问题 问答题 简答题

埋弧焊时为什么容易产生氢气孔?如何防止?

答案

参考答案:

氢气孔主要来源于焊丝、焊剂等的水分;防止之一是去除焊丝和焊件表面的水分、铁锈、油和其他杂物,并要求焊剂要烘干;二是通过冶金手段去除已混入熔池中的氢。

材料分析题

青春误区 异性冲突

为集体加油 互学互助

以上是男女生交往中的部分情景。阅读情景图回答以下问题:

(1)男女生正常交往有何益处?

                                                                                                                                                               

(2)你认为男女生应该怎样正常交往?

                                                                                                                                                               

                                                                                                                                                              

(3)你欣赏怎样的男生(女生)?请写出来与大家分享。

                                                                                                                                                             

                                                                                                                                                            

单项选择题