新型环保纸模制品用不锈钢模具材料的开发

设计的试验钢(0.45C-12.5Cr-0.41Mo-0.22V钢和0.85C-10.5Cr-0.91Mo-0.25V钢)由50 kg真空感应炉熔炼并锻造成试验用钢样。试验研究了淬火温度(950~1150℃)、回火温度(一次回火200~400℃,二次回火500~600℃)对钢的组织、强度、延伸率、硬度和冲击功的影响。结果表明,1 050℃淬火+500℃二次回火处理后0.45C-12.5Cr-0.41Mo-0.22V钢的性能最佳:抗拉强度为1 712.3 MPa、屈服强度为1 476.5 MPa、延伸率为7.8%、HRC硬度值为69.3以及冲击功为7.3 J。二次硬化会提升模具钢的硬度值,而回火过程中碳化物的长大以及分布不均匀容易造成冲击韧性的降低。试验的新型不锈钢模具的强度指标高于普通商用模具钢42Cr3Mo2MnV1。     

Fe-1.5C-1.5Cr-1.5Al超高碳钢碳化物的球化和力学性能

对Fe-1.5C-1.5Cr-1.5Al超高碳钢碳化物的球化工艺及力学性能进行了研究.扫描电镜观察表明,加入铝,可抑制锻后空冷条件下先共析网状碳化物的析出;利用铝合金化作用和成分不均匀化奥氏体加热控制,提出了2种无形变球化处理工艺:①离异共析等温球化;②预冷淬火 高温回火.2种球化处理工艺均能获得良好的球化组织和良好的综合力学性能:Rm≥1 000 MPa,Re≥700 MPa,A10=10%～14%.拉伸断口具有明显的缩颈,断口形貌呈具有典型的韧窝特征.     

冷处理及回火次数对刀剪用M390粉末钢组织和性能的影响

通过对M390粉末不锈钢进行淬火、冷处理和低温回火，研究了热处理对合金显微组织和力学性能的影响。结果表明：冷处理降低合金中残余奥氏体的数量，大幅度提高材料硬度和抗弯强度；1 180℃淬火试样冷处理后，随回火次数的增加，单位面积碳化物颗粒总数和平均粒径增加，硬度下降，一次回火后硬度达到61.1 HRC;1 130℃淬火试样冷处理后，随着回火次数增加，单位面积颗粒总数不断增加，平均粒径和硬度下降，一次回火后硬度达到60.0 HRC；淬火温度和回火次数对抗弯强度影响不大，合金抗弯强度为4 000 MPa左右。     

回火工艺对含Ce轴承钢440C组织性能影响

为探究不同回火工艺对440C轴承钢组织性能的影响，以含Ce超洁净440C轴承钢为研究对象，通过SEM、XRD、TEM等对比研究了球化退火-淬火-回火工艺与球化退火-淬火-回火-冷处理-回火工艺对440C轴承钢显微组织与性能的影响。试验选择的淬火温度为1 050℃、回火温度为200℃、冷处理温度为-78.5℃。结果表明，两种工艺下试验钢中的物相均为马氏体+残余奥氏体+M₂₃C₆型碳化物。相比于仅对试验钢进行球化退火-淬火-回火的情况，在球化退火-淬火-回火-冷处理-回火工艺条件下，试验钢中残余奥氏体的体积分数由11.06%降至7.63%,一次碳化物的尺寸及数量基本无变化，二次碳化物的个数增加了49.4%、平均面积下降了24.0%;在力学性能方面，冲击功由90.5 J提高到115.0 J,拉伸试样断后伸长率由5.3%增加到8.3%,而抗拉强度仅由2 039.24 MPa增加到2 060.14 MPa,洛氏硬度由58.70HRC提升到59.09HRC,提升幅度较小。力学性能的转变归因于组织及碳化物的共同作用，本试验条件下球化退火-淬火-回火-冷处理...     

