Heat Treatment and Wear of High-Alloyed Irons

高合金铸铁的热处理和磨损

• 批准号: 06650807
• 负责人: KAWAMOTO Makoto
• 金额: $ 1.47万
• 依托单位: Osaka Prefecture University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06650807/
• 关键词: High alloyed iron; Hot rolling mill; Quenching; Secondary temper hardening; Retained austenite; Wear; Rolling fatigue; 炭化物

The heat treatment and the wear resistance under unlubricated rolling-and-sliding condition and lubricated rolling condition of high-alloyed irons (the white iron of high-speed steel type) were investigated. The carbide forming elements, 6mass%Cr, 2mass%Mo, 4mass%W and 6mass%V,were added to irons and the carbon content was varied from 1.5mass% to 2.5mass%. 4mass% or 8mass%Co was also added to the 2.0mass%C iron to strengthen the matrix structure. These irons were melted in a high-frequency furnace and cast in a sand mold. Results were summarized as follows.(1) The matrix structure transformed to martensite by quenching of austenitizing temperature of 1373K and cooling rate 5-10K/min, and the secondary temper hardening occurred sufficiently by tempering at 823K.The secondary temper hardening was insufficient in the case of quenching from 1273K.(2) The amount of carbides increased and the as-cast hardness became high with the carbon content of iron. However, the hardness of 2.5%C iron was lower than 2.0%C iron at the secondary temper hardening. This is due to that carbon and alloying elements in the martensite decreased with the carbon of iron.(3) By addition of Co to iron, its quenching properties naturally deteriorated and the hardness of the quenched atructure decreased, but MC type carbide became granular and M_2C,M_6C and M_7C_3 being small : besides, the secondary temper hardening appeared remakably and the retained austenite became stable.(4) The wear resistance under unlubricated rolling-and-sliding was considerably improved by adding 8mass%Co to the iron.(5) The rolling fatigue life of the white iron of high-speed steel type under lubrication was about 10 times as long as high Cr white iron. The white iron became particularly excellent by adding 8mass%Co.(6) The addition of Co improved the wear resistance of the white iron of high-speed steel type. However, a small amount of Co addition was ineffective and Co over 8mass% should be necesarry to improve.

研究了高合金铸铁(高速钢型白口铸铁)在无润滑滚动滑动条件和润滑轧制条件下的热处理及耐磨性。在球墨铸铁中加入碳化物形成元素，分别为6质%铬、2MASS%Mo、4质%W和6质%V，碳含量在1.5%~2.5%之间变化。在2.0质量%C铁中还加入了4或8质量%的Co，以强化基体组织。这些铸铁在高频炉中熔化，然后在砂型中浇注。结果表明：(1)奥氏体化温度为1373K，冷却速度为5~10K/min时，基体组织转变为马氏体组织，在823K回火时，二次回火硬化充分，而1273K淬火时，二次回火不充分。(2)随着铁中碳含量的增加，碳化物增多，铸态硬度提高。但在二次回火时，2.5%C铁的硬度低于2.0%C铁。(3)在铁中加入Co后，其淬火性能自然恶化，淬火组织硬度降低，但MC型碳化物呈颗粒状，M_2C、M_6C和M_7C_3较小。高速钢型白口铸铁在润滑条件下的滚动疲劳寿命约为高铬白口铸铁的10倍。加入质量分数为8%的Co后，白口铸铁的耐磨性变得尤为优异。(6)Co的加入提高了高速钢型白口铸铁的耐磨性。但少量Co的加入效果不明显，Co的质量分数应在8%以上才能改善。