Valve Material Selection Guidelines
Different types of Steels are used in Valve manufacturing. Due to wide variety of steels available in market, overwhelmed by the variety of material available and different name by which they are called. Here I have tabulated 20 different types steels that are most widely used depending on their usage.
Steel is of various categories: a) Carbon Steel b) High Temperature Steel c) Low Temperature Steel d) Stainless Steel. Each Category of Steel is produced from two different manufacturing technique known as Casting and Forging.
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 this category, there is two sub categories 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 degrees 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.
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. There are different grades of steels are produced combining different chemical components in proper percentages. These chemicals components are Iron, Carbon, Nickel, Chromium, Molybdenum, Manganese.
a) Iron: Iron is one of the most commonly found chemical element on earth. Atomic No. 26 Denoted with symbol Fe Iron is basically soft material, when mixed with carbon( 0.02 to 2 %), steel is produced which is harder material. There is another item called Cast Iron which is Iron- Carbon Alloy. In Cast Iron Carbon > 2%. Cast Iron is very brittle in nature
b) Carbon: Carbon is fourth most abundant material on earth. Carbon when mixed