阅读说明：本技术 防止高碳当量真空特厚复合坯焊缝开裂的焊后加热工艺 (Postweld heating process for preventing high-carbon equivalent vacuum super-thick composite blank welding seam from cracking ) 是由 马成 金百刚 刘文飞 李超 韩旭 苏小利 鲁强 于 2019-09-06 设计创作，主要内容包括：本发明涉及一种防止高碳当量真空复合坯焊缝开裂的焊后加热工艺,所述特厚复合坯的碳当量为0.6％～1.8％,厚度≥500mm；焊后加热工艺包括：1)将真空电子束焊接后的特厚复合坯继续在真空室内缓冷1～3h,之后破空；2)将复合坯运至电阻加热炉分段加热；3)复合坯入室式炉加热,入炉前在复合坯的上表面覆盖一层普碳钢冷轧板,采取分段升温的加热方式加热。本发明通过对真空电子束焊接后的复合坯进行缓冷及多级加热,避免了复合坯焊后直接入炉加热轧制导致轧制过程出现裂纹的情况发生。(The invention relates to a postweld heating process for preventing a high-carbon-equivalent vacuum composite blank from cracking in a welding seam, wherein the carbon equivalent of an extra-thick composite blank is 0.6-1.8%, and the thickness of the extra-thick composite blank is more than or equal to 500 mm; the postweld heating process comprises: 1) continuously slowly cooling the extra-thick composite blank welded by the vacuum electron beam in a vacuum chamber for 1-3 hours, and then breaking the blank; 2) conveying the composite blank to a resistance heating furnace for segmented heating; 3) the composite blank is heated in a chamber furnace, a layer of plain carbon steel cold-rolled plate is covered on the upper surface of the composite blank before the composite blank is fed into the furnace, and the composite blank is heated in a heating mode of sectional temperature rise. According to the invention, by slowly cooling and heating the composite blank welded by the vacuum electron beam in multiple stages, the condition that cracks occur in the rolling process due to the fact that the composite blank is directly fed into a furnace for heating and rolling after being welded is avoided.)

1. the post-welding heating process for preventing the high-carbon equivalent vacuum super-thick composite blank from cracking is characterized in that the carbon equivalent of the super-thick composite blank is 0.6-1.8%, and the thickness is more than or equal to 500 mm; the postweld heating process comprises the following steps:

1) Continuously slowly cooling the ultra-thick composite blank welded by the vacuum electron beam in a vacuum chamber for 1-3 h, then breaking the blank, and taking out the composite blank;

2) conveying the composite blank to a resistance heating furnace, and heating for 0.8-1.2 hours at the temperature of 330-370 ℃ in sequence; heating for 1-1.5 h at 480-420 ℃; heating for 1-2 h at 570-630 ℃;

3) Taking out the composite blank from the resistance heating furnace, putting the composite blank into a chamber furnace for heating, and covering a layer of plain carbon steel cold-rolled plate with the thickness of 0.8-1.2 mm on the upper surface of the composite blank before the composite blank is put into the furnace; in a chamber furnace, the composite blank is heated by a sectional heating mode, the temperature is kept for 5-7 h at the temperature section below 700 ℃, 6-9 h at the temperature section of 700-1230 ℃, and the temperature is kept for 7-12 h at the soaking section of 1200 +/-20 ℃.

Technical Field

the invention relates to the technical field of metal composite plate production, in particular to a post-welding heating process for preventing a high-carbon equivalent vacuum super-thick composite blank welding seam from cracking.

Background

High carbon equivalent steels are very sensitive to the formation of cold cracks due to their greater tendency to quench and to form high carbon martensite. Meanwhile, the martensite structure formed in the welding heat affected zone has hard and brittle properties, which leads to great reduction in the plasticity and toughness of the joint. Therefore, the high carbon equivalent steel has extremely poor weldability, and is liable to hot cracking and cold cracking at the time of welding.

