采用等效模拟技术研究热轧及轧后冷却工艺

近年来,热轧技术的进步突出表现在节约能源与节约资源的技术开发方面。具体表现为: (1)采用连铸技术,尽可能使用圆、方、扁、中空、异形铸坯直接进行轧制。 (2)采用板型及几何尺寸控制技术,提高钢板横向厚度精度,提高钢材利用率。     

立辊轧机宽度自动控制设计与应用

立辊轧机宽度手动控制方式精度低。随着热轧钢板厚度精度要求的不断提高提出了宽度自动控制改进方案:采用位置闭环控制取代了原来的速度开环控制,并取消了原来的机械同步轴,提高了宽度控制精度和控制方式的灵活性,降低了钢板切边损耗、减小头尾剪切量、提高钢板成材率,为热轧生产创造较大的直接经济效益。     

CSP板带热连轧中氧化铁皮的控制技术

在实验室对不同工艺不同厚度的CSP热轧钢板进行了酸洗速度、表面粗糙度、氧化皮厚度与组成等一系列实验,与传统热轧钢板进行了对比。研究发现CSP生产的钢板的氧化皮组成与传统热轧板接近,但氧化皮厚度、酸洗后钢板表面粗糙度均大于传统热轧钢板,酸洗速度快于传统钢板。     

700 MPa级厚规格高强钢板剪切分层原因分析

采用直读光谱仪、显微硬度计、金相显微镜、扫描电子显微镜等研究了700 MPa级高强钢板剪切分层的原因。结果显示：钢板1/2厚度处的带状组织、含铌和钛的第二相夹杂物是造成高强钢板剪切分层的主要原因，分层从剪切面的带状组织开始并沿其扩展。带状组织降低了钢板的低温冲击韧性，分层处-40℃横向冲击吸收能量的平均值仅为9 J,远小于正常部位的26 J,从而增加了钢板成形开裂的风险。钢板的带状组织及第二相夹杂物的产生与铸坯质量密切相关，提高连铸设备精度，控制钢水过热度，采用合理的动态轻压下及电磁搅拌工艺，增大热轧道次压下量，能改善或消除钢板的剪切分层。     

X射线测厚技术在热轧钢板生产中的应用

结合英国Thermo Radiometrie公司生产的RM312多功能板型仪,分析使用X射线测量技术测量热轧板带尺寸时存在的问题及解决办法。该方法测量热轧钢板厚度时,需要解决各种干扰对测量精度的影响。采用合金补偿、温度补偿、双射线源立体测量和在线标准化等技术,较好地消除了合金成分、温度、位移变化及噪声对测量精度的影响,为轧线控制系统提供了丰富的实时测量数据,有力地支持了热轧钢板的板形控制。     

资讯

2014年3月初．日本JFE钢铁公司开发出了具有高成形性．含碳量035％的高碳热轧钢板”SuperHot-G”。“SuperHot—G”具有与冷轧钢板相媲美的板厚精度．板厚仅为3mm．可将厚度允许偏差控制在±80um以下。该高碳热轧钢板的开发进一步扩大了对复杂形状部件实施;中压成形的范围,适于加工齿轮及无级变速箱（CVT）的活塞等反复转动或往复运动的驱动类部件。     

TMCP技术在Q345B低合金化生产中的应用

采用TMCP控轧控冷技术,用普碳钢成分生产出了Q345B高强度热轧带钢。生产中通过调整中间坯厚度与成品厚度之比,同时控制终轧温度和卷取温度,将铁素体晶粒细化和珠光体相变强化相结合,得到了高强高韧性热轧钢板。钢板冷成型性和焊接性良好,实现了Q345B的合金减量化生产。     

空分设备用1100/3004/1100合金复合板带材工艺研究

研究了新型铝合金复合板带材的热轧工艺、冷轧工艺、成品热处理制度,确定了包覆层厚度精度和成品厚度精度控制方法.总结出新型铝合金复合板带材热轧、冷轧、热处理等工艺参数.     

