圆管铝型材挤压模具失效分析及其热处理工艺优化

采用残骸分析法研究H13钢圆管铝型材挤压模具失效的凸模发现,分流桥脆性开裂的主要原因是热处理不当,并用正交试验法对热处理工艺参数进行优化。结果表明:经过优化工艺热处理后,退火态组织为颗粒状渗碳体弥散在铁素体上的球状珠光体,淬火态组织为细针马氏体+残余奥氏体+剩余碳化物,回火态组织为碳化物颗粒细小、分布均匀的回火屈氏体+回火马氏体+残余渗碳体,材料的各项力学性能为:抗拉强度为1549 MPa、屈服强度为1420 MPa、冲击韧性为34.7 J·cm-2、伸长率为15.2%、断面收缩率为36.7%和硬度为49.6 HRC,为避免模具脆性开裂失效提供了良好的金相组织和力学性能保证。     

Q-P-T工艺中C配分对4Cr5MoSiV1Ti钢力学性能的影响

采用扫描电镜(SEM)、洛氏硬度计、电子拉伸试验机和夏比冲击摆锤等分析了 4Cr5MoSiV1Ti钢经Q-P-T(淬火+碳分配+回火)热处理后的组织性能.结果表明:当碳配分温度为400℃和碳配分时间为3 min时,试验钢的冲击韧性达到26.25 J·cm-2,碳配分时间增加到20 min和60 min,其强度和硬度均呈上升趋势;当碳配分温度为370℃和碳配分时间为3 min时,试验钢的硬度值为49.66 HRC,冲击韧性为25J·cm-2,断面收缩率为51.2％;当碳配分温度升高到400℃和430℃,试验钢的强度提高,冲击韧性和断面收缩率呈先上升后下降的趋势.     

60CrNiMo轧辊钢的热处理工艺

通过光学显微镜观察试验钢的显微组织,利用万能试验机、摆锤冲击试验机和布氏硬度计分别检测试验钢的强度、塑性、冲击性能和硬度,研究了热处理工艺对60CrNiMo轧辊钢组织性能的影响。结果表明,400℃等温淬火时得到的贝氏体和珠光体的混合组织其强度和塑韧性较差;相比较于马氏体等温淬火+高温回火工艺,采用两相区亚温淬火,形成的铁素体和回火马氏体双相组织,可有效改善试验钢的力学性能,并且可以避免淬火裂纹的产生;试验钢经马氏体等温淬火+亚温淬火+高温回火热处理后其布氏硬度为318 HBW,规定塑性延伸强度(R_(p0.2))为797 MPa,抗拉强度为981 MPa,伸长率15%,断面收缩率为46%,室温冲击吸收能量达到66 J,各项性能指标均优于国家标准JB/T 6401—2017中的要求。     

回火工艺对高速列车用DZ2车轴钢组织及力学性能的影响

通过试验研究了不同热处理工艺对高速列车用DZ2车轴钢组织及力学性能的影响。结果表明,在580～700℃之间回火时,新开发的高速列车用DZ2车轴钢组织均为回火索氏体组织;随着回火温度的升高,试验料中马氏体位相逐渐消失,位错密度下降,碳化物逐渐析出和球化;随着回火温度的提高,试验钢抗拉强度和屈服强度逐渐下降,断面收缩率、断后伸长率和冲击韧性逐渐增加,其中,在640℃以下回火时,冲击韧性增加的幅度比较显著,当回火温度高于640℃时,冲击韧性提高幅度较小。     

回火温度对低合金高强度无缝钢管组织和性能的影响

研究了淬火后回火温度对一种新型低合金高强度无缝钢管的组织和力学性能的影响。结果表明:试验钢管经930℃淬火和0～750℃回火后,抗拉强度为959～1 375 MPa; 200和700℃回火后冲击吸收能量最高,400及500℃回火后冲击吸收能量最低,并出现了回火马氏体脆性。200℃回火后抗拉强度为1 375 MPa,断后伸长率为13.8%,断面收缩率为60.9%,冲击吸收能量为63.4 J。700℃回火后抗拉强度为981 MPa,断后伸长率为18.8%,断面收缩率为51%,冲击吸收能量为68.7 J。200℃回火组织为回火马氏体和少量残留奥氏体,700℃回火组织为回火索氏体。     

热处理工艺对RAFM钢组织与性能的影响

现有低活化铁素体/马氏体(RAFM)钢的室温力学性能和高温力学性能都还不能完全满足下一代聚变反应堆的高效率运行条件,选用电渣重熔技术熔炼了一种新的RAFM钢.研究了淬火温度和回火温度对新RAFM钢微观组织和力学性能的影响,利用光学显微镜和扫描电镜对其性能进行了测试与分析.结果表明,RAFM试验钢采用980 ℃淬火+780 ℃回火热处理工艺时,组织为板条马氏体;室温抗拉强度为680.79 MPa,伸长率为31.1%,断面收缩率为71.91%.     