淬火温度对M4粉末高速钢组织和性能的影响

为了研究淬火温度对M4粉末高速钢组织和性能的影响, 利用光学显微镜观察高速钢试样的金相组织, 对淬火组织的晶粒度进行评级, 并对回火组织中碳化物的组成和分布进行统计; 采用洛氏硬度计和材料万能试验机测试试样的硬度和抗弯强度。结果表明: 随淬火温度的升高, M4粉末高速钢淬火后硬度先上升后下降, 在1200 ℃时出现最大值HRC62.9;淬火态试样的晶粒度随淬火温度的升高而降低。经三次回火后M4粉末高速钢硬度值较淬火态均有提高, 且随淬火温度的升高, 先增高后下降, 在淬火温度为1190 ℃时达到最大值HRC66.4。随淬火温度的升高, 回火态试样的抗弯强度逐渐下降, 碳化物聚集长大倾向明显, 尺寸均匀性下降。M4粉末高速钢的最优淬火温度区间为1180~1190 ℃。     

轴承钢的组织与强韧性

本文研究了GCr15轴承钢经碳化物固溶微细球化预处理及固溶贝氏体预处理后,淬火、回火及等温状态下,碳化物细化及马氏体混合组织对断裂韧性及强度的影响。试验结果表明,经固溶贝氏体处理及固溶微细球化预处理并淬火、回火后,可得到碳化物平均颗粒尺寸≤0.5μm的细小碳化物组织,与一般球化退火并淬火、回火组织相比,在相同的淬火温度下具有较高的强度与硬度,但其断裂韧性仍保持不变(或略有所提高);固溶微细球化处理后经一定时间保温的等温淬火,得到马氏体加贝氏体条状基体中分布着细小碳化物的微细混合组织,其断裂韧性及强度均显著提高,具有最佳配合的强韧性,且其第Ⅱ类显微内应力明显减小。扫描电镜观察分析表明,淬火、回火组织的断裂韧性试样,是以晶界断裂为主具有少量韧窝的混合型断口;经等温淬火得到马氏体与贝氏体组织,其断口为穿晶准解理断裂,且具有较高的撕裂棱。     

Q&P(淬火和分配)工艺对25Si2Ni3钢组织和力学性能的影响

对0.24C-1.72Si-2.96Ni钢进行Q&P处理:880℃15 min-淬火至150～260 ℃(QT)5 min-300℃10min油淬.结果表明,Q&P处理的钢为板条马氏体、残余奥氏体、孪晶马氏体和ε碳化物的复合组织;QT影响钢中马氏体量,随QT由150℃升高至260℃,钢的抗拉强度由1 580 MPa降至1 505 MPa,冲击功由45 J升至50 J.与传统淬-回火工艺相比,Q&P处理钢的抗拉强度降低25～100 MPa,冲击功提高5～8 J,伸长率没有明显变化.     

T8钢淬火及回火组织转变的研究

通过制定相应的淬火及回火工艺,研究了T8钢在不同温度淬火回火后的组织转变过程。应用金相显微镜和扫描电子显微镜对热处理后的组织进行观察,并且应用洛氏硬度计对试样的宏观硬度进行测量。经过试验可知:T8钢最佳淬火温度为850℃,温度过高和过低都是不可取的;随着回火温度的升高,T8钢回火组织依次以回火马氏体、回火托氏体和回火索氏体进行演变;试样在回火后的硬度先升高后下降,在200℃回火时的硬度达到最大值,这是由于马氏体中碳原子的偏聚以及大量弥散的ε-碳化物析出造成的。     

复合变质与热处理对Al-18Si-4Cu-0.5Mg合金组织和性能的影响

采用室温拉伸实验、金相组织观察和扫描电镜观察研究了复合变质处理和T6热处理对过共晶Al-18Si-4Cu-0. 5Mg合金力学性能和显微组织的影响。结果表明,过共晶Al-18Si-4Cu-0.5Mg合金经P-RE-Sr复合变质处理后,初晶硅由粗大不规则板块状细化为细小片状,尺寸明显减小,共晶硅由细长针状转变为珊瑚状、短棒状和蠕虫状,经T6热处理后,初晶硅尺寸无明显变化,共晶硅发生熔断、球化;经P-RE-Sr复合变质处理后,抗拉强度由222MPa提高至236MPa,延伸率由3.22%提高至4.03%;复合变质合金经T6热处理后,抗拉强度大幅度提高,提高至320MPa,但延伸率略有下降,下降至3.37%。     

