工艺参数对热冲压成型钢组织性能及硼偏聚的影响

通过Gleeble1500热/力模拟实验机对轧后含硼钢板进行了热冲压过程模拟,分析了各种热处理条件对含硼钢组织性能的影响,并采用X射线衍射技术和径迹照相技术分析了硼的偏聚和硼相析出情况。研究结果表明:提高加热温度或延长保温时间,可促进钢的奥氏体化和硼的偏聚。通过偏聚合适含量的硼,能够很好地起到提高淬透性作用,使材料得到全部马氏体组织。热冲压成型过程中的变形破碎了奥氏体组织,促进相变,更易获得细小的马氏体组织。当冷却速度不高时,钢中"硼相"会沿晶界连续析出,从而降低了硼钢的淬透性。     

热镀锌钢板用冷轧板退火工艺的确定

采用盐浴退火方法分别对牌号为SSGrade40,SSGrade33和SSGrade50的热镀锌钢板的冷轧硬卷进行了不同工艺的退火处理,研究了退火工艺对三种热镀锌钢板用冷轧板显微组织和力学性能的影响,以确定三种冷轧板的再结晶温度及最佳退火温度范围。结果表明：SSGrade40冷轧板的再结晶温度在720℃左右,退火温度在720℃较佳;SSGrade33冷轧板的再结晶温度在680℃左右,考虑到力学性能的稳定性,退火温度选择在720℃左右较佳;SSGrade50冷轧板的再结晶温度在700℃以上,为了保证其强度富余量和性能稳定性,退火温度选择在780℃左右较佳。     

On Optimizing Batch Annealing for the Production of IF Steels

Batch annealing characterized by a long heating cycle and low heating temperature is widely used to produce sheet steels including interstitial-free (IF) steels. Optimizing batch-annealing conditions would be helpful in cutting lead time and saving energy while keeping the necessary deep drawability; however, little research has been done on it. The effects of batch-annealing parameters on the deep drawability of a Ti-stabilized IF steel and Nb+Ti-stabilized IF steel have been investigated. In general, a slight improvement in r_mvalue was found with the increase of annealing temperature. Because of the higher recrystallization temperatures of Nb+Ti-IF steel, it showed higher sensitivity to annealing temperature than Ti-IF steel. In addition, greater dependency of mechanical properties and deep drawability on soaking time was observed when annealing temperature was lower. Moreover, a heat transfer analysis showed that the annealing time could be reduced by 40% if the temperature decreases from 730°C to 650°C. The industrial production has verified that the analytical results are in good agreement with the recorded annealing temperature curve. Meanwhile, it has been shown that Ti-IF steels annealed at 650°C have very close deep drawability and other tensile properties compared with these annealed at 730°C.     

汽车用烘烤硬化板 BH340 及深冲板 St 15 成形性能分析

进行了汽车用烘烤硬化钢板 BH340 及深冲钢板 St15 的力学性能、时效特性和烘烤硬化性能实验,并利用有限元方法模拟了 2 种钢板的成形极限和破裂点应变路径。 分析后指出, BH340 烘烤硬化效应较显著,时效效应不明显,对于汽车外覆盖件成形、涂漆烘烤工艺具有较好的适应性; St15 经形变强化后仍具有良好的塑性,适用于多道次成形工艺。 另外,2 种钢板均具有较为明显的面内异向性。     

Ferrite recrystallisation and intercritical annealing of cold-rolled low alloy medium carbon steel

Static recrystallisation of cold-rolled AISI 4130 medium carbon steel in the ferritic regime and its response to intercritical annealing treatment are studied. A fine and recrystallised microstructure with improved mechanical properties is obtained via subcritical annealing of cold-rolled sheet, where the subsequent intercritical annealing results in the enhancement of tensile strength via the formation of dual-phase microstructure. Intercritical annealing of the cold-rolled sheet is characterised by an initial drop in hardness due to recrystallisation and subsequent rise in hardness as a result of austenitisation. It is revealed that continuous martensite phase can result in a higher deformation resistance. Finally, the effects of intercritical annealing at temperatures below pearlite dissolution finish temperature (Ac_1f) are discussed.     

