外加颗粒法制备双金属复合材料的组织与性能研究

发布时间：2018-03-22 20:03

本文选题：离心铸造　切入点：高碳铬铁　出处：《河南科技大学》2011年硕士论文　论文类型：学位论文

【摘要】：本文采用一台炉子冶炼复合轧辊表面工作层和芯部所需铁水,并通过外加高碳铬铁颗粒法和离心铸造,将高碳铬铁颗粒直接加入旋转的离心机模具中,制备轧辊辊身,再采用重力铸造法浇注辊芯而制成了尺寸为Φ180mm×500mm的高铬铸铁/球墨铸铁双金属复合轧辊铸件。利用HR-150D型洛氏硬度计和JB-300B型摆锤式冲击试验机等力学性能检测设备测试不同热处理状态下试样的力学性能;借助MH-3数显显微硬度仪对高铬铸铁与球墨铸铁结合界面附近的显微硬度进行测量;采用光学显微镜、配备了EDAX能谱仪的JSM-5610LV型电子扫描电镜和德国布鲁克D8型X射线衍射仪等微观分析仪器观察和分析试样的微观组织;采用MMS-1G高速销-盘摩擦磨损实验机,对不同热处理状态下试样的高速摩擦磨损特性进行研究,并借助电子扫描电镜分析其磨损机理。上述试验结果表明: 1.采用外加颗粒法制备的高铬铸铁-球墨铸铁双金属复合轧辊,热处理工艺对其表面工作层的力学性能具有一定的影响。在900~1000℃奥氏体化温度范围内,随着奥氏体化温度的升高,宏观硬度的变化趋势为先增大后减小,而冲击韧度略微下降,在950℃奥氏体化时,力学性能匹配良好。其力学性能可达到:冲击韧性5.2~6.6J/cm~2;硬度HRC56.7~64.8。 2.复合轧辊表面高铬铸铁层铸态下的微观组织为:合金碳化物+珠光体+残余奥氏体。经热处理,其微观组织变为:回火马氏体+Cr_7C_3+残余奥氏体+少量Cr_(23)C_6和Cr3C,初生碳化物的形貌呈条状、块状和菊花状等;在马氏体基体上分布有大量颗粒状回火碳化物,经EDS分析,这些碳化物是含有Fe、C和Cr等元素的复合式碳化物。 3.所制备的双金属复合轧辊,其高铬铸铁与球墨铸铁的连接界面清晰,两种合金呈犬牙状相互交织在一起,结合处无气孔、夹杂、裂纹和空隙等铸造缺陷;从球墨铸铁一侧向高铬铸铁层,球状石墨的数量越来越少,尺寸越来越小;从高铬铸铁一侧向球铁层,条、块状碳化物的数量越来越少,尺寸越来越小。在结合界面高铬铸铁侧的显微硬度约为800HV,球墨铸铁侧的显微硬度约为350HV,可见,复合界面两侧显微硬度的差别比较大,但是在结合界面处显微硬度的降低比较缓和。表明,合金元素在结合界面处发生了扩散,两种金属达到良好的冶金结合。 4.高速摩擦磨损试验表明,奥氏体化温度、外加法向载荷和摩擦线速度均对复合轧辊耐磨层材料的高速摩擦磨损性能具有显著影响。在试验温度范围内,磨损失重量随着奥氏体化温度的升高发生变化,在950℃奥氏体化时磨损失重量最小,此时耐磨性最佳;在摩擦线速度不变时,随着外加法向载荷的增加,复合轧辊耐磨层试样的线磨损率逐步增大,而摩擦系数逐步减小;在外加法向载荷不变时,随着摩擦线速度的增大,复合轧辊耐磨层试样的线磨损率逐步增大,而摩擦系数逐渐减小。据分析,耐磨层材料的磨损机制主要为磨粒磨损、氧化磨损和粘着磨损。在相同的试验条件下,所制备复合轧辊耐磨层材料销试样的磨损失重量、线磨损率和摩擦系数均小于高合金耐磨钢的磨损失重量、线磨损率和摩擦系数,表明所制备复合轧辊耐磨层材料的高速摩擦磨损性能优于高合金耐磨钢。
[Abstract]:This paper uses a furnace smelting composite roller surface layer and the core of the work required by the external hot metal, and high carbon ferrochrome particle method and centrifugal casting, high carbon ferrochrome particles directly into the centrifuge rotating mold, preparation roll, high chromium cast iron / by gravity casting casting roller core and made the size of 180mm in diameter and 500mm ductile cast iron bimetal composite casting roll. Pendulum impact testing machine and other mechanical properties of specimens under mechanical properties testing equipment to test different heat treatment using HR-150D Rockwell hardness tester and JB-300B type; with the help of MH-3 digital display micro hardness of high chromium cast iron and ductile iron binding the hardness near the interface were measured by optical microscope, JSM-5610LV; scanning electron microscope equipped with a EDAX spectrometer and the German Brook D8 type X ray diffraction analysis of microscopic observation and analysis of test instrument The microstructure and wear characteristics of samples under different heat treatment conditions were investigated by means of MMS-1G high-speed pin disc friction and wear test machine, and the wear mechanism was analyzed by electron scanning electron microscope.
The results of the above test show that:
1. used the high chromium cast iron particles prepared by the ductile cast iron bimetal composite roll, has certain effect of heat treatment on the surface of the working layer of the mechanical properties. At 900~1000 DEG C austenitizing temperature range, with the increase of austenitizing temperature, the change trend of macro hardness was increased first and then decreased, while the impact toughness decreased slightly at 950 DEG C during austenitizing, mechanical properties, good mechanical properties. It can be achieved: the impact toughness of 5.2~6.6J/cm~2 hardness of HRC56.7~64.8.;
