1. Once in a while, a tragedy occurs which touches even the most case-hardened heart. 悲剧不时发生，连那些麻木不仁的人们也有所触动。
2. They argued that if he were crowned right away, he would become case-hardened and no longer afraid, and that it would be better to let him go home and crown him some other day. 对于那些挟恩自重的人，我们最好不要欠情，即使欠暸，我们也要把心一横，有些事情我不能办，办不暸。
3. In order to solve the problems of over tanned sheep skin, the experiments were carried out, and the results showed that there are several remedies suitable to the case-hardened sheep skin. 针对铬污染绵羊毛皮的质量问题，进行试验处理，解决了铬污染影响毛被美观和皮板厚硬等问题。
