ASTM A193This specification covers alloy steel and stainless steel bolting material for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. Ferritic steels shall be properly heat treated as best suits the high temperature characteristics of each grade. Immediately after rolling or forging, the bolting material shall be allowed to cool to a temperature below the cooling transformation range. The chemical composition requirements for each alloy are presented in details.B7Alloy steel, AISI 4140/4142 quenched and tempered

B8Class 1 Stainless steel, AISI 304, carbide solution treated.

B8MClass 1 Stainless steel, AISI 316, carbide solution treated.

B8Class 2 Stainless steel, AISI 304, carbide solution treated, strain hardened

B8MClass 2 Stainless steel, AISI 316, carbide solution treated, strain hardened

B16A heat-treated chromium-molybdenum-vanadium steel for high-pressure, high-temperature service.

Mechanical PropertiesBolt -Grade Identification MarkingsGradeSizeTensile ksi, minYield, ksi, minElong, %, minRA % min

B7Up to 2-1/21251051650

2-5/8 - 4115951650

4-1/8 - 7100751850

B8 Class 1All75303050

B8M Class 1All75303050

B8 Class 2Up to 3/41251001235

7/8 - 1115801535

1-1/8 - 1-1/4105652035

1-3/8 - 1-1/2100502845

B8M Class 2Up to 3/4110951545

7/8 - 1100802045

1-1/8 - 1-1/495652545

1-3/8 - 1-1/290503045

Material Chemical CompositionElementB7 (AISI 4140)B8 (AISI 304)B8M (AISI 316)

Carbon0.37 - 0.49%0.08% max0.08% max

Manganese0.65 - 1.10%2.00% max2.00% max

Phosphorus, max0.035%0.045%0.045%

Sulfur, max0.040%0.030%0.030%

Silicon0.15 - 0.35%1.00% max1.00% max

Chromium0.75 - 1.20%18.0 - 20.0%16.0 - 18.0%

Nickel8.0 - 11.0%10.0 - 14.0%

Molybdenum0.15 - 0.25%2.00 - 3.00%

Recommended Nuts,Bolts & WasherBolt GradeNutsWashers

B7A194 Grade 2HF436

B8 Class 1A194 Grade 8SS304

B8M Class 1A194 Grade 8MSS316

B8 Class 2A194 Grade 8SS304

B8M Class 2A194 Grade 8MSS316