NBK logo

Date Published:Jun. 18. 2015

Mechanical Properties of Fasteners Made of Carbon Steel and Alloy Steel

PDF
Mechanical Properties of Fasteners Made of Carbon Steel and Alloy Steel

Mechanical property for the tensile strength ranking

Mechanical property
 Tensile strength ranking
3.6 4.6 4.8 5.6 5.8 6.8 8.8(1) 9.8(2) 10.9 12.9
d≦16 d＞16(3)
Nominal tensile strength Rm and nom N/mm2 300 400 500 600 800 800 900 1,000 1,200
Minimum tensile strength Rm and min(4) N/mm2 330 400 420 500 520 600 800 830 900 1,040 1,220
Vickers hardness HV
F≧98N		 Min.
 95 120 130 155 160 190 250 255 290 320 385
Max.
 220(5) 250 320 335 360 380 435
Brinell hardness HB
F＝30D2/0.102		 Min.
 90 114 124 147 152 181 238 242 276 304 366
Max.
 209(5) 238 304 318 342 361 414
Rockwell hardness
 Min.
 HRB 52 67 71 79 82 89 - - - - -
HRC - - - - - - 22 23 28 32 39
Max.
 HRB 95.0(5) 99.5 - - - - -
HRC - - 32 34 37 39 44
Surface hardness HV0.3 Max.
 - (6)
Lower yield point ReL(7) N/mm2 Nominal Diameter
 180 240 320 300 400 480 - - - - -
Min.
 190 240 340 300 420 480 - - - - -
0.2% durability Rp0.2(8) N/mm2 Nominal Diameter
 - - 640 640 720 900 1,080
Min.
 - - 640 660 720 940 1,100
Guarantee load stress Sp Sp/ReL or Sp/Rp0.2 0.94 0.94 0.91 0.93 0.9 0.92 0.91 0.91 0.9 0.88 0.88
N/mm2 180 225 310 280 380 440 580 600 650 830 970
Rupture elongation % Min.
 25 22 - 20 - - 12 12 10 9 8
Notes:
  1. If a bolt of tensile strength ranking 8.8 and d ≦ 16mm is tightened exceeding its guarantee load, the nut thread may be sheared.
  2. Tensile strength ranking 9.8 only applies to those with nominal diameter of thread smaller than 16mm.
  3. Steel structure bolt of tensile strength ranking 8.8 is categorized into nominal diameter of thread 12mm.
  4. The minimum tensile strength only applies to those with nominal length of 2.5 d or above. The minimum hardness applies to those of nominal length below 2.5 d or those that cannot go through the tensile test (e.g. those with special head shape).
  5. Hardness of thread tip surface of bolts, screws and implant bolts shall be 250HV, 238HB or 99.5HRB or below.
  6. The surface hardness of products of tensile strength ranking 8.8 - 12.9 must have no difference from the internal hardness by over 30 points with the Vickers hardness HV0.3.
    However, the surface hardness of products of tensile strength ranking 10.9 must not exceed 390HV.
  7. For those that cannot go through the lower yield point ReL measurement, durability Rp0.2 of 0.2% applies. ReL values for the tensile strength ranking 4.8, 5.8 and 6.8 are only for calculation, not for testing.
  8. The yield stress ratio and minimum 0.2% durability Rp0.2 according to the tensile strength ranking indication manners apply to testing with shaved test samples, so obtained values may vary due to differences in manufacturing methods or nominal screw diameter.

 

Lower yield point or ratio of durability and tensile strength

Lower yield point or durability at temperature above normal temperature

Tensile strength ranking
 Temperature
20℃ 100℃ 200℃ 250℃ 300℃
Lower yield point ReL or 0.2% durability Rp0.2 N/mm2
 5.6  300  270 230 215 195
 8.8  640  590 540 510 480
10.9  940  875 790 745 705
12.9 1100 1020 925 875 825

The mechanical property of bolts, screws and implant bolts varies as the temperature increases. The left table indicates rough values of lower yield point 0.2% durability at high temperature. These data may not be used as test requirements.
If high temperature continues, relaxation that must be focused may occur. As a representative case, when 300°C ambient temperature is retained for 100 hours, the initial tightening force is thought to decrease by 25% to lower the yield points.


Mechanical property of hex socket head cap screw and maximum tightening torque (Tensile strength ranking 10.9 and 12.9 for coarse screws)

