【作者】 宋绪丁；

【导师】 谷立臣；

【作者基本信息】 长安大学 ， 机械设计及理论， 2008， 博士

【摘要】 传统的耐磨材料都是以合金碳化物为抗磨骨架,本论文创新性地提出以硬度更高、稳定性更高的硼化物和硼碳化合物为抗磨骨架,以高强韧性马氏体为基体的高硼铁基系列铸造耐磨合金。高硼铁基系列铸造耐磨合金以我国富有的硼、铬、钛为主要合金元素,不含有镍、钼、钨、钒等合金元素,具有低成本、高硬度、良好耐磨性和强韧性,同时,铸态硬度低,成型工艺性好,容易切削加工,克服了高铬铸铁和高锰钢铸态难以加工的问题,适用制造尺寸精度要求高的耐磨零件。因此,高硼铁基系列耐磨合金是一种新型的耐磨材料,可以部分替代高铬铸铁和高锰钢材料。本学位论文依托于国家863计划项目,在以下方面进行了实验研究。在论文中,将高硼铁基系列耐磨合金分为低碳低硼系列(0.2～0.4%C、1.0%B左右)、中碳硼变化系列(0.3～0.45%C固定, 0.5～3.0%B)和高碳高硼系列(0.5～1.0%C, 2%B左右)三个系列,对其合金的熔炼方法、合金的净化精炼工艺、铸造凝固过程和组织、热处理工艺和热处理后的组织和性能、合金在二体磨损和三体动载磨损条件下的耐磨性能及工业应用进行了较为全面的研究。本研究采用铝、钛脱氧和定氮、冲入法稀土变质处理的熔炼工艺,并开发了钢包底部安装透气塞吹入氩气工艺,通过陶瓷透气塞向钢液中吹入氩气净化钢液。吹氩净化后钢液中的夹杂物明显减少,有利于改善高硼铸钢的强韧性能。借助于光学显微镜、扫描电镜SEM、透射电镜TEM、X衍射和Leica图像分析仪等手段,研究了高硼铁基系列耐磨合金的铸态组织、热处理后的组织及合金元素对组织和性能的影响。结果表明:①低碳低硼系列合金的铸态组织主要由两部分组成:珠光体和铁素体基体+鱼骨状的共晶硼化物和晶界分布的硼碳化合物。中碳、硼变系列合金铸态组织受含硼量影响很大,随着含硼量的增加,共晶硼化物和二次硼碳化合物的体积分数明显增加。当硼含量超过2%时,铸态组织中会出现(γ+Fe2B+ Fe3(B,C))三元包晶组织,而硼含量对基体组织没有影响;高碳高硼系列的合金铸态组织除了有大量的共晶组织外,还会出现(γ+Fe2B+ Fe3(B,C))三元包晶组织,随着含碳量增加,三元包晶组织有所增加。②在950～1100℃奥氏体化淬火+200℃回火后,合金的鱼骨状共晶硼化物和菊花状的包晶组织变化不大,部分网状二次硼碳化合物有断网现象,基体组织全部转变为马氏体组织。低碳低硼系列合金的基体主要由宽度约0.1～0.2μm的板条马氏体组成,当奥氏体化温度超过1050℃时,合金基体中会出现部分针状马氏体;中碳和高碳高硼系列合金的基体主要由混合马氏体组成。③含碳量和含硼量对高硼铁基合金中硼化物和硼碳化合物体积分数的影响为:在硼量一定的情况下,碳含量的增加使硼碳化合物的体积分数增加,根据实验数据,含碳量每增加0.1%,硼碳化合物的体积分数增加1%左右,说明碳量的变化对硼碳化合物的体积分数的影响比较小;在含碳量一定情况下,硼含量对硼碳化合物的体积分数有十分明显的影响,呈y = 7.078e0.822x指数曲线变化,其中y-硼碳化合物,x-含硼量。④X射线物相分析结果表明:当高硼铁基合金奥氏体化温度超过1000℃时,合金内部的二次Fe23(C,B)6相消失,有利于消除“硼脆”现象,提高合金的韧性。借助于洛氏硬度试验、一次摆锤冲击试验、断裂韧性试验、ML-10销盘式和MLD-10冲击磨损试验,三个系列合金热处理后的力学性能及耐磨性试验结果为:①低碳低硼系列合金的硬度低、冲击韧性和断裂韧性较高;中碳硼变化系列合金含硼量的变化对其热处理后的宏观硬度、冲击韧性和断裂韧性有明显的影响;高碳高硼系列合金随着含碳量的增加,合金的硬度明显增加,而碳量变化对合金的冲击韧性的影响较小,高碳高硼系列的冲击韧性在7.5~10 J/cm2范围。②在二体磨粒磨损的条件下,无论低载荷还是高载荷,低碳低硼系列合金的磨损性能相对于高铬铸铁要低;中碳硼变化系列合金当硼含量小于1.5%时,高硼铁基合金的耐磨性与高铬铸铁相当,当硼含量超过1.5%时,高硼铁基合金的耐磨性明显大于高铬铸铁,含硼量越高,高硼铁基合金的耐磨性越高;高碳高硼系列合金的耐磨性都明显的优于高铬铸铁,耐磨性最好的合金接近于高铬铸铁的3倍。③在三体动载磨粒磨损的条件下,低碳低硼系列合金的三体磨粒磨损的耐磨性比高铬铸铁稍好;中碳硼变化系列合金硼含量低于2.0%的高硼铁基合金的耐磨性优于高铬铸铁,而硼含量大于2.0%的高硼铁基合金的耐磨性比高铬铸铁差;高碳高硼系列合金的三体磨粒磨损的耐磨性明显低于高铬铸铁,且随着含碳量的增加,耐磨性下降。低碳高硼铁基合金在磨球机磨球上的工业应用效果表明:低碳高硼铁基合金磨球比高铬铸铁磨球的耐磨性稍好,但低碳高硼铁基合金中合金元素加入量少,不含有镍、钼、钴等合金元素,生产成本比高铬铸铁降低30%以上,具有很好的经济效益。高碳高硼铁基合金在泥浆泵上的应用效果正在实际试验过程。更多还原

【Abstract】 Traditional wear resistant material is based on carbide as strong support of matrix. The dissertation innovatively presents high boron iron-based wear-resistant alloy which matrix is martensite. The material is based on boride and boron carbide compound which have high hardness and high stability as strong support of matrix. High boron iron-based wear-resistant cast alloy has no noble elements such as nickel, molybdenum ,wolframium, wanadium. The main alloy element of the material are boron, titanium and chromium, its has not only low cost , high hardness, good wear resistance and good strength and toughness used as but also low as-cast hardness good processe and excellent machining properties. So, high boron iron-based wear-resistant alloy (HBIA) is a kind of new wear-resistant material and its can substitute for