The ASTM A320 B8M stud bolt is a threaded bar that is threaded across its length, while the middle section is unthreaded. Stud Bolts are designed with a chemical content of chromium, nickel, molybdenum, and other alloys. The versatile Stud Bolt ASTM A320 Gr B8M has enhanced corrosion resistance properties and good performance.

ASTM A320 was specially engineered for low temperature performance. These fasteners are commonly used for valves, flanges, fittings, and pressure vessels . ASTM A320 specifications recommend a minimum Charpy impact value all grades except for a few exclusions (listed below). The Charpy impact test determines the total amount of energy that is absorbed by a material during fracture, thereby indicating the material’s notch “toughness”.

ASTM A320 B8M Stud Bolts Specification

The ASTM A320 B8M stud bolts specification covers alloy steel bolting materials and bolting components for pressure vessels,valves,flanges,and fittings for low-temperature service.See SpecificationA962/A962M for the definition of bolting. The bars shall be hot-wrought and maybe further processed by center less grinding or by cold drawing. Austenitic stainless steel may be solution annealed or annealed and strain-hardened.When strain hardened austenitic stainless steel is ordered, the purchaser should take special care to ensure that Appendix X1 is thoroughly understood.

 Full Size Fasteners, Wedge Tensile Testing When applicable. Headed fasteners shall be wedge tested full size in accordance with Annex A3 of Test Methods and Definitions A 370 and shall conform to the tensile strength shown in Table 1. The minimum full size breaking strength(1bf) for individual sizes shall be as follows:

TS = UTS x AS

where:

Ts=Wedge tensile strength

UTS=Tensile strength specified in Table 1, and

As=Stress area, square inches, as shown in ANSI Bl.1or calculated as follows:

As =0.785 (D-(0.974/n))

where:

D= Nominal thread size, and

n= The number of threads per inch.

ASTM A320 B8M Stud Bolts Material

Bolts A320 Grade B8M

B8M Class 1 Stainless steel	AISI 316, carbide solution treated
B8M Class 2 Stainless steel	AISI 316, carbide solution treated, strain hardened

Chemical Composition of ASTM A320 B8M Stud Bolts

The main chemical components of ASTM A320 B8M bolts are Chromium , Nickel, Molybdenum, etc. The presence of these elements gives the bolts good corrosion resistance and low temperature resistance.

CHEMICAL	LIMITS	C	Mn	P	S	Si	Ni	Cr	Mo
ASTM A320 B8M	MIN						10.00	16.00	2.00
	MAX	0.08	2.00	0.050	0.030	1.00	14.00	18.00	3.00

ASTM A320 B8M stud bolts have high strength, and their minimum tensile strength is usually above 750MPa. This means that when subjected to large tensile loads, the bolts can maintain their structural integrity without breaking or deforming.

Mechanical Properties of ASTM A320 B8M Stud Bolts

Grade	Size	Tensile ksi, min	Yield, ksi, min	Elong, %, min	RA % min	Hardness,
						Max
B8M Class 1	All	75	30	30	50	223 HBW or 96 HRB
B8M Class 2	3/4 [20] and under	110	95	15	45	321 HBW or 35 HRC
	Over 3/4 to  1 [20 to 25],incl	100	80	20	45	321 HBW or 35 HRC
	Over 1 to 1 1/4 [25 to 32],incl	95	65	25	45	321 HBW or 35 HRC
	Over 11/4 to 1 1/2 [32 to 40],incl	90	50	30	45	321 HBW or 35 HRC

Bolting A320 Grade B8M

B8M Class 1 Stainless steel	AISI 316, carbide solution treated
B8M Class 2 Stainless steel	AISI 316, carbide solution treated, strain hardened

ASTM A320 Recomended Nuts and Washer

Bolt Grade	Nuts	Washers
B8M Class 1	A194 Grade 8M	SS316
B8M Class 2	A194 Grade 8M	SS316

Stud Bolts Application Areas

Cryogenic Pressure Vessels: such as liquefied natural gas (LNG) storage tanks, liquid oxygen tanks, liquid nitrogen tanks, etc. In these containers, the temperature of the medium is usually very low, and the low-temperature performance requirements of the bolts are extremely high. Stud bolts can maintain good mechanical properties and sealing properties in low-temperature environments to ensure the safe and reliable operation of the container.

Cryogenic Pipeline System: used for pipeline connections for transporting cryogenic media, such as cryogenic oil pipelines in the petrochemical industry, cryogenic natural gas pipelines in natural gas liquefaction plants, etc. In these pipeline systems, bolts need to withstand the pressure and temperature changes of cryogenic media, and the low-temperature resistance and high strength of ASTM A320 B8M bolts can meet these requirements.

Marine Engineering: In the marine environment, due to the strong corrosiveness of seawater, some equipment may need to work under low-temperature conditions, such as the connection of cryogenic equipment on deep-sea oil and gas production platforms. The stainless steel material of ASTM A320 B8M stud bolts makes it have good seawater corrosion resistance, and its low-temperature performance can also adapt to the special requirements of the marine environment.