Nominal Diameter of Thread
 Effective sectional area
（mm2）		 Minimum tensile load（N） 0.2% durability load（N） Maximum allowed axial force（N） Maximum tightening torque（N・m）
K＝0.25 K＝0.4
10.9 12.9 10.9 12.9 10.9 12.9 10.9 12.9 10.9 12.9
M1.6   1.27   1,320   1,550   1,140   1,370    790    950    0.32    0.38    0.5    0.6
M2   2.07   2,150   2,530   1,860   2,230   1,300   1,560    0.65    0.78    1.0    1.2
M2.5   3.39   3,530   4,140   3,050   3,660   2,130   2,560    1.33    1.6    2.1    2.6
M3   5.03   5,230   6,140   4,520   5,430   3,160   3,800    2.37    2.85    3.8    4.6
M4   8.78   9,130  10,700   7,900   9,480   5,530   6,630    5.53    6.63    8.8   10.6
M5  14.2  14,800  17,300  12,700  15,300   8,930  10,700   11.2   13.3   17.9   21.4
M6  20.1  20,900  24,500  18,000  21,700  12,600  15,200   18.9   22.8   30.2   36.5
M8  36.6  38,100  44,600  32,900  39,500  23,000  27,600   46.0   55.2   73.6   88.2
M10  58  60,300  70,800  52,100  62,600  36,500  43,800   91.3  109  146  175
M12  84.3  87,700 103,000  75,800  91,000  53,000  63,700  159  191  254  305
M14 115 120,000 140,000 103,000 124,000  72,700  87,200  254  305  407  488
M16 157 163,000 192,000 141,000 169,000  98,700 118,000  394  472  631  755
M18 192 200,000 234,000 173,000 207,000 121,000 145,000  544  652  871 1,040
M20 245 255,000 299,000 220,000 264,000 154,000 185,000  770  925 1,230 1,480
M22 303 315,000 370,000 273,000 327,000 191,000 229,000 1,050 1,250 1,680 2,010
M24 353 367,000 431,000 317,000 380,000 222,000 266,000 1,330 1,590 2,130 2,550
M27 459 477,000 560,000 413,000 496,000 289,000 347,000 1,950 2,340 3,120 3,740
M30 561 583,000 684,000 504,000 605,000 353,000 423,000 2,640 3,170  4,230 5,070
Remarks:
  1. The minimum tensile load in the above table is according to JIS B 1051：2000.
  2. 0.2% durability load=0.2% durability × Effective sectional area
  3. Maximum allowed axial force=0.7×0.2% durability load
  4. Maximum tightening torque=Torque coefficient [K]×Maximum allowed axial force×Nominal diameter
  5. Torque coefficient：In case of lubricant K=0.25 ,  in case of non-lubricant (plated product, etc.) K=0.4

Minimum tensile strength for 12.9 is 1220N/mm2 , and 0.2% durability is 1080N/mm2
Minimum tensile strength for 10.9 is 1040N/mm2 , and 0.2% durability is 900N/mm2
The torque coefficient varies depending on use conditions. Please use as a reference value.


 

Mechanical property of hex socket head cap screw and maximum tightening torque (A2-50 and A2-70 for coarse screws)

Nominal Diameter of Thread
 Effective sectional area
(mm2)		 Minimum tensile load（N) 0.2% durability load（N) Maximum allowed axial force（N) Maximum tightening torque (N・m）
K=0.1 K=0.3 K=0.5
A2-50 A2-70 A2-50 A2-70 A2-50 A2-70 A2-50 A2-70 A2-50 A2-70 A2-50 A2-70
M2   2.07   1,030   1,450   430    930   300   650  0.06   0.13   0.18   0.39   0.3   0.7
M2.5   3.39   1,690   2,370   710   1,520   490  1,060  0.12   0.27   0.37   0.80   0.6   1.3
M3   5.03   2,510   3,520  1,050   2,260   730  1,580  0.22   0.47   0.66   1.42   1.1   2.4
M4   8.78   4,380   6,140  1,840   3,940  1,280  2,750  0.51   1.1   1.54   3.30   2.6   5.5
M5  14.2   7,090   9,920  2,970   6,380  2,070  4,460  1.04   2.23   3.11   6.69   5.2  11.2
M6  20.1  10,000  14,000  4,220   9,050  2,950  6,330  1.77   3.8   5.31  11.3   8.9  19
M8  36.6  18,300  25,600  7,680  16,400  5,370 11,500  4.3   9.2  12.8  27.6  21.5  46
M10  58  28,900  40,500 12,100  26,000  8,510 18,200  8.5  18.2  25.5  54.6  42.6  91
M12  84.3  42,100  58,900 17,600  37,900 12,300 26,500 14.7  31.8  44.2  95.4  74 159
M14 115  57,700  80,800 24,200  51,900 16,900 36,300 23.6  50.8  70.9 152 118 254
M16 157  78,300 109,000 32,900  70,500 23,000 49,300 36.8  79 110 236 184 394
M20 245 122,000 171,000 51,400 110,000 35,900 77,100 72 154 215 462 359 771
Remarks:
  1. 0.2% durability load=0.2% durability ×Effective sectional area
  2. Maximum allowed axial force=0.7×0.2% durability load
  3. Maximum tightening torque= Torque coefficient[K]×Maximum allowed axial force×Nominal diameter
  4. Torque coefficient：With surface treatment K=0.1 , Without surface treatment K=0.3 , and Clean wash product K=0.5

Minimum tensile strength of A2-70 is 700N/mm2 , and 0.2% durability is 450N/mm2
Minimum tensile strength of A2-50 is 500N/mm2 , and 0.2% durability is 210N/mm2
The torque coefficient varies depending on use conditions. Please use as a reference value.


 


Engineering Tips HINTS for NEW IDEAS

Examples to help you resolve any issues you may have.

Technical Data Others Machine Tools Semiconductor Manufacturing Equipment Food Machinery Automotive Manufacturing Process Medical Equipment FA Devices Technical Data Special Screws