high-chromium cast-iron and high-manganese steel material. The dissertation has been supposted by the high-tech planing project(863) of Chinses government.The high boron wear resistant alloy include low carbon-low boron alloy(0.2～0.4%C、1.0%B), medium carbon- alterable boron alloy(0.3 - 0.45%,0.5～3.0%B) and high carbon-high boron alloy(0.3-0.45%,0.5～3.0%B). The methods of alloy melting process , solidification process for casting, heat treatment process, the structures and properties after heat-treatment, wear-resistance and industry application of two-body abrasion and three-body wear have been investigated on the system.Our principal research methods are aluminium-titanium deoxidizing technology kjeldahl,pour-over melting process. It also develope ladle bottom-blowing argon process. The inclusion in steel decreased significantly and Improve strength and toughness and life time of high boron cast steel, after the blowing argon process.The influence on microstructure, mechanical properties of the as-cast, heat treatment structures and alloying agent on wear resistant of high-boron casting steel have been investigated by means of optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscope(TEM), X-ray diffraction(XRD) and Leica image analyzer. The results show that:①the as-cast of low carbon-low boron alloy consists of the pearlite and ferrite matrix and fishbone eutectic boride and carbon-boride distributing along grain boundary. The as-cast structure of medium carbon- alterable boron alloy is greatly affected by the boron content and interdendritic eutectic boride and two boron carbide compound volume fraction increase obviously with increaseing boron content. When the boron content is more than 2% ,(γ+Fe2B+ Fe3(B,C) peritectic structure appears in the as-cast structure, but the boron content had no effect on matrix. The as-cast of high carbon-high boron alloy appeared(γ+Fe2B+ Fe3(B,C))peritectic structure besides a large amount of eutectic structure and peritectic structure increases with increasing carbon content.②There has a little change fishbone eutectic boride and chrysanthemum-shaped peritectic structure of alloy after quenched at 950～1100℃and tempered at 200℃.some two boron carbide compound show fracture phenomenon and all matrix structure transformed into martensitic structure. Matrix of low carbon-low boron alloy mainly consists of lath martensite which width is about 0.1～0.2μm and matrix of medium carbon and high carbon-high boron alloy is mainly composed of multi-martensite.