leometwu的部落格

       Untinted, colors produced  naturally. Specimen was from a ductile iron casting severely over-heated because of failure of the temperature controller. Incipient melting occurred, leaving a  honey-comb-shape white delineation of carbide on the grainboundaries. This shape has a special meaning----grains grow to their maxima, no more grain growth will continue.   Photo taken with ZEISS microscope--an amazing product from Germany.

紅十字假調質, 稍重蝕. 碳化物凸出基地許多. 兩者處於不同聚焦平面. 聚焦碳化物, 故基地模糊. 後五張以暗視場攝. 就是這些碳化物薄膜常常讓高週波業者揹黑鍋----應該是材料商的問題. AISI 4140, as-rolled, faked as quenched and tempered. Heavily etched.  Carbide film sticking out of the matrix. The last 5 photos: dark field.

   500x
  200x

高溫軋延後直接空冷, 鋼材硬度會有HRC 20~30. 有黑心廠商把此冒充為調質鋼賣, 大賺黑心錢. 這種鋼材內部的碳化物形貌(有尖銳者,有薄片形者), 對韌性極具殺傷力, 直接使用還不會出問題, 淬火後使用一定會出問題, 因為這些碳化物會引發微裂, 導致破裂. 高週波淬火也很難不裂, 常使熱處理者背黑鍋. 即使淬後未裂, 日後還是會裂. 買鋼材時要事先約定好, 千萬不要被矇騙.

軋延態(假調質) 1. 晶粒粗大 2. 有許多不易被看出的尖銳的碳化物薄膜, 故 高週波淬火時極易淬裂.  應先做調質或正常化 再高週波淬火.

Nothing will be said about these photos. Just to feast your eyes only.

相片N, O, P: 淬火回火後. 枝晶偏析仍存在, 但較緩和. H~L 中的致命的鑄態尖角沃斯田鉄已消失. Ｐhoto N ~ P: Quenched and tempered. dendritic segregation is less severe than as-cast condition.  Harmful angular Austenite areas  has gone into solution and helped form martensite.

鋼與鑄鉄水之間的擴散現象 (一)

過渡區, 左邊是素材, 右邊是感應硬化區. 素材硬度太軟, 機件受重負荷時, 對硬化層支撐力不夠, 硬化層常會被壓裂, 甚至於剝殼掉落. 正常作業是: 素材需先調質到HRC35 +/- 5左右, 切削後再感應淬火. 要注意調質組織內必需是"回火M", 肥粒鉄不能>5%, 也不能呈細線狀.