气阀钢２１－１２Ｎ与４Ｃｒ１０Ｓｉ２Ｍｏ的摩擦焊焊缝存在机械混合区、微扩散区和局部区域的相变区，但不存在熔化区。在强烈机械变形作用下，紧靠摩擦焊接触面两侧为超细微晶或细晶区，接着是再结晶区、回复区和形变区。但它们在接触面两侧的具体情况并不完全相同。 Friction welding seam of valve steel 21-12N and 4Cr10Si2Mo exists in the area of ​​mechanical mixing zone, micro-diffusion zone and local transformation zone, but there is no melting zone. In the strong mechanical deformation, close to the friction welding on both sides of the interface for the fine grain or fine grain region, followed by the recrystallization zone, the recovery zone and deformation zone. However, their specific conditions on both sides of the contact surface are not exactly the same.