阅读说明：本技术 一种用于液氮储罐的304l焊接件的焊后热处理方法 (Postweld heat treatment method for 304L welding part of liquid nitrogen storage tank ) 是由 陈葵芬 于 2019-10-25 设计创作，主要内容包括：本发明提供了一种用于液氮储罐的304L焊接件的焊后热处理方法,其能用于液氮储罐304L材料的焊接件以消除残余应力,并且效果好。其包括以下步骤：a、将焊接件加热至570℃,升温速率为55-220℃/h,保温时间至少保证焊接件均匀热透；b、以55-280℃/h进行降温处理,当炉温低于400℃后将焊接件从炉中取出,在静止空气中冷却。(The invention provides a postweld heat treatment method for a 304L welding part of a liquid nitrogen storage tank, which can be used for the welding part of a 304L material of the liquid nitrogen storage tank to eliminate residual stress and has good effect. Which comprises the following steps: a. heating the welded part to 570 ℃, wherein the heating rate is 55-220 ℃/h, and the heat preservation time at least ensures that the welded part is uniformly and thoroughly heated; b. and (4) cooling at the temperature of 55-280 ℃/h, taking the welded piece out of the furnace when the furnace temperature is lower than 400 ℃, and cooling in static air.)

1. A postweld heat treatment method for a 304L welded part of a liquid nitrogen storage tank is characterized by comprising the following steps: which comprises the following steps: a. heating the welded part to 570 ℃, wherein the heating rate is 55-220 ℃/h, and the heat preservation time at least ensures that the welded part is uniformly and thoroughly heated; b. and (4) cooling at the temperature of 55-280 ℃/h, taking the welded piece out of the furnace when the furnace temperature is lower than 400 ℃, and cooling in static air.

2. The method of post-weld heat treatment of a 304L weldment for a liquid nitrogen storage tank as recited in claim 1 wherein: the temperature rise rate in the step a is 100 ℃/h, and the temperature reduction treatment is carried out at 100 ℃/h in the step b.

Technical Field

The invention relates to the technical field of postweld heat treatment, in particular to a postweld heat treatment method for a 304L welding part of a liquid nitrogen storage tank.

Background

Most of the compression elements and stress elements of the ultra-low carbon stainless steel liquid nitrogen storage tank work at the temperature of-196 ℃ and need to bear alternating stress, and the austenitic stainless steel welding joints in related standards at home and abroad are not required or are prohibited to adopt postweld heat treatment, so that stress relief heat treatment is preferably carried out on the compression element welding joints and the welding joints with higher requirements on dimensional stability, the structural precision and the dimensional stability of the elements are improved, and the service performance of the system is further improved. However, in the prior art, the postweld heat treatment method suitable for the welding part of the material 304L of the liquid nitrogen storage tank is difficult to find.

Disclosure of Invention

Aiming at the problem that the stress of a 304L material welding piece of a liquid nitrogen storage tank needs to be eliminated, the invention provides a post-welding heat treatment method for the 304L welding piece of the liquid nitrogen storage tank, which can be used for the welding piece of the 304L material of the liquid nitrogen storage tank to eliminate residual stress and has good effect.

The technical scheme is as follows: a post-weld heat treatment method for a 304L weld of a liquid nitrogen storage tank comprises the following steps: the method is characterized in that: which comprises the following steps: a. heating the welded part to 570 ℃, wherein the heating rate is 55-220 ℃/h, and the heat preservation time at least ensures that the welded part is uniformly and thoroughly heated; b. and (4) cooling at the temperature of 55-280 ℃/h, taking the welded piece out of the furnace when the furnace temperature is lower than 400 ℃, and cooling in static air.

Furthermore, the temperature rise rate in the step a is 100 ℃/h, and the temperature reduction treatment is carried out at 100 ℃/h in the step b.

After the postweld heat treatment is carried out on the welding part made of the liquid nitrogen storage tank 304L material by adopting the method, the metal structure of the welding seam is not changed, the generated precipitates are few, meanwhile, the impact toughness of the welding seam is maintained at a higher value, and the stress of the center part of the welding seam can be fully released, so that the structural precision and the dimensional stability of the welding joint are effectively improved.

Drawings

FIG. 1 is the golden phase diagram (1000 x) of the weld center of example 1;

FIG. 2 is the metallographic picture (1000X) of the weld line of example 1;

FIG. 3 is the golden phase diagram (1000 x) of the weld center of example 2;

FIG. 4 is the metallographic image (1000X) of the weld line of example 2;

FIG. 5 is the golden phase diagram (1000 x) of the weld center of example 3;

FIG. 6 is the metallographic image (1000X) of the weld line of example 3;

FIG. 7 is the golden phase diagram (1000 x) of the weld center of example 4;

FIG. 8 is the metallographic image (1000X) of the weld line of example 4;

FIG. 9 is the golden phase diagram (1000 x) of the weld center of example 5;

FIG. 10 is the metallographic image (1000X) of the weld line of example 5;

FIG. 11 is the golden phase diagram (1000 x) of the weld center of example 6;

FIG. 12 is the metallographic image (1000X) of the weld line of example 6;

FIG. 13 is a graph showing the results of hardness test in example 1;

FIG. 14 is a graph showing the results of hardness test in example 2;

FIG. 15 is a graph showing the results of hardness test in example 3;

FIG. 16 is a graph showing the results of hardness test in example 4;

FIG. 17 is a graph showing the results of hardness measurement in example 5;

FIG. 18 is a graph showing the results of hardness measurement in example 6.

Detailed Description

The following is illustrated by 6 examples, wherein the test panel material is 304L, the thickness is 16mm, and the dimensions are 150mm x 500mm, and the chemical composition and related properties are shown in table one below:

according to the WPS welding test plate, welding parameters are shown in the following table II: