Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed Interstitial-Free Steel

The processing conditions of the texture formation and deep drawability of a Ti-IF steel strip hot-rolled in ferritic region and subsequently annealed were investigated. The r-value increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the r-value is raised up to 1.75, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the r-value is below 1.0 in the case of unlubricated rolling. The X-ray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong { 111 }//ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of { 110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and （110}//ND recrystallization texture is strong, which deteriorates the formability.     

加钛深冲钢的工艺优化实践

为了获得深冲性能优良的冲压用冷轧板,对济钢加钛深冲钢的化学成分进行了优化设计,即降低了碳质量分数,并采用高温终轧、高温卷取、适宜的冷轧变形量(70%～75%) 等优化的热轧、冷轧和退火工艺。工艺优化后的加钛深冲钢具有比原工艺更低的下屈强比、更高的塑性应变比、更高的应变硬化指数和更多的有利的{111}取向织构比例,最终使其具有优异的深冲性能,满足了市场的深冲压要求。     

Evolution of Grain-Boundary Microstructure and Texture in Interstitial-Free Steel Processed by Equal-Channel Angular Extrusion

The equal-channel angular extrusion (ECAE) of Ti-bearing interstitial-free (IF) steel was performed following two different routes, up to four passes, at a temperature of 300 °C. The ECAE led to a grain refinement to submicron size. After the second pass, the grain size attained saturation thereafter. The microstructural analysis indicated the presence of coincident-site lattice (CSL) boundaries in significant fraction, in addition to a high volume fraction of high-angle random boundaries and some low-angle boundaries after the deformation. Among the special boundaries, Σ3 and Σ13 were the most prominent ones and their fraction depended on the processing route followed. A deviation in the misorientation angle distribution from the Mackenzie distribution was noticed. The crystallographic texture after the first pass resembled that of simple shear, with the {112}, {110}, and {123} aligned to the macroscopic shear plane.     

微碳深冲钢的生产工艺研究

研究了采用连续退火方式生产微碳深冲钢的工艺。通过实验室模拟的方法研究了工艺参数热轧卷取温度，冷轧压下率及退火温度对宝钢微碳深冲钢性能的影响，从而为实际生产过程的工艺参数优化提供参考。实验结果表明，热轧卷取温度为730℃，冷轧压下率在75％，退火温度在830℃时，深冲板的综合性能最佳，此时轧向试样的塑性应变比r值可达到2．0，延伸率δ可达到48％。     

Optimization of Friction Welding Process Parameters for Joining Carbon Steel and Stainless Steel

 Friction welding is a solid state joining process used extensively currently owing to its advantages such as low heat input, high production efficiency, ease of manufacture, and environment friendliness. Materials difficult to be welded by fusion welding processes can be successfully welded by friction welding. An attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AISI 1040 grade medium carbon steel and AISI 304 austenitic stainless steel, incorporating the process parameters such as friction pressure, forging pressure, friction time and forging time, which have great influence on strength of the joints. Response surface methodology was applied to optimize the friction welding process parameters to attain maximum tensile strength of the joint. The maximum tensile strength of 543 MPa could be obtained for the joints fabricated under the welding conditions of friction pressure of 90 MPa, forging pressure of 90 MPa, friction time of 6 s and forging time of 6 s.     

CSP热轧无取向电工钢的织构特征

研究了CSP生产的无取向电工钢(w(Si Al)=1%)热轧板的织构特征,并与传统流程产品进行了比较.发现两种工艺生产的产品在板厚1/2处的主织构均为{001}《110》织构,即典型的{001}//轧面的α纤维织构.二者的织构沿厚度方向均呈不均匀分布,其强度及对称性从表层到中心逐渐加强.     

Impact Toughness of Ultrafine-Grained Interstitial-Free Steel

Impact toughness of an ultrafine-grained (UFG) interstitial-free (IF) steel produced by equal-channel angular extrusion/pressing (ECAE/P) at room temperature was investigated using Charpy impact tests. The UFG IF steel shows an improved combination of strength and impact toughness compared with the corresponding coarse-grained (CG) one. The CG IF steel samples underwent a transition in fracture toughness values with decreasing temperature because of a sudden change in fracture mode from microvoid coalescence (ductile) to cleavage (brittle) fracture. Grain refinement down to the submicron (??320?nm) levels increased the impact energies in the upper shelf and lower shelf regions, and it considerably decreased the ductile-to-brittle transition temperature (DBTT) from 233?K (?40?°C) for the CG steel to approximately 183?K (?90?°C) for the UFG steel. Also, the sudden drop in DBTT with a small transition range for the CG sample changed to a more gradual decrease in energy for the UFG sample. The improvement in toughness after UFG formation was attributed to the combined effects of grain refinement and delamination and/or separation in the heavily deformed microstructure. Although an obvious change from the ductile fracture by dimples to the brittle fracture by cleavage was recognized at 233?K (?40?°C) for the CG steel, no fully brittle fracture occurred even at 103?K (?170?°C) in the UFG steel.     

