Forming mechanism of integral serrated high fins by plowing-extruding based on variational feed

Plowing-extruding tool was designed and plowing-extruding process was investigated.Then,a manufacturing method of integral serrated high-finned tube,plowing-extruding based on variational feed was proposed,in which plowing-extruding tool moved forward at two different feeds,f1 and f2,in turn.In this method,overlaps that are usually avoided in practical application were utilized to manufacture high fins and average height of fins was up to 1.58 mm.The critical feed(fc) of overlaps forming and terms of high f...     

铝合金高速铣削过程切屑成形机制研究

高速铣削加工中,切削力、切削热和机床振动等被广泛研究,而对切屑的研究相对较少.本文针对立铣刀高速铣削的特点,对切屑的成形进行了研究.根据理论分析,在UG环境下对切屑进行了绘制,其形状与实际切屑基本吻合,证明了研究方法的可靠性.通过切屑的研究反馈设计过程,对立铣刀的结构设计提供支持.     

斜轧钢质高翅片管成形过程的数值模拟

针对斜轧钢质高翅片管变形机理研究相对落后的问题,通过Pro/E的曲面建模功能建立了轧辊的三维实体几何模型.利用DEFORM-3D软件,采用三维刚一塑性有限元法对斜轧钢质高翅片管进行了数值模拟.分析了轧件变形区的应力、应变场分布,得到了斜轧钢质高翅片管的成形规律.该研究成果为斜轧钢质高翅片管的深入研究提供了理论依据.     

Surface treatment of 3D outside serrated integral-fin tube manufactured by rolling and extrusion

The outside serrated integral-fin tubes fabricated by rolling-plowing-extrusion processing were surface-treated through different processes of annealing in hydrogen atmosphere, electrochemical corrosion or sandblasting. The purpose was to eliminate residual stress, clear secondary micro-fins and enhance heat transfer performance. By comparing the surface characteristics, it is found that the finned tubes treated by electrochemical corrosion have the most glabrous surfaces where the fins are almost perfectly reserved. Clear layer cracks can be observed on the top of the fins. These structures are effective in enhancing heat transfer performance when being applied to flow heat exchange. Therefore, the finned tubes treated by electrochemical corrosion are proper for the tubular exchanger with water coolant. The finned tubes treated by sandblasting have rougher surfaces with layer cracks and micro gaps removed. As these structures are useful to clearing adhesive feculence, the tubes are more suitable for the tubular heat exchanger with oil coolant.     

高温合金筒内旋压锯齿形沟槽微观组织特征

采用焊接板预制坯以及内旋压的方法制造了一种带壁锯齿槽的大直径薄高温合金筒。研究了筒内锯齿槽的显微硬度和显微组织特征。坯料的焊接导致了接头处微观组织为粗大且不均匀的树枝状支晶,这致使焊接接头与其外区域之间的显微硬度差异较大。内旋压促使锯齿槽上焊接接头区外的初始晶粒和焊接接头处的树枝状支晶都发生细化。锯齿槽的微观力学性能不均匀性因剧烈的塑性变形而明显得到改善。     

Compound forming technology of outside 3D integral fin of copper tubes

Using rolling-ploughing-extrusion compound processing methods, a 3D integral-fin structure on outside surface of red copper tube with diameter of 16.0 mm and wall thickness of 1.5 mm was obtained. When both rolling depth and ploughing-extrusion (P-E) depth were 0.2 mm, rotating speed was 50 r/min, feed speed was 0.16 mm/r, 3D fin structures with height of 0.25 mm were gotten. Two different fin structures were obtained in grooves formed with rolling-ploughing-extrusion compound forming technology and observed by scanning electron microscope(SEM). One is the compound structure with V-shaped groove and U-shaped groove, and the other is the single structure with V-shaped grooves. Two kinds of groove structures obtained by rolling processing and ploughing extrusion processing are restricted together by groove interval and rolling depth, and pitch and P-E depth, respectively. Based on the analysis of interaction of rolling and P-E processing, it is found from the result that the outside 3D integral-fin can be achieved by rolling-ploughing-extrusion compound processing when single V-shaped groove structures are formed by both rolling and P-E processing.     

两步热处理制备高延性TiAl基合金机理

研究了两步热处理对锻造Ti 4 7Al 2Cr(摩尔分数 ,% )组织演变和室温拉伸性能的影响。经 12 90℃ ,4h FC12 4 0℃ ,4h ,FC 90 0℃ ,2 4h热处理后 ,锻造TiAl基合金中形成了均匀细小的双态组织 ,其室温伸长率 ,室温抗拉强度和室温屈服强度分别为 3.5 % ,6 77MPa和 5 97MPa。在热处理过程中 ,锻造TiAl基合金发生了复杂的相变 ,其相变过程为 :变形组织→γf αf→γf (αf γs αs)→γf Lf γs Ls。当第二步热处理温度偏低时 ,αs 转变为脆性α2 相颗粒 ,降低了合金的室温拉伸性能     

芯管间隙对JAC590Y高强钢矩形管绕弯成形质量的影响

为了判断JAC590Y高强钢矩形管180°绕弯时芯棒与管坯之间的间隙大小对弯管成形质量的影响,基于Dynaform软件对4种芯管间隙下JAC590Y高强钢薄壁矩形管的绕弯成形分别进行了模拟,得出了不同芯管间隙值下弯管的主要畸变参数。结果表明:在芯管间隙处于一定范围内时,弯管的宽度扩展率受芯管间隙值的影响很小,而中面高度缩减率会随着芯管间隙的增大而变大;弯管上最大的壁厚减薄率出现于紧邻距芯棒最远芯头的横截面上顶板与两侧板的交角处,选取较大的芯管间隙有助于降低弯管的最大壁厚减薄率;JAC590Y高强钢薄壁矩形管180°绕弯成形时芯管间隙率的合理范围为0. 01~0. 025。     

铝合金高功率激光-MIG复合焊热源形态特征

为深入理解铝合金大功率激光-MIG复合焊热源空间分布特征,设计了以激光功率、电弧功率以及激光与电弧之间的距离为因素的全因子试验,采用高速摄影和图像处理技术得到等离子体的宽度和面积.结果表明,复合焊中热源功率存在一定的阈值,随着功率的增加低于这个数值等离子体尺寸减小而超过这个数值等离子体呈膨胀趋势,在高功率复合焊中等离子体宽度随光束功率的增加而增大.激光束与电弧之间的距离影响等离子体空间的几何分布,但是随着激光束与电弧之间距离的逐渐增加,复合焊焊接过程中的等离子体存在一个维持、膨胀和恢复的不断重复的周期过程.     

焊后时效处理和固溶处理对接头组织和性能的影响

通过以2519高强铝合金为研究对象,研究了单独时效处理和固溶再时效处理对接头组织和性能的影响.结果表明,时效处理对接头的强度提升有一定的帮助,当时效温度为150 ℃时接头的抗拉强度达到最大;固溶再时效处理能使接头的抗拉强度显著增加,且随着固溶温度的增加,接头的抗拉强度随之增加,但当固溶温度达到540 ℃时,接头中容易产生液化裂纹,接头强度反而降低.采用强化固溶的方法,可以将固溶温度提升至540 ℃,显著提升接头的强度.