Effect of Microstructure on Impact Fatigue Resistance and Impact Wear Resistance of Medium Cr-Si Cast Iron

 A great amount of iron grinding balls in tube mills have been consumed. Under this impact abrasive wear working condition, the failure of wear resistant alloying white irons grinding balls is mainly caused by fatigue spalling. The impact wear resistance of martensitic high chromium cast iron (Cr of 15%) is not high sometimes, but its cost is not low. Thus, medium Cr Si wear resistant cast iron is recommended. The influence of the iron on impact fatigue resistance and impact wear resistance is pronounced. Ball on ball impact fatigue test and high stress impact wear test of the grinding balls have been carried out. The results show that the impact fatigue resistance (IFR) and impact wear resistance (IWR) of medium Cr Si cast iron are superior to those of martensitic high chromium cast iron (Cr of 15%). The main reasons are that (1) the stress in medium Cr Si cast iron is released in the as cast state; (2) the matrix is fine pearlite with better toughness and plasticity; (3) the pearlite is more stable compared with a retained austenite under repeated impact load and less phase transformation can take place; (4) high silicon content improves the morphology of eutectic carbide; (5) there is no secondary carbide which results in less crack sources. All these factors are beneficial to improvement of impact fatigue spalling resistance. The eutectic carbide M7C3 is the main constituent to resist wear.     

高铬铸铁残余奥氏体测定方法的探讨

对高铬铸铁残余奥氏体的几种测定方法进行了比较，X射线衍射法和磁性法均有其局限性，对有择优取向的组织来说，用旋转摆动的X射线法可准确测定高铬铸铁中残余奥氏体的含量。     

含钛中锰钢淬火-配分组织及力学性能

为了研究淬火配分含钛中锰钢的组织与力学性能,借助扫描电子显微镜,透射电子显微镜、电子背散射衍射技术与万能拉伸试验机、磨粒磨损试验机等,分析与测试了含钛中锰钢在165～240℃淬火380℃配分处理后组织、强度、塑性与磨粒磨损性能.结果 表明,试验钢淬火-配分组织主要为板条状一次马氏体、块状二次马氏体及残余奥氏体,同时含有...     

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

 Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50-300 N at 400 ℃ by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 ℃, then decreased at up to 1220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 ℃ (tempered sorbite), 200 ℃ (tempered martensite), 440 to 650 ℃ (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 ℃, quenched in oil, then tempered at 440 to 650 ℃ for 2 h.     

Effect of Heat Treatment on Structure and Wear Re- sistance of High Chromium Cast Steel ContainingBoron

The microstructure, mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy （OM）, the scanning electron microscopy （SEM）, X-ray diffraction （XRD）, hardness, impact toughness, tensile and pin-on-disc abrasion tests. The results show that as cast microstructures of boron-free high chromium steel consist of martensite and a few （Cr, Fe）_7C_3 carbide, and the macro-hardness of boron-free high chromium steel is 55-57 HRC. After 0.5 mass% B was added into high chromium cast steel, as-cast structure transforms into eutectic （Fe, Cr）2B, （Cr, Fe）7 （C, B）a and martensite, and the macro-hardness reaches 58-60 HRC. High temperature quenching leads to the disconnection and isolated distribution of boride, and there are many （Cr,Fe）_23 （C,B）_6 precipitated phases in the quenching structure. Quenching from 1050 ℃, high chromium steel obtained the highest hardness, and the hardness of high chromium cast steel containing boron is higher than that of boron-free high chromium steel. The change of quenching temperature has no obvious effect on impact toughness of high chromium steel, and the increase of quenching temperature leads to tensile strength having an increasing tendency. At the same quenching temperature, the wear resistance of high chromium cast steel containing boron is more excellent than that of boron-free high chromium steel. High chromium cast steel guide containing boron has good performance while using in steel bar mill.     