Technique for partially strengthening electrical steel sheet of IPM motor using cavitation peening

Abstract

Cavitation peening (CP), which utilises the impact caused by cavitation bubbles collapsing, can improve the fatigue strength of metallic materials as well as the yield stress and tensile strength. The rotor cores in interior permanent magnet motors use electrical steel sheet. In order to increase the permissible rotating speed of the motor and achieve high efficiency, the mechanical strength of the stress concentration area in the steel sheet where the magnet is pressed needs to be enhanced. In the present paper, to improve the yield stress and tensile strength, the steel sheet was peened by CP. The peening effect on these mechanical properties was evaluated by tensile and indentation tests. The experimental results from the tensile tests revealed that CP can increase the yield stress by 22% compared to that before CP. In addition, the yield stress and tensile strength increased along with the CP processing time.     

304不锈钢消音蜂窝钎焊工艺、组织及力学性能分析

采用镍基BNi2钎料钎焊制备了304不锈钢消音蜂窝,对蜂窝芯体与面板钎焊界面组织和蜂窝的力学性能进行了分析和测试,并研究了钎焊热循环次数对钎焊界面组织和蜂窝拉伸力学性能的影响,为实际工程应用确定未焊合缺陷补焊次数提供了依据。液态钎料的毛细作用使钎料沿蜂窝芯箔材表面铺展并与箔材发生显著的元素扩散反应,蜂窝芯与面板之间的钎缝由Ni、Cr、Si等互溶而成的Ni基固溶体组织组成,未生成脆性共晶组织或金属间化合物。钎料中的B和Si元素显著扩散于面板材料中,形成钎料-面板反应区,因B元素的沿晶界快速扩散效应,面板侧组织呈现晶界元素渗入特征。随着钎焊次数增加,钎料对母材的溶解和晶界渗透增加,钎焊界面组织发生显著变化。制备的304不锈钢消音蜂窝拉脱强度为7.21MPa,呈现板/芯界面附近蜂窝芯破坏特点,多次钎焊时蜂窝拉脱强度呈下降趋势。制备的304不锈钢消音蜂窝平压、侧压和弯曲力学性能测试过程均经历弹性变形、塑性变形和失稳三个阶段,强度值分别为5.67MPa、33.85MPa和105.87MPa,平压和弯曲失效模型为蜂窝失稳,侧压破坏除蜂窝失稳外,发生穿孔面板与蜂窝芯体剥离的现象。鉴于多次钎焊热循环对蜂窝拉脱强度的不利影响,建议304不锈钢蜂窝钎焊缺陷的最大补焊次数为一次。     

Effect of Cooling History on Yield Ratio of Fine-grain Ferrite/Pearlite Steel

1. IntroductionGrain refinement is the only way to enhance strengthand impact toughness. It has become a new investhotspot for metallurgy industry to produce fine-grain orultra-fine grain high strength steel with a low cost bythermo-mechanical controlled processing (TMCP), com-pact strip production (CSP), ultra-fast cooling processand so on. In the meantime, grain refinement increasesyield ratio of steel, which deteriorates the cold formingperformance, and also arouses the attention of dome…     

Interface sheet-constrained groove pressing as a modified severe plastic deformation process

In this paper, a new severe plastic deformation (SPD) process entitled interface sheet-constrained groove pressing (ISCGP) as a new variant of conventional CGP has been developed for producing ultrafine-grained metallic materials. In this process, repetitive shear deformation is imposed into the sheet material by utilising symmetrically grooved die along with two interface sheet on both sides. To study the applicability, mild steel sheets were processed by both ISCGP and CGP processes, and mechanical and microstructural properties of the processed samples were investigated. The results show a considerable improvement in mechanical properties including hardness, yield strength, and ultimate tensile strength, though the ductility sacrifice was reduced. Comparing ISCGP and conventional CGP revealed interesting results, which are shown that ISCGP can result in better surface quality and ductility.     

