行业新闻

原文
Natural gas pipeline valve defect analysis valve casting process defects (1) hole type defects such as porosity, shrinkage, porosity, slag hole, trachoma and iron beans, and other. They may extend into the hidden dangers in use. Most of the distribution of pores in the surface or near surface of cast iron, spherical or pear-shaped; slag hole of irregular shape, rough surface, showing a variety of different colors; shrinkage and loose inverted cone, pore surface roughness, are distributed in the cast body axis heart parts, trachoma and iron beans are more scattered in the cast iron surface. Hole type defect is due to irregular or sand mold slag mixed with a large number of defects caused by the cast. (2) crack type defects, hot cracks and cold cracks. Thermal cracks are formed at high temperatures, cold crack is formed in the cooling temperature. Therefore, the former was oxidized surface cracks color, shape and tortuous and irregular cracks; the latter was slightly oxidized color crack, crack straight, not forked. The causes of their chemical composition may be cast microstructure segregation or CB7216-87 less than the minimum requirements specified in the standards, local excellent, easy to run when there is not high pressure valve rupture accident. So this situation should be respected. (3) structural shape and size of defects, if there is more than meat, body casting, poured enough off the sand, deformation and damage defects. The existence of the above types of defects the actual strength of body count is far below the theoretical value of juice, especially in the valve body casting defects like cracks in high pressure occurs when the fracture is not an important reason for blasting.
原文来自：http://www.jianyafa.org

是由上海一环流体控制设备有限公司提供的阀门新闻，中文译文仅供参考，以下提供站内导航搜索：

中国减压阀网减压阀产品减压阀知识减压阀厂商减压阀博客减压阀行业新闻

译文：
　　阀门铸造时工艺性缺陷　　(1)孔眼类缺陷，如气孔、缩孔、疏松、渣孔、砂眼和铁豆等。它们可能在使用中扩展成隐患。气孔多数分布于铸铁表面或近表面，呈球状或梨状;渣孔形状不规则，表面粗糙，呈各种不同颜色;缩孔和疏松呈倒锥形，气孔表面粗糙，多分布在铸造体轴心部位，砂眼和铁豆则多散布在铸铁表面。孔眼类缺陷是由于砂模不规则或有大量渣质混铸所造成的缺陷。　　(2)裂纹类缺陷，有热裂纹和冷裂纹。热裂纹是在高温下形成的，冷裂纹是在冷却低温下形成的。因此，前者裂口表面呈氧化色，裂纹形状曲折而不规则;后者裂纹呈轻微氧化色，裂纹较直，没有分叉。它们产生的原因可能是铸造化学成分偏析或金相组织达不到CB7216-87标准所规定的最低要求，局部过硬，易在运行压力不高时就出现阀门破裂事故。因此这种情况应引起格外重视。　　(3)结构形状尺寸缺陷，是指阀体铸件是否存在多肉、浇不足、落砂、变形及损伤缺陷。　　上述各类缺陷的存在使阀体实际强度远远低于理论汁算值，尤其是裂纹类铸造缺陷是阀体在承压不高时即发生断裂爆破的重要原因。

更多新闻：