不锈钢管冷旋压成形试验

介绍了3种奥氏体不锈钢材料的特性,主要旋压工艺参数对旋压成形的影响.在不同工艺参数下,采用三旋轮错距、无中间退火、直接强力冷旋压工艺,对3种奥氏体不锈钢管材料进行反旋压成形,分析了不同参数下奥氏体不锈钢管旋压成形的特点,提出了针对3种奥氏体不锈钢管冷旋压的合理工艺参数.     

带横向内筋张紧轮旋压成形分析

目的解决某型号带横向内筋张紧轮旋压成形困难的问题。方法运用有限元模拟软件,建立了张紧轮的有限元模型,选取了不同的坯料壁厚和旋轮圆角半径,对张紧轮旋压成形过程进行了数值模拟。结果获得了旋压成形过程中坯料壁厚大小和旋轮圆角半径大小对旋压力和成形质量的影响,并对结果进行了总结。结论通过分析壁厚和预成形轮形状对张紧轮旋压成形质量的影响,得出了最优的工艺参数值,对实际生产具有指导意义。     

碟形封头冷旋压成形时的数值分析及旋压力计算

建立了碟形封头冷旋压的三维有限元数学模型,分析了封头在冷旋压成形过程中应力应变的分布规律,计算了旋压力并分析了其变化的原因,为更有效地进行旋压加工前的科学预测、工艺优化和进一步定量控制提供了可靠方法和依据.     

Al/Cu双金属管内旋压增量成形有限元数值模拟与分析

目的 分析Al/Cu双金属管在内旋压增量成形时应力、应变、剪切结合强度的分布情况,研究主要工艺参数对双金属管剪切结合强度的影响规律。方法 基于有限元模拟软件,对Al/Cu双金属管内旋压成形过程进行有限元数值模拟;研究了内旋压增量成形时工艺参数：内管减薄率ψ、两管之间的初始间隙c、旋轮进给比f对剪切结合强度的影响。结果 随着工艺参数内管减薄率ψ、两管之间的初始间隙c、旋轮进给比f的增大,剪切应力数值也随着增大;基管与衬管的高剪切应力值主要集中在旋压结束部分,衬管的长度被拉长,模拟与实验的剪切应力在旋压成形的末端数值明显增大。结论通过有限元数值模拟分析,得出不同的工艺参数对成形质量的影响规律,对实际成形有重要的作用。     

变厚度轮辐强力旋压成形过程的分析

利用ABAQUS/Explicit模拟了变厚度轮辐双道次强力旋压过程,给出了建模和分析结果.轮辐旋压成形伴随板坯的剧烈减薄,收口区域较难成形,减薄率达50%,在计算中,轮辐有限元网格畸变严重,为此运用ALE技术改善网格质量,提高了计算精度.对模拟的旋压轮辐厚度与实验测量值进行了对比,二者吻合较好,验证了计算模型和结果的可靠性.通过ABAQUS/Standard计算了轮辐旋压成形后的回弹变形量和残余应力,分析成形后轮辐等效应变分布及回弹特征,研究发现,回弹变形量与旋压成形时壁厚变化量成正比.     

筒形件强力旋压工艺模拟及实验研究

采用有限元与工艺实验相结合的方法,对筒形件强力旋压工艺进行了研究。对于旋压加工工艺,利用有限元模拟软件建立三维弹塑性模型并进行数值模拟,然后在此基础上分析进给比、减薄率2个工艺参数对筒形件强力旋压成形过程的影响规律。根据数值模拟结果,设计并制造了工装与模具,同时进行了工艺试验,成功试制了壁厚减薄效果良好的筒形件强力旋压样件。     

双辊夹持板料旋压成形过程塑性变形行为的研究

双辊夹持式板料旋压成形是用来加工薄壁回转体法兰零件的新工艺。为了研究其旋压成形过程中的塑性变形行为,利用ABAQUS软件建立了双辊夹持旋压成形过程的三维有限元模型,并进行了薄壁回转体法兰零件的旋压成形过程的数值模拟,获得了成形过程中等效应力、应变及壁厚的分布。研究了翻边长度对成形件应力应变及壁厚减薄率的影响规律。结果表明等效应力、应变及最大壁厚减薄率均随着翻边长度的增大而增大,由此根据不同的毛坯材料可以确定相应的最大翻边长度。     

