高速钢丝锥的切削性能

目前,丝锥主要采用高速钢制作。为了解钢的冶炼工艺和显微组织,如碳化物的尺寸和分布、晶粒度等,对丝锥切削性能的影响,采用喷射冶炼和粉末冶金HSF825K、HOP2030和HSF838高速钢制作了螺旋槽丝锥,检测了丝锥的硬度、显微组织和切削性能。结果表明:3种钢丝锥热处理后的硬度均高于66HRC,钢的碳化物的尺寸、圆整度和分布对丝锥韧性的影响比淬火、回火后的硬度和冶炼工艺的影响大。弥散、细小、圆整、均匀分布的碳化物有利于提高丝锥的韧性和切削性能。采用喷射冶炼的HSF825K钢制作的丝锥的切削性能最佳。     

S390粉末高速钢真空气淬的显微组织及性能

研究了不同淬火温度、不同冷却方式对S390粉末高速钢进行真空热处理的显微组织及性能的影响。试验结果表明,经不同工艺淬火后,S390粉末高速钢的晶粒度在13级左右,其中的合金碳化物数量减少、尺寸变小,硬度均大于63.2 HRC。经真空气淬后的S390粉末高速钢试样中均可得到下贝氏体组织,且在下贝氏体片状组织中及残留合金碳化物周围有纳米椭圆(球)状合金碳化物析出。     

W18Cr4V钢真空气淬和普通油淬的组织与性能比较

采用真空气淬法和普通空气加热油淬法分别对W18Cr4V钢进行热处理。利用金相显微镜和洛氏硬度计对热处理后W18Cr4V高速钢的组织和硬度进行了比较观察和测试分析。结果表明,两种淬火工艺处理的试样组织基本一致,均为隐晶形的淬火马氏体基体组织、大颗粒状的共晶碳化物和细小点粒状的二次碳化物及残留奥氏体,气淬后的组织更均匀;回火后的组织也很相似,为回火马氏体及未溶解的共晶碳化物和二次碳化物。经真空气淬的试样硬度（65HRC）仅比普通空气加热油淬的（66HRC）略有降低,但能满足工模具的硬度要求,而且试样表面光洁,呈银灰色,变形微小,对于要求精度不太高的零件,无需进行后续加工,对环境也无污染。     

低铬抗磨白口铸铁热处理的研究

本文研究了经稀土变质处理的低铬白口铸铁在热处理过程中显微组织的变化,主要包括共晶碳化物形态的变化和二次碳化物的析出,并研究了热处理工艺参数对冲击韧性和硬度的影响。结果表明,低铬白口铸铁在淬火加热和保温阶段,其网状共晶碳化物向基体中溶解引起薄弱处断开,因而改善了共晶碳化物的形态和分布,这是淬火能提高低铬白口铸铁韧性的主要因素。低铬白口铸铁经950℃×2h加热空淬,可获得较好的韧性和最高的硬度。     

经真空热处理和盐浴热处理的30CrMnSiA钢力学性能的研究

本文对经真空淬火、回火和盐浴炉加热等温淬火、回火并达到四种不同硬度要求的30CrMnSiA钢的力学性能进行了系统的试验研究。结果表明，除个别情况外，先进的真空热处理工艺可以取代传统的盐炉加热等温淬火工艺。     

整体淬火和感应淬火

本文比较了整体淬火和感应淬火钢中马氏体组织演变,性能及断裂之间的异同点。感应粹火由于加热速度比炉体加热速度快得多,因此其马氏体组织更细小相应的硬度也更高。同时由于感应加热限制了碳化物的溶解时间,为此,在有些加热条件下,珠江体层间的碳化物的仍残留在奥氏体中,并保留在随后转变的马氏体组织中。一般地,低合金碳钢淬火后的硬度和强度随钢中碳含量的增加而升高,但当ｗ（Ｃ）〉０．５％时,则碳钢经这两种方法淬火后     

