铸钢件冒口离开热节动态顺序凝固补缩特性的研究

采用正交设计现场浇注，试验研究了铸钢件冒口离开热节动态补缩特性。结果表明，冒口位置对补缩效果影响显著，铸钢件冒口在离开铸件的几何热节处，实施动态顺序凝固补缩，提高了冒口补缩效率和工艺出品率。在试验条件下，冒口离开何热节的距离为一倍热节圆直径时，补缩效果良好。     

15MnVN钢的氢致硬化和氢致软化

研究了不同氢含量、应变速率条件下１５ＭｎＶＮ钢氢致硬化和氢致软化现象。试验证实，氢的存在首先造成氢致硬化，而当塑性变形开始后又导致氢致软化。这一作用受钢中氢偏聚控制，并受应变速率的诱导作用。氢的存在对钢的抗拉强度无明显影响。     

Effects of laser beam energy and incident angle on the pulse laser welding of stainless steel thin sheet

This paper reports an experimental study of laser spot welding on stainless steel sheets. A pulsed Nd:YAG laser was used to weld the stainless steel specimen in the range of laser energy 0.6–1.2 J and incident angle 30–75° (the angle of the laser beam incident direction to the sheet surface). Metallography was applied to measure the cross-sectional size and shape of the welded spot. From the experimental results, it is found that as the laser energy increases, the penetration depth, bead length, and bead width of the welded spot increase. As the laser incident angle increases, the penetration depth and the bead width increase while the bead length decreases. The results illustrate that the shape and size of the welded spot depend not only on the laser energy, but also on the incident angle of laser beam.     

成形参数对AZ91D镁合金触变成形性与缺陷形成的影响

研究了不同成形工艺参数,如坯料加热温度、加热时间和模具预热温度(模具温度)对AZ91D镁合金触变成形性与缺陷形成的影响。结果表明:成形性、缺陷形成与加工参数紧密相关。合适的成形参数为:坯料加热温度在575～595℃,加热时间超过75min,模具预热温度超过275℃;主要有冷隔、液相偏析、缩松、裂纹和氧化夹杂5种缺陷。其中,裂纹和氧化夹杂是主要的缺陷。     

触变成形AZ91D镁合金在NaCl水溶液中腐蚀特征

通过SEM观察及采用EPMA测定和失重法，对3．5％NaCl水溶液中金属型铸造和触变成型镁合金AZ91D腐蚀行为及腐蚀后微观组织特征进行分析，表明触变成形镁合金的腐蚀速率小于金属型铸造合金的腐蚀速率，原因是微观组织的差异导致其耐蚀性不同；镁合金腐蚀电偶对是以α相和共晶α相作为阳极，β相作为阴极。阳极是被腐蚀相，腐蚀是分阶段分层次进行的，α相是腐蚀初期的被腐蚀相，共晶α相是后期被腐蚀的主要相，β相和共晶α相的相对位置和结构决定着后期腐蚀速率；触变成型中β相的偏析提高了合金的耐蚀性。     

数控加工模具型腔中的数据处理

模具型腔在数控加工中需要一套控制刀具运动轨迹的算法，本文给出了从模具型面的几何描述，加工数据的生成到形成Ｇ格式指令进行数控加工这一生产过程的数据处理，实验和现场加工的结果表明：该数据处理算法成功地解决了模具型面的加工制造问题。     

A SOLUTION OF SHAPE EXTRUSION OR DRAWING BASED ON DEFORMATION THEORY

ＡＳＯＬＵＴＩＯＮＯＦＳＨＡＰＥＥＸＴＲＵＳＩＯＮＯＲＤＲＡＷＩＮＧＢＡＳＥＤＯＮＤＥＦＯＲＭＡＴＩＯＮＴＨＥＯＲＹＹｕａｎＸｉ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅ...     

半固态镁合金中液相的凝固方式及组织形貌

采用快速液淬方法分析研究了AZ91D镁合金半固态液相的凝固方式和组织形貌,结果表明:镁合金半固态液相的凝固方式与冷却速度所决定的过冷度有重要关系.在液淬快冷的条件下,液相先析出α相,部分依附于初生固相晶粒结晶生长,部分在液相中独立形核生长.较大的过冷度使α相长成"毛刺状"或树枝晶状.共晶凝固按离异生长和共生生长两种方式进行,离异生长形成粗大的晶界β相,共生生长形成层片状组织.初生固相晶粒中形成的小液池,其凝固方式和结晶组织与晶间液相基本相同,但由于液相量少,共晶凝固主要以离异方式进行.     

高膜厚PU防腐系统在油气管道上的应用

高膜厚PU防腐系统可解决防腐工程上的死角，包括异形、补口、三通、弯头、法兰、阀门等几何形状复杂金属外表面的防腐，以及老龄在役管线的防腐结构的修复。这种防腐系统的使用寿命可达30a。对国内油气管道防腐涂层常用的国产环氧粉末防腐结构和高膜厚PU防腐结构各项技术性能指标进行了对比，又以环氧粉末和高膜厚PU防腐系统用于管道防腐和储罐防腐进行了详细的对比，论证了使用高膜厚PU防腐系统技术的可行性和经济性。     

Monitoring and self-learning fuzzy control for wire rupture prevention in wire electrical discharge machining

Wire breaking is a serious problem in the application of wire electrical discharge machining (WEDM). A WEDM sparking frequency monitoring and control system based on the characteristics of the voltage waveform of WEDM is developed. A new self-learning fuzzy controller is proposed to control the sparking frequency at a safe level by regulating the pulse off-time in real time for avoiding wire rupture and maintaining a state of high metal removal rate. The developed control strategy is tested under the conditions of cutting a workpiece with continuous sharp angles, a change in workpiece height during machining process, and machining with a high feed-rate. Experimental results show that this monitoring and control system can control the sparking frequency at a predetermined level without the risk of wire rupture.