J55钢级SEW管坯焊缝压扁开裂问题研究

为了解决J55钢级SEW管坯生产中焊缝压扁开裂问题，对压扁开裂的原因进行了分析，同时针对性的对喷水控冷工艺进行了研究，对管坯卷板化学成分进行了改进并批量试制。分析表明，管端出现回火马氏体和微量贝氏体等脆性组织是造成SEW J55管坯焊缝压扁开裂的直接原因。研究结果显示，在管坯控冷前增加风冷环以减少管坯西端内壁进水量、降低管坯入水冷环前的温度和控冷水量，可改善管坯的压扁性能。批量试制结果说明，Ti元素是SEW J55管坯控冷工艺生产中管坯压扁开裂的主要影响因素；在卷板生产时增加Nb含量、控制并降低Ti的含量，能够解决管坯控冷后压扁开裂问题。

Study on the Weld Cracking Problem of Flattening the SEW J55 Tube Blank

In order to solve the problem of weld cracking in SEW J55 tube blank production， the causes of flattening cracking was analyzed. At the same time，the control technology of water-cooling was studied in detail， and batch trial production after the chemical composition of the tube blank was improved. The analysis shows that the brittle structure such as tempered martensite and micro-bainite at the end of the pipe is the direct cause of the flattening cracking of the SEW J55 tube blank weld. The results show that the air-cooling ring can be added before the tube blank is controlled to reduce the water inflow at the inner end of the tube blank， reduce the temperature before the tube blank enters the water-cooling ring， and control the amount of cold water, which can improve the flattening performance of the tube blank. The results of batch trial production show that Ti element is the main influencing factor of tube blank cracking in SEW J55 tube blank controlled cooling process production.