20CrMnTiH钢锯切断锯条原因分析

对齿轮钢钢材锯切下料时遇到的锯切障碍现象进行了系统的分析,认为引起这种现象的原因是钢材的局部区域存在着比较多的大颗粒硬质夹杂物,导致了该区域的硬度升高。     

J100A钢高速冷锯的热处理

钢材冷态高速切割的应用已日渐广泛，对高速冷锯的需求量逐年增加。高速锯切冷态钢材的冷据，要求能承受很大的冲击力，而用来制造热切四锯的65Mn钢，由于其冲击韧度值a。较低（10～14）／cm2），在锯切过程中银极极易破裂，不能满足快速生产的需要。为此我们选用了鞍山钢铁公司生产的J100A钢来制造高速冷锯。1高速冷锯的性能要求及JIOoA钢的成分用J100A钢（表1）制造的高速冷锯（图1），经过热处理后应满足如下要求：①硬度30～40HRC；②常温冲击值。。＞4U八m’；③低温。人一20℃）＞301／。m’；④热处理后平面度＜0．smm；⑤具有…     

运动参数对圆盘锯锯切过程的影响

合理选择锯切过程中的运动参数可以提高生产率和锯切断面质量,减少锯切力和锯切能耗,不产生“塞齿”现象。本文分析了运动参数对锯切生产率、锯切力、断面质量和“塞齿”现象的影响,实验研究与理论分析完全相符合。     

45钢棒材冷拔断裂原因分析

采用化学成分分、金相分析、断口扫描电镜及电子探针分析等手段，对45钢棒材冷拔断 裂的原因进行了分析研究。结果表明：钢中Cu元素含量偏高；轧钢加热期间钢坯 表面氧化严重造成钢材表面附近区域Cu元素富集，冷拔过程 中钢材表面附近的Cu富集区域首先开裂，导致钢材冷拔断裂。     

金刚石框架锯锯切研究(1)-锯切加工运动学分析

金刚石水平式框架锯锯切是在大面积大理石板材加工中占主导地位的加工工艺。在金刚石框架锯锯切中的加工运动学锯切破碎过程、锯切力、锯切结块磨损、锯条张紧力调整、锯切可加工性评定等问题，均是实现高效率低成本地加工出高质量石材大板的关键。本文首先阐述了金刚石框架锯锯切过程中的运动学问题，提出了单颗粒金刚石在锯切加工过程中同石材接触的运动模型，以及结块和锯条平均切削厚度的概念；分析了金刚石结块同石材侧表面的接触面积和金刚石结块顶面同石材接触面积的变化特征，为研究锯切过程中的各种现象打下了理论基础。     

薄型织针锯槽片耐用度的研究

一、前言锯槽片是纺器行业制针厂生产上必用的刀具，它的使用批量多，消耗量大。几十年来，国内锯槽片大多采用GCrls‘CI06等钢制造，通常淬火工艺为专用淬火炉加热，温度为840±10℃，保温6秒，出炉后在专用压床上压淬，即长期来一直沿用常规淬火方法，锯槽片的使用寿命不长，约加工针槽时间为20－25分钟后，锯槽片发生“胖槽”现象，即锯槽片磨损，锋利度降低，使被切削针槽达不到尺寸要求而报废。国外同类名牌刀片的使用寿命远高于国产的锯槽片，例如加拿大产的锯槽片的使用寿命比国产锯槽片的使用寿命约高6倍。为了提高国产锯槽片的使…     

金刚石绳锯的锯机轨迹及锯切机理研究

本文从理论上分析了金刚石绳锯的锯切轨迹及锯切机理，并对大理石和花岗石进行了锯切试验，以验证论分析的分析。理论分析和锯切试验约表明：（1）金刚石绳锯的锯切轨迹近似为圆的渐开线，锯切过程中单位长度绳锯对石材的压力，绳锯张紧紧力决定了该渐开线的形状；（2）金刚石绳锯锯切线速度高，锯切过程中单颗粒金刚石施加在石材上的压力很小，不足以使石材产生体积破碎，切屑细小，其主要碎岩方式是赫北破碎（Hertzian fracture)，通过高速磨削实现锯切，根据金刚石绳锯的碎岩机理，锯切时应适当控制绳锯拉力和绳锯线速度，选用耐磨蚀性好的金刚石和胎体，保证良好冷却，以提高锯切速度，延长绳锯寿命。     

