未再结晶区控轧工艺对HQ60钢的显微组织与力学性能的影响

研究了未再结晶区的不同压下率对含Ｎｂ－Ｖｉ的ＨＱ６０低合金钢的组织和性能的影响。结果表明，当未再结晶区的累计压下率由４０％提高到７０％时，ＨＱ６０钢的晶粒由４．８５μｍ细化到２．７７μｍ，强度和韧性都有较大提高，使得这种由铁素体、贝氏体和珠光体等复相组织组成的钢的强韧性得到了改善。     

Kinetic analysis of the austenitic grain growth in HSLA steel with a low carbon content

The austenitic normal grain growth of the 16MnNi4 HSLA steel has been investigated by means of the simplified kinetic model developed by Burke and Turhbull. The equation involved in the model allows the setting of a correlation between the kinetic parameters and the microstructure features of the materials. The grain growth exponent (n) has been studied to interpret the mechanism of grain growth in the samples with different heat treatments. It was noted that the kinetic n exponent value increases when the temperature decreases. The variation in the n values (from 2 until 8) has been associated with the solubility or precipitation of the different microalloyed elements presented in the HSLA steel. Also, the activation energies have been calculated obtaining different values depending on the heat treatment.     

高强度低合金SA633D钢的研制

叙述了ＳＡ６３３Ｄ钢的工业性试制工艺，对ＳＡ６３３Ｄ钢的组织和低温韧性进行了试验研究，测定出钢板晶粒度为９－１１级，其脆性转变温度为－５２℃。结果证明：舞钢生产的ＳＡ６３３Ｄ钢质量已达到美国ＡＳＭＥ ＳＡ６３３标准中Ｄ级钢要求。     

DYNAMIC CRACK PROPAGATION AND CRACK ARREST INVESTIGATED WITH A NEW SPECIMEN GEOMETRY: PART II: EXPERIMENTAL STUDY ON A LOW-ALLOY FERRITIC STEEL

The novel experiment developed in our Institute to investigate crack initiation, rapid crack propagation and crack arrest with one specimen, the ring test, was applied to a ferritic HSLA pipeline steel. The maximum crack speed achieved in these experiments was between 230 m/s and 1165 m/s. The fracture toughness at crack arrest, K_Ia, was determined by a static analysis of this specific test. In all cases, it was found that K_Ia was much lower than K_Ic. The values of K_Ia decrease when the maximum crack speed increases, the results being largely scattered. The fracture toughness at crack arrest is therefore not an intrinsic parameter of the material for a given temperature. Cleavage fracture obtained under these conditions is characterized by the existence of numerous cleavage microcracks, mechanical twins and unbroken ligaments. The decrease in fracture toughness when crack speed increases is related, using the Beremin or the RKR model, to the high strain rates at the tip of a rapid propagating crack. A model which takes into account the effect of unbroken ligaments left in the wake of a propagating crack is developed to account for the large values of K_Ia which were occasionally measured.     

低冷却速度下700MPa级V，Ti微合金化高强钢组织和性能

采用光学显微镜、扫描电镜和透射电镜观察700MPa级钒微合金化低合金高强钢热轧后在3~5,1.5~2和0.3~0.5℃/s三个不同冷却速度下获得的微观组织,对晶粒度、珠光体体积分数、珠光体片层间距进行了定量分析,测定了拉伸性能并观察了拉伸断口。结果显示,冷却速度为1.5~2℃/s时产品性能最佳。这是因为该冷却速度下铁素体基体上纳米碳化物数量增加且弥散细小,析出强化效果随析出物数量呈线性增加。     

奥氏体化温度对900 MPa级HSLA钢显微组织和晶体学演变的影响

采用OM和SEM研究了奥氏体化温度对HSLA钢组织演变和低温韧性的影响.结果 表明:奥氏体化温度由850℃升高至950℃(实验钢的AC3温度为819℃)并保温30 min后,奥氏体的平均晶粒尺寸由7.22 μm增大到17.39 μm,在850～950℃淬火后的显微组织均为板条马氏体,屈服强度和抗拉强度均呈下降趋势,延伸...     

Effect of heat-input and cooling-time on bead characteristics in SAW

Load-carrying capacity of weld joints could be identified by its shape and size where weld bead geometry and shape relationship parameters are of utmost importance. Heat input and preheating temperature together can control the cooling time of weld, which in turn determines the weld microstructure and its mechanical properties. To control the shape and geometry of weld bead, it is necessary to understand its relationship with cooling time. In present work, preheating temperature is used as process variable along with heat input varying parameters for understanding their effects on weld bead geometry and shape relationship parameters using submerged arc welding process on high-strength low alloy pipeline steel. The experimental investigation was then analyzed by using the mathematical modeling in context with response surface methodology. The mathematical model predicts the influential dependency of cooling time on the preheating temperature than the other weld process parameters. The associated effects in relation to the process parameters have been discussed and analyzed in the present study.     

Measurement of springback

Springback, the elastically-driven change of shape of a part after forming, has been measured under carefully-controlled laboratory conditions corresponding to those found in press-forming operations. Constitutive equations emphasizing low-strain behavior were generated for three automotive body alloys: drawing-quality silicon-killed steel; high-strength low-alloy steel; and 6022-T4 aluminum. Strip draw-bend tests were then conducted using a range of die radii (3<R/t<17), friction coefficients (0<μ<0.20), and controlled tensile forces (0.5<F_b/F_y<1.5). Springback angles and curvatures were measured for bend and bend–unbend areas of the specimen, the latter corresponding to the “sidewall curl” region, which dominates the geometric change and the dependence on process variables. Friction coefficient and R/t (die-radius-to-sheet-thickness) greater than 5 have modest but measurable effects over the ranges tested. As expected, strip tension dominates the springback sensitivity, with higher forces reducing springback. For 6022-T4, springback is dramatically reduced as the tensile stress approaches the yield stress, corresponding to the appearance of a persistent anticlastic curvature. The presence of this curvature, orthogonal to the principal curvature, violates the simple two-dimensional models of springback reported in the literature. The measured springback angles and curvatures are reported both in graphical summary and tabular form for use in assessing analytical models of springback.     

HSLA钢组织—性能对应关系的预测模型

通过HSLA钢中各组成相的体积分数、铁素体晶粒尺寸、析出相的尺寸和体积分数等参数,分别考虑了细晶强化、相变强化和析出强化等强韧化机制对强度和韧性等机械性能的影响,建立了HSLA钢组织一性能对应关系的预测模型。模型的预测精度通过两种HSLA钢实验室控轧控冷的组织一性能实验数据获得验证。     

用添加合金粉末埋弧焊工艺焊接16MnR钢

用添加合金粉末埋弧焊工艺可以大线能量焊接１６ＭｎＲ钢,单道焊缝的熔深２０ｍｍ,焊接熔敷速度大于２６．６ｋｇ／ｈ熔敷系数大于３４．６ｇ／ｈ．Ａ,焊缝和ＨＡＺ的显微组织良好,焊接接头常温力学性能达到国家标准要求。