SAE J415标准中对等温淬火是这样描述的:
1、条目3.70
“Martempering”—(a) A hardening procedure in which an austenitized ferrous workpiece is quenched into an appropriate medium whose temperature is maintained substantially at the Ms of the workpiece, held in the medium until its temperature is uniform throughout but not long enough to permit bainite to form and then cooled in air. The treatment is frequently followed by tempering. (b) When the process is applied to carburized material, the part is quenched to a temperature below the core Ms but above the case Ms temperature. This variation of the process is frequently called marquenching.
2、条目3.8
“ Austempering”—Quenching a ferrous alloy from a temperature above the transformation range, in a medium having a rate of heat extraction sufficient to prevent the formation of ferrite or pearlite, and then holding the alloy just above Ms until transformation to bainite is complete.
根据目的的不同,以这两个热处理术语分别定义我们所说的“等温淬火”. 从“Austempering”术语的英文含义中,可知获得“贝氏体”不在“淬硬”范畴内,所以用了“quenching”来定义;而“Martempering”术语的英文含义中,可知最终获得 “马氏体”才算“淬硬”,术语的定义中才用“hardening”一词。
在GB/T 7232中,也用两个热处理术语来分别定义:
4.15 “贝氏体等温淬火,等温淬火Austempering”工件加热奥氏体化后快冷到贝氏体转变温度区间等温保持,使奥氏体转变为贝氏体的淬火。
4.16“马氏体分级淬火,分级淬火Martempering”工件加热奥氏体化后浸人温度稍高或稍低于Ms点的碱浴或盐浴中保持适当时间,在工件整体达到介质温度后取出空冷以获得马氏体的淬火。
GB/T 7232的“贝氏体等温淬火”“马氏体分级淬火”这两个术语,都含有不管是获得了马氏体还是贝氏体,都认为是“淬硬”了,即“淬(上)火”了。
从上面可见,我在241#帖子中对两个标准关于“淬火”定义的差异的认知是正确的:GB/T 7232在“淬火”的定义中认为出现“贝氏体”转变为主也算“淬硬”,而SAE J415标准只认可出现“马氏体”转变为主才算“淬硬”。
[ 本帖最后由 凌云谷 于 2009-8-5 10:32 编辑 ] |