上贝氏体是550～350℃范围内形成的贝氏体，金相组织呈羽毛状，脆性，硬度较高。500倍光学显微镜下基本能够识别清楚。
接合部组织由晶界铁素体及晶内上贝氏体组成。
Themicrostructure of bonded zone consist of upper bainite and grain boundary ferrite.
上贝氏体转变与珠光体分解有着本质上的区别，但又有密切的联系；
The upper bainite transformation has not only essential difference but also intimate relation with pearlite decomposition;
采用大的线能量焊接，形成较多的上贝氏体和粒状贝氏体组织，对改善接头性能有利。
With large welding heat input, more upper Bainite and granular Bainite form, which is benefit to improve the property of HAZ.
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