回火温度对3Cr2MnNiMoV钢组织与力学性能的影响

采用OM、SEM、TEM和硬度测试等手段,研究了不同回火温度对3Cr2MnNiMoV预硬型塑料模具钢组织和力学性能的影响。结果表明:在380~640℃回火,随回火温度升高,试验钢的回火硬度、抗拉强度和屈服强度,总体呈相同的下降趋势,而冲击功和断面收缩率显著增加;经560℃回火后,试验钢具有最佳的综合力学性能:硬度44 HRC,冲击功65J,抗拉强度1450 MPa,屈服强度1300 MPa,断面收缩率61%;在380℃回火时,钢的基体组织析出了不规则短杆状渗碳体导致室温冲击韧性较低。随温度升高,渗碳体形貌由短杆状变为细小颗粒状且分布均匀使室温冲击韧性不断提高。     

38CrSi合金结构钢

正38CrSi合金结构钢具有高强度、中等韧性、较高耐磨性、淬透性比40Cr稍好、在油中临界淬透直径达Φ25～Φ83. 5 mm;耐回火性好、可切削加工性尚好、但热处理时有回火脆性倾向,且冷变形塑性低、焊接性差。力学性能:抗拉强度σ_b≥960 MPa;屈服强度σ_(0. 2)≥840 MPa;伸长率δ_5≥12%;断面收缩率ψ≥50%;冲击功A_(k v)≥55 J;冲击韧性值α_(k v)≥69 J/cm~2;布氏硬度≤255 HBS_(100/3000)(退火或高温回火)。     

固溶-高温回火对D2钢组织性能的影响

对D2钢进行不同处理后,利用OM、SEM和XRD进行了微观组织分析,并测试了硬度与冲击韧性,研究固溶-高温回火球化预处理对D2钢微观组织与性能的影响。结果表明:D2钢经固溶-高温回火处理后碳化物偏析程度明显降低,高温回火时碳和合金元素从过饱和的马氏体基体中析出,均匀聚集长大形成合金碳化物颗粒,改善了基体中碳化物的形态和分布;最佳的预处理工艺参数为780℃回火6 h,经最佳预处理-淬回火后,材料冲击韧性提高了23.8%。     

回火温度对Cr5NiMoVNb支承辊用钢组织与性能的影响

为了研究回火温度对Cr5NiMoVNb支承辊用钢显微组织及力学性能的影响,采用扫描电镜、X射线衍射仪、洛氏硬度计、拉伸试验机和冲击试验机对不同回火温度下Cr5NiMoVNb钢进行了测试。结果表明:Cr5NiMoVNb钢的回火态组织以回火马氏体为主,并含有少量的残留奥氏体。回火过程中伴随有碳化物的析出和马氏体相变。随着回火温度的升高,Cr5NiMoVNb钢的强度(抗拉强度与屈服强度)与硬度逐渐降低,塑性(伸长率与断面收缩率)与韧性(冲击吸收能量)逐渐提高。在试验选定范围内,520 ℃回火的Cr5NiMoVNb钢的硬度、抗拉强度、断面收缩率和冲击吸收能量分别达到53.5 HRC、1735 MPa、25.2%和7.3 J,综合力学性能最优。     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

胫骨生物陶瓷复合材料的微结构增韧机理

扫描电镜观察显示胫骨是一种由羟基磷灰石和胶原蛋白组成的自然生物陶瓷复合材料.羟基磷灰石具有层状的微结构并且平行于骨的表面排列.观察也显示这些羟基磷灰石层又是由许多羟基磷灰石片所组成,这些羟基磷灰石片具有长而薄的形状,也以平行的方式整齐排列.基于在胫骨中观察到的羟基磷灰石片的微结构特征,通过微结构模型分析及实验,研究了羟基磷灰石片平行排列微结构的最大拔出能.结果表明,羟基磷灰石片长而薄的形状以及平行排列方式增加了其最大拔出能,进而提高了骨的断裂韧性.     

Mechanism of Nucleation of Precipitates of Carbides of Refractory Metals Under Hot Rolling of Automotive Sheet Steel

Metal Science and Heat Treatment - The problem of formation of properties in microalloyed sheet steels is considered. The cause and the possible mechanism of precipitation of carbides of refractory...     

燃煤机组锅炉烟气脱硝灰中氨含量测定

NOx是大气环境的主要污染物之一,其主要来源为火力发电机组。依靠低氮燃烧技术,远达不到排放要求。选择性催化还原脱硝(简称SCR)技术是目前效率最高、最成熟、应用最广泛的电厂烟气脱硝技术。目前,在线氨逃逸监测技术存在诸多问题,影响了氨逃逸监测数据的准确度和稳定性。在燃料种类、炉膛结构、受热面布置、过量空气量、炉膛气流分布以及脱硝催化剂类型等条件确定的情况下,控制好氨加入量及其逃逸量是保证NOx脱除率的关键所在。燃煤锅炉除尘飞灰氨含量可侧面反映脱硝氨逃逸率的状况。根据国外的文献报道,正常情况下,电除尘灰中氨含量一般在50mg/kg-100mg/kg范围内。由于国内尚无灰中氨含量的测定方法,亦无脱硝运行对飞灰含氨量影响的数据积累。本文通过大量试验,确定了灰中氨溶解条件(如溶解时间、搅拌状态、灰水比、灰样量及其稳定性等),制定了灰中氨含量测定方法。     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.