Effect of Baking Process on Microstructures and Mechanical Properties of Low Silicon TRIP Steel Sheet with Niobium

After 2% predeformation,the baking treatment with different schedule was carried out for low silicon TRIP steel sheet with niobium.The effects of baking temperature and time on microstructures and mechanical properties were investigated.The results showed that with increasing the baking temperature and time,the volume fraction of retained austenite decreases,and the volume fraction of tempered martensite increases;as baking temperature ranges from 80 ℃ to 170 ℃,the bake-hardening(BH)value increases obviously,while from 170 ℃ to 230 ℃,the variation of BH value is very slight;as baking time ranges from 2 min to 20 min,the BH value increases significantly,while the BH value decreases when baking time exceeds 20 min.So that when the baking temperature is 170 ℃ and the baking time is 20 min,the low silicon TRIP steel sheet exhibits good bake-hardening behavior,and the highest BH value is above 70 MPa.     

Phase Transformation and Mechanical Properties of an Ultrahigh Strength Steel

The present study deals with the development of a low carbon high strength steel by thermomechanical controlled processing on a pilot scale.The continuous cooling transformation has yielded a flat top "C" curve with the phase field occupied by a mixture of bainite and martensite.The microstructure of water quenched steel essentially consists of highly dislocated lath martensite along with fine (Ti,Nb)CN precipitates and twins.High strength steel with 1217-1298 MPa yield strength and 1372-1513 MPa ultimate tensile strength along with 16-12% total elongation has been obtained in the range of 850 to 750℃ finish rolling temperature.The impact toughness value in the range of 45-72J was also achieved in the present steel.     

控冷返红温度对Q460GJE高建钢组织和力学性能的影响

利用Gleeble热力学模拟机、扫描电镜、透射电镜、着色腐蚀金相等方法研究了控冷返红温度对TMCP交货态低屈强比(不大于0.80)Q460GJE高建钢组织和力学性能的影响。结果表明:随着返红温度的升高,一方面,粒状贝氏体数量减少,针状铁素体数量增加,晶粒显著粗化,屈服强度降低;另一方面,硬相M-A岛的数量增多、尺寸增大,抗拉强度略有上升,屈强比和冲击功(-40℃)降低。拉伸和冲击性能均满足低屈强比Q460GJE钢要求的返红温度范围是590~620℃。     

回火温度对Q960级高强结构钢组织及力学性能的影响

 以屈服强度960MPa级高强调质结构钢板开发为目标,研究了在相同轧制及淬火条件下,回火温度对试验钢显微结构及力学性能的影响。结果表明：随回火温度的升高,试验钢强度下降,韧塑性总体上呈现升高趋势,其中在300~450℃范围内出现一个韧塑性能的恶化区。当回火温度为600℃时,试验钢呈回火索氏体组织,屈服强度为1030MPa,抗拉强度为1080MPa,伸长率为15.9%,-40℃冲击功达144J,各项指标均满足国标GB/T 16270—2009要求。并对试验钢的拉伸力学性能进行了探讨。     

Effect of Cooling Method on Microstructure and Mechanical Properties of Hot-Rolled C-Si-Mn TRIP Steel

 The controlled cooling technology following hot rolling process is a vital factor that affects the final microstructure and mechanical properties of the hot-rolled transformation induced plasticity (TRIP) steels. In the present study, low alloy C-Si-Mn TRIP steel was successfully fabricated by hot rolling process with a 450 hot rolling mill. To maximize the volume fraction and stability of retained austenite of the steel, two different cooling methods (air-cooling and ultra-fast cooling “AC-UFC” and ultra-fast cooling, air-cooling and ultra-fast cooling “UFC-AC-UFC”) were conducted. The effects of the cooling method on the microstructure of hot-rolled TRIP steel were investigated via optical microscope, transmission electron microscope and conversion electron Mssbauer spectroscope. The mechanical properties of the steel were also evaluated by conventional tensile test. The results indicated that ferrite and bainite in the microstructure were refined with the cooling method of UFC-AC-UFC. The morphology of retained austenite was also changed from small islands distributing in bainite district (obtained with AC-UFC) to granular shape locating at the triple junction of the ferrite grain boundaries (obtained with UFC-AC-UFC). As a result, the TRIP steel with a content of retained austenite of 1152%, total elongation of 32% and product of tensile strength and total elongation of 27552 MPa·% was obtained.     

