| 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. |
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