The common method of the current high-carbon steel welding is preheating before welding, heat preservation after welding, the methods are easy to realize under the conventional welding condition, but the vacuum electron beam welding is rarely adopted, and particularly, the method for welding the extra-thick steel plate with the thickness of more than or equal to 500mm by adopting the vacuum electron beam is not reported

The vacuum composite rolling technology is a novel method for producing the super-thick steel plate, compared with the traditional ingot casting, the method greatly improves the internal structure and the performance of the rolled product, solves the problem that the thickness of the produced super-thick steel plate is limited due to the limitation of the thickness of a continuous casting billet and the restriction of a reduction ratio, has wide rolled blanks, is beneficial to mass production, and can greatly improve the yield.

the electron beam welding equipment of the vacuum chamber does not have a heating function, and the prior published documents propose that the mode of preheating before welding is adopted to avoid the generation of welding cracks, but practice proves that the production requirements of high-carbon steel composite plates cannot be met only by preheating before welding, and although cracks are avoided in the welding process, the cracking phenomenon still occurs in the heating and rolling process.

disclosure of Invention

the invention provides a post-welding heating process for preventing a high-carbon equivalent vacuum ultra-thick composite blank from cracking, which avoids the cracking condition in the rolling process caused by directly entering a furnace for heating and rolling after the composite blank is welded by slowly cooling and heating in multiple stages for the composite blank welded by a vacuum electron beam.

In order to achieve the purpose, the invention adopts the following technical scheme:

The post-welding heating process for preventing the weld joint of the high-carbon equivalent vacuum super-thick composite blank from cracking comprises the following steps of (1) forming a super-thick composite blank with the carbon equivalent of 0.6-1.8% and the thickness of more than or equal to 500 mm; the postweld heating process comprises the following steps:

1) Continuously slowly cooling the ultra-thick composite blank welded by the vacuum electron beam in a vacuum chamber for 1-3 h, then breaking the blank, and taking out the composite blank;

2) conveying the composite blank to a resistance heating furnace, and heating for 0.8-1.2 hours at the temperature of 330-370 ℃ in sequence; heating for 1-1.5 h at 480-420 ℃; heating for 1-2 h at 570-630 ℃;

3) Taking out the composite blank from the resistance heating furnace, putting the composite blank into a chamber furnace for heating, and covering a layer of plain carbon steel cold-rolled plate with the thickness of 0.8-1.2 mm on the upper surface of the composite blank before the composite blank is put into the furnace; in a chamber furnace, the composite blank is heated by a sectional heating mode, the temperature is kept for 5-7 h at the temperature section below 700 ℃, 6-9 h at the temperature section of 700-1230 ℃, and the temperature is kept for 7-12 h at the soaking section of 1200 +/-20 ℃.

compared with the prior art, the invention has the beneficial effects that:

1) According to the invention, the composite blank welded by the vacuum electron beam is slowly cooled and heated in multiple stages, so that the occurrence of hot cracks of the high-carbon-equivalent composite plate blank after welding can be effectively avoided, and a practical technical support is provided for the production of the vacuum composite welded high-carbon-equivalent composite blank;

2) The upper surface of the composite blank is covered with a layer of plain carbon steel cold-rolled plate before the composite blank is heated in a chamber furnace, so that the iron scale generated by directly heating the top of the composite blank can be avoided, the step of surface descaling is omitted, and the phenomenon of slipping caused by surface descaling in the rolling process of the composite blank can be avoided.

Detailed Description

according to the post-welding heating process for preventing the high-carbon-equivalent vacuum super-thick composite blank from cracking in welding seams, the carbon equivalent of the super-thick composite blank is 0.6-1.8%, and the thickness of the super-thick composite blank is more than or equal to 500 mm; the postweld heating process comprises the following steps:

1) Continuously slowly cooling the ultra-thick composite blank welded by the vacuum electron beam in a vacuum chamber for 1-3 h, then breaking the blank, and taking out the composite blank;

2) Conveying the composite blank to a resistance heating furnace, and heating for 0.8-1.2 hours at the temperature of 330-370 ℃ in sequence; heating for 1-1.5 h at 480-420 ℃; heating for 1-2 h at 570-630 ℃;

3) Taking out the composite blank from the resistance heating furnace, putting the composite blank into a chamber furnace for heating, and covering a layer of plain carbon steel cold-rolled plate with the thickness of 0.8-1.2 mm on the upper surface of the composite blank before the composite blank is put into the furnace; in a chamber furnace, the composite blank is heated by a sectional heating mode, the temperature is kept for 5-7 h at the temperature section below 700 ℃, 6-9 h at the temperature section of 700-1230 ℃, and the temperature is kept for 7-12 h at the soaking section of 1200 +/-20 ℃.

the following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.