阅读说明：本技术 一种铬钼埋弧焊管的焊后热处理工艺 (Postweld heat treatment process of chromium-molybdenum submerged arc welded pipe ) 是由 李建朝 李样兵 赵国昌 李�杰 袁锦程 吴艳阳 龙杰 柳付芳 牛红星 尹卫江 侯 于 2019-08-19 设计创作，主要内容包括：本发明公开了一种铬钼埋弧焊管的焊后热处理工艺,所述焊后热处理工艺包括焊管预热、升温、保温、缓冷和冷却工序。本发明焊后热处理工艺创造性增加了前期预热工艺,结合铬钼焊管成分优化了升降温速率、总在炉时间、缓冷工艺等关键技术参数,焊后热处理后焊管焊接裂纹缺陷大幅减少,有效解决了铬钼焊管在实施焊接后容易在焊缝及热影响区产生热裂纹和延迟裂纹问题。本发明焊后热处理工艺处理后的铬钼焊管壁厚1/2处性能：平均屈服强度≥390MPa、平均抗拉强度520-570MPa,壁厚1/2处-20℃冲击功≥150J,焊管力学性能稳定、良好。(the invention discloses a postweld heat treatment process of a chromium-molybdenum submerged arc welded pipe, which comprises the working procedures of preheating, heating, heat preservation, slow cooling and cooling of the welded pipe. The postweld heat treatment process creatively increases the early preheating process, optimizes key technical parameters such as temperature rise and drop rate, total in-furnace time, slow cooling process and the like by combining the components of the chromium-molybdenum welded pipe, greatly reduces the welding crack defects of the welded pipe after postweld heat treatment, and effectively solves the problems that the chromium-molybdenum welded pipe is easy to generate heat cracks and delay cracks in a welding seam and a heat affected zone after welding. The performance of the chromium-molybdenum welded pipe treated by the postweld heat treatment process of the invention at the 1/2-part of the wall thickness is as follows: the average yield strength is more than or equal to 390MPa, the average tensile strength is 520-570MPa, the impact energy at the wall thickness of 1/2 ℃ below zero is more than or equal to 150J, and the mechanical property of the welded pipe is stable and good.)

1. The postweld heat treatment process of the chrome molybdenum submerged arc welded pipe is characterized by comprising the working procedures of preheating, heating, heat preservation, slow cooling and cooling of the welded pipe, and specifically comprises the following steps:

(1) preheating a welded pipe: the welding tube is put into a furnace at the temperature of 20-25 ℃, and is heated to the temperature of 300-350 ℃ at the heating rate of 30-150 ℃/h and is kept for 20-25 min;

(2) heating the welded pipe: after the preheating of the welding tube is finished, the welding tube is not taken out of the furnace, and the temperature is uniformly increased to 695-plus 705 ℃ at the temperature increase rate of 30-150 ℃/h;

(3) heat preservation of welded pipes: heating the welding pipe to 695-705 ℃, and keeping the temperature for 2-2 h8 min;

(4) Slow cooling of welded pipes: after the heat preservation is finished, slowly cooling to 300-400 ℃ at a slow cooling rate of 30-150 ℃/h at a constant speed;

(5) Repeating the heating, heat preservation and slow cooling processes of the steps (2), (3) and (4) for four times, wherein the total heat preservation time is 8-8 h32 min;

(6) cooling the welded pipe: after the heating, heat preservation and slow cooling processes are repeatedly executed for four times, the welded pipe is taken out of the furnace and is cooled to 20-25 ℃ in air.

2. the post-weld heat treatment process for a chrome molybdenum submerged arc welded pipe according to claim 1, wherein the wall thickness of the chrome molybdenum submerged arc welded pipe is 25.88-40.56 mm.

3. The post-weld heat treatment process for a chrome molybdenum submerged arc welded pipe according to claim 1, wherein in the chrome molybdenum submerged arc welded pipe: cr: 0.94 to 1.10%, Mo: 0.40-0.44%.

4. The post-weld heat treatment process for the chrome-molybdenum submerged arc welded pipe according to any one of claims 1 to 3, wherein the performance of the chrome-molybdenum submerged arc welded pipe after the post-weld heat treatment process at the wall thickness of 1/2 parts of the chrome-molybdenum steel pipe is as follows: the average yield strength is more than or equal to 390MPa, the average tensile strength is 520-570MPa, and the impact energy at the wall thickness of 1/2 ℃ below zero is more than or equal to 150J.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a postweld heat treatment process of a chromium-molybdenum submerged-arc welded pipe.