旋转式热飞锯切斜原因分析

针对旋转式热飞锯在实际生产过程中出现的切斜现象，从工艺设备和电气控制等方面分析了其原因，并提出了解决办法，切斜量可控制在２ｍｍ以内．     

环形电镀金刚石线锯锯切工艺参数的优化

电镀金刚石线锯为环形，无惯性力，适于高速切削。本文对环形电镀金刚石线锯锯切花岗岩时的工艺参数进行了正交试验研究。分别分析了金刚石粒度、进给压力和锯丝速度对锯切效率、锯切力和锯切比的影响，分析结果表明：采用较大的金刚石粒度不会大幅度提高锯切效率，金刚石的粒度对切向锯切力的影响不大．锯切花岗岩时，要保证较高的锯切效率和锯切比，在本试验范围内，最佳工艺参数为：采用金刚石粒度为200～230^#的锯丝，进给压力为9N，锯丝速度为20m／s。     

圆柱工件变锯深工况下恒定锯切力约束多目标进给速度优化方法

针对国内金属锯切过程中，变锯深工况下带锯床加工效率低、加工振动大的问题，提出基于恒定锯切力约束的进给速度优化方法。基于锯切力动力学模型，以提高圆柱零件加工效率和降低最大锯切力为优化目标，以恒定锯切力范围、临界锯切力、机床进给速度、机床功率为约束条件，建立进给速度优化模型，并采用基于精英控制的非支配排序遗传算法(NSGA-II算法)对锯切过程中的进给速度进行优化。实例验证了恒定锯切力约束的进给速度优化模型的有效性，达到了恒定锯切力约束目标，提高了加工效率，降低了最大锯切力。最后，通过ANSYS有限元分析软件对锯条的瞬态响应进行动力学分析，验证了变进给速度锯切的加工稳定性。     

Fractional Cooling Strategy of the Hot-Stamping Process and Its Influence on Formability and Mechanical Properties of Ultra-High-Strength Steel Parts

The effects of forming temperature on the formability and product properties of hot-stamping boron steel B1500HS were investigated. Based on the fractional cooling strategy, boron steel sheets were heated to achieve full austenitization before they were removed from the furnace and cooled to the forming temperature using different cooling methods. Subsequently,they were simultaneously press-formed and quenched inside the tool until the martensitic transformation was finished. A series of thermal tensile tests were conducted to study the effects of forming temperatures on the stamping performance indices, including elongation, yield ratio, and hardening exponent. Then, the mechanical properties and microstructures of the hot-stamped products were characterized. Finally, an irregular part was formed using different fractional cooling strategies, while its formability and springback phenomena were discussed. The results show that using a fast-cooling method to reach 650 °C as the forming temperature optimizes the formability of the tested B1500HS boron steel. The best mechanical properties and smallest springback values were achieved using this optimal strategy.     

Dynamic observations of welding phenomena and finite element analysis in high-frequency electric resistance welding

High-frequency electric resistance welding (hereinafter referred to as HFW) pipes and tubes are used for high-grade line pipes. To cope with the high need for weld seam reliability, the clarification of welding phenomena is important. To clarify the HFW phenomena, at first we developed a HFW simulation system by using electromagnetic, heat conductive and elastic plastic finite element analysis (FEA) methods. Continuous electromagnetic and heat conduction analysis was conducted by subdividing the cross section containing the electrode and the welding point into a large number of two-dimensional models. The temperature distribution in the HFW pipe welding procedure can be successfully simulated by this system. The deformation behaviour in which a portion of the weld rises to the inner and outer surfaces as the result of pressurization from welding rolls can be analysed with this system. Secondly, HFW phenomena have been visualized dynamically using a high-speed video camera technique. The high-intensity part visualized by high-speed images has good accordance with the temperature distribution of the FEA result. High-speed images have visualized the dynamic phenomena of molten metal flow and sputtering of molten steel. Very rapid movement of molten metal in the forming direction along the welding line was observed at the V-convergence point with a speed of 2–50 m s^?1, which was far faster than the welding speed. This rapidly moved molten metal generated the peculiar sputtering which spread the molten metal particles as describing an arc perpendicular to the welding line. These phenomena were assumed to be caused by the electromagnetic force concerning the molten steel at the V-convergence point.     

南海大气环境下304不锈钢的点蚀特性研究

目的 研究南海大气环境中服役的304不锈钢的点蚀原因与机理。方法 以不同暴露周期的304不锈钢试样为研究对象,采用动电位极化、电化学交流阻抗谱、扫描电镜和Kelvin 探针技术对其进行分析研究。结果 随着暴露时间的延长,304不锈钢表面的点蚀坑数量和深度均逐渐增加,其极化曲线中,钝化区间缩短,点蚀电位负移,阳极极化曲线斜率明显减小,并出现反复再钝化现象,钝化曲线逐渐消失,同时阻抗测试中的膜层电阻越来越小。SEM分析表明,304不锈钢暴露初期出现不连续的点蚀,点蚀坑向纵深发展,暴露后期出现点蚀群,局部有多个点蚀坑连成一片形成溃疡状的腐蚀表面,同时随暴露时间的延长,扫描试样微区的Kelvin表面电位不均匀性逐渐增强。结论 304不锈钢试样的耐蚀能力随暴露时间的增加而不断下降,点蚀现象不断增加。暴露初期,点蚀坑主要向纵深发展;暴露后期,点蚀坑的宽度达到一定程度后,本体溶液向坑内迁移,稀释了坑内溶液的酸度,点蚀坑向纵深和横向同时发展。     

