After check the stems made by imported ferric stainless steel bars inside the 4-way reversing valve had cracks,The cracking stems was studied by Metallography,SEM and EDAX.

• 对失效产品进行检查、分析发现空调四通换向阀中的不锈钢封头有开裂,封头采用进口铁素体不锈钢棒材。