In-process evaluation of grit protrusion feature for fine diamond grinding wheel by means of electro-contact discharge dressing

This paper introduces a new in-process evaluation method for grit protrusion feature on wheel surface by monitoring discharge current trace during electro-contact discharge (ECD) dressing of metal-bonded fine diamond grinding wheel. First an impulse discharge machining experiment was carried out to investigate the correlation between metal bond removal and discharge parameters, namely discharge current I_e and discharge pulse duration τ_e. Then ECD dressing experiment for #600 diamond grinding wheel was conduced to analyses the quantitative effect of the discharge parameters (I_e and τ_e), derived from discharge current trace between wheel and dresser (electrode), on grit protrusion feature of wheel surface. The result shows that the grit protrusion feature is sensitive to the discharge parameters (I_e and τ_e) with reference to mean diamond grit size d_gm. Further, the discharge parameters (I_e and τ_e) in ECD dressing should conform to the discharge variables’ requirement of , by which the grit protrusion feature may be evaluated and the dressing process variables may be determined. Finally, the in-process evaluation method was successfully applied to ECD dressing of #1500 diamond grinding wheel for valid grinding of hard-brittle materials.     

热力系统新型停用保护缓蚀剂

通过高压釜试验和电化学极化曲线测试并结合硫酸铜 点滴和水滴评价试验，研究了新型停用缓蚀剂LP对不同钢材及已锈蚀碳钢的停用保护缓蚀性 能和LP的缓蚀作用机理.研究结果表明：LP是一种性能良好的热力设备停用保护缓蚀剂.     

PHASE DIAGRAM OF Nd-Pd(Nd≤50at.-％) BINARY SYSTEM

采用X射线衍射,示差热分析和金相等方法研究了Nd-Pd系相图中含0—50at-％Nd的区域。发现在该区域内存在6个金属间化合物:NdPd_5,NdPd_3,NdPd_2,Nd_2Pd_3,Nd_1Pd_5和NdPd。其中,NdPd_3,Nd_4Pd_5和NdPd是固液共熔化合物。还测出NdPd_5为SmPt_5型结构,NdPd_?为AuCu_3型结构,低于708±4℃的NdPd为CrB型结构。在该区域内共有3个共晶反应和3个包晶反应。     

实现曲面刻字的调和方法

曲面刻字的首要问题在于如何选择刀位点，使得文字笔划角度在曲面上与平面时相同。本文的解决方法是将文字图像调和映射到曲面上确定刀位点，由调和映射的保角性质保证角度不变。描述了平面到曲面调和映射的求解过程，并以球面印字为例，进行了数值试验。     

Gas chromatographic thermodynamics on hydration processes of magnesium chloride with low water

1　INTRODUCTIONMagnesiumchlorideisabasicmaterialforchem icalindustry ,andithaswideapplicationsinmetallur gy,architecturalmaterialandtextileindustry .Itisalsoamaterialforfire resistantproducts ,cryogenandcompoundfertilizerproductions[1] .Thefullydehy dratedmagnesiumchlorideisagoodmaterialforelec trolyticmetalmagnesium production .Becausemag nesiumchloridehasastrongadsorptiveability ,itisalsousedasadryingagent .Manysuccessfulworkshavebeendoneonthedehydrationofbischophite[2 10 ] .Butinfact,…     

铁路钢轨接续线爆压冷焊技术

介绍了利用爆压冷焊技术研制开发的一种新型的“爆压冷焊式钢轨接续线技术”的设计原则、设计方案，焊接效果及技术性能。     

俄罗斯航空修理厂无损检测状况一瞥

介绍俄罗斯某厂航空修理中无损检测技术的应用及方法，包括磁粉探伤中的围磁法和弹簧通电磁化法，超声瑞利波探伤的沟槽探头，涡流探伤的旋转探头，荧光渗透检验中的湿法显示以及复合材料的声阻法检测。上述方法能有效发现缺陷隐患，保证航空修理质量，值得借鉴。     

Effect of welding current on strength and microstructure in resistance spot welding of AZ31 Mg alloy

In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β（ Mg17All2 ） in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N.     

方波交流埋弧焊电源的设计与分析

交流方波埋孤焊具有电孤稳定、无磁偏吹、焊接熔敷率高等优点，是埋孤焊技术发展的一个新方向。提出了一种三相输入、单相输出交流方波埋弧焊电源的新电路，详细分析了这种晶闸管整流、互感换向实现交流方波电路的工作原理和控制方法。实验结果表明，利用互感换向实现交流方波的埋孤焊电源，其电流过零的di／dt很大，电孤稳定性不亚于直流电孤。     

消除304不锈钢板坯纵向凹陷微裂纹的研究

针对太钢生产的304不锈钢板坯存在纵向凹陷微裂纹缺陷的问题，在分析其产生机理和原因的基础上，采取增加结晶器锥度，降低保护渣粘度和减弱结晶器冷却强度的工艺，取得了显著效果。