leometwu的部落格

A ticket to hell for iron and steel parts, esp. left after Q/T, as often found in H13.

鑄鉄與一些中高碳(合金)鋼由於枝晶凝固偏析, 鑄態下常會有此枝晶界碳化物薄膜出現, 隨後(鑄錠)的均質退火(1100~1200C x 很長時間)如未落實, 將會使延伸率(韌性)大幅度劣化. 對高週波熱處理者 這種碳化物常會引起淬裂. 要是沒淬裂, 日後使用中也會裂. Elongation/toughness of cast irons,  or alloyed steels with medium to high C%,  will be greatly reduced if such carbides are present in the microstructure. Remains of it after hardening are very minute .Most of the time,  it is difficult to see them clearly under, LM, light microscope. Quench cracking is prone to happen with this carbide films exist in the microstructure.
 
 
 
  

Below: Another set of photos of a grey iron.