ASTM A193 Grade B7 stud bolts are high-strength, high-durability fasteners manufactured in accordance with the American Society for Testing and Materials (ASTM) A193 standard. They are made of alloy steel, quenched and tempered, and have excellent mechanical properties. They are widely used in various industrial equipment and structural connections that need to withstand high pressure and high temperature, such as petrochemical equipment, pressure vessels, pipeline flange connections, etc.

ASTM A193 Grade B7 Stud Bolts Specification

Standard Specification Of	ASTM A193 Grade B7 Stud Bolts
Type Of Head	Hex, Threading, Square, Round
Size Type	Inches 3/8 to 3
Surface Finish	Plain / Zinc plated / Hot dip galvanized
Standard Dimensions Of	ASME B18.2.1

ASTM A193 Standard

This specification” covers alloy and stainless steel bolting for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. See Specification A962/A962M for the definition of bolting. Bars and wire shall be hot-wrought and may be further processed by center less grinding or by cold drawing. Austenitic stainless steel may be carbide solution treated or carbide solution treated and strain-hardened.When strain hardened austenitic steel is ordered, the purchaser should take special care to ensure that Appendix X1 is thoroughly under-stood.

High Temperature Tests

Tests to determine high temperature properties shall be made in accordance with Test Methods E21, E139, and E292, and Practices E150 andE151.

Charpy Impact Tests

Charpy impact tests based on the requirements of specification A320/A320M, shall be made as agreed between the manufacturer and the purchaser. When testing temperatures are as low as those specified in specification A320/A320M, bolting should be ordered to that specification in preference to this specification

100 % Hardness Testing of Grade B7M

Each Grade B7M bolt or stud shall be tested for hardness by indentation method and shall meet the requirements specified in tables

 Length Tolerances for Bolts

Nominal Length	Nominal Size
	1/4 to 3/8	7/16 and 1/2	9/16 to 3/4	7/8 and 1	1 1/8 to 11/2	Over 1 1/2
Up to 1 in,incl.	+0.02	+0.02	+0.02		·	…
	-0.03	-0.03	-0.03	·		·
Over 1 in.to 2 1/2 in,incl	+0.02	+0.04	+0.06	+0.08	+0.12	+0.18
	-0.04	-0.06	-0.08	-0.10	-0.12	-0.18
Over 2 1/2 in.to 4 in,incl	+0.04	+0.06	+0.08	+0.10	+0.16	+0.20
	-0.06	-0.08	-0.10	-0.14	-0.16	-0.20
Over 4 in.to 6 in,incl	+0.06	+0.08	+0.10	+0.12	+0.18	+0.22
	-0.10	-0.10	-0.10	-0.16	-0.18	-0.22
Longer than 6 in.	+0.10	+0.12	+0.14	+0.16	+0.22	+0.24
	-0.18	-0.18	-0.18	-0.20	-0.22	-0.24

ASTM A193 Grade B7 Stud Bolts Material

ASTM A193 Grade B7 Chemical Composition

CHEMICAL	LIMITS	C	Mn	P	S	Si	Cr
ASTM A193 Grade B7	MIN	0.37	0.65			0.15	0.75
	MAX	0.49	1.10	0.035	0.040	0.35	1.20

Manganese is usually between 0.65 and 1.10%. Manganese helps to improve the strength, hardness and toughness of steel, and can improve the deoxidation and desulfurization effects of steel, enhancing the overall performance of steel.

ASTM A193 B7 Mechanical Property

Grade	Size	Tensile ksi, min	Yield, ksi, min	Elong, %, min	RA % min	HBW	HRC
B7	Up to 2-1/2	125	105	16	50	321 max	35 max
	2-5/8 – 4	115	95	16	50
	4-1/8 – 7	100	75	18	50

The minimum elongation of ASTM A193 Grade B7 stud bolts is 16%. A certain elongation indicates that the bolt has a certain plastic deformation capacity, which is very important when subjected to dynamic loads or uneven loads. It can adapt to stress changes through plastic deformation and prevent the bolt from breaking suddenly.

ASTM A193 Grade B7 Recommended Hardware

Bolt Grade	Nuts	Washers
B7	A194 Grade 2H	F436

Difference Between A193 Grade B7 & A193 Grade B7M Stud bolts

Hardness is probably the most important difference between A193 B7M & A193 B7. The maximum hardness of ASTM A193 B7M is 235 HB or 99 HRB, while the maximum hardness of ASTM A193 Grade B7 stud bolts are 321 HB or 35 HRC. The most notable difference from a manufacturing perspective is that when supplying A193 B7M bolts, each individual bolt or stud in the batch must be tested for hardness. A193 B7M fasteners also require a different type of heavy-duty hex nut than A193 B7, namely ASTM A194 Grade 2HM.

While A193 B7 is specified relatively often in the construction industry, A193 B7M is a specification not seen as regularly. This makes it important to understand the differences between the two specifications so that the right material is ultimately supplied.