中厚板大钝边对接打底焊接方法及工艺研究

Research on blunt edge root welding method and procedure of medium and thick plate

16MnR钢具有强度高、塑韧性好等优点,常用于核废料储运容器的专用制造。但中厚板16MnR钢采用传统背加衬板的打底焊接工艺存在效率低、工序复杂、焊缝成形质量不稳定等问题。采用等离子弧焊、低/高频脉冲TIG焊工艺对16MnR进行对接打底焊实验。工艺实验研究表明,采用填丝等离子焊接工艺可实现钝边8 mm的单面焊双面成形,获得良好的焊缝成形,但其工艺参数调节区间较窄,面对生产过程中的较小波动,焊接过程易失稳;采用低频脉冲直流TIG焊时可稳定实现5 mm钝边的全熔透,焊缝正面形貌呈现出间隔较大的鱼鳞纹,焊接热影响区有较多的板条状马氏体,增加了焊缝的强度和韧性;采用高频脉冲直流TIG焊时,焊接热输入减小,电弧发生明显收缩,熔深增加,可焊最大熔深7 mm,焊接过程稳定,焊接效率高,焊缝区和熔合区有较多的网状魏氏体组织,热影响区有较多的下贝氏体组织,在低温下有较好的韧性。

Medium-thick 16MnR steel plate has the advantages of high strength and good plastic,and is commonly used for the special manufacture of storage container for nuclear waste. However,there are some disadvantages of welding the medium-thick 16MnR steel plate by using the traditional root welding procedure with backing plate, including low efficiency,complicated process and instable quality of appearance of weld. Based on this problem,the plasma arc welding and low/high frequency pulse TIG welding are used to realize double-sided forming of single-sided welding of 16MnR steel plate without backing plate. The experimental research shows that the double-sided forming of single-sided welding with 8 mm thick blunt edge can be realized by the wire-filling plasma welding procedure,and the defect-free appearance of weld is obtained,but its parameter adjustment interval is narrow,the welding process is tend to lose stability when facing small fluctuation in the production process;When using low-frequency pulsed DC TIG welding,the full penetration of the 5 mm thick blunt edge can be stably realized,the front surface of the weld shows fish scale pattern with a large gap,and the weld heat affected zone has more lath martensites,which increases the strength and toughness of weld. When using high-frequency pulsed DC TIG welding,the welding heat input reduces,the arc obviously shrinks,and the penetration increases,the maximum penetration of 7 mm can be welded. With the stable welding process and high welding efficiency,there are many wedmanstatten structures in the weld zone and the fusion zone,and numbers of lower bainite structure with better toughness at low temperature in the heat affected zone.