超高碳钢的回火组织及力学性能

用CM200型透射电子显微镜研究了超高碳钢双相区淬火 中、高温回火后的组织,用Instron型拉伸试验机测定了力学性能.结果表明:650℃的回火组织为等轴状的铁素体与球状的渗碳体,屈服强度σ0.2=1127MPa,抗拉强度σb=1 266 MPa,均匀伸长率δu=8.26%,总伸长率δt=9.71%,维氏硬度HV为397;450℃回火组织的铁素体保持淬火的形态,回火碳化物为ε碳化物在基体上以断续的片状析出,σ0.2=1 911 MPa,σb=2 028MPa,δu=δt=1.88%,HV为595;400℃回火组织中的铁素体保持淬火的形态,回火碳化物在位错处几乎呈网状析出,拉伸无塑性,HV为703.     

Effect of Heat Treatment on Delayed Fracture Resistance of High Strength Steel 30CrMnSi2NiNb

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Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Cr_eq/Ni_eq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software^® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software^® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Cr_eq/Ni_eq equation should be developed or the thermodynamic database of Thermo-Calc software^® should be corrected.     

Anisotropy in Thermal Expansion of Bainitic Ferrite

The evolution of local d-spacings between lattice planes of bainitic ferrite in a high strength quenched and tempered structural steel, S690QL1 (Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt pct)), has been determined to calculate the thermal expansion behavior. For this purpose, in-situ continuous cooling tests have been carried out in a high-energy synchrotron X-ray diffractometer. The results indicate thermal anisotropy in the bainitic ferrite planes.     

In-Situ Synchrotron Diffraction Studies on Transformation Strain Development in a High Strength Quenched and Tempered Structural Steel—Part I. Bainitic Transformation

In-situ phase transformation behavior of a high strength (830 MPa yield stress) quenched and tempered S690QL1 (Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt pct)) structural steel during continuous cooling under different mechanical loading conditions has been studied. Time-temperature-load resolved 2D synchrotron diffraction patterns were recorded and used to calculate the phase fractions and lattice parameters of the phases during heating and cooling cycles under different loading conditions. In addition to the thermal expansion behavior, the effects of the applied stress on the elastic strains during the formation of bainite from austenite and the effect of carbon on the lattice parameter of bainitic ferrite were calculated. The results show that small tensile stresses applied at the transformation temperature do not change the kinetics of the phase transformation. The start temperature for the bainitic transformation decreases upon increasing the applied tensile stress. The elastic strains increase with increase in the applied tensile stress.     

Effects of Rare Earth and Alkaline Earth on Spheroidizing of Eutectic Carbides in Low Tungsten White Cast Iron

Tungsten Alloy White Cast Iron(TAWCI) has great brittleness and narrow application scope. The influences of Rare earth element(Ce) and alkaline earth elements ( K, Na) on the microstructures and performances of TAWCI were researched, and the idea estimating spheroidizing effect of carbides using Circular Degree (C. D) were put forward. The result shows that eutectics carbide tums into sphericity from network after modification, and carbide is refined and uniformly distributed and the C. D of eutectic carbide increases. The mechanism of carbide spheroidizing was analyzed. The impact toughness and wear resistance of TAWCI obviously improve with the rise of C. D of carbides.The service life of modified TAWCI roll is 35 % higher than that of high chromium cast iron roll, and its production cost is reduced by 25 %.     

还原铁粉对Fe-1.1Ni-0.5Mo-0.5Cr合金组织与性能的影响

在惰性气体雾化法制备的Fe-1.1Ni-0.5Mo-0.5Cr预合金粉末中添加1.5％的Cu粉和0.6％的C粉(均为质量分数)以及还原铁粉(添加量分别为0、10％、20％和30％),混合均匀后在600 MPa压力下模压,在1 180℃烧结1h.烧结合金经180℃/1h回火处理后,进行密度、硬度、拉伸力学性能检测以及显微...     