整体淬火和感应淬火

本文比较了整体淬火和感应淬火钢中马氏体组织演变,性能及断裂之间的异同点。感应淬火由于加热速度比炉体加热速度快得多,因此其马氏体组织更细小,相应的硬度也更高。同时由于感应加热限制了碳化物的溶解时间,为此,在有些加热条件下,珠光体层间的碳化物仍残留在奥氏体中,并保留在随后转变的马氏体组织中。一般地,低合金碳钢淬火后的硬度和强度随钢中碳含量的增加而升高,但当w(C)>0.5％时,则碳钢经这两种方法淬火后,其晶间脆断趋势均增大。需要进一步探讨晶间脆断所导致的高碳钢感应淬火之应用的局限性。     

热处理工艺对5Cr8MoVSi钢组织结构的影响

研究了5Cr8MoVSi钢经不同工艺热处理后的组织与结构，分析讨论了淬火温度对马氏体形态的影响。研究表明，5cr8MoVSi钢退火碳化物类型以M23C6为主，并有少量的MC和M7C3；淬火组织中剩余碳化物以MC和M7C3为主，M23C6型碳化物在淬火加热时大部分溶解。该钢随淬火加热温度升高，淬火马氏体由板条状和针状马氏体混合组织过渡到以板条状马氏体为主。经485℃回火后，针状马氏体仍显示原马氏体针；而板条状马氏体的板条状方向性几乎被完全切断，显微组织呈均匀化。该钢在1000～1050℃淬火时，残留奥氏体量为10．7％～123％Vol，淬火、回火后最高硬度为58～60HRC。     

真空热处理对超硬高速钢M2Al组织性能的影响

Ｍ２Ａｌ是一种无钴超硬高速钢，真空加热促进异常晶粒长大。充入惰性气体施行真空加热可以提高加热速度，阻碍异常大晶粒的形成，提高Ｍ２Ａｌ钢的强韧性。影响Ｍ２Ａｌ钢强韧性的最主要因素不是混晶和奥氏体晶粒度的大小，而是钢中碳化物的形态和分布。为了发挥Ｍ２Ａｌ钢的超硬性，可以提高真空淬火温度，使其硬度达６６ＨＲＣ以上。     

轴承用8Cr4Mo4V钢真空气淬及等温盐浴淬火后的性能对比分析

通过显微组织观察及性能测定,对轴承用8Cr4Mo4V钢真空气淬及等温盐浴淬火处理后的性能进行了对比分析。结果表明,8Cr4Mo4V钢真空气淬后得到马氏体组织,等温盐浴淬火后得到马氏体+贝氏体混合组织。真空气淬后钢的晶界有碳化物析出,腐蚀后晶界特征明显,而等温盐浴淬火后晶界碳化物析出量少,钢的晶界特征不明显。再经回火处理后,钢中析出大量碳化物,与真空气淬相比,等温盐浴淬火钢中析出的碳化物在尺寸和数量上都更大。钢的硬度和耐磨性测试表明,等温盐浴淬火钢的硬度为61.78 HRC,而真空气淬钢的硬度为60.28 HRC,硬度提高了1.5 HRC,等温盐浴淬火钢的摩擦磨损性能比真空气淬钢高。与真空气淬相比,等温盐浴淬火处理后钢的力学性能提升,室温拉伸强度提高了164 MPa,高温拉伸强度提高了50 MPa,冲击吸收能量提高了46.9%,旋转弯曲疲劳强度极限由860 MPa提高至1050 MPa,提高了22%。     

Rapid Tempering of Martensitic Stainless Steel AISI420: Microstructure,Mechanical and Corrosion Properties

In this research, the effect of rapid tempering on the microstructure, mechanical properties and corrosion resistance of AISI 420 martensitic stainless steel has been investigated. At first, all test specimens were austenitized at 1050 °C for 1 h and tempered at 200 °C for 1 h. Then, the samples were rapidly reheated by a salt bath furnace in a temperature range from 300 to 1050 °C for 2 min and cooled in air. The tensile tests, impact, hardness and electrochemical corrosion were carried out on the reheated samples. Scanning electron microscopy was used to study the microstructure and fracture surface. To investigate carbides, transmission electron microscopy and also scanning electron microscopy were used. X-ray diffraction was used for determination of the retained austenite. The results showed that the minimum properties such as the tensile strength, impact energy, hardness and corrosion resistance were obtained at reheating temperature of 700 °C. Semi-continuous carbides in the grain boundaries were seen in this temperature. Secondary hardening phenomenon was occurred at reheating temperature of 500 °C.     