Structures and Properties of Iron Matrix Composites with Tungsten Carbide Particle by EPC-V Process

Ｍｏｄｅｒｎｉｎｄｕｓｔｒｙｍａｋｅｓｄｅｍａｎｄｓｏｎｗｅａｒｒｅｓｉｓ－ｔａｎｃｅｏｆｅｎｇｉｎｅｅｒｉｎｇｍａｔｅｒｉａｌｓ．Ａｓａｋｉｎｄｏｆｓｕｒｆａｃｅｔｒｅａｔｍｅｎｔｔｅｃｈｎｏｌｏｇｙ,ｃａｓｔｉｎｇｐｅｒｍｅａｔｉｎｇｔｅｃｈｎｏｌｏ－ｇｙｃａｎｓａｔｉｓｆｙｔｈｅｎｅｅｄｓｏｆｗｅａｒｒｅｓｉｓｔａｎｃｅｏｆｍａｔｅｒｉ－ａｌｓ,ｂｕｔｔｈｅｒｅａｒｅｍａｎｙｄｉｓａｄｖａｎｔａｇｅｓｉｎｔｒａｄｉｔｉｏｎａｌｃａｓｔｉｎｇｐｅｒｍｅａｔｉｎｇｔｅｃｈｎｏｌｏｇｙｗｈｉｃｈ…     

温度对40Cr钢温挤压成形的摩擦--磨损性能影响

采用温挤压技术对40Cr钢进行成形试验，考察了不同温度下温挤压试样的摩擦-磨损行为.通过扫描电镜、能谱仪和X射线衍射仪分析了40Cr钢磨损后表面形貌、化学元素分布和物相组成，讨论了40Cr钢温挤压的磨损机理.结果表明，在挤压温度为550℃时试样晶粒尺寸细小，残余奥氏体含量较高，硬度最高，其磨损性能为最佳；而当温度为650℃和750℃时，晶粒尺寸较粗大，残余奥氏体含量降低.在5N载荷作用下，挤压温度为550℃时，摩擦因数为0.7667；当挤压温度达到650℃，摩擦因数为0.8587，提高了12.01%，磨损性能降低；750℃时，摩擦因数为0.8764，相比550℃提高了14.31%，磨损性能进一步变差；在550、650和750℃时，磨损形式主要为磨粒磨损.      

Application of Rietveld Refinement to Investigate the High Chromium White Cast Iron Austempered at Different Temperatures

 The effect of austempering temperature on the microstructure and properties of a high chromium white cast iron was investigated with the Rietveld refinement method. The result shows that the upper bainite exists in the sample austempered at 623 K and the martensite, lower bainite, M7C3, and retained austenite exist in the samples austempered at 563 K and 593 K. The relative content of the retained austenite increases with increasing the austempering temperature from 563 K to 623 K. The higher hardness, impact toughness and impact abrasive wear resistance can be obtained for the specimen austempered at 593 K.     

Microstructure and Abrasive Wear Behavior of Medium Carbon Low Alloy Martensitic Abrasion Resistant Steel

The effect of processing parameters such as hot rolling and heat treatment on microstructure and mechanical properties was investigated for a new 0.27mass% C and Ni,Mo-free low alloy martensitic abrasion resistant steel.The three-body impact abrasive wear behavior was also analyzed.The results showed that two-step controlled rolling besides quenching at 880℃and tempering at 170℃could result in optimal mechanical property:the Brinell hardness,tensile strength,elongation and-40 ℃impact toughness were 531,1 530 MPa,11.8% and 58J,respectively.The microstructure was of fine lath martensite with little retained austenite.Three-body impact abrasive wear results showed that wear mechanism was mainly of plastic deformation fatigue when the impact energy was 2J, and the relative wear resistance was 1.04times higher than that of the same grade compared steel under the same working condition.The optimal hardness and toughness match was the main reason of higher wear resistance.     

Abrasive Wear Behavior of High Chromium Cast Iron and Hadfield Steel-- A Comparison

 Abstract： Wear properties of two different crushers used for grinding raw materials of cement industry are compared using pin-on-disk wear test. The wear test was carried out with different loads on a pin. Abrasive wear behavior of two alloys was evaluated by comparing mass loss, wear resistance, microhardness and friction coefficient. The microstructure of the specimens was detected using optical microscope. The results showed that abrasive wear of high chromium cast iron is lower than that of Hadfield steel. Due to the presence of M7C3 carbides on the high chromium cast iron matrix, impact crushers exhibited higher friction coefficient.     

Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel

 The influence of cryogenic treatment on the wear resistance of En 19 steel was studied. Furthermore, a comparative analysis on the effect of Deep Cryogenic Treatment (DCT, -196 ℃×24 h), Shallow Cryogenic Treatment (SCT, -80 ℃×5 h) and Conventional Heat Treatment (CHT) was done through dry sliding wear testing. The microstructures of CHT, SCT and DCT samples were also examined through scanning electron microscopy. The results indicated that the wear resistance of shallow and deep cryogenically treated samples is higher when compared to that of conventionally treated samples. X-ray diffraction pattern revealed that the transformation of retained austenite into martensite is responsible for the wear resistance improvement.     

高铬白口铸铁低速重载条件下的干滑动摩擦磨损特性

研究了不同类型碳化物和不同基体组织的高铬白口铸铁在低速（滑动速度为0.4187～1.0467m/s），重载（接触应力为1～21MPa）条件下与淬火40Cr钢（硬度HRC51～53）配副的干滑动摩擦磨损特性，结果表明，在（Fe,Cr)7C3、（Fe,Cr）3C和（Fe,Cr）33C63种碳化物中，（Fe,Cr）7C3有利于提高高铬白口铸铁的耐磨性，（Fe,Cr）3C有利于降低摩擦系数，共析组织，奥氏体和马氏体3种基体相比，共析组织基体使合金具有较高的摩擦系数，而奥氏体基体合金的耐磨性最好，存在一个临界摩擦应力，当摩擦应力大于此值时，磨损率急剧上升。     

Wear Behavior and Mechanism of Spheroidal Graphite Cast Iron

Wear behavior and mechanism of spheroidal graphite cast iron were studied on a pin-on-disk elevated temperature wear tester. The phase and morphology of worn surfaces were examined by X-ray diffraction and scanning electron microscopy. Results show that with an increase of load, wear rate of spheroidal graphite cast iron gradually increases under low loads, rapidly increases or potentially increases under high loads; wear rate increases with increasing ambient temperature. At 25–200 °C, adhesive wear prevails; oxidative wear and adhesive wear coexist at 100 °C. As load surpasses 150 N at 100 °C, extrusive wear appears. The elevated-temperature wear of spheroidal graphite cast iron is a physical and chemical process including the following reactions: xFe + y/2O₂?Fe_xO_y, 2C + O₂?2CO and Fe_xOy + yCO?xFe+yCO₂. Hence, at 400 °C, the amount of graphite and tribo-oxides are substantially reduced because of reductive function of graphite. It can be suggested that wear-reduced effect of graphite and tribo-oxides is impaired.     

载荷对Fe-Cr-C-Nb堆焊合金松散磨粒磨损行为的影响

采用熔化极气体保护焊技术（gas metal arc welding,GMAW）制备了Fe-Cr-C-Nb堆焊合金,对合金在不同法向载荷（70~190 N）下进行干砂/橡胶轮松散三体磨粒磨损实验。通过X射线衍射分析、扫描电子显微镜观察、能谱分析、磨损失重测试、体视显微镜观察、激光扫描共焦显微镜观察和维氏硬度测量等手段表征了合金显微组织与磨痕特征,研究了合金在不同法向载荷作用下磨损行为的变化。结果表明:堆焊合金显微组织主要由初生奥氏体基体、网状共晶组织及分布于基体上的NbC硬质相组成;合金磨损损失、磨痕深度随法向载荷增大而增大,磨损机制主要为奥氏体基体的微切削及NbC、M₇C₃的脆性剥落;法向载荷的提高加剧了磨痕亚表面的加工硬化,从而提高了奥氏体基体耐磨性,这导致磨损损失及磨痕深度增长幅度缓慢。     

