组织因数对双相钢拉伸性能的影响

本文研究了经不同热处理获得的双相钢的显微组织特征及其对拉伸性能的影响。结果表明,铁素体的相硬化和马氏体的相软化现象的存在是双相钢的一个重要的组织特征;双相钢的强度除主要决定于马氏体含量外,还随马氏体岛长度直径比的增大而升高;用纤维复合材料混合律来估价不同组织状态的双相钢强度偏差均较大。     

双相钢复合板制封头成型工艺与材料要求

主要阐述复合板材料封头的成型工艺及材料要求,针对双相不锈钢复合板材料本身的特性,在原材料采购和验收时分别对基层、覆层以及复合板提出相关要求与检查。通过对封头板材料的分析及制造经验,封头成型时选择热压成型,并对随炉试板进行理化分析和力学性能试验,验证原材料的性能没有降低,确定封头成型工艺的可行性,为今后制造类似材料的封头提供一定经验。     

双相钢的力学性能和对成形极限的影响

对两个来自不同生产线的冷轧双相钢DP780试样的主要力学性能进行比较,发现相同牌号的DP钢产品性能有显著差异。建立拉伸过程的有限元模型,将拉伸试验和有限元仿真相结合,利用材料失效点主应变二次导数的变化规律准确预测DP780在拉伸过程中的缩颈和破裂。研究发现相同牌号的DP钢产品成形极限亦有明显不同。最后从延伸长度和极限应变两方面定量分析应变强化指数n值和强度系数K值的变化对拉伸过程成形极限的影响。发现应变强化指数n值的变化对成形极限影响较大,强度系数K值的变化对成形极限影响较小。增大n值可以提高发生缩颈和破裂时的延伸长度和极限应变。     

20钢薄板质量对冷冲压加工性能的影响

本文以某厂生产的２０钢薄板冷冲离合器底盘为例，选取其中的合格件和开裂件各一只进行检验。采用宏观断口分析和光学金相显微分析等方法，对冷冲压加工质量出现的差异，作了较为全面的分析和比较。结果表明：钢的化学成分，组织和非金属夹杂物缺陷等是影响冷冲性能的主要原因。     

超级双相钢复合板16MnR+SAF2507热成型工艺

对目前国际范围内应用较少、耐腐蚀强的超级复合双相钢板16MnR＋SAF2507的成型特点进行了试验分析，归纳了其成型工艺，并提出了应用的注意事项，得出了经验性结论。     

终轧温度对热轧双相钢微观形貌的影响

利用实验室轧机、光学显微镜、透射电镜等研究了终轧温度对高强热轧双相钢微观形貌的影响.结果表明:得到的双相钢的显微组织主要是纤维状双相混合型组织;随终轧温度的降低,过冷度加大,铁素体的形核驱动力加大,形核率增加,使晶粒明显细化.     

冷轧薄板冲压件成型影响因素及实例分析

本文概述了冷轧薄板冲压件成型性能的评价指标及其对冲压性能的影响,从材料的化学成分、厚度及表面质量、晶体的形态及加工工艺三个方面简述了其对冲压性能各个指标的影响机理,并对冲压实例进行了简要分析,有利于提高冷轧薄板的冲压成型质量。     

Ti及中间温度对双相钢强度影响规律研究

本文在已有的强度预测模型基础上,增加考虑了第二相析出强化对双相钢抗拉强度的影响,对已有强度预测模型进行了完善。利用完善后模型并结合Thermo-Cal软件讨论了不同Ti元素添加量和不同淬火温度对双相钢抗拉强度的影响。结果显示,在0.12%的Ti含量内,随着Ti含量的增加双相钢的强度逐步增大。高温时析出相以TiN为主,随着温度的降低,析出相逐渐转变为TiC。随淬火温度的升高马氏体体积分数增加,马氏体含C量下降,双相钢的强度增加。     

应变时效对双相钢和低合金高强钢屈服强度及应变硬化率的影响

通过力学性能测试和显微组织观察研究了应变时效对双相钢和低合金高强钢屈服强度及应变硬化率的影响。结果表明:经过2%预应变之后,双相钢的屈服强度提高了106MPa,低合金高强钢的屈服强度提高了28MPa;预应变之后再经历烘烤,双相钢的屈服强度提高了149MPa,而低合金高强钢的屈服强度只提高了66MPa;预应变或烘烤硬化之后,两种钢的应变硬化率均降低,但双相钢仍然具有很强的应变硬化能力,其应变硬化率接近于低合金高强钢未预应变条件下的;铁素体马氏体组织赋予了双相钢比低合金高强钢更强的应变硬化能力。     