汽车大梁用热轧黑皮表面钢板355L的研制

通过对热轧钢板的氧化层形成机制及影响因素的分析研究,确定了汽车大梁用热轧黑皮表面钢板 355L的成分及热轧工艺制度。采用金相组织观察、分析、X-射线衍射仪分析、力学性能测试等方法,分析了钢板的组织、性能、氧化层形貌和结构组成,结果表明：所试制的热轧黑皮表面钢板氧化层结合良好,氧化层中的Fe3O4含量大于85%,氧化层厚度不大于10μm,用于无酸洗工序直接冲压汽车大梁件,氧化层脱落较少,效果良好。     

正火温度对钒氮微合金化WH630E钢板组织和性能的影响

利用转炉炼钢底吹氮气和炉外精炼工艺实现钒氮微合金化,利用连铸坯,采取控轧控冷工艺轧制8~30 mm厚度的WH630E钢板,取热轧态钢板进行正火处理试验,对比热轧态和不同正火态钢板的力学性能和组织变化发现,正火处理可进一步细化热轧态钢板的铁素体晶粒,提高钢板的低温冲击吸收能量,正火态钢板的强化以晶粒细化为主,晶粒细化作用强于V(CN)的析出强化作用。     

Braze‐welding of electrical conductors to concentric plugs

In resistance spot welding of thin sheet–thick sheet–thick sheet joint, when the sheet thickness ratio is large (sheet thickness ratio = total thickness of sheet joint/thickness of the thin sheet positioned on the outside of the joint), how to stably secure the nugget between the thin sheet and the adjoining thick sheet is a key issue. If the sheet thickness ratio is so large, nugget formation between the thin sheet and thick sheet is extremely difficult. In order to control of the nugget (position of formation, shape, etc. of the nugget) during welding for three sheets joint with a high sheet thickness ratio, optimum welding process was investigated. The developed ‘two-step force, two-step current’ welding process was suitable for high sheet thickness ratio joint and relaxed the constraints on the sheet thickness ratio. In Step 1 (first part of welding period) of the welding process, a nugget is reliably formed between the thin sheet and thick sheet by applying conditions of low electrode force, short welding time, and high current. In the subsequent Step 2 (second part of welding period), a nugget is formed between the two thick sheets by applying high welding force and a long welding time. In the weld results of a three sheet joint (0.7+2.3+2.3 mm; sheet thickness ratio: 7.6) using mild steel GA (0.7 mm) as the thin sheet and 780 MPa high strength GA (2.3 mm) in the two thick sheets, ‘two-step force, two-step current’ spot welding process showed the wide available welding current range.     

Weld growth mechanisms during resistance spot welding of two and three thickness lap joints

Abstract

Understanding the mechanisms of weld growth during resistance spot welding is a prerequisite for the development of optimum welding conditions which ensure high levels of joint quality in autobody manufacture. This study compared the heat development/weld growth of double and triple sheet lap joints as a means of understanding the role of welding conditions, sheet thickness configuration, and physical material properties on joint microstructure and performance. High temperature heat patterns have been determined using metallographic and thermographic techniques for double and triple sheet lap joints in uncoated low carbon steel. In the case of double sheet joints, initial heat generation and weld nugget formation was observed to occur where the resistance to the flow of current was the greatest, i.e. at the sheet/sheet interface. This was also the case for heat generation in triple sheet joints, but in this more complex case weld nugget formation was dependent on sheet thickness and joint configuration. Furthermore, the incubation period to weld nugget formation was dependent on total joint thickness with a longer weld time required for joints of greater thickness. For non-uniform triple sheet joints, heating was observed to be concentrated around the thinnest sheet as a result of the way heat was dissipated by the steel substrate.     

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 借助X-射线三维取向分布函数（ODF）研究了低碳冷轧用热轧卷板在奥氏体区热轧的织构特征及其沿板宽和板厚方向的变化规律。结果表明：热轧板卷表层、1/4层和1/2层的主织构分别为{110}<111>和{001}<110>织构。热轧板卷沿板宽方向的边部的织构强度相对较高的原因是由于热轧时板卷的边部的冷却速度较快所致。热轧板卷表层织构沿板宽方向的变化的规律性不强主要是因为该层的变形量较小且变形状态复杂及其温度变化较大造成的。热轧板卷头部的平均织构强度弱,尾部的平均织构强度高,这是由于热轧板卷尾部的温度相对较低所致。     

微细黄铜板料尺寸效应

为研究微细尺度下材料的晶粒尺寸d、厚度t对其力学性能的影响,引入尺寸效应影响因子φ=t/d,在常温下对具有不同晶粒尺寸和板厚的H62黄铜薄板试样进行单向拉伸实验。结果表明,随着φ的减小,流动应力减小,延伸率下降;板料硬化指数n值,随板料厚度的增加而增大,随晶粒尺寸的增大而增大。拉伸试样均为韧窝微孔聚合型断裂,0.5mm和1.0mm厚度试样断口处韧窝多而浅,且为抛物线形,材料韧性好,塑性强;板厚0.1mm和0.2mm的试样断口韧窝深而大,硬化指数n值大,但塑性差。     