14Cr 1Mo 15V高铬白口铸铁的深冷硬化机理

 采用X射线衍射、磁性法和硬度测量等方法研究了深冷处理对高铬白口铸铁显微组织和硬化行为的影响。结果表明，去稳+深冷处理铸铁的硬度比未深冷处理铸铁明显提高，从HRC 641提高到HRC 670。这是因为深冷处理使高铬白口铸铁的残余奥氏体量大大下降，马氏体的大量形成和细微二次碳化物的析出强化作用显著提高了高铬白口铸铁的硬度。深冷处理后铸铁组织中仍存在少量残余奥氏体。     

变温超固相线液相烧结工艺对15Cr系高铬铸铁显微组织及性能的影响

为解决常规定温超固相线液相烧结出现的烧结温度窗口狭窄和产品力学性能对烧结温度波动敏感的问题,采用变温超固相线液相烧结工艺制备了粉末冶金高铬铸铁,研究了变温超固相线液相烧结的高温阶段工艺参数对15Cr系高铬铸铁显微组织和力学性能的影响,并与定温超固相线液相烧结制备的合金进行了对比.研究发现,变温超固相线液相烧结制备的合金...     

Microstructure, Impact Fatigue Resistance and Impact Wear Resistance of Wear Resistant Low Cr-Si Cast Iron

Wear parts are greatly consumed in metallurgi-cal industry,fire power stations and cement works.The consumption of grinding balls and lining platesmay be the greatestunder such impactabrasive wearconditions.In China,annual consumption of ballsand plates is close to 1× 10 6 t.Therefore,develop-ing a new material for impact wear conditions is veryimportant.　　 The martensitic high chromium cast iron(WCr= 15 % ) is widely studied and used as wear resis-tance material[1— 8] ,especially for ma…     

载荷对高氮不锈钢和304不锈钢磨损行为的影响

以高氮不锈钢(18.8%Cr-12.6%Mn-4.5%Ni-0.55%N)和304不锈钢为研究对象,利用沙盘磨损试验机在不同载荷下进行干摩擦磨损试验,通过场发射扫描电镜(SEM)分别对试样磨损表面进行观察。结果表明,在低、中和高载荷下,高氮不锈钢的耐磨性均优于同条件下的304不锈钢,高氮不锈钢的耐磨性分别为0.48、0.30和0.22 h/g,而304不锈钢的耐磨性分别为0.44、0.25和0.18 h/g。在低载荷下,304不锈钢的磨损机制主要为犁削和凿削,随着载荷的增加,磨损机制变为塑性变形和微切削;对于高氮不锈钢,在低载荷下磨损机制为犁削和微切削,随着载荷的增加,磨损机制为微切削。在高载荷(100 N)下,304不锈钢和高氮不锈钢的XRD图谱显示基体组织仍为单相奥氏体,说明未发生明显的马氏体转变。     

The Properties and Performance of Cast Iron Grinding Media

Cast iron balls have been used for decades as a grinding media in all types of grinding applications. Early applications of cast iron grinding balls in mineral processing operations were disastrous due to spalling and premature breakage. Better control and understanding of a high chromium cast iron metallurgical system have led to the use of high chromium cast iron balls in all types of grinding. This paper reviews the wear properties of cast iron grinding media materials during dry and wet grinding conditions. The media wear mechanisms and the factors influencing the grinding ball wear during grinding are discussed, giving special importance to the corrosion and abrasion properties of cast iron media materials.     

90Cr6MoRE耐磨铸钢的研究

本文研究了中铬钢的化学成、分淬火温度、回火温度、显微组织、相结构与力学性能和耐磨性的关系。结果得出,中铬钢在同一热处理条件下,随碳含量的提高耐磨性随之提高,对同一碳含量大,随淬少温度的提高耐磨性亦随之提高。90Cr-6MoRE钢在磨损试验条件下,耐磨性接近于高铬钢或高铬铸铁,明显地高于高锰钢和低合金钢。90Cr6MoRE钢的碳化物为M_7C_3型加少量M_3C型。90Cr6MoRE钢衬板装机试验寿命比同机高锰钢衬板提高1倍以上。