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。大口径直缝焊管主要生产流程说明：
Longitudinal welded pipe is made of steel plate or strip after bending and welding. According to the weld form, it can be divided into straight welded pipe and spiral welded pipe. According to its use, it can be divided into general welded pipe, galvanized welded pipe, oxygen-blowing welded pipe, wire sleeve, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, welded thin-walled pipe, welded special-shaped pipe and spiral welded pipe. Description of main production process of large diameter straight seam welded pipe:
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;
1. Plate prospecting: After the steel plate used to manufacture large diameter submerged arc welded straight seam steel pipe enters the production line, the whole plate ultrasonic inspection is carried out first.
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;
2. Milling: Double-sided milling of steel plate edges by milling machine to achieve the required width, parallelism and groove shape;
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;
3. Pre-bending edge: Pre-bending edge with pre-bending machine, so that the edge of the plate has the required curvature;
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
4. Forming: On JCO forming machine, first half of the pre-bended steel plate is stamped into "J" shape by several steps, then the other half of the steel plate is also bent into "C" shape, and finally the "O" shape of the opening is formed.
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;
5. Pre-welding: to make the formed straight seam welded steel pipe seam and use gas shielded welding (MAG) for continuous welding;
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;
6. Internal welding: Longitudinal multi-wire submerged arc welding (up to four wires) is used to weld the inside of the straight seam steel pipe.
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;
7. External welding: Longitudinal multi-wire submerged arc welding is used to weld the outer side of longitudinal submerged arc welded steel pipe.
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;
8. Ultrasound Inspection I: 100% Inspection of the inside and outside welds and the base metal on both sides of the weld of the longitudinal welded steel pipe;
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;
9. X-ray inspection I: 100% X-ray industrial television inspection of internal and external welds, image processing system to ensure the sensitivity of flaw detection;
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;
10. Diameter enlargement: The whole length of submerged arc welded straight seam steel pipe is enlarged to improve the dimensional accuracy of steel pipe and the distribution of internal stress of steel pipe.
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;
11. Hydraulic test: The expanded steel pipe is inspected one by one on the hydraulic test machine to ensure that the test pressure meets the standard requirements. The machine has the function of automatic recording and storage.
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;
12. Chamfering: The qualified steel pipe will be processed to meet the required pipe end groove size;
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;
13. Ultrasound Inspection II: Ultrasound Inspection is carried out one by one again to inspect the possible defects of longitudinal welded steel pipe after diameter enlargement and hydraulic pressure.
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;
14. X-ray inspection II: X-ray industrial television inspection and photography of weld seam of pipe end after diameter enlargement and hydraulic test;
15.管端磁粉检验：进行此项检查以发现管端缺陷;
15. Tube end magnetic particle inspection: this inspection is carried out to find the defect of the tube end;
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。
16. Anti-corrosion and coating: qualified steel pipes are anticorrosive and coated according to user's requirements.