微量磷(P)对等原子比NiAl的微观组织与力学性能的影响

研究了微量P对挤压态等原子比NiAl的微观组织与高温力学性能的影响.结果表明:微量P的添加对NiAl的晶格常数有一定的影响,P偏聚于NiAl晶界处;并对其高温延伸率有重要影响.P偏聚于晶界阻碍了合金变形过程中的动态回复和再结晶,加剧了晶界处孔洞的形成,造成了NiAl-P合金与二元NiAl合金高温力学性能的显著差异,主要表现在:应力-应变曲线经历了较长的加工硬化阶段;最大延伸率明显下降;变形激活能升高,应变速率敏感指数下降.NiAl-P合金的高温变形机制为变形过程中位错的滑移与攀移共同作用.     

铜对低碳HSLA钢力学性能的影响

研究了不同铜含量对低碳ＨＳＬＡ钢力学性能的影响。结果表明,铜能显著提高该钢的强度,但降低该钢的韧性。铜含量对ＨＳＬＡ钢强韧性的作用受时效温度的影响,提高时效温度可使不同铜含量的ＨＳＬＡ钢的强韧性差异减小。     

Microstructure and mechanical properties of the T23 steel after long-term ageing at elevated temperature

The paper presents the results of research on the microstructure and mechanical properties of T23 steel after long-term ageing up to 70 000 h at the temperature of 550 and 600 °C. It has been shown that the main mechanisms of degradation of the T23 steel microstructure were: recovery of the matrix, disintegration of the bainitic microstructure, growth of carbide diameter and precipitation of M6C carbides. These processes were more advanced in the steel aged at higher temperature. The changes in the microstructure resulted in a 10–15% decrease in mechanical properties (YS, TS) and hardness HV10, and a 30–40% decrease in the impact energy kV. A greater fall of impact strength occurred in the steel aged at the lower temperature. This was ascribed to the segregation of phosphorus to grain boundaries, which has a well-known adverse effect on ductility of low-alloy steels.     

汽车覆盖件冲压成形灰色关联选材法研究

汽车覆盖件形状结构复杂,冲压时经常多发性地产生不同的成形缺陷,为了解决冲压选材问题,分析了以往选材研究的技术思想,通过试验检测冲压板料的性能数据,揭示当前冲压选材中仍然存在的问题,并使用灰色系统理论表征了冲压成形性能的灰色系统性质,提出应用灰色关联分析对覆盖件进行冲压选材的新方法,且针对行李箱盖内板实例性地说明使用这种方法进行冲压选材的决策过程.研究表明,采用本文方法可以解决传统冲压选材中离散性评判冲压板料各种性能指标的问题.     

Superhardenability behavior of vanadium in 40CrNiMoV steel

The effects of vanadium on the hardenability, microstructures and mechanical properties of 40CrNiMoV steel were investigated after stabilizing nitrogen with aluminum by using an electron microprobe, a scanning electron microscope, a transmission electron microscope, and a hardness tester, etc. The existence state of vanadium in steel was also analyzed. Results showed that aluminum can effectively stabilize nitrogen by producing aluminum nitride. This phenomenon promoted the segregation of solid solution vanadium in grain boundaries, delayed the transformation of ferrite and improved the stability of austenite. Thus, vanadium can potentially improve the hardenability of steels. Excellent mechanical properties of 40CrNiMoV steel were obtained during slow cooling with the addition of vanadium, and this process can be used to produce heavy section steel components.     