TRIP钢显微组织与性能关系的评述

概述了近20年来汽车材料中TRIP钢的研究进展情况。对影响TRIP钢强度和塑性的显微组织从其大小、形貌及含量等多方面进行了分析和比较，认为要使TRIP钢具优良的强度和塑性匹配，应优化该钢显微组织中各相含量的配比。     

Effect of Controlled Cooling After Hot Rolling on Mechanical Properties of Hot Rolled TRIP Steel

A three-step cooling pattern on the runout table（ROT）was conducted for the hot rolled TRIP steel.Microstructural evolution during thermomechanical controlled processing（TMCP）was investigated.Processing condition of controlled cooling on a ROT in the laboratory rolling mill was discussed.The results indicated that the microstructure containing polygonal ferrite,granular bainite and a significant amount of the stable retained austenite can be obtained through three-step cooling on the ROT after hot rolling.TMCP led to ferrite grain refinement.Controlled cooling after hot rolling resulted in the stability of the remaining austenite and a satisfactory TRIP effect.Excellent mechanical properties were obtained through TMCP for the hot rolled TRIP steel.     

稀土在金刚石圆锯片节块烧结中的作用

本文从胎体对金刚石的把持力、烧结对金刚石性能以及胎体的机械性能的影响等方面探讨了稀土对金刚石节块烧结性能的影响。实验结果表明，由于稀土的加入，起到活化烧结和类似预氧化烧结的目的，使得加入该元素的金刚石节块在锯切中的使用寿命得到显著提高，该元素在组合锯节块烧结中的作用尤为重要。     

Effects of Warm Deformation on Mechanical Properties of TRIP Aided Fe-C-Mn-Si Multiphase Steel

 Warm deformation tests were performed using a kind of tubby heater. The microstructures and mechanical properties of an Fe-C-Mn-Si multiphase steel resulting from different warm deformation temperatures were investigated by using LOM (light optical microscopy), SEM and XRD. The results indicated that the microstructure containing polygonal ferrite, granular bainite and a significant amount of the stable retained austenite can be obtained through hot deformation and subsequent austempering. Warm deformation temperature affects the mechanical properties of the hot rolled TRIP steels. Ultimate tensile strength balance reached maximum (881 MPa) when the specimen was deformed at 250 ℃, and the total elongation and strength-ductility reached maximum (38% and 28614 MPa·%, respectively) at deforming temperature of 100 ℃. Martensite could nucleate when austenite was deformed above Ms, because mechanical driving force compensates the decrease of chemical driving force. The TRIP effect occurs in the Fe-C-Mn-Si multiphase steel at deforming temperature ranging from 15 to 350 ℃. The results of the effects of warm deformation on the mechanical properties of the Fe-C-Mn-Si multiphase steel can provide theoretical basis for the applications and the warm working of the hot rolled TRIP sheet steels in industrial manufacturing.     

Si-Mn系超高强度热成形淬火钢板的点焊性能

 采用不同的点焊工艺参数对研发的1700MPa级Si-Mn系热成形淬火钢板与低碳钢板DC04进行异种材料之间点焊,并对焊接接头的拉伸性能、显微硬度分布及微观组织特征等进行了分析。结果表明,焊接电流对点焊接头熔核直径和抗剪强度具有显著的影响,而焊接时间的影响相对较小。超高强度钢板侧的热影响区存在两个明显的软化区和硬化区,即在靠近母材处存在一个硬度明显低于母材的软化区,其组织为回火马氏体;在靠近熔核处存在一个硬度明显高于母材的硬化区,其组织为细小的马氏体。点焊接头熔核部位为柱状粗大马氏体组织,其硬度明显低于超高强度钢板母材且远高于低碳钢板母材。低碳钢板热影响区低的硬度和明显粗化的铁素体组织,使得点焊接头单向拉伸时均从低碳钢板的热影响区一侧破断。     

温度参数对铌微合金高强度结构钢组织性能的影响

通过控轧控冷试验,力学性能检验和组织的光学显微观察,研究了温度参数对铌微合金钢组织性能的影响。结果表明:两阶段控轧及控冷所获晶粒尺寸明显小于常规轧制+快速冷却的晶粒尺寸;随冷却速率的增大或终冷温度的降低或精轧开轧温度的降低,试验钢晶粒细化,混晶程度加重,强度增大,塑性降低;精轧低温开轧利于韧性提高;铁素体混晶可能源于因铸坯中Nb(C,N)的不均匀分布造成的原始奥氏体混晶,粗轧大压缩比轧制可以消除这种混晶现象。     

The Effects of Strain Rate and Temperature on the Deformation Behavior of Cold‐Rolled TRIP800 Steel

In the present study, the influences of temperature and strain rate on the deformation behavior of cold‐rolled TRIP800 steel were investigated. Microstructural observation and tensile tests were performed and volume fractions of retained austenite were measured at various temperatures and strain rates. The results reveal that both temperature and strain rate affect the volume fractions of retained austenite that transforms into martensite. The strain‐induced transformation of retained austenite is retarded with increasing temperature and the retained austenite becomes more stable against straining. The amount of retained austenite that transforms into martensite is not influenced significantly by strain rate. The variation in mechanical properties with temperature and strain rate was related to the effects of dynamic strain aging, tempering of banite, high temperature softening, and the volume fractions of retained austenite.     