2. composite roll surface of high chromium cast iron layer cast microstructure state for alloy carbide + pearlite + residual austenite. After heat treatment, the microstructure becomes: tempered martensite +Cr_7C_3+ residual austenite and a small amount of Cr_ (23) C_6 and Cr3C, the morphology of the primary carbide is strip, block shaped and chrysanthemum; in the martensite and granular tempered carbide, by EDS analysis, these carbides containing Fe, composite carbide C and Cr elements.
Double metal composite roll 3. preparation, the high chromium cast iron and ductile iron with clear interface, two kinds of alloys in the shape of a canine tooth intertwined, with no pores, inclusions, cracks and voids casting defects; ductile iron from one side to the high chromium cast iron layer number and spherical graphite the less, the size is getting smaller and smaller; from one side to the high chromium cast iron ductile iron layer, an increasing number of blocky carbides is less, the size is getting smaller and smaller. The micro hardness of high chromium cast iron side interface is about 800HV, the micro hardness of nodular cast iron side is about 350HV, can be seen, the composite interface on both sides of the hardness difference is relatively large, but in reducing the interface hardness of ease. Show that the alloy elements in the interface has spread, two kinds of metal to achieve good metallurgical combination.
4. high speed friction and wear test shows that the austenitizing temperature, applied normal load and friction velocity of composite roll wear layer materials of high-speed friction and wear properties have significant influence. In the experimental temperature range, the wear weight loss with the increase of austenitizing temperature change at 950 DEG C during austenitizing minimum weight losses at this time, the best wear resistance; the friction velocity is constant, with the increase of normal load, the wear resistant composite layer roll sample linear wear was gradually increased, while the friction coefficient gradually decreases; in addition to the load change, with the increase of friction velocity, the wear resistant composite layer sample rate of linear wear of roll gradually increased, and the friction coefficient decreases gradually. According to the analysis, the wear mechanism of the wear-resistant layer material is mainly abrasive wear, oxidation wear and adhesive wear. Under the same experimental conditions, the preparation of composite rolling The wear loss, wear rate and friction coefficient of the roll wear resistant material pin specimen are smaller than those of the high alloy wear resistant steel. The wear rate and friction coefficient indicate that the high speed friction and wear properties of the composite roll wear resistant material is better than that of the high alloy wear resistant steel.

【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TB331

【参考文献】