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。     

时效处理对05Crl7Ni4Cu4Nb马氏体沉淀硬化不锈钢力学性能及组织的影响

试验研究了 1040 ℃固溶的马氏体沉淀硬化不锈钢05Cr17Ni4Cu4Nb在480~620 ℃时效5 h的组织,强度和硬度。结果表明,随时效温度升高,马氏体基体逐渐分解,碳化物析岀而降低;在时效处理过程中,随时效温度升高,富Cu相最初以球形析出,逐渐发展成椭圆形及杆状,尺寸增大,与基体共格界面消失,强化效果减弱;05Cr17Ni4Cu4Nb钢经1040 °C固溶,480 °C 5h时效后,其HRC硬度值44.3,满足钢材HRC硬度值43的要求。     

合金碳化物对剪板机刃具钢HM的组织和性能的影响

试验研究了HM钢(%:0.48C、5.1Cr、2.0Mo、1.0V、2.0W)和H13钢(%:0.38C、5.1Cr、1.4Mo、1.0V)的组织、冲击韧性和耐磨性。结果表明,HM钢中W、Mo元素含量较H13钢高,存在更多未溶碳化物阻碍奥氏体晶粒长大,细化晶粒,使平均冲击值比H13钢提高35.5%;HM钢高温回火时,马氏体基体弥散析出更多的碳化物,二次硬化效果显著,平均耐磨性比H13钢提高34.8%。     

V-N微合金化含钨改型Cr5W冷轧工作辊用钢

开发了加V-N合金的含钨改型Cr5W工具钢(%:0.70～0.90C、≤1.00Si、0.20～0.60Mn、4.50～5.50Cr、1.00～1.50W、≤0.15Mo、≤0.3V;300×10^-6～350×10^-6N)。Cr5W钢960℃淬火后组织为马氏体+碳化物,平均HRC硬度值为63.5,180℃回火后的平均HRC值为63.2,高于Cr5钢(%:0.70～0.90C、≤1.00Si、0.20～0.60Mn、4.50～5.50Cr、0.15～0.70Mo;80×10^-6～120×10^-6N)180℃的回火硬度(HRC值62.3),在相同硬度下,Cr5W钢的相对耐磨性较Cr5钢提高50%。     

热加工对含氮马氏体不锈钢组织转变和性能的影响

采用Thermal-calc计算了含氮马氏体不锈钢20Cr13的合金相图,据此进行了关键热加工工艺参数设计。采用金相、扫描电镜、X射线衍射、高温热模拟试验、拉伸试验和硬度测试等方法,研究了高温下均热温度对高温组织转变的影响以及高温铁素体对高温塑性的影响,同时研究了退火和淬火工艺对组织和性能的影响。结果表明:铸锭中的少量δ铁素体在单相奥氏体区高温长时间均热后并未消除;δ铁素体的存在降低了马氏体不锈钢的高温塑性;在临界温度长时间退火后,组织为铁素体基体上弥散分布球状碳化物的索氏体及沿晶界呈断续分布的点状碳化物,随退火温度的提高,索氏体晶粒尺寸增大,碳化物选择性地在晶界粗化长大,并呈断续状点状分布;950~1100℃奥氏体化淬火后的组织为板条马氏体+碳化物+少量残余奥氏体。淬火温度较低时,碳化物和残余奥氏体含量较高,淬火后马氏体硬度较低,提高淬火温度,碳化物充分溶解,奥氏体中的碳含量增加,淬火后板条马氏体硬度升高。     

淬火温度对NM400马氏体耐磨钢残余应力的影响

采用热处理实验、X射线衍射(XRD)、光学显微镜(OM)、扫描电镜观察(SEM)等方法,研究了不同淬火温度对NM400马氏体耐磨钢的组织、硬度与表面残余应力的影响规律。结果表明,随着淬火温度的升高,原始奥氏体逐渐均匀化并粗化长大,实验钢表面轧制方向的残余应力逐渐增大。淬火温度940℃以下,随着温度升高,马氏体板条束逐渐增多,板条块逐渐减少,实验钢硬度随淬火温度的升高而增加;淬火温度1 150℃时,马氏体板条块增多,马氏体板条粗化,表面硬度明显下降。     

卷取机助卷辊表面堆焊研制

采用埋弧堆焊工艺在20CrNiMo表面堆焊6-8mm的Cr13系列新型马氏体不锈钢熔覆材料，分析熔覆金属的组织形貌，并进行耐磨性和硬度测定。研究结果表明，熔覆金属的焊态组织主要为板条状马氏体和大量的残余奥氏体，并伴有少量的回火马氏体，同时在马氏体间可见少量较小的碳化物。经500℃回火后其组织为回火马氏体和少量残余奥氏体，碳化物析出相增多。焊态硬度值为46-50HRC,回火后硬度值为54-58HRC,磨损失重是45#淬火钢的0.31倍。经过六个月的使用后，助卷辊的单边磨损量1.13mm,辊面平均硬度值在54.2HRC,说明该熔覆金属具有优异的耐磨性能。     