The Strain-Hardening Behavior of Partially Austenitized and the Austempered Ductile Irons with Dual Matrix Structures

In the current study, an unalloyed ductile iron containing 3.50 C wt.%, 2.63 Si wt.%, 0.318 Mn wt.%, and 0.047 Mg wt.% was intercritically austenitized (partially austenitized) in two-phase regions (α + γ) at different temperatures for 20 min and then was quenched into salt bath held at austempering temperature of 365 °C for various times to obtain different ausferrite plus proeutectoid ferrite volume fractions. Fine and coarse dual matrix structures (DMS) were obtained from two different starting conditions. Some specimens were also conventionally austempered from 900 °C for comparison. The results showed that a structure having proeutectoid ferrite plus ausferrite (bainitic ferrite + high-carbon austenite (retained or stabilized austenite)) has been developed. Both of the specimens with ∼75% ausferrite volume fraction (coarse structure) and the specimen with ∼82% ausferrite volume fraction (fine structure) exhibited the best combination of high strength and ductility compared to the pearlitic grades, but their ductility is slightly lower than the ferritic grades. These materials also satisfy the requirements for the strength of the quenched and tempered grades and their ductility is superior to this grade. The correlation between the strain-hardening rates of the various austempered ductile iron (ADI) with DMS and conventionally heat-treated ADI microstructures as a function of strain was conducted by inspection of the respective tensile curves. For this purpose, the Crussard-Jaoul (C-J) analysis was employed. The test results also indicate that strain-hardening behavior of ADI with dual matrix is influenced by the variations in the volume fractions of the phases, and their morphologies, the degree of ausferrite connectivity and the interaction intensities between the carbon atoms and the dislocations in the matrix. The ADI with DMS generally exhibited low strain-hardening rates compared to the conventionally ADI.     

淬火硝盐的劣化和再生

使用扫描电镜及能谱分析、化学分析方法,全面分析了使用硝盐浴进行分级淬火和等温淬火时,淬火硝盐劣化产物。结果表明:硝盐反应生成物(Na₂CO₃、NaOH),设备(主要是盐槽、盐泵、管道)、夹具、料盘及工件等氧化产物(FeO·Fe₂O₃·Fe₃O₄),外来物(灰尘,炭黑)是造成硝盐劣化的主要原因。据此,提出了预防淬火硝盐劣化措施:选用品质好的基盐;选用热稳定性较高的混合盐;保持淬火盐浴温度均匀,淬火前后温升可控,尽量避免“瞬间”过热使用;尽量避免外来杂质进入;做好日常维护。并简要介绍了淬火硝盐再生处理方法。     

磁场对25CrMo48V超高强度钢回火组织与力学性能的影响

为研究磁场作用下热处理工艺对超高强度钢组织调控及碳化物种类、形态、尺寸和演变规律的影响,采用OM、SEM、TEM、EBSD和力学性能测试等技术手段研究了磁场作用对含有Nb、V、Ti等微合金元素的25CrMo48V超高强度钢中组织演变与力学性能的影响。试样均在1000 ℃下进行30 min奥氏体化处理,水淬之后在1 T磁场作用下,在200~600 ℃温度范围内回火1 h。结果表明,磁场的施加会抑制马氏体板条合并,促进M₂₃C₆和M₇C₃型碳化物的析出。经外加1 T磁场不同温度回火后,试样的硬度均高于未加磁场的常规回火处理试样,而其强度低于常规回火处理。     

GCr15轴承钢中渗碳体的奥氏体化行为研究

利用光学显微镜、扫描电镜(SEM)、维氏硬度计以及thermo-cale和photoshop软件对经不同温度奥氏体化、淬火后的GCr15轴承钢试样的显微组织进行了分析研究.结果表明:720～750℃奥氏体化时.碳原子进行短程扩散,几乎无奥氏体生成;755℃为奥氏体化的转折点,碳原子进行长程扩散,奥氏体出现;奥氏体化温度为780℃时,不但珠光体中的渗碳体全部粒化,先共析渗碳体也溶解碎断,剩余渗碳体以细小弥散的颗粒状分布在奥氏体基体中.     

