①閥門毛坯的製造工藝及檢驗工藝比較複雜。 閥門的鑄件毛坯是結構叫複雜的薄壁殼體件。其鑄件要求表麵光潔、鑄字清晰，特別是要有致密的缺陷。為了滿足上述要求，鑄造時應采取一係列工藝措施，如選用 高耐火度的造型材料並控製型砂水份、造型時應分層打實以保證砂型硬度，采用合理的澆帽口係統及嚴格控製澆注速度和溫度等。由於技術要求較高，閥門毛坯的鑄 造工藝遠較一般鑄件複雜。 此外，閥門毛坯除檢查尺寸，位置精度及外觀外，有的還有作金相組織、力學性能、耐腐蝕性能及無損探傷等多種檢驗，故閥門的檢驗工藝也較複雜。 (1) the manufacturing process and inspection process of the valve billet are more complex. The casting blank of the valve is a complex thin-walled shell structure. Requirements of its smooth surface castings, cast the word clear, especially to have dense defects. In order to meet the above requirements, the casting process should take a series of measures, such as the selection of high refractoriness of the molding materials and control sand moisture, other fight should be stratified to ensure that the sand hardness, using reasonable pouring cap system and strict control of casting speed and temperature. Because of the high technical requirements, the casting process of the blank of the valve is much more complex than that of the general casting. Besides, apart from checking the size, locations accuracy and appearance, some of the valve blanks include many other tests, such as metallographic structure, mechanical properties, corrosion resistance and NDT, so the inspection process of valves is more complicated. ②閥門零件在機床上安裝比較困難 閥門主要零件的結構、形狀比較複雜，有些零件屬壁薄、細長件，剛性差。在機床上加工時，定位和裝夾都比較困難，因此往往需要複雜的專用夾具。 有的閥門零件，定位基麵的精度較低，表麵粗糙度較高，有時甚至采用非加工表麵定位。而被加工密封麵等部位的精度和表麵粗糙度要求都很高，故得難保證加工質 量。因此，為滿足工藝上的需要，往往須提高定位基麵的精度和降低表麵粗糙度，或在非加工表麵上加工出定位基麵，這就增加了閥門製造工藝的複雜性。 The structure and shape of the main parts of the valve parts which are difficult to be installed on the machine tool are complex, and some parts are thin and thin, and the rigidity is poor. When machining on machine tools, it is difficult to locate and clamp, so complex special fixture is often needed. Some valve parts, the positioning base surface precision is lower, the surface roughness is high, and sometimes even use non machining surface positioning. The precision of the machined sealing surface and the surface roughness are very high, so it is difficult to ensure the processing quality. Therefore, in order to meet the needs of technology, we often need to improve the accuracy and reduce the surface roughness of the positioning base, or to locate the base surface on the unmachined surface, which increases the complexity of the valve manufacturing process. ③機械加工難度大 由於閥門材料的各類繁多，除各種鑄鐵、碳素鋼外，其大部分高強、耐腐蝕和高硬材料的切削性能都很差，很難使零件達到規定的加工精度和表麵粗糙度。而閥門密 封麵的幾何型狀精度和表麵粗糙度的要求很高，因此更增加了閥門機械加工難度。同時，閥門材料的切削性能差，又給閥門的加工方法、刀具材料、切削用量、工藝 裝備等方麵帶來了很多新的問題。 (3) machining is difficult because valve materials are various. Except for all kinds of cast iron and carbon steel, most of the cutting performance of high strength, corrosion resistance and high hardness materials is very poor. It is difficult for parts to reach the specified machining accuracy and surface roughness. The geometric shape precision and the surface roughness of the valve seal are very high, so the machining difficulty of the valve is increased. At the same time, the cutting performance of valve materials is poor, which brings many new problems to the valve processing methods, tool materials, cutting parameters, process equipment and so on.