ASTM A194 specification covers carbon steels, stainless steel alloys and materials suitable to be used in “on-order” high pressure and / or “on-order” high temperatures. The high resistance ASTM A194 2H nuts are commonly used in the market, but they are often replaced by ASTM A563 grade DH nuts because of the reduced availability.

 
2      Carbon steel heavy hex nuts

2H     Quenched & tempered carbon steel heavy hex nuts

2HM     Quenched & tempered carbon steel heavy hex nuts

4     Quenched & tempered carbon-molybdenum heavy hex nuts

7     Quenched & tempered alloy steel heavy hex nuts

7M     Quenched & tempered alloy steel heavy hex nuts

8     Stainless AISI 304 heavy hex nuts

8M     Stainless AISI 316 heavy hex nuts

>> MECHANICAL PROPERTIES GRADE IDENTIFICATION MARKINGS

Grade Identification Marking5	Specification	Material	Nominal Size, In.	Tempering Temp. °F	Proof Load Stress, ksi	Hardness Rockwell min - max	See note
	ASTM A194 Grado 2	Medium Carbon Steel	1/4 - 4	1000	150	159 - 352	1,2,3
	ASTM A194 Grado 2H	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	1000	175	C24 - C38	1,2
	ASTM A194 Grado 2HM	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	1000	150	159 - 237	1,2,3
	ASTM A194 Grade 4	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24 - C38	1,2
	ASTM A194 Grado 7	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24 - C38	1,2
	ASTM A194 Grado 7M	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	150	159 - 237	1,2,3
	ASTM A194 Grado 8	Stainless AISI 304	1/4 - 4	-	80	126 - 300	4
	ASTM A194 Grado 8M	Stainless AISI 316	1/4 - 4	-	80	126 - 300	4