无缝气瓶热旋压收口成形工艺数值模拟研究

本文采用有限元分析软件ABAQUS对无缝气瓶热旋压收口成形工艺进行模拟研究,分析了不同工艺参数对气瓶热旋压成形的影响。模拟结果表明,无缝气瓶热旋压收口成形过程中,随着旋压温度的升高和进给比的增加,起旋点处最小壁厚减薄,瓶肩最大壁厚处壁厚增加;随着旋压温度的升高,最大等效应力不断减小,最大等效应变不断增加;随着进给比增加最大等效应力应变都略有增加;旋压力随着温度的升高和进给比的减小而降低。     

大型筒体对轮强力旋压成形特征与规律研究

目的 研究大直径薄壁筒体在对轮强力旋压过程中的应力–应变分布情况和材料流动特征,探明减薄率、进给比和主轴转速等工艺参数对成形结果的影响规律。方法 利用Forge仿真平台建立2.25 m级5052铝合金筒体对轮强力旋压的有限元模型,分析筒体成形过程中的应力–应变状态和主要工艺参数对成形精度与旋压成形力的影响规律。结果 在对轮旋压成形过程中,筒体内外侧应力–应变呈对称分布,成形区域内材料呈扇形流动。工艺参数对成形工件壁厚精度和旋压成形力的影响主次顺序为:减薄率＞进给比>主轴转速。结论 各工艺参数的增大均会降低工件的壁厚精度,减薄率和进给比的增大会引起旋压成形力增大,而主轴转速增大会使旋压成形力轻微减小。     

分形旋压成形技术研究进展

综述了分形旋压成形技术的国内外研究现状,分析了分形旋压的成形特点,总结了分形旋压可能的变形失效形式,提出了该领域亟待解决的瓶颈问题,并对分形旋压有限元建模过程中的关键技术难题进行了探讨和展望.     

Cold model for process of a Ni-aluminide/steel clad pipe by a reactive centrifugal casting method

A novel method (reactive centrifugal casting method) to fabricate a Ni-aluminide/steel clad pipe has been proposed. Ni powder was placed on a spinning steel pipe, and Al liquid was poured into the steel pipe. The Al liquid and Ni powder exothermically reacted and produced a composite layer consisting of Ni-aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. However, during the process, the Ni powder moves along the flow of the Al liquid. In this study, in order to obtain a better understanding of the Ni powder motion in the spinning steel pipe, a cold model centrifugal casting is employed. We focus on the effects of the angle between the spinning and horizontal axes on the type of centrifugal casters, because it is difficult to obtain the same data by the proper experiments.     

Rate dependent cyclic behavior simulation of cold worked AISI 316L stainless steel pipe member

This research aims to simulate rate-dependent cyclic behavior of cold worked AISI 316L stainless steel pipe member using a developed FE analysis program. A rate-dependent cyclic plasticity model for cold worked AISI 316L stainless steel is derived based on the monotonic and cyclic loading experiments within quasi-static and dynamic strain rate ranges. Validity of the FE simulation program is presented by comparing analytical results to experimental data. Cyclic behavior of cold worked AISI 316L stainless steel pipe member is clearly simulated as a function of loading rate.     

TP304不锈钢薄壁管的表面残余应力

利用X射线应力测试仪分别测定了TP304不锈钢无缝薄壁管管身的表面轴向和切向残余应力,并分析了表面残余应力的形成原因。结果表明:该不锈钢管表面存在较大的残余应力,且分布极不均匀;另管表面的切向残余应力大于轴向残余应力,前者为后者的1.5~2.5倍;该不锈钢管生产过程中的冷拔、冷矫直等工艺、固溶保温时间不足以及钢管表面存在局部缺陷等都是导致其表面残余应力较大的原因。     

Corrosion failures of high temperature heat pipes

Over 30 years heat pipe technology has found many applications in various industries and is proven to be a highly efficient heat transfer technology. There is therefore an emerging problem to ensure the safe operation and long term service life of heat pipes. In the present paper a high temperature life test is conducted on the heat pipes of low-alloy ferritic steels and a stainless steel with alkali metals as working fluids. The corrosion mechanisms of the alkali metals at elevated temperature are studied and measures are suggested for improving the design and manufacturing technology of high temperature heat pipes.     

