Iron is soft element. When carbon( 0.2 to 2%) is mixed with Iron, steel is formed. Steel has higher mechanical strength required for making mechanical items. Steel is of various categories: a) Carbon Steel b) High Temperature Steel c) Low Temperature Steel d) Stainless Steel.
ASME B 16.34 defines the material to be selected for a valve body construction depending on its pressure, temperature Class. ASME B 16.34 is basically a Valve Design Standard, whereas ASTM is material standard. ASTM defines the chemical components and manufacturing process of a material.
1) Carbon Steel: It is most widely used material for valve manufacturing. Within these category , there is two sub category namely casting and forging. Casting and forging are two different manufacturing process. Grades of Carbon Steel under Casting are WCB and WCC. WCB and WCC follow ASTM A216 material standard. Grades of Carbon Steel under Forging is ASTM A105. There is a single grade under Forging Carbon Steel category. So, name of the standard and material are the same. Carbon Steel should not used beyond 425 Degree Centigrade as per ASME B16.34
2) High Temperature Steel: This category of material is normally used where process temperature is more than 400 degree centigrade. Commonly used grades of High Temp Steel under casting category are WC6 and WC9. They follow ASTM A217. Commonly used grades of High Temp Steel under forging category are F11, F12, F21, F22, F91. They follow ASTM A182.
3) Low Temperature Steel: In this category only casting is used. Commonly used materials are LCB and LCC and ASTM A352 is followed.
4) Stainless Steel : For Casting subcategory most popular materials are CF3, CF8, CF3M and CF8M. Related ASTM standard is A351. For Forging subcategory most popular materials are 304,304L,316 and 316L. Related ASTM standard is A182.
These different grades of steels are produced combining different chemical components in proper percentages. These chemicals components are Iron, Carbon, Nickel, Chromium, Molybdenum, Manganese.
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