This paper introduces a manufacturing technology of thick-walled integrated cylinder with large-sized side nozzles for nuclear reactor pressure vessel. This forging integrates the inlet nozzle and the outlet nozzle on the nozzle shell with integral flange to form an integrated forging. China First Heavy Industry (CFHI) has successfully realized the manufacturing process of this forging. During the forming stage of the forging, with the help of numerical simulation method, the size of the forging blank is reduced to the greatest extent, and a thick-walled cylinder with a convex structure is designed and forged, and then the punching guide hole is machined at the convex structure of the cylinder, which plays the role of positioning and guiding in the forging process of the side nozzle. We use special-structured forging aids to transfer the load of the forging press to the punch to complete the hot extrusion of the side nozzles, and finally realize the integrated near-net shape of the forging. The forging flow line of the forging is preserved to the greatest extent, and the best forging effect of each part of the forging is guaranteed. After the final heat treatment process of the forging, all parts of the forging obtained excellent mechanical properties.
某高强度合金钢螺栓在使用存放期间发生断裂,为找出其断裂原因,根据螺栓生产过程和使用环节开展分析研究.经过分析排查,发生断裂失效的螺栓内部氢含量高于同时段生产的其它螺栓,螺栓断口形貌经过电镜扫描分析在断裂源位置存在沿晶断裂特征形貌,表明该螺栓失效模式为氢脆断裂.进一步研究发现,产生螺栓氢脆的原因为螺栓电镀时使用的电镀槽液镀覆产品过多,槽液中杂质含量偏高,导致渗氢量增加并在螺栓内部积聚,在螺栓装配预紧力形成的持续静载荷作用下,发生延迟断裂.为预防此类螺栓失效的再次发生,针对其原因制定了控制电镀槽液质量和优化螺栓除氢工艺的预防措施.
20SiMn材质常用于水电水轮机、发电机轴锻件上,钢水纯净度的提升是提高轴类锻件使用寿命的关键所在.通过采用Al镇静钢工艺生产下注20SiMn钢锭的试验,分析了各个节点炉渣成分、夹杂物形貌及成分变化.研究表明:精炼结束炉渣碱度为6.3,VD后炉渣中CaO含量降低、SiO2 含量升高,炉渣碱度降低至 4.9.整个精炼过程夹杂物主要为CaO-SiO2-Al2O3-MgO、SiO2-MnO-Al2O3 两类,不同节点夹杂物类型单一.精炼结束、软吹后钢水中夹杂物以CaO-SiO2-Al2O3-MgO为主,软吹后夹杂物中SiO2、Al2O3 含量有所增加.VD后钢水中夹杂物以SiO2-MnO-Al2O3 为主,Al2O3 含量较低,该类夹杂物在软吹后大量去除.通过对锻件无损检测缺陷处进行取样分析,缺陷处形貌为微裂纹,缺陷区域未发现夹杂物和元素偏析,说明缺陷是由于锻造或锻后热处理过程内应力过大导致开裂造成的.
直径7.8m的特大型管板由于自由锻压机开裆尺寸的限制,通常只能采用分段锻造—拼焊成形的技术方案,本文提出了采用分步分区、不同阶段不同旋压控制的整锻技术方案.为保证管板心部压实效果,同时避免饼形锻件片状缺陷的产生,对锻造工艺参数进行了讨论分析.并且通过数值模拟研究了锤砧宽度和压下量对中心及边缘成形质量的影响,确定了合理的锤砧宽度和压下量.根据讨论分析和数值模拟结果制定了直径7.8m特大型管板的整体锻造工艺方案,并通过实际生产验证了工艺方案的可行性和合理性.
1Mn18Cr18N是一种高强度、高抗腐蚀性的不锈钢,通常用于发电机护环上.它的主要成分为 18%的锰、18%的铬和0.47%以上的氮.通过1Mn18Cr18N钢中氮的溶解度计算,确定了其成分控制目标.通过氮的合金化方案控制,得到了成分合适的电极;通过在常压100%N2 气氛下进行电渣重熔,成功冶炼了一支重量20t级的1Mn18Cr18N高氮钢电渣锭,该钢锭成分均匀、纯净度良好,N能达到0.65%及以上的良好水平.