AZ31B镁合金热拉伸流变应力研究

针对不同加工方法制备的AZ31B镁合金薄板,利用热拉伸试验机和金相显微镜对其在不同温度和变形速率下的流变应力进行了实验研究。结果表明,变形温度和变形速率对热拉伸时镁合金的流变应力有显著影响,峰值流变应力随应变速率的降低和变形温度的升高而降低。峰值流变应力随板材的厚度增加而发生变化,低温时厚度效应较为明显。退火处理对冷轧板的峰值流变应力影响较小,冷轧板可直接用于热加工成形。峰值流变应力变化规律:挤压板>热轧板>冷轧板。     

板料零件数控渐进成形工艺研究

板料零件数控渐进成形工艺是一种通过数字控制设备 ,采用预先编制好的控制程序逐点成形板料零件的柔性加工工艺。本文就板料零件数控渐进成形工艺的成形过程、变形机理、极限半顶角等方面进行了探讨。认为 ,板料零件数控渐进成形是使板料的厚度减薄 ,表面积增大 ,靠逐次的变形累积产生整体的变形。变形区厚度的变化与成形半顶角有关 ,其中 ,成形极限半顶角是数控渐进成形能否成功的关键 ,它不仅与材料有关 ,而且与板料厚度有关。     

基于冲压与数控渐进成形的复合成形

针对冲压工艺难以成形形状复杂板材件、冲压模具难以制造或加工成本高以及单独采用数控渐进成形加工效率低的问题,提出基于冲压工艺与数控渐进成形工艺相结合的复合成形方法,并给出了基于冲压与数控渐进成形的复合成形的数值模拟方法。采用冲压成形、数控渐进成形和复合成形3种成形方式,以有限元分析软件数值模拟分析同一形状板材件,对比分析数值模拟后的板材件的轮廓尺寸精度与厚度分布。结果可知,采用复合成形得到的板材件轮廓尺寸精度与厚度分布能够满足实际应用,所提出的复合成形方法具有可应用性。     

Critical sheet thickness for weld nugget growth during resistance spot welding of three‐steel sheets

Abstract

One of the most important issues in resistance spot welding of three‐sheet stack joints is the insufficient growth of the weld nugget, which may cause problems in places needing larger weld nuggets (i.e. sheet/sheet interface). In this paper, the effect of sheet thickness on the pattern of weld nugget development during resistance spot welding of three‐steel sheets of equal thickness is studied. Results showed that there is a critical sheet thickness of 1·5?mm at which the fusion zone size at the sheet/sheet interface is nearly equal to the fusion zone size at the geometrical centre of the joint. Increasing the sheet thickness beyond the critical size causes a shift in the location of weld nugget formation from the geometrical centre to the sheet/sheet interfaces. Below the critical sheet thickness, the weld nugget growth in the geometrical centre of the joint is higher than that in the sheet/sheet interface.     

常化工艺对高牌号无取向硅钢组织和织构的影响

以Si质量分数为3.3%的高牌号无取向硅钢为研究对象,研究了常化处理对试验钢厚度方向组织和织构的影响。结果表明：高牌号无取向硅钢热轧板沿厚度方向组织及织构不均匀导致常化板沿厚度方向出现织构梯度;常化处理可以明显改善热轧板组织和织构,促进晶粒粗大均匀,降低α纤维织构强度,增强λ纤维织构强度,减弱γ纤维织构强度。950 ℃常化时,常化板沿厚度方向晶粒粗大均匀,λ纤维织构强度最大。     

Microstructure,texture and grain boundaries character distribution evolution of ferritic stainless steel during rolling process

In order to better understand the texture, microstructure and grain boundaries character distribution evolution of ferritic stainless steel, the texture, microstructure and grain boundaries character distribution of ferritic stainless steel (hot rolled sheet, cold rolled sheet and annealing sheet) with 11 wt%Cr content were studied using X-ray diffraction and electron back scattered diffraction technique. The texture of the hot and cold rolled sheets has a through-thickness texture gradient. In the center layer of the hot and cold rolling sheet, α-fiber texture was observed which was attributed to ideal plane strain deformation. Close to the surface a Gross orientation was detected which was attributed to shear deformation. During annealing, the γ-fiber was formed attributed to recrystallization process. The microstructure of the hot and cold rolled sheets was non-homogeneous through the sheet thickness, while, the microstructure of annealing sheets was homogeneous through the sheet thickness. Grain boundaries character distribution results show that there are many low angle grain boundaries in hot and cold rolled sheets and many high angle grain boundaries and coincidence site lattice after annealing. The above results indicated that the changes in texture are closely related to the grain boundaries type.