空间低温热管的设计与实验研究

介绍了为空间辐射制冷器研制开发的一种干道吸液芯氮气低温热管 ,该热管直径为6mm ,长度210mm ,工作温度80 .0～120 .0K ,最大传热功率可达2.5W ;并对其传热性能进行了实验研究。实验结果表明低温热管的传热性能远远优于固体的导热性能 ,完全能够满足辐射制冷器冷焦面耦合需要     

Eddy current detection of changes in stainless steel after cold reduction

An investigation was conducted to explore the applicability of eddy current technique to characterize austenitic variation during cold reduction in various stainless steels. A series of stainless steel samples were cold rolled for this purpose. It was observed that eddy current flow and its phase are affected due to the variation in volume percent of austenite. It is suggested that eddy current measurement technique is a useful tool for the characterization of austenite variation during the cold working of stainless steels.     

制动系统不锈钢管端部精密成形工艺研究

目的改善铁路货车制动系统管系现有的连接方式,对不锈钢管端部进行精密成形,以得到力学性能较好的锻造接头。方法根据原有管系的连接方式及钢管塑性成形特点,提出对不锈钢管端部进行多工步镦挤的工艺方法。采用Deform-3D三维有限元模拟软件对工艺过程进行数值模拟,分析成形过程中锻件成形情况,以及锻件和模具的受力、温度、金属流动情况等。结果在高温条件下采用的多工步镦挤工艺可以使钢管端部达到成形要求。结论提出的钢管端部塑性成形工艺是可行的,对铁路货车制动系统管系连接方式的改善有重要的参考意义。     

Influence of initial microstructure on microstructural stability of 20% cold worked Ti modified austenitic stainless steel

Abstract

The influence of initial microstructure at different solution annealing conditions on the stability of 20% cold worked microstructure of a Ti modified austenitic stainless steel has been studied. Solution annealed and 20% cold worked samples were isothermally annealed at different temperatures in the range 923-1123 K for 1-1000 h. Mechanical property measurements, ultrasonic velocity measurements, and optical metallography were carried out to assess the stability of the cold worked microstructure during annealing. The extent of recrystallisation was measured using quantitative metallography. The variation of hardness and velocity with annealing time exhibited a three stage behaviour for the conditions leading to complete recrystallisation. Based on the microstructural observations, the three stages identified are recovery, progress of recrystallisation and completion of recrystallisation. There is one to one correspondence between the hardness and velocity measurements in assessing the microstructural changes. However, variation in the velocity measurements with annealing time correlated well with the extent of recrystallisation compared to that of the variation of hardness with annealing time. With an increase in solution annealing temperature from 1173 K to 1473 K, more primary TiC precipitates dissolve into the matrix and there is an increase in the secondary precipitation of TiC during annealing of the 20% cold worked alloy. The increase in secondary precipitation of TiC retards recovery and recrystallisation of the cold worked microstructure effectively and hence enhances the stability of cold worked microstructure. Thus, an increase in the solution annealing temperature from 1373 K to 1473 K enhances the stability of cold worked microstructure in Ti modified austenitic stainless steel.     

Cold roll bonding of bimetallic sheets and strips

Abstract

The successful production of wide bimetallic sheets and strips by cold roll cladding depends on the technical solution of reduction of rolling load while still guaranteeing good bond quality. In the present paper, systematic experimental data on the cold roll cladding of aluminium–stainless steel, copper–stainless steel, and mild steel–stainless steel are correlated and the basic mechanism is discussed, aided by a scanning electron microscopy study of the separated interface. The effects of conventional rolling and cross-shear rolling (i.e. between rolls of differing peripheral speeds) on roll force and bonding strength are critically compared. It is found that use of the cross-shear cold rolling technique results in a significant reduction in rolling load for equal primary bonding strength and that the incorporation of an optimum final heat treatment considerably decreases the requirement on rolling.

MST/971