EFFECT OF CUTTING CONDITIONS ON THE SERRATED CHIP FORMATION IN HIGH-SPEED CUTTING

Titanium alloy Ti6A14V has been widely used in many engineering fields due to its attractive specific strength and corrosion resistance. A deep understanding of the material's machinability is of primary importance. This article investigates the serrated chip formation mechanism of Ti6Al4V alloy under high-speed cutting by finite element analysis. The effect of the cutting conditions on the serrated chip formation is analyzed comprehensively. The study found that when the initial chip thickness becomes small or when the rake angle becomes large, the size of sawtooth decreases and the number of sawtooth increases. The serrated chip morphology is more sensitive to the initial chip thickness. The severe fluctuation of cutting forces is caused by the formation of sawtooth in chipping. To minimize the serrated chipping in high-speed machining, the initial chip thickness is the most important factor to consider.     

循环应力应变关系对碳素钢疲劳寿命预测的影响

通过试验对拉压载荷下材料的循环应力应变关系进行测试,建立了表达式σ＝ｋεｐ＾ｍ中常数κ、ｍ与材料的静抗拉强度间的经验式,并用该方程式可以直接由材料的静抗拉强度比较简便地预测材料的疲劳强度。最后与国外常用的拉压状态下的应力应变经验式σ＝１．７３σｂεｐ＾０．１６进行了比较;得到了两种材料疲劳寿命预测结果。     

300M钢冲击疲劳裂纹起始的超载效应

本文研究了超载对300M超高强度钢冲击疲劳裂纹起始寿命的影响。结果表明,在一定范围内,拉伸超载可以延长冲击疲劳裂纹起始寿命;超载造成的残余应力是引起该钢超载效应的主要机制而超载造成的材料性能变化对超载效应的贡献不大;超载后冲击疲劳裂纹起始寿命Ni与缺口根部残余应变εR之间的关系可表示为：NI=N0·exp（λεR）。     

管道钢断裂韧性尺寸效应的研究

断裂韧性作为评估管道结构完整性的一个重要参数,对其进行尺寸效应研究具有重要的科学意义和工程价值。当前对金属材料断裂韧性尺寸效应的研究主要集中于线弹性断裂参数应力强度因子K,且大多仅考虑试件厚度的影响。为建立试件尺寸对高强度高韧性管道钢材料断裂韧性的系统影响规律,基于Gurson-Tvergaard-Needelman (GTN)模型对单边切口梁(SENB)试件三维断裂过程进行模拟,选用裂纹尖端张开位移(CTOD)与裂纹尖端张开角(CTOA)对其断裂韧性进行表征,分析两者沿试件厚度的分布规律,并研究裂纹深度与试件厚度对其影响。同时选取应力三轴度对试件约束水平进行评估,以此解释断裂韧性尺寸效应存在的原因。研究结果表明:断裂韧性在试件厚度方向一定范围内基本保持不变,在自由表面处取得最大值;裂纹深度对断裂韧性几乎没有影响,而试件厚度越大,断裂韧性越低,且临界CTOA比临界CTOD更能反映断裂韧性的变化规律。     

缓冲层对硬质合金环与钢体钎焊接头残余应力的影响

采用有限元软件对硬质合金圆环与钢基体钎焊接头残余应力的分布状态进行模拟,研究缓冲层对接头残余应力的影响,结果表明, 在钎缝与硬质合金一侧接触面上残余应力最大,在接触面上靠近中心侧区域为最危险区域.通过添加缓冲层,可以大大缓解焊后的残余应力,且缓冲层的厚度存在最佳值.经试验验证,计算结果与试验基本一致.     