T10钢低温盐浴渗铬直接淬火回火工艺的研究

研究了Ｔ１０钢在低温盐浴渗铬后直接淬火并回火工艺。结果表明,低温盐浴渗铬后进行直接淬火回火的Ｔ１０钢,表面硬度高,渗层和基体的硬度过渡较平滑,且渗后存在比较厚的扩散层。     

Diffusion Boronizing of H11 Hot Work Tool Steel

The H11 hot work tool steel was boronized at various processing parameters, austenitized, quenched, and tempered to a core hardness of 47-48 HRC. Microstructure, phase constitution, and microhardness of boronized layers were investigated. Effect of boronized region on the bulk properties was determined by the Charpy impact test. Structure of boronized regions is formed by the compound layers and diffusion inter-layer. The compound layers consisted of only (Fe,Cr)₂B phase, but in the case of longer processing time, they contained also of the (Fe,Cr)B-phase. The inter-layer contained enhanced portion of carbides, formed due to carbon diffusion from the boride compounds toward the substrate. Microhardness of boronized layers exceeded considerably 2000 HV 0.1. However, boronizing led to a substantial lowering of the Charpy impact toughness of the material.     

Microstructure evolution,fracture and hardening mechanisms of quenched and tempered steel for large sized bearing rings at elevated quenching temperatures

Based on 42CrMo steel, a steel with a higher C and Ni content is developed for use in large sized bearing rings. The impact energy and hardness of the quenched and tempered steel increase with the quenching temperature, but then decrease when the temperature is above 925 °C. When the temperature is below 925 °C, some larger M₂₃C₆-type carbides (with average diameters of 255.6 μm) exist in the quenched and tempered microstructure. The number of carbides is reduced as the quenching temperature increases. At the same time, the fracture modes change from microvoid coalescence and quasi-cleavage to microvoid coalescence. The number of round quasi-cleavage fractures, which are formed around the carbides, decrease as the number of carbides decrease. The existence of larger M₂₃C₆-type carbides leads to round quasi-cleavage fractures and decrease the impact energy. The precipitation strengthening of M₂₃C₆-type carbides increases the hardness at a quenching temperature of 925 °C.     

The Nature of the Tensile Fracture in Austempered Ductile Iron with Dual Matrix Microstructure

The tensile fracture characteristics of austempered ductile irons with dual matrix structures and different ausferrite volume fractions have been studied for an unalloyed ductile cast iron containing (in wt.%) 3.50 C, 2.63 Si, 0.318 Mn, and 0.047 Mg. Specimens were intercritically austenitized (partially austenitized) in two phase region (α + γ) at various temperatures for 20 min and then quenched into a salt bath held at austempering temperature of 365 °C for various times and then air cooled to room temperature to obtain various ausferrite volume fractions. Conventionally austempered specimens with fully ausferritic matrix and unalloyed as-cast specimens having fully ferritic structures were also tested for comparison. In dual matrix structures, results showed that the volume fraction of proeutectoid ferrite, new (epitaxial) ferrite, and ausferrite [bainitic ferrite + high-carbon austenite (stabilized or transformed austenite)] can be controlled to influence the strength and ductility. Generally, microvoids nucleation is initiated at the interface between the graphite nodules and the surrounding ferritic structure and at the grain boundary junctions in the fully ferritic microstructure. Debonding of the graphite nodules from the surrounding matrix structure was evident. The continuity of the ausferritic structure along the intercellular boundaries plays an important role in determining the fracture behavior of austempered ductile iron with different ausferrite volume fractions. The different fracture mechanisms correspond to the different levels of ausferrite volume fractions. With increasing continuity of the ausferritic structure, fracture pattern changed from ductile to moderate ductile nature. On the other hand, in the conventionally austempered samples with a fully ausferritic structure, the fracture mode was a mixture of quasi-cleavage and a dimple pattern. Microvoid coalescence was the dominant form of fracture in all structures.