Evolution and Coarsening of Carbides in 2.25Cr-1Mo Steel Weld Metal During High Temperature Tempering

Transformation and coarsening of carbides in 2.25Cr-1Mo steel weld metal during tempering at 700 ℃ for different time intervals ranging from 1 to 150 h were examined by transmission electron microscopy and scanning electron microscopy. M3C carbides were observed in the as-welded specimens and when tempered, the precipitates were mainly composed of M3C, M7C3, and M23C6 carbides. A sequence for corresponding carbide transformation during tempering with initial precipitation of M3C and the subsequent precipitation of M7C3 and M23C6 was proposed. The precipitation of M7C3 with higher chromium content was the main factor contributing to the decrease in coarsening rate of precipitates after prolonged tempering. The decrease in hardness of the tempered specimens agreed well with the prediction of the weakening of precipitation strengthening owing to the coarsening of carbides.     

0.05C-14Mn-19Cr-0.7N高氮奥氏体不锈钢电渣锭的高温塑性

试验0.05C-14Mn-19Cr-0.7N钢经1t非真空感应炉冶炼,并重熔成电渣锭。在电渣锭中心取样,通过Gleeble 3800热模拟试验机对试验钢进行800~1250℃,应变速率0.005~10s^-1的高温拉伸试验,得出温度和应变速率对试验钢断面收缩率的影响,并观察了各温度拉伸后的组织。试验结果表明,随着温度从800℃升高至1250℃,试验钢抗拉强度从327 MPa下降到68 MPa,断面收缩率由22%升至55%;1200℃时,应变速率从0.01s^-1增加到10s^-1时,试验钢的抗拉强度从43 MPa增加至109 MPa,断面收缩率从38%提高至71%。综合实验结果,高氮奥氏体不锈钢0.05C-14Mn-19Cr-0.7N最优的变形参数为:1200~1250℃,应变速率1~10s^-1。     

粉末活化烧结制备高性能铁基合金

将机械球磨后的预合金粉分别与雾化铁粉及羰基铁粉混合,通过真空烧结法制备Fe-3Mo-3Cr-1.2V-0.5Mn-2C铁基粉末冶金材料,研究机械球磨活化预合金粉以及羰基铁粉的加入对材料显微组织结构和力学性能的影响。结果表明:对预合金粉进行机械球磨活化有利于合金元素在雾化铁粉中的烧结扩散,可促进铁基粉末冶金材料的致密化;当采用高表面活性的羰基铁粉作为原料替代雾化铁粉时,能够使样品在低的烧结温度下获得更高的密度及力学性能。其中,在1120℃下烧结条件,铁基合金材料孔隙率较低,晶粒尺寸适中,样品密度为7.68 g/cm³,布氏硬度高达538,抗弯强度为1222 MPa。     

Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment

Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated.Fractographies and microstructures of heat treated samples were observed using a scanning electron microscope and mechanical properties were measured by a universal tensile test machine.The results indicated that during isothermal annealing at 750°C,the tensile strength of pearlitic ductile cast iron was increased to a peak value at 0.5h,and decreased gradually thereafter but the elongation was enhanced with the increase of annealing time.Moreover,the diffusion coefficient of carbon atoms could be approximately calculated as 0.56μm2/s that could be regarded as the shortrange diffusion.As the holding time was short(0.5h),diffusion of carbon atoms was incomplete and mainly occurred around the graphites where the morphology of cementites changed from fragmentized shape to granular shape.In addition,the ductile cast iron with tensile strength of 740MPa and elongation of 7% could be achieved after graphitization annealing heat treatment for 0.5h.Two principal factors should be taken into account.First,the decomposition of a small amount of cementites was beneficial for increasing the ductility up to elongation of 7%.Second,the diffusion of carbon atoms from cementites to graphites could improve the binding force between graphites and matrix,enhancing the tensile strength to 740 MPa.