BS 4882

Table 1 - Bolts in low alloy and martensitic stainless steels complying with BS 1506

Bolt grade identification marks Material designations
(from BS 1506)		 Alloy type Mechanical properties at room temperature (1) Charpy V-notch (KCV) impact strength at sub-zero temperatures Heat treatment Suitable grades of nuts
Limiting ruling section (4) Tensile strength Rm Yield strength Re
min.		 Elongation A
(% based on a gauge length of 5.65 √So)		 Izod impact strength
(mean of three values)		 Hardness HB Harden Temper (6)
Metric series Inch series min. max. min. max. Temperature Mean of three values Temperature Cooling media Temperature Cooling media for metric bolts for inch bolts
mm N/mm 2 N/mm 2 N/mm 2 %min. ft lb J °C J °C °C
MB7, ML7 B7L7 630–790 1% Cr¼%Mo > 63 < 100 790 1000 655 14 40 54 223 302 -100
-75		 20(2)
27(2) 		850 to 880 (5) Oil 600 min Air M2H M4 M7 M8 2H 4 7 8
630–860 1% Cr¼%Mo < 63 860 1070 725 14 40 54 248 331 -100 27(2) 850 to 880 (5) Oil 600 min Air ML4 ML7 or 8 with ML7 bolts L4 L7 or 8 with L7 bolts
MB7M(3)
ML7M		 B7M(3)
L7M		 630–690 1% Cr/¼%Mo < 63 690 800 550 16 40 54 201 235 -100 27(2) 850 to 880(5) Oil 620(min) Air M2HM M4M M7M M8A, ML4M ML7M M8A with ML7M bolts (3) 2HM 4M 7M 8A L4M L7M 8A with L7M bolts (3)
MB7A B7A 631–850 1% Cr/½%Mo >100 < 200 850 1000 635 14 20 27 248 302 -- -- 850 to 900 Oil or water 600(min) Air M2H M4 M7 M8 2H 4 7 8
>63 < 100 850 1000 665 14 40 54 248 302 -- -- 850 to 900 Oil or water 600(min) Air
>63 850 1000 695 14 40 54 248 302 -- -- 850 to 900 Oil or water 600(min) Air
MB16 B16 670–860 1% Cr½%Mo¼%V < 100 860 1000 725 16 35 47 248 302 -- -- 930 to 970 Oil 600(min) Air M4 M7 M8 4 7 8
MB16A B16A 681–820 1%CrMoVBTi < 250 820 1000 660 15 20 27 241 302 -- -- 660 to 700 followed by 970 to 990 Air
<50 mm water or oil> 50 mm water 		680 to 720 Air M7 M7A M8
M16 M16B		 7 7A 8
16 16B
MB16B B16B 671–850 1¼%CrMoV >100 < 200 850 1000 635 14 20 27 248 302 -- -- 930 to 970 Oil or water 650(min) Air M7 M7A M8 7 7A 8
< 100 850 1000 665 14 35 47 248 302 -- -- 930 to 970 Oil 650(min) Air
MB6 B6 410S21–690 12% Cr >100 < 200 690 840 540 15 -- -- 197 248 -- -- 950 to 1020 Oil or air 600(min) Air M6 M6K M8 6 6K 8
410S21–760 < 100 760 910 585 15 -- -- 217 269 -- -- 950 to 1020 Oil or air 600(min) Air
MB6K B6K 410S21–720 >63 < 100 720 870 570 15 25 34 212 262 -- -- 950 to 1020 Oil or air 600(min) Air M6K M8 6K 8
410S21–750 >29 < 63 750 900 580 14 20 27 215 262 -- -- 950 to 1020 Oil or air 600(min) Air
410S21–770 < 29 770 930 590 12 20 27 223 227 -- -- 950 to 1020 Oil or air 600(min) Air
ML9 L9 509–650 9% Ni < 75 650 850 480 18 -- -- -- -- –196 40 880 to 930 followed by
770 to 820		 Air
Air 		540 to 600 Air or water ML9 ML9A L9 L9A
ML9A L9A 509–690 9% N < 100 690 850 580 18 -- -- -- -- –196 40 770 to 820 Oil or water 540 to 600 Air or water ML9A L9A

(1) Room temperature properties: time dependent properties to be taken into account for high temperature service see appendix A and 1.3.1).
(2) Charpy impact tests for bolt B7/L7 grade. Charpy impact tests are only required for L7 grade.
(3) Grades for sour gas service:
bolts: MB7M, ML7M, B7M, L7M
nuts: M2HM, M4M, M7M, M8A : 2HM, 4M, 7M, 8A : ML4M, ML7M : L4M, L7M
Treatment:
(a) all bolting heat treated after all machining and forming completed;
(b) nut grades 2H, 4, L4, 7 and L7 to be treated to HB 235 max. (HRC 22).
(4) Limiting ruling section as defined in BS 1506.
(5) Information extracted from BS 1506 and given for guidance. Austenitizing at temperatures outside this range may significantly effect stress rupture values.
(6) Minimum tempering temperatures are mandatory.
NOTE: See table 4 for general notes.