③Influence of carbon content and boron content on boride and boron carbide compound of high boron iron-based alloy is: under the certain boron content , boron carbide compound volume fraction increases with increasing carbon content and boron carbide compound volume fraction increases about 1% when carbon content increase 0.1% every time in terms of experimental data. So ,changes in carbon content has less effect on boron carbide compound volume fraction .Under the certain carbon content ,boron content showed the strong effect of boron carbide compound volume fraction and shows a rule of exponential curve y= 7.078e0.822x;④When the quenching temperature of the high boron wear-resistant alloy is over 1000℃, the fracture toughness of it can be improved by the disappear of grain boundary Fe23(C,B)6.By means of rockwell hardness test, pendulum impact test ,fracture toughness test, ML-100 model pin-disk and MLD-10 impact abrasion test, the result of mechanics property and wear-ability of three types alloy after heat-treatment is:①L ow carbon-low boron alloy has low hardness, high impact toughness and high fracture toughness. Changes in boron contents during medium carbon alterable boron alloy has an obvious effect on macro-hardness after heat-treatment, impact toughness and fracture toughness. The hardness of high carbon-high boron alloy obviously increased with increasing of carbon content but changes in carbon content has less effect on impact toughness. the impact toughness (ak.) was 7.5—10 J/cm2.②U nder two-body abrasion ,wear characteristics of low carbon-low boron alloy is lower than high chromium casting iron regardless of low load or high load. When boron content of medium carbon-alterable boron alloy is less than 1.5%,wear resistance of high boron iron-based alloy is equal to that of high chromium casting. When boron content of alloy is more than 1.5%, wear resistance of high boron iron-based alloy is significantly higher than that of high chromium casting. The higher the boron content ,the higher wear resistance of high boron iron-based alloy. Wear resistance of high carbon-high boron alloy is better than that of high chromium cast and wear resistance of the best alloy is close to that of high chromium cast three times.③U nder two body abrasion, wear resistance of high carbon-high boron alloy is a little better than that of high chromium cast. When boron content of medium carbon-alterable boron alloy is less than 1.5%, wear resistance of high boron iron-based alloy is better than that of high chromium cast. When boron content is more than 2.0%, wear resistance of high boron iron-based alloy is worse than that of high chromium cast and wear resistance is almost decreased with increasing carbon content.The application of iron-based alloy on ball crusher grinding ball indicates that grinding ball of Low carbon-high boron iron-based alloy has no noble elements such as nickel, molybdenum ,cobalt. Comparing with high chromium cast, production costs is reduced by more than 30%.Using grinding ball of high boron iron-based alloy can reduce the material, reduce frequency of shutdown and grinding ball times, increas productivity of ball crusher and have very good economic benefits. The application effect of high boron iron-based alloy on mud pump is being tested in the laboratory.更多还原