INFLUENCE OF MACHINING PARAMETERS ON THE WHITE LAYER FORMATION PROCESS AND ITS CHARACTERISTICS IN TURNING OF HARDENED STEEL

This article contains results of experimental research activities of white layer formation (WLF) and its characteristics during a process of turning hardened steels (THS), which have been carried out in laboratories of DD Cimos TMD Ai Grada?ac. WLF. Characteristics during the THS process were analyzed from the aspects of influence caused by machining parameters as well as tool flank wear width. Experimental tests of tool wear have been performed. The tool used in experimental tool wear was ceramic cutting insert CNGA 120408T, catalogue mark IN22 Al2O3-TiCN. In accordance with achieved results, value of tool flank wear 220 µm has been set as the criterion of wear. In accordance with defined wear criterion, determination of level and type of influence that machining parameters have on WLF and its characteristics were carried out in accordance with planned experimental methodology. Experiments have shown that cutting speed and tool flank wear width (for all other machining conditions unchanged) can be used for control of WLF and its characteristics. Structural changes in surface layer of the working piece, during the cutting process of hardened material, except for the WLF are also presented through a transition zone, e.g., dark layer, which has lower hardness than the initial material. Hard WL can take over a protection role for a machined surface from abrasive actions, while softened zone (dark layer) can take over a function of WL solder with the initial material. Analysis of achieved results points to a possibility of controlling the WLF and its characteristics, and therefore a possibility of using WL in a positive context. The basis for the above mentioned is the effect of additional plastic deformation of WL (APDWL), which occurs only under certain machining conditions. The effect seen, if follows WLF, results in decrease of machined surface roughness compared to its expected value. Accordingly there is a possibility for identification of WL on a machined surface by measuring the roughness parameters without previous metallographic preparation of samples.     

DISTRIBUTION OF Cu AND ITS EFFECT ON MICROSTRUCTURE OF Cu-BEARING STEEL

In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These steels are annealed at 1 260℃, 1 100℃and 1 000℃respectively for one hour and followed by furnace cooling to room temperature to simulate the heat treatment before the rolling process. The results show that Cu did not obviously segregate in annealed steels. The scanning electron microscope (SEM) observation show that the main microstructures in Cu-bearing steel are ferrite and pearlite; The volume fraction of pearlite in steel increase with increasing Cu content. The grain size reduces with the decrease of annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that the Cu content in pearlite is higher than that in ferrite, which means that the microstructure-segregation of Cu exists. However, the cast specimens show that Cu content in MnS and S-rich phase is very high, and Cu changed the distribution of MnS in steel. In addition, the optimal Cu content in steel between 0.2%-0.4% and the optimal annealing temperature between 1 100-1 200℃are determined by the economical and practical principles.     

扭转预应变对45钢低周疲劳性能的影响

介绍４５钢在不同扭转预应力变下的低周疲劳性能,包括循环应力－应变特性,循环硬化软化特性及低周疲劳寿命的研究工作。结果表明,扭转预应变降低周疲劳寿命,循环应力随扭转预应变的增大而增大。     

EFFECT OF DYNAMIC LOADING ON FRACTURE BEHAVIOR OF WELDED JOINTS OF STRUCTURAL STEEL

To investigate the effect of dynamic loading on fracture behavior of welded joints of structural steel Q23SB and 16Mn in common use and compare the earthquake resistances of the two kinds of materials, dynamic tension and fracture toughness tests are carried out at room temperature. On the basis of the tests, the stress-strain fields near the crack tip of the compact specimens are analyzed by three-dimensional finite element model. The test results and finite element analysis results show that, the fracture toughness of welds and base metal of 16Mn steel increases with the increment of loading rate. Compared with 16Mn steel, Q235B steel is more sensitive to dynamic loading. The fracture toughness of welds of Q235B is comparatively low under static loading and dynamic loading at room temperature. Compared with the static loading, the fracture toughness of Q235B parent metal under dynamic loading decreases by about four times. Therefore, it can be concluded that compared with 16Mn steel, the earthquake re     

EFFECT OF TENSILE STRESS AND RESIDUAL STRESS ON THE SPONTANEOUS STRAY FIELD SIGNALS FROM THE SURFACE OF 0.45%C STEEL

In order to explore the quantitative method of metal magnetic memory testing(MMMT) and clarify the relationship between Hp(y), the normal component of spontaneous stray field, and applied stress or residual stress, the static tensile tests of 0.45%C steel sheet specimens are carried out on a servo hydraulic MTS810 machine. Hp(y) values are measured during the test process by an EMS-2003 metal magnetic memory diagnostic apparatus and a non-magnetic electric control displacement instrument. Residual stresses of some points on the surface of a specimen are measured by a Stress Tech X-Stress 3000 X-ray diffraction instrument. The results show that the same variation rules of Hp(y) value versus applied tensile stress are presented under the different conditions of load-on and load-off. However, the same rule does not exist between the Hp(y) value and residual stress. The variation of Hp(y) value reflects the history of applied tensile stress.