Microstructure and Mechanical Properties of Ultrafine-Grained Interstitial-Free Steel Processed by ECAP

Equal-channel angular pressing (ECAP) of interstitial-free (IF) steel at equivalent strain, ε_vm = 12 has been employed to develop ultrafine-grained (UFG) microstructure with high fraction of low angle grain boundaries, that enhances strength significantly with reduced tensile ductility. ECAPed IF steel has been deformed further by cold rolling/cryorolling at ?50 °C to >90 % reduction in area. It is observed that the UFG structure gets refined with an improvement in high angle grain boundary fraction and heavily stressed non-equilibrium grain boundaries in cryorolled state resulting in significant strengthening. However, the decrease in grain size to an ultrafine level with the increased lattice strain lowers the work hardening ability of the material that limits its ductility. Hence, the rolled samples are flash annealed at 675 °C in order to recover the ductility of the material by achieving partially recrystallized structures. Consequently, the increased subgrain size as well as the grain size, the reduced residual lattice strain, lower hardness and strength with marginal recovery of ductility is maintained in order to attain the yield strength 2–3 times compared to that of as-received coarse-grained IF steel.     

帘线钢轧制工艺优化改进

通过提高连铸坯加热温度和轧制过程温度,优化控冷工艺,盘条的抗拉强度提高了28MPa,断面收缩率提高了3.4%,金相组织明显改善,索氏体化率提高了0.97%,氧化铁皮厚度增加了46.58%,利于机械除鳞,最终产品质量达到重点用户的要求。     

Modeling Deformation Texture and Anisotropy during the Tensile Test of an Interstitial-Free Steel Sheet by Means of a Self-Consistent Viscoplastic Model

A self-consistent viscoplastic (VPSC) model was employed to simulate the evolution of the r value and stress during a tensile test. To perform the calculation, the one-site approximation (a grain embedded in an infinite medium) was used. The anisotropic responses of both the grain and the medium were considered. The model calculations were compared with experimental results measured on an interstitial-free (IF) steel, including evolution of texture, stress, and r during deformation. The model shows qualitatively good agreement with the experimental results; however, an overestimation of the r value when the tensile test is performed in the diagonal direction was observed. The origin of this discrepancy needs further investigation. The role of work hardening (latent hardening) and grain rotation on the evolution of r is described. Finally, the VPSC results were compared to the Taylor-based model results.

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Ratcheting Behavior of a Titanium-Stabilized Interstitial Free Steel

Engineering stress-control ratcheting behavior of a titanium-stabilized interstitial free steel has been studied under different combinations of mean stress and stress amplitude at a stress rate of 250 MPa s^?1. Tests have been done up to 29.80 pct true ratcheting strain evolution in the specimens at three maximum stress levels. It is observed that this amount of ratcheting strain is more than the uniform tensile strain at a strain rate of 10^?3 s^?1 and evolves without showing tensile instability of the specimens. In the process of ratcheting strain evolution at constant maximum stresses, the effect of increasing stress amplitude is found to be more than that of increasing the mean stress component. Further, the constant maximum stress ratcheting test results reveal that the number of cycles (N) required for 29.80 pct. true ratcheting strain evolution exponentially increases with increase of stress ratio (R). Post-ratcheting tensile test results showing increase of strength and linear decrease in ductility with increasing R at different constant maximum stresses indicate that stress parameters used during ratcheting tests influence the size of the dislocation cell structure of the steel even with the same amount of ratcheting strain evolution. It is postulated that during ratcheting fatigue, damage becomes greater with the increase of R for any fixed amount of ratcheting strain evolution at constant maximum stress.     