热处理对工模具钢5Cr8MoVSi组织及硬度的影响

工模具钢5Cr8MoVSi(0．55C，8．13Cr，1．38Mo，0．45V，0．72Si)经840℃退火硬度为HB218，钢中碳化物以M23C6为主，并有少量的MC和M7C3。该钢合适的淬火温度为980—1050℃，最高硬度为HRC60—61。随淬火温度升高，淬火马氏体由板条状和针状马氏体组织过渡到板条状马氏体组织，剩余碳化物主要为MC和M7C3，为减少残余奥氏体量，该钢应进行二次或三次回火。     

热处理工艺对塑料模具钢10Ni2Cr2MnCuMoVAl组织和性能的影响

研究了固溶温度、时效温度及时间对10Ni2Cr2MnCuMoVAl塑料模具钢热处理后的微观组织和力学性能的影响。结果表明:固溶处理后,10Ni2Cr2MnCuMoVAl钢的组织主要是板条马氏体构成,且随固溶温度的升高,马氏体板条发生明显宽化,并在890℃固溶后达到硬度最高值。时效处理后的组织由板条马氏体、粒状贝氏体和析出碳化物构成。当时效温度区间为460~520℃,随着时效温度的升高,材料的强度逐渐升高,韧性逐渐降低,并在520℃达到强度峰值;时效温度高于520℃时,随着温度升高,材料硬度降低,冲击韧性升高。分析在540℃不同时效时间处理后的性能可知,试验钢在8h达到力学性能峰值。通过比较试验钢在不同时效处理后的力学性能数据,10Ni2Cr2MnCuMoVAl钢的最佳热处理工艺为:880℃固溶处理2h+空冷,随后在520℃时效处理4h+空冷。     

卷取机夹送辊表面堆焊层组织性能研究

采用埋弧堆焊工艺在Q235B表面堆焊8-10mm的Cr8系列新型熔覆材料,测定其耐磨性和硬度变化,分析熔覆金属的组织形貌和高温工况下的合金元素扩散。研究结果表明,熔覆金属打底层主要是以铁素体为主,伴随着少量的贝氏体。盖面层的焊态组织主要为马氏体和残余奥氏体,伴有少量的回火马氏体,同时在枝晶马氏体间可见少量较小的碳化物。经550℃回火后其盖面层组织为回火马氏体和残余奥氏体,碳化物析出相均布较焊态呈增多趋势。焊态硬度值为530-580HV300,回火后硬度值为720-830HV300,磨损失重是45#淬火钢的0.31倍。在使用3个月后发现在熔覆层表面出现了元素偏移并形成了由Cr2O3、WO等组成的氧化膜,降低了夹送辊的粘钢倾向,提高使用寿命。     

Microstructure and Mechanical Properties of Martensitic Stainless Steel 6Crl5MoV

 Martensitic stainless steel containing Cr of 12% to 18% (mass percent) are common utilized in quenching and tempering processes for knife and cutlery steel. The properties obtained in these materials are significantly influenced by matrix composition after heat treatment, especially as Cr and C content. Comprehensive considered the hardness and corrosion resistance, a new type martensitic stainless steel 6Cr15MoV has been developed. The effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel is emphatically researched. Thermo-Calc software has been carried out to thermodynamic calculation; OM, SEM and TEM have been carried out to microstructure observation; hardness and impact toughness test have been carried out to evaluate the mechanical properties. Results show that the equilibrium carbide in 6Cr15MoV steel is M23C6 carbide, and the M23C6 carbides finely distributed in annealed microstructure. 6Cr15MoV martensitic stainless steel has a wider quenching temperature range, the hardness value of steel 6Cr15MoV can reach to HRC 608 to HRC 616 when quenched at 1060 to 1100 ℃. Finely distributed carbides will exist in quenched microstructure, and effectively inhabit the growth of austenite grain. With the increasing of quenching temperature, the volume fraction of undissolved carbides will decrease. The excellent comprehensive mechanical properties can be obtained by quenched at 1060 to 1100 ℃ with tempered at 100 to 150 ℃, and it is mainly due to the high carbon martensite and fine grain size. At these temperature ranges, the hardness will retain about HRC 592 to HRC 616 and the Charpy U-notch impact toughness will retain about 173 to 20 J. A lot of M23C6 carbides precipitated from martensite matrix, at the same time along the boundaries of martensite lathes which leading to the decrease of impact toughness when tempered at 500 to 540 ℃. The M3C precipitants also existed in the martensite matrix of test steel after tempered at 500 ℃, and the mean size of M3C precipitates is bigger than that of M23C6 precipitates.     