初始晶粒尺寸对高温交叉轧制镁合金板材组织和力学性能的影响

目的 揭示晶粒尺寸对多道次高温交叉轧制AZ31镁合金板材组织和力学性能的影响规律及机制.方法 通过对不同初始晶粒尺寸的镁合金板材进行高温交叉轧制变形及热处理,获得不同状态的镁合金板材,采用金相显微分析、X射线衍射(XRD)分析及室温拉伸实验等手段研究镁合金板材的晶粒组织(形态、尺寸、取向)及力学性能.结果 经过多道次交叉轧制后,不同初始晶粒尺寸的板材均发生了孪生现象,但粗晶板材的晶粒尺寸仍明显大于细晶板材.退火处理后,细晶退火态板材组织均匀性较好,而粗晶退火态板材的组织虽有细化,但并不均匀.随着交叉轧制次数的增加,两种板材内非基面取向晶粒都有所增加.退火后粗晶板材中非基面取向晶粒更多.结论 晶粒细化和晶粒取向强化导致退火后的交叉轧制细晶镁合金板材具有更高的强度.粗晶板材伸长率较高主要与其具有更多的非基面取向晶粒有关.     

Evaluation of electroslag remelting in TiC particle reinforced 304 stainless steel

This study is focused on the effect of electroslag remelting (ESR) on microstructure and mechanical properties of TiC particle reinforced 304 stainless steel synthesized by in situ reaction in vacuum introduction melting (VIM). Microstructure observations revealed that applying ESR process resulted in a more uniform distribution of TiC particles with reduced size, however, a slight aggregation with large TiC particles existed in the VIM ingot was found. Additionally, some tiny TiC precipitates with nano-scale were observed in the microstructure of the TiC reinforced steel after ESR process. Introduction of in situ TiC particles into the 304 stainless steel caused a significant increase of tensile properties, creep properties and wear resistance, but a decrease in ductility. Moreover, further improvement on tensile properties, creep properties, wear resistance as well as the ductility of the steel were obtained by using ESR process successfully.     

Relationship of the anisotropy of properties and fracture resistance characteristics to crystallographic texture of 09Khl6N15M3b thin sheet steel

The anisotropy of mechanical properties and crack resistance of 09Khl6N15M3B thin sheet steel is discussed in connection with the change in its crystallographic texture caused by rolling of the sheet to different degrees of reduction. A concept of the relationship of mechanical test results to occurrence of the grain reorientation process during the test is developed.Translated from Problemy Prochnosti, No. 2, pp. 31–36, February, 1991.     

Plastic anisotropy and strain-hardening behavior of Mg–6%Li–1%Zn alloy thin sheet at elevated temperatures

An Mg–Li–Zn (designated as LAZ61) alloy containing about 6 wt% of Li has been prepared by melting and solidification in a carbon steel crucible, and extruded at a billet preheating temperature of 200 °C. The extruded plate was then cold-rolled to a final thickness of 0.6 mm with a total reduction of approximately 82%. Tensile tests were carried out in the rolling and transverse directions and at various temperatures to explore the effects of anisotropy and temperature on mechanical properties and strain-hardening behavior. Kocks–Mecking type plots were used to illustrate different stages of strain hardening. Anisotropic behavior of LZ61 sheet were observed in the mechanical properties at all test temperatures due to the development of texture in α phase during cold-rolling and a low content of BCC β phase. The cold-rolled LZ61 alloy sheet showed stage II and stage III strain-hardening behavior at test temperatures of room temperature and 100 °C. The specimens tested at 200 °C did not show stage II strain hardening. Higher initial strain-hardening rates were observed in the transverse direction as a result of the cold-rolled fibrous structure providing more strong barriers to the dislocation movement.     

The effect of annealing treatment on mechanical properties of aluminum clad steel sheet

In this paper, the effects of annealing temperature and time on mechanical properties and bond strength of aluminum clad steel sheet are evaluated. The results indicate that there exist an optimum annealing temperature and time for achieving a suitable formability and bonding strength between the clad layer and base metal. At this annealing time and temperature, the brittle intermetallic layer at the intimate interface of the layers is minimized.     

Q460C钢板力学性能不合格原因分析

利用光学显微镜和扫描电子显微镜分析了某厂生产的多个批次Q460C钢板力学性能低于GB/T 1591-2008技术要求的原因.结果表明:钢板中心偏析造成的贝氏体组织、微裂纹、MnS以及铌和钛复合夹杂物的存在是导致该Q460C钢板力学性能不合格的主要原因;另轧制工艺控制不当造成的魏氏体组织也会降低钢板的力学性能.