品种钢生产连铸工艺优化

介绍了新疆八一钢铁股份公司第二炼钢厂品种钢生产实践过程中,针对铸坯存在中心偏析、中心疏松、缩孔、夹杂等缺陷,通过连铸工艺改进,采用保护浇注、中间包挡墙、电磁搅拌参数优化、二冷优化等措施使产品质量提高的过程。     

UCM轧机轧制高强钢工艺控制参数优化

探讨了通过优化某厂UCM轧机各项工艺参数,可实现稳定批量化生产高强系列用钢,利用CSP(薄板坯连铸连轧)+TCM(冷连扎)机组生产抗拉强度超过540 MPa的高强冷硬钢带的可行性,采用新设计的轧制规程和工艺制度可实现稳定生产高强度冷硬钢带。     

IF钢的二次加工脆性及其评定方法

随着现代真空冶炼技术的采用,钢中的碳、氮含量可以降到很低的水平,Ｃ＜５０×１０－６,Ｎ＜３０×１０－６;只需添加少量的钛或（和）铌来固定钢中的碳和氮,可生产出无间隙原子钢,即ＩＦ钢。ＩＦ钢是目前成形性能最好,级别最高的冲压用钢。它是继沸腾钢、铝镇静钢之后第三代冲压用钢。超低碳无间隙原子（ＩＦ）钢中的碳、氮原子被钛或铌固定钢质十分纯净。ＩＦ钢中的晶界上诸如碳、氮等固溶原子,使晶界的结合力大大降低,从而使深冲钢板在低温高速时发生晶界断裂现象。另一方面,为了生产高强钢常采用加磷固溶强化,加磷ＩＦ钢受到…     

Biaxial Stretching Behavior of a Copper-Alloyed Interstitial-Free Steel by Bulge Test

Biaxial stretching behavior of a promising high-strength copper-alloyed interstitial-free (IF) steel has been investigated under various processing conditions using bulge tests. Hill theory and von Mises yield criterion have been used to analyze the results. It is revealed that copper-alloyed IF steel in continuous-annealed (CA) condition exhibits the highest equivalent strain at fracture and largest limiting dome height (LDH) among all the processing conditions. However, these values are lower in copper-alloyed interstitial steel than in traditional interstitial-free–high-strength (IF-HS) steels due to the presence of solute copper and copper precipitates in the former.     

Silicon Pick-up of Interstitial-Free Steel From MgO-SiC Refractories

The silicon pick-up of interstitial-free steel （IF steel） from resin bonded MgO-SiC refractories is studied via a medium frequency induction furnace. Samples of IF steel were heated in MgO-SiC crucibles with mould flux cover at 1 600 ℃ for 180 min. The silicon contents of IF steel samples taken from the molten steel in every 30 min were examined and the refractories after heating were investigated by electron probe microanalysis （EPMA） with energy dispersive spectrometer （EDS）. The silicon content of steel rapidly increased in the first 90 min of beating, and then decreased because of the formation of liquid layer on the refractory. Liquid layer separated the liquid steel from the bulk refractory and stopped the pick-up of silicon. At the same time, desilication via oxygen through the liquid layer and flux started to reduce the silicon content of the liquid steel     

挤压工艺参数优化

挤压速度及温度极限与挤压机能力，合金的高温屈服强度，变形程度，表面质量和组织性能有关，本文主要阐述利用计算机确定挤压极限图，优化挤压工艺参数的方法。     

热轧工艺对409L铁素体不锈钢深冲性的影响

对含有单一柱状晶的409L铁素体不锈钢连铸坯,采用不同终轧温度的热轧工艺,由常规热轧转变为温轧,再经过相同后续工艺;较低终轧温度的成品获得了较高rm值和较低△r值.终轧温度的降低使组织演变发生变化:热轧和冷轧组织中晶界和晶内剪切带增多,变形组织被细化、硬化,尤其是中心层附近的粗大带状晶粒;两者的增多又增加了退火过程中的再结晶形核点,使退火组织细化、均匀化.终轧温度的降低也使织构演变发生变化:热轧及其退火织构由{001～114}(110)向高ρ1和Φ值区域移动;冷轧织构峰值由{001}(110)转移至{335}(110);冷轧退火织构的γ组分增多,峰值由{334}(483)转移至{111}(112),而{001～114}(110)和(0°<Φ<35°,ρ1≈25°)组分减少.     

Laser Quenching of Ionic Nitrided Steel: Effect of Process Parameters on Microstructure and Optimization

The surface properties of 40CrMnMo7 steel have been increased by ionic nitriding thermo chemical treatment followed by laser quenching. Nitriding treatment increases the wear resistance and decreases the wear coefficient, guaranteeing an uniform, though shallow, hardening depth. Combining nitriding with laser quenching has been shown to increase of the hardening depth, while retaining the advantages obtained by the first treatment. In this work the effect of laser quenching parameters on microstructure and mechanical properties of 40CrMnMo7 steel have been investigated and predictive models developed suitable for further optimization of the process. DoE has been exploited to reduce the number of experiments and for evaluating by statistic methods the optimized process parameters.