调质热处理对55NiCrMoV7模具钢组织与力学性能的影响

采用扫描电镜(SEM)、硬度测试、Ⅴ型冲击实验和单向拉伸实验结合有限元建模仿真,研究了55NiCrMoV7模具钢在不同淬火温度(790～910℃)、回火温度(100～650℃)下的微观组织演化和力学性能的变化规律.结果表明,随着淬火温度升高,球状碳化物逐渐溶解到马氏体基体中,马氏体组织不断长大、粗化,残余奥氏体逐渐增多...     

钼钨钒合金化热作模具钢高温回火组织演变

为适应热冲压技术的发展需求,开发了一种新型高热导率高耐磨性能热冲压用模具钢材料。采用扫描电镜（SEM）、透射电镜（TEM）等检测手段对钼钨钒合金化新型模具钢的高温回火性能与组织特征进行了研究。阐明了新型热冲压模具钢回火过程碳化物析出与演变规律。实验结果表明:实验用钼钨钒合金化模具钢材料具有良好的回火二次硬化性能,在500～600 ℃温度区间回火时,回火组织硬度上升;在600 ℃回火出现二次硬化峰值;当回火温度超过600 ℃后,组织软化程度明显,回火硬度开始下降。实验模具钢在高温回火过程中的硬度变化与其合金碳化物的偏聚、析出和聚集长大密切相关。当在560 ℃以下回火时,实验钢组织中未有合金碳化物析出;当回火温度大于560 ℃时,回火组织中开始析出M₂C型碳化物;当回火温度高于600 ℃后开始析出MC型碳化物;当在620 ℃长时间回火后M₂C型碳化物转化为M₆C型碳化物,此时实验钢硬度开始明显下降;而当回火温度高于660 ℃时,新型实验钢组织中主要为M₆C和MC型合金碳化物。      

Study on microstructure and mechanical properties of martensitic stainless steel 6Cr15MoV

Martensitic stainless steel containing 12%-18%Cr have high hardness due to high carbon content. These steels are common utilized in quenching and tempering processes for knife and cutlery steel.The properties obtained in these materials are significantly influenced by matrix composition after heat treatment,especially as Cr and C content.Comprehensive considered the hardness and corrosion resistance,a new type martensitic stainless steel 6Cr15MoV has been developed.This study emphatic researches the effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel.Thermo-Calc software has been carried out to thermodynamic calculation;optical microscope（OM）,scanning electronic microscope（SEM） and transmission electron microscope（TEM） have been carried out to microstructure observation;hardness and impact toughness test have been carried out to evaluate the mechanical properties.Results show that the equilibrium carbide in 6Cr15MoV steel is M₂₃,C₆ carbide,and finely distributed of M₂₃C₆ carbides can be observed on annealed microstructure of 6Cr15MoV stainless steel.6Cr15MoV martensitic stainless steel has a wider quenching temperature range,the hardness value of steel 6Cr15MoV can reach to 60.8 -61.6 HRC when quenched at 1060 - 1100℃.Finely distributed carbides will exist in quenched microstructure,and effectively inhabit the growth of austenite grain.With the increasing of quenching temperature,the volume fraction of undissolved carbides will decrease.The excellent comprehensive mechanical properties can be obtained by quenched at 1060-1100℃with tempered at 100-150℃,and it is mainly due to the high carbon martensite and fine grain size.At these temperature ranges,the hardness will retain about 59.2-61.6 HRC and the Charpy U-notch impact toughness will retain about 17.3-20 J.The morphology of impact fracture surface of tested steel is small dimples with a small amount of cleavage planes.The area of cleavage planes increases with the increasing of tempering temperature.     

Microstructure and Properties of Hot Working Die Steel H13MOD

Compared with H13 steel, the influences of different heat treatment process on the microstructure and properties of the new type of hot working die steel H13MOD were studied. The results show that the complete austenitizing temperature of H13MOD is around 1030 °C and the quenching hardness achieves the maximum value at this temperature. While for H13, the complete austenitizing temperature is above 1100 °C and the quenching hardness rise constantly with the quenching temperature increasing. In quenching process, the undissolved MC carbides can prevent the coarsening of grain in both steels. With the rise of quenching temperature, when MC carbides dissolve completely, the grain grows quickly. The hardness and strength of H13MOD at higher tempering temperature (above 570 °C) are nearly the same as those of H13, but its toughness is higher than that of H13. Mo₂ C carbide is the main strengthening phase in H13MOD, which is attributed to the higher content of Mo. The quantity of VC eutectic carbides is reduced because of lower content of V in H13MOD, which plays an important role in enhancing the impact toughness of H13MOD. Under a certain strength condition, H13MOD steel can be used in the environment that higher toughness is required and the service life of die casting mold can be improved.     