Background

the chrome molybdenum steel pipe has good obdurability matching, excellent welding performance and good forming performance, and is widely applied to the design and manufacture of auxiliary pipelines of key core equipment in petrochemical industry and coal chemical industry. However, with the rapid development of petrochemical and coal chemical industries in China, the technical requirements of users on the chromium-molybdenum steel pipe are higher and higher, and part of the requirements are even close to or reach the limit level of the steel.

The purpose of the heat treatment after welding of the chromium molybdenum steel pipe is generally to eliminate welding stress and reduce or avoid the generation of welding crack defects. Under the new situation, the conventional postweld heat treatment process of the chromium-molybdenum steel pipe is adopted, so that the phenomenon of incomplete elimination of welding stress of the chromium-molybdenum steel pipe after welding is easily caused, the unplanned rate (rejection rate) of welding pipe cracks is more than or equal to 4.5 percent, welding defects such as welding cracks and the like are caused, and great hidden danger is brought to equipment safety while economic loss is caused.

in order to meet the requirements of the development trend, optimization and innovation of the heat treatment process of the chromium-molybdenum steel pipe are urgently needed to solve the problems that the chromium-molybdenum welded pipe is easy to generate hot cracks and delayed cracks in a welding seam and a heat affected zone in the welding process.

disclosure of Invention

the invention aims to solve the technical problem of providing a postweld heat treatment process of a chromium-molybdenum submerged arc welded pipe. The welding crack defect of the postweld heat treatment process is greatly reduced, and the problems that the chromium-molybdenum welded pipe is easy to generate heat cracks and delay cracks in a welding seam and a heat affected zone in the welding process are effectively solved; meanwhile, the obtained chromium-molybdenum welded pipe has stable and good mechanical property.

in order to solve the technical problems, the invention adopts the technical scheme that: a postweld heat treatment process of a chromium-molybdenum submerged arc welded pipe comprises the working procedures of preheating, heating, heat preservation, slow cooling and cooling of the welded pipe, and specifically comprises the following steps:

(1) preheating a welded pipe: the welding tube is put into a furnace at the temperature of 20-25 ℃, and is heated to the temperature of 300-350 ℃ at the heating rate of 30-150 ℃/h and is kept for 20-25 min;

(2) heating the welded pipe: after the preheating of the welding tube is finished, the welding tube is not taken out of the furnace, and the temperature is uniformly increased to 695-plus 705 ℃ at the temperature increase rate of 30-150 ℃/h;

(3) Heat preservation of welded pipes: heating the welding pipe to 695-705 ℃, and keeping the temperature for 2-2 h8 min;

(4) Slow cooling of welded pipes: after the heat preservation is finished, slowly cooling to 300-400 ℃ at a slow cooling rate of 30-150 ℃/h at a constant speed;

(5) repeating the heating, heat preservation and slow cooling processes of the steps (2), (3) and (4) for four times, wherein the total heat preservation time is 8-8 h32 min;

(6) Cooling the welded pipe: after the heating, heat preservation and slow cooling processes are repeatedly executed for four times, the welded pipe is taken out of the furnace and is cooled to 20-25 ℃ in air.

The wall thickness of the chromium-molybdenum submerged arc welded pipe is 25.88-40.56 mm.

the invention relates to a chromium-molybdenum submerged arc welding pipe, which comprises the following components in percentage by weight: cr: 0.94 to 1.10%, Mo: 0.40-0.44%.

the performance of the chromium-molybdenum submerged arc welded pipe treated by the postweld heat treatment process at the position of 1/2 parts of the wall thickness of the chromium-molybdenum steel pipe is as follows: the average yield strength is more than or equal to 390MPa, the average tensile strength is 520-570MPa, and the impact energy at the wall thickness of 1/2 ℃ below zero is more than or equal to 150J.

adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. compared with the conventional heat treatment process, the postweld heat treatment process creatively increases the early preheating process, optimizes key technical parameters such as temperature rise and drop rate, total in-furnace time, slow cooling process and the like by combining the components of the chromium-molybdenum welded pipe, greatly reduces the welding crack defects of the welded pipe after the postweld heat treatment, ensures that the planned external rate of the welded pipe cracks is less than or equal to 1 percent, and effectively solves the problems of heat cracks and delayed cracks easily generated in a welding seam and a heat affected zone after the welding of the chromium-molybdenum welded pipe is implemented. 2. The performance of the chromium-molybdenum welded pipe treated by the postweld heat treatment process of the invention at the 1/2-part of the wall thickness is as follows: the average yield strength is more than or equal to 390MPa, the average tensile strength is 520-570MPa, the impact energy at the wall thickness of 1/2 ℃ below zero is more than or equal to 150J, and the mechanical property of the welded pipe is stable and good.

Detailed Description

the present invention will be described in further detail with reference to specific examples.