SA320

Alloy steel and stainless steel bolting materials for low temperature service.

SA320

SA320 Grades

L7 Alloy steel AISI 4140/4142 Quenched and tempered
L43 Alloy steel AISI 4340 Quenched and tempered
B8 Class 1 Stainless steel AISI 304, carbide solution treated
B8M Class 1 Stainless steel AISI 316, carbide solution treated
B8 Class 2 Stainless steel AISI 304, carbide solution treated, strain hardened
B8M Class 2 Stainless steel AISI 316, carbide solution treated, strain hardened

 

TABLE 1 Mechanical Requirements SA-320

Type of Steel Class and Grade, Diameter, in [mm] Heat Treatment Minimum
Tempering
Temperature
°F [°C]
Tensile Strength, min, ksi [MPa] Yield Strength,
min, ksi
[MPa] (0.2 %
offset)
Elongation
in 2 in.
or 50
mm min,

Ferritic Steels

L7, L7A, L7B, L7C, L70, L71, L72, L73 Upto 2-1/2 quenched and tempered 1100
[593]
125
[860]
105
[725]
16
L43 Upto 4 quenched and tempered 1100
[593]
125
[860]
105
[725]
16
L7M Upto 2-1/2 quenched and tempered 1150
[620]
100
[690]
80
[550]
18

Austenitic Steelsc

Class 1: B8, B8C, B8M, B8P, B8F, B8T, B8LN, B8MLN, ALL carbide solution treated   75
[515]
30
[205]
30
Class 1A: B8A, B8CA, B8MA, B8PA, B8FA, B8TA, B8LNA, B8MLNA, ALL carbide solution treated in the finished condition   75
[515]
30
[205]
30

Class 2: B8M:

Upto 3/4

carbide solution treated and strain
hardened

  110
[760]
95
[655]
15
7/8 to 1   100
[690]
80
[550]
20
1-1/8 to 1-1/4   95
[655]
65
[450]
25
1-3/8 to 1-1/2   90
[620]
50
[345]
30

A. These upper diameter limits were established on the basis that these were the largest sizes commonly available that consistently met specification property limits. They are not intended as absolute limits beyond which bolting materials could no longer be certified to the specification.

B. To meet the tensile requirements, the Brinell hardness shall not be less than 200 HBW or 93 HRB.

C. Class 1 products are made from solution-treated material. Class 1A products are solution treated in the finished condition for corrosion resistance; heat treatment is critical for enhancing this physical property and meeting the mechanical property requirements. Class 2 products are made from solution-treated material that has been strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the cross section, particularly in sizes over 2/4 in. [20 mm] in diameter.

D. For sizes 3/4 in. [20 mm] in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.

Table 3 Chemical Requirement (Compositionm,%)

GRADE : L7, L7M, L70
(AISI 4140)
L43
(AISI 4340)
B8, B8A
(AISI 304)
B8M, B8MA
(AISI 316)
Steel Type / ELEMENTS % Ferritic Steels Ferritic Steels Austenitic Steels, Classes 1, 1A, and 2D Austenitic Steels, Classes 1, 1A, and 2D
Carbon 0.38-0.48c 0.38-0.43 0.08 0.08
Manganese 0.75-1.00 0.60-0.85 2 2
Phosporous, Max 0.035 0.035 0.045 0.045
Sulfur, Max 0.04 0.04 0.03 0.030 max
Silicon 0.15-0.35 0.15-0.35 1 1
Nickel ... 1.65-2.00 8.0-11.0 10.0-14.0
Chromium 0.80-1.10 0.70-0.90 18.0-20.0 16.0-18.0
Molybdenum 0.15-0.25 0.20-0.30   2.00-3.00

 

A320 Recommended Hardware

Grade Nuts Washers
L7 A194 Grade 4 or 7 F436
L43 A194 Grade 4 or 7 F436
B8 Class 1 A194 Grade 8 SS304
B8M Class 1 A194 Grade 8M SS316
B8 Class 2 A194 Grade 8 SS304
B8M Class 2 A194 Grade 8M SS316