Influence of Heat Treatment Parameters on the Carbide Morphology of PM High-Speed Steel HS 6-5-3-8

The influence of heat treatment parameters on the carbide morphology of the powder metallurgic high-speed steel HS 6-5-3-8 is examined. To that end, diverse heat treatment parameters are selected and applied by quenching dilatometry. In particular, different austenitizing temperatures, as well as an isothermal holding stage during quenching in the temperature regime of the transformation gap at temperatures between 450 and 600 °C, are produced. Extensive computer-aided image analysis is performed to investigate the carbide morphology. It is found that the circularity of the tungsten-rich M₆C carbides increases significantly after short holding times at a temperature of 550 °C due to the carbide precipitation from metastable and supersaturated austenite onto pre-existing carbides. Longer holding times lead to further growth of the carbides, while the circularity of the carbides does not change. It is further shown that the hardness of the isothermally treated material is increased, all other parameters being equal. Increased carbide circularity might be helpful for increasing the toughness while reaching the same hardness and wear resistance as the conventional heat-treated material. Moreover, it might be possible to enhance the austenitizing temperature with regain of positive carbide morphology properties during the isothermal holding stage. Thus, improved material properties could be achieved.     

固溶处理对GH2036合金组织和硬度的影响

利用光学显微镜、扫描电镜、布氏硬度仪等研究了GH2036合金Φ150 mm棒材在1120~1240 ℃固溶处理的组织演化和硬度变化规律。研究表明,GH2036合金锻后空冷锻材组织中主要存在富Cr和Nb-V两种类型的碳化物,在1220 ℃固溶处理后碳化物大部分回溶,晶粒尺寸基本均匀。合金HB硬度值随热处理温度的升高而降低,但在1160~1200 ℃处理时,硬度随温度的升高,HB硬度值由185升至193,这主要与碳化物大幅度向基体回溶有关。     

Effect of quenching temperature on microstructure and fracture toughness of high carbon steel

The effect of quenching temperatures on microstructure and fracture toughness of high carbon steel was investigated. Plane strain fracture toughness was tested with compact tension specimen. Microstructure and fracture morphology of KIC samples after quenching and tempering treatment were examined by scanning electron microscope (SEM).The results show that the residual carbides of steel in hardened state decreasea with the quenching temperature increasing and totally disappear after quenched at 920??;the grain size grows up obviously when the quenching temperature is more than 960??. The microstructure in high temperature tempered state is composed of residual carbides, precipitated carbides and ferrite matrix;plasticity decreases monotonically; the fracture toughness gradually decreases in the range from 800?? to 960??,and then almost invariant; the fracture type of KIC specimens is gradually changed from cleavage fracture to intergranular fracture. The main reason for the changes of fracture toughness has close relationship with the plasticity.     

Nb对2000 MPa桥索钢再加热过程中组织变化的影响

针对不同Nb含量的2种桥索钢,采用热膨胀仪、光学显微镜、扫描电子显微镜和硬度测试仪对其在箱式电阻炉连续加热过程中的组织演变和水冷淬火后的硬度进行了对比分析。结果表明:Nb元素可以细化桥索钢的原始组织,使其存在大量的铁素体和渗碳体的晶界,在连续加热过程中的开始阶段提供更多的奥氏体形核位置,使得奥氏体逆共析转变的起始温度降低,而终了温度升高,逆共析转变区域增大。同时,Nb元素形成的碳化物在加热阶段对奥氏体晶粒的长大具有拖拽作用,降低桥索钢在奥氏体形核后的长大速度,使得淬火后得到马氏体的硬度值降低,因此需要较高的温度来溶解合金碳化物使桥索钢充分奥氏体化。     

淬火温度对添加B_4C的ASP30粉末冶金高速钢组织及力学性能的影响

采用粉末冶金方法制备添加B_4C的全致密ASP30高速钢,样品在1 040℃到1 200℃范围内淬火,并且经过560℃三次回火,研究淬火温度对其力学性能及显微组织的影响。采用扫描电子显微镜、洛氏硬度计和材料力学性能测试机研究高速钢的组织和力学性能。结果表明:添加质量分数为0.025%B_4C的ASP30粉末冶金高速钢在1 160℃下烧结2 h后会形成月牙形液相碳化物,从而获得全致密的烧结组织。随淬火温度升高,显微组织中碳化物的数量明显减少,基体中合金元素固溶含量提高,基体晶粒长大,断口形貌呈准解理断裂但断口平整度下降。随淬火温度升高,钢的硬度提高,最高值达到69 HRC。抗弯强度、断裂韧性均下降,抗弯强度最高值达4 357MPa,断裂韧性最高值为48.6 MPa/m1/2。冲击韧性先升高后下降,在1 080℃最高为18.85 J/cm2。