The grade 4 Carbon and Alloy Steel Nuts for Bolts of High Pressure or High Temperature Service

The ASTM A194 grade 4 specification covers carbon, alloy, and stainless steel nuts intended for use in high-pressure and/or high-temperature service. Unless otherwise specified, the American National Standard Heavy Hex Series (ANSI B 18.2.2) shall be used. Nuts up to and including 1-inch nominal size shall be UNC Series Class 2B fit. Nuts over 1-inch nominal size shall be either UNC Series Class 2B fit or 8 UN Series Class 2B fit. High strength ASTM A194 grade 4 nuts are common in the marketplace and are often substituted for ASTM A563 grade DH nuts due to the limited availability of DH nuts in certain diameters and finishes.

4

Carbon steel Hex Nut, Heavy hex nut

Property class	Chemical composition
	C.	Mn.	Si.	P.	S.	Cr.	Ni.	Mo.	V.	Ti.
4	0.40-0.50	0.70-0.90	0.15-0.35	0.035	0.040	-	-	0.20-0.30	-	-

Class	Diameter, [mm]	Brinell Hardness	Rockwell Hardness
			C Scale	B Scale
4	All	248-327	24-35	-