终轧温度对低硅含磷系TRIP钢组织性能的影响

通过实验室热轧试验,研究了不同终轧温度下低硅含磷系热轧TRIP钢的组织特征及性能特点。结果表明：终轧温度由900℃降低到790℃,铁素体体积分数增加,贝氏体体积分数降低,残余奥氏体体积分数变化不太明显;终轧温度900和820℃时,得到贝氏体为基体的室温组织;终轧温度降低到790℃时,低温变形促进了奥氏体到铁素体的相变率...     

光整对热镀锌IF钢板力学性能的影响

在生产DQ级以下的热镀锌机组上进行了Ti—IF钢热镀锌实验,研究了光整对Ti-IF钢热镀锌板力学性能的影响。实验结果表明,在正常情况下,热镀锌钢板其屈服强度在150MPa左右,r,n平均值分别为2．5和0．25。但是光整后,屈服强度明显提高,n值明显降低。实验结果,提出了根据用户的不同要求,采用不同的工艺路线来保证Ti—IF钢的力学性能。并且对热镀锌Ti—IF钢力学性能的控制问题进行了一些讨论。     

控轧控冷工艺对低合金高强钢Q460力学性能的影响

通过改变终轧温度及轧后冷却速度,研究了终轧温度及轧后冷却速度对力学性能的影响。研究结果表明：采用轧后加速冷却的方法,可以显著细化Q460的铁素体晶粒,从而提高其强韧性能。当冷速从2℃/s提高到3.86℃/s时,铁素体晶粒直径从11.5μm细化到8.33μm。当冷速达到2.96℃/s以上时,Rel≥475MPa,Rm≥600MPa,屈强比为70%-80%。     

1000MPa级TRIP钢的组织性能及强化机理

鉴于热镀锌TRIP钢在成分和工艺上的特殊性,试验采用低Si含P以及V微合金化的成分设计思路,并进行镀锌连续退火工艺模拟,分析其微观组织和性能。探讨了残余奥氏体稳定性的影响因素及强化机理。结果表明,添加P和采取较高的冷轧变形量均有利于提高残余奥氏体量及其稳定性。在残余奥氏体的形变诱导马氏体相变、贝氏体和V析出的强化作用以及铁素体晶粒细化的共同作用下,抗拉强度和强塑积分别达到1 035 MPa和25 875 MPa·%。     

热机械控制工艺对热轧TRIP钢力学性能的影响

通过实验室热轧机研究了热机械控制工艺(TMCP)对热轧TRIP钢力学性能的影响.结果表明:在热轧变形过程中应变诱导铁素体相变,低温大变形量造成铁素体晶粒细化.随终轧温度的降低和终轧变形量的增加,残余奥氏体的稳定性增加,相变诱发塑性(TRIP)效果更好.在700 ℃终轧且终轧变形量为50%时,抗拉强度、屈服强度和总伸长率分别达到791 MPa,538 MPa和36%的最大值.     

Effect of Prestrain on Microstructures and Properties of Si-Al-Mn TRIP Steel Sheet with Niobium

Paint baking treatment was carried out in a silicon oil bath at 170℃ for 20min for Si-Al-Mn TRIP Steel sheet with different prestrains,and effect of prestrain on microstructures and properties was studied before and after baking.The results show that with the increasing of prestrain amount during prestraining and baking,the volume fraction of retained austenite decreases,and the volume fraction of martensite and bainite increases as well as yield strength increases;as prestrain ranges from 0 to 4%,the baking-hardening(BH)value increases;while the prestrain ranges from 4% to 16%,the BH value decreases;when the prestrain amount is 4%,the highest BH value is about 70MPa for Si-Al-Mn TRIP steel sheet with niobium,which displays excellent baking-hardening behavior.     

应变速率对钛合金室温拉伸性能的影响

拉伸速率对金属材料的室温拉伸性能影响很大,文章介绍了不同应变速率对钛合金Ti6Al4V(TC4)、TA15和Ti1023室温拉伸性能影响的研究进展,并通过分析和归纳,阐述了第一应变速率和第二应变速率对钛合金的抗拉强度、屈服强度、断后伸长率及断面收缩率的影响程度和规律,最后对应变速率对钛合金室温拉伸性能影响研究的发展方向进行了展望。