Introduction to the production process of large-diameter straight seam welded pipes in the country.
2014-09-16
国内大口径直缝焊管生产工艺介绍
直缝焊管是用钢板或钢带经过弯曲成型，然后经焊接制成。按焊缝形式分为直缝焊管和螺旋焊管。按用途又分为一般焊管、镀锌焊管、吹氧焊管、电线套管、公制焊管、托辊管、深井泵管、汽车用管、变压器管、电焊薄壁管、电焊异型管和螺旋焊管。
一、大口径直缝焊管主要生产流程说明：
1. 板探：用来制造大口径埋弧焊直缝钢管的钢板进入生产线后，首先进行全板超声波检验;
2. 铣边：通过铣边机对钢板两边缘进行双面铣削，使之达到要求的板宽、板边平行度和坡口形状;
3. 预弯边：利用预弯机进行板边预弯，使板边具有符合要求的曲率;
4. 成型：在JCO成型机上首先将预弯后的钢板的一半经过多次步进冲压，压成"J"形，再将钢板的另一半同样弯曲，压成"C"形，最后形成开口的"O"形
5. 预焊：使成型后的直缝焊钢管合缝并采用气体保护焊(MAG)进行连续焊接;
6. 内焊：采用纵列多丝埋弧焊(最多可为四丝)在直缝钢管内侧进行焊接;
7. 外焊：采用纵列多丝埋弧焊在直缝埋弧焊钢管外侧进行焊接;
8. 超声波检验Ⅰ：对直缝焊钢管内外焊缝及焊缝两侧母材进行100%的检查;
9. X射线检查Ⅰ：对内外焊缝进行100%的X射线工业电视检查，采用图象处理系统以保证探伤的灵敏度;
10. 扩径：对埋弧焊直缝钢管全长进行扩径以提高钢管的尺寸精度，并改善钢管内应力的分布状态;
11. 水压试验：在水压试验机上对扩径后的钢管进行逐根检验以保证钢管达到标准要求的试验压力，该机具有自动记录和储存功能;
12. 倒棱：将检验合格后的钢管进行管端加工，达到要求的管端坡口尺寸;
13. 超声波检验Ⅱ：再次逐根进行超声波检验以检查直缝焊钢管在扩径、水压后可能产生的缺陷;
14. X射线检查Ⅱ：对扩径和水压试验后的钢管进行X射线工业电视检查和管端焊缝拍片;
15. 管端磁粉检验：进行此项检查以发现管端缺陷;
16. 防腐和涂层：合格后的钢管根据用户要求进行防腐和涂层。
二、大口径厚壁焊管干焊接技术解析说明：
全自动焊接大口径、厚壁(大于21mm)管线经常采用U型坡口或复合型坡口，由于U型坡口、复合坡口加工耗时、耗力制约管道焊接效率。V形坡口加工简单，省时、省力，但大口径、厚壁管线V型坡口全自动焊接时，如焊接工艺参数选择不当，将导致焊接缺陷产生。
焊接方法采用STT根焊+CRC-P260自动焊机热焊、填充、盖面。焊接设备：林肯STT焊机、林肯DC-400、 CRC-P260自动焊机。保护气体：STT根焊保护气100%CO2，全自动焊保护气为80%Ar+20%CO2。
自动焊常用复合坡口或U型坡口，在小壁厚管线中也可使用V型坡口，它们共同的特点就是坡口上口间隙较小。西气东输二线管道壁厚为21.0mm，V型坡口的上口宽度约为22mm，此宽度已接近CRC-P260焊枪摆幅极限。这样的坡口型式对自动焊接是一个巨大的挑战。根据以往经验确定了自动焊试验焊接工艺参数。
采用以上参数进行自动焊接试验，试验焊接中发现自动焊缝易出现缺陷有层间未熔合、侧壁未熔合、密集气孔、仰焊部位余高超标等。
为了保证良好的盖面成型效果，盖面焊在选择较小的
焊接速度的同时尽量减小焊枪摆动频率，使的盖面焊缝薄而宽，从而减小了熔池存在时间，达到了减少仰焊位置余高的目的。根据试焊结果及分析最后确定西气东输二线联络线STT根焊+CRC全自动焊填充、盖面工艺参数。依据表3焊接参数焊接，焊缝经检测无气孔、裂纹、未熔合等缺陷，焊缝表面成型情况，宏观金相良好。
焊缝机械性能经过中国石油天然气管道科学研究院焊接技术中心检测，各项指标符合西气东输二线联络线接施工要求。STT根焊+CRC-P260自动焊接在大口径、厚壁(V型坡口)管道上的成功应用，充分体现了自动焊接技术优质、高效、低劳动强度的特点。
三、直缝焊管的技术要求与质量检验：
According to the GB3092 standard for welded steel pipes for low-pressure fluid transportation, the nominal diameter of the welded pipe is 6~150mm, and the nominal wall thickness is 2.0~6.0mm. The length of the welded pipe is usually 4~10 meters and can be shipped in fixed or multiple lengths. The surface quality of the steel pipe should be smooth, and defects such as folds, cracks, delamination, and overlap welding are not allowed. Minor defects such as scratches, gouges, misalignment of weld seams, burns, and scars that do not exceed the negative deviation of wall thickness are permitted on the surface of the steel pipe. Thickening at the weld seam and internal weld reinforcement are allowed. Welded steel pipes should undergo mechanical performance tests, flattening tests, and expansion tests to meet standard requirements.
The steel pipe should be able to withstand a certain internal pressure; if necessary, a pressure test at 2.5Mpa should be conducted for one minute without leakage. Eddy current testing may be used as an alternative to hydrostatic testing. Eddy current testing is performed according to GB7735 standards for eddy current testing methods for steel pipes. The method involves fixing the probe on a frame while maintaining a distance of 3~5mm from the weld seam; it scans the weld seam comprehensively with rapid movement of the steel pipe. The testing signals are automatically processed and sorted by an eddy current tester to achieve detection purposes. After testing, welded pipes are cut to specified lengths using a flying saw and then transferred via a flipping frame. Both ends of the steel pipe should have flat heads with bevels, marked with printing; finished pipes are bundled in hexagonal packaging before leaving the factory.
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Shenyang Tengfei Iron Corporation
Shenyang Tengfei Steel Pipe Co., Ltd.
Address: No.6 A 3, No.13 Road, Economic and Technological Development Zone, Shenyang City, Liaoning Province
E-mail:tfwelcome@163.com
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