heating and cooling speed of 10-20 ℃ / min, holding time of 1-4 hours, holding temperature of 580-630 ℃, final hardness after heat treatment of 160-190HB, three-zone hardness and NDT testing, all meet the requirements.

Embodiment 2

[0016] Embodiment 2: For CrMo(V) low-alloy steel material, the hardness of the third welding zone after the final heat treatment is required to reach ≤240HB. After the defects are repaired by welding, the hardness is controlled at 280-340HB, and local induction post-weld heat treatment can be carried out if this requirement is met. Specific process parameters of induction heat treatment The temperature rise and fall speed is 10-20°C / min, the holding time is 1-4h, the holding temperature is 660-720°C, and the final hardness after heat treatment is 150-220HB. Three-zone hardness and NDT testing, all meet the requirements.

Embodiment 3

[0017] Embodiment 3: For the material of CrNi(Mo) martensitic stainless steel, the hardness of the third welding zone after the final heat treatment is required to reach 220-320HB. After the defects are repaired by welding, the hardness is controlled at 240~360HB, and local induction post-weld heat treatment can be carried out if this requirement is met. Specific process parameters of induction heat treatment The heating and cooling speed is 10-20°C / min, the holding time is 1-4h, the holding temperature is 580-630°C, and the final hardness after heat treatment is 240-310HB. Three-zone hardness and NDT testing, all meet the requirements.

[0018] The above-mentioned heat preservation temperature is the normal post-weld heat treatment temperature + 20 ~ 40 ℃, and the heating depth is 30 ~ 100mm. The choice of heat preservation time is mainly based on the comprehensive consideration of the depth of the defect, that is, 2min / mm and the wall thickness. The heat preservation tempera...

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Abstract

The invention relates to a method of a local postweld heat treatment of a steel casting, and particularly relates to a method used for a local postweld heat treatment of a large-size steel casting after rewelding. The method comprises the following steps of: firstly, carrying out hardness detection on a welding zone after rewelding, wherein the hardness does not exceed 40-60 HB (heavy barrel) of a standard requirement maximally; carrying out an induction heat treatment, wherein the specific processing parameter of the induction heat treatment is that the lifting temperature speed is 10-20 DEG C / min, the holding time is 1-4 hours, the holding temperature is +20-40 DEG C of normal postweld heat treatment temperature, and the heating depth is 30-100 mm; and carrying out hardness detection and NDT detection on a welding meat region, a welding seam region and a base material of a treatment defect after induction heat treatment, wherein after the detection results meet the requirement, the local postweld heat treatment is finished. The method provided by the invention has the advantages that the technological method is unique, the operation is simple, the method is suitable for the large-size steel casting and can improve a local postweld heat treatment effect, the product quality is guaranteed and the production efficiency is improved, and the cost is reduced.

Description

technical field [0001] The invention relates to a method for local post-weld heat treatment of steel castings, in particular to a method for local post-weld heat treatment of large-scale steel castings after welding repairs for defects. Background technique [0002] At present, welding repairs for defects in large-scale steel castings, such as steel castings for steam turbines, gas turbines, hydropower, and nuclear power plants, most customers require that welding repairs should not be performed after the final post-weld heat treatment, otherwise it needs to be put into the furnace before the overall welding Heat treatment, especially for parts with large amount of welding repair or serious defects. However, for the welding repairs of a small number of small defects that have been fully inspected by NDT and found after the final post-weld heat treatment, if they are put into the furnace for overall post-weld heat treatment, some side effects will also be brought about. For ...

Claims

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Application Information

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IPC IPC(8): C21D9/50B23P6/00
Inventor 马进何建民张俊勇李文辉李永新李成志张宏凯罗永建姚加利杨翔
Owner KOCEL GROUP
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