TIG and A-TIG welding experimental investigations and comparison with simulation

Abstract

In this part II, the comparison of physical mechanisms between tungsten inert gas (TIG) and active TIG (A-TIG) welding is shown. The plasma was monitored by a high speed camera to present the arc constriction phenomena while passing from TIG to A-TIG. The elemental analysis and the arc temperature measured by optical emission spectroscopy were performed according to the type of welding and the different fluxes in A-TIG welding. The two-dimensional axial symmetric model presented in part I was used to simulate the flow behaviour in the melting pool realised on a stainless steel disc (304L) melted by a stationary heat source and to study the influence of energy density.     

Corrosion of carbon steel through a thin film of solution

The corrosion phenomena of carbon steel covered with a thin film of solution were examined by using a vertical rotating disk electrode dipped partially in the corroding solution. The diffusion rate of oxygen through the thin film of solution, obtained from the cathodic polarization curve, was the rate-determining step of the corrosion process. This rate was much larger than that through the bulk solution. The effect of carbon content in the steel on the corrosion is discussed and the corrosion of the steel containing copper is also discussed.     

含Nb管线钢动态再结晶特性的实验研究

为了消除利用CSP技术生产管线钢时较易出现的混晶缺陷，在Gleeble-1500热模拟实验机上对X60含Nb管线钢进行了高温压缩变形实验，研究了变形条件对其动态再结晶行为的影响，从而为利用CSP技术生产X60含Nb管线钢的工艺优化提供了一定的理论依据。     

某高强钢板汽车结构件多工位级进模设计

为达到轻量化目的,汽车上越来越多地使用高强钢板结构件。通过对某高强钢板汽车安装座件的冲压工艺性及冲压工艺方案的分析,确定了采用13工位级进模来进行制件成形的冲压工艺方案;通过对制件的单排和双排排样方案进行分析比较,选择了双排排样方案,并对级进模的主要零部件进行设计。试冲结果表明,提出的双排样方案和设计的13工位级进模是合理可行的,能满足某高强钢板汽车安装座件的大批量生产需要。     

A method of measuring the heat generation parameters in the resistance spot welding in single phase AC machines

In the fabrication of reactors (made of Cr–Mo steel modified with vanadium) operating in high hydrogen pressure and high-temperature service, internal cladding in austenitic stainless steel (typically made of AISI 347) is required in order to guarantee satisfactory corrosion resistance against the process fluids desulphurized hydrocarbons. Application of an electro-slag strip cladding (ESSC) process for internal weld overlay and clad restoring on heads, barrels and nozzles of 2¼Cr–1Mo–¼V reactors (with single-layer or double-layer technique) is described in the paper. The first part of the paper is focused on metallurgical aspects, cracking phenomena (hydrogen cracking, solidification cracking, under-clad cracking and hydrogen-induced disbonding) and cladding residual stresses referable to ESSC process. The second part of the paper is focused on operating aspects of the ESSC process and UT examination of weld overlay and clad restoring, optimized for the detection of planar defects under cladding.     

Analyses of diffusion-related phenomena in steel process

In steel production processes, there are various diffusion-related phenomena, and these are controlled to obtain the required steel quality. In the refining process, the slag-metal reaction that is controlled by the diffusion of various reactants and products in boundary layers in both the slag and metal side along the slag-metal interface is analyzed by a coupled reaction model. Solidification microsegregation is controlled by the solute diffusion in the liquid and solid phases, and various analytical microsegregation models have been proposed. The tertiary precipitation of nonmetallic inclusions is also affected by solute diffusion in the solid phase and is analyzed by a coupled precipitation model, the modified solidification segregation model. The formation of a carbon (C)-rich band structure along the centerline of steel plates and weld cracking are also prevented by regulating the diffusion of C by accelerated cooling and by encouraging hydrogen to diffuse out by preheating the weld part, respectively. A key element of intragranular ferrite precipitation for ferrite grain refinement is the formation of manganese (Mn)-depleted zone by slow Mn diffusion around a precipitate.     

热浸镀锌板生产过程中的腐蚀与对策

    综述了镀锌板生产和储运过程中的腐蚀问题,并提出了改进镀锌板耐腐蚀性能的对策.