12CrNi3A钢零件的碳氮共渗

Carbonitriding of the 12CrNi3A Steel Part

12CrNi3A钢轴承座需进行碳氮共渗,要求渗层深度0.55~0.65 mm,淬火后表面硬度82~85 HRA。采用井式渗碳炉对轴承座进行了碳氮共渗,温度840℃,渗剂为煤油加氨气。检验结果发现,轴承座渗层中有点状和网状黑色组织,这与炉气成分和氨气流量有关。热处理试验表明,碳氮共渗层中的黑色组织不能通过正火等热处理消除。对于要求高表面硬度的12CrNi3A零件,为避免黑色组织的产生和达到要求的表面硬度,应采用高碳势的气氛和控制气氛炉进行碳氮共渗。

Bearing seats of 12 CrNi3 A steel need to be carbonitrided to depth of 0.55 to 0.65 mm and surface hardness of 82 to 85 HRA after quenching.The bearing seats were carbonitrided at 840℃in atmasphere consisting decomposition products of kerosene and ammonia in a pit-type carburizing furnace.It was discovered from the examination that the bearing seat case exhibited dot-like and reticular dark structures which related to both atmosphere composition and flow rate of ammonia.From heat treatment test it was seen that the dark structure in carbonitrided case could not be eliminated by heat treatment process such as normalizing.The 12 CrNi3 A steel parts that need high surface hardness should be carbonitrided in atmosphere having high carbon potential in atmospherecontrolled furnace,to prevent formation of dark structure and to reach desired surface hardness.