to steel

• 磨炼得坚强起来了

  temper so as to make strong

• 经得起磨炼

  withstand tempering

• 经受长期的磨炼

  be tempered over a long period

• 经过一次又一次斗争的磨炼

  go through the trials of repeated struggles

• 在革命斗争中得到磨炼

  be tempered in the process of revolutionary struggle