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How to modify the hardness on a workpiece?

The required hardness of a workpiece could be defined by its functionality. If a harder or softer hardness on the workpiece is required, heat treatment will be helpful for modifying it specification. Typically, we are using some kinds of differnt heat treatment below to meet the requirements:

 

1.) quenching

The way to increase the hardness of workpiece made of carbon steel or alloy steel is general performed by quenching which is to heat the workpiece above its critical temperature and hold for a period of time. After that, the workpiece have to be rapidly cooling in the water, oil or air to complete the quenching process. In that way, quenching could increase the hardness but decrease the ductile of the workpiece.

 

2.) tempering

Tempering is used to increase the toughness of the tooling or spring made of carbon steel or alloy steel. For parts featuring with excess hardness or becoming too hard/brittle after quenching, a consequently tempering process could reduce the hardness and increase the ductile by heating the workpiece to a temperature below its critical point and then steadily cooling to a lower termperature

 

3.) anealing

Anealing is similar to tempering which is also capable of altering the properties of a workpiece to reduce its hardness and increase its ductile. Under a proper heating temperature, the freedom moving atoms of the metal workpiece could achieve a more equilibrium state. After the heating stage, the workpiece is usually left in the oven for steadily cooling while recrystallization and grain growth are happening. For parts made of carbon steel or alloy steel, if it is a terminal or connector spare part for crimping, a anealing heat treatment might be required.

 

4.) case hardening

There are a lots of heat treatment methods to partially harden the workpiece. Case hardening is capable of increasing the stiffness of the outer case of a carbon steel of alloy steel, and keep its core area soft as before for better ductile property. The hardened outer case of the workpiece can be much more durable and wear resistant. However, the hardened surface will be no longer suitable for machining. Therefore, case hardening is generally applied once the workpiece has been completed from CNC machining process.

Tensile Strength Rm 820-2180 [MPa]

 

Tensile Strength

Rm 820-2180

[MPa]

Hardness Vickers

[HV]

Hardness Brinell

[HB]

Hardness Rockwell C

[HRC]

820 255 242 23,1
835 260 247 24
850 265 252 24,8
865 270 257 25,6
880 275 261 26,4
900 280 266 27,1
915 285 271 27,8
930 290 276 28,5
950 295 280 29,2
965 300 285 29,8
995 310 295 31
1030 320 304 32,2
1060 330 314 33,3
1095 340 323 34,4
1125 350 333 35,5
1155 360 342 36,6
1190 370 352 37,7
1220 380 361 38,8
1255 390 371 39,8
1290 400 380 40,8
1320 410 390 41,8
1350 420 399 42,7
1385 430 409 43,6
1420 440 418 44,5
1455 450 428 45,3
1485 460 437 46,1
1520 470 447 46,9
1555 480 [456] 47,7
1595 490 [466] 48,4
1630 500 [475] 49,1
1665 510 [485] 49,8
1700 520 [494] 50,5
1740 530 [504] 51,1
1775 540 [513] 51,7
1810 550 [523] 52,3
1845 560 [532] 53
1880 570 [542] 53,6
1920 580 [551] 54,1
1955 590 [561] 54,7
1995 600 [570] 55,2
2030 610 [580] 55,7
2070 620 [589] 56,3
2105 630 [599] 56,8
2145 640 [608] 57,3
2180 650 [618] 57,8

 

Vickers: F ≥ 98 N, diamond pyramid (HV)
Brinell: F = 29.421 N, ball ø 10 mm (HB)
Rockwell: F = 1,471 N, diamond cone (HRC)

 

Tensile Strength Rm 255-930 [MPa]

1 MPa = 1 N/mm²

Tensile Strength

Rm 255-930

[MPa]

Hardness Vickers

[HV]

Hardness Brinell

[HB]

Hardness Rockwell B

[HRB]

255 80 76  
270 85 80,7 41
285 90 85,5 48
305 95 90,2 52
320 100 95 56,2
335 105 99,8  
350 110 105 62,3
370 115 109  
385 120 114 66,7
400 125 119  
415 130 124 71,2
430 135 128  
450 140 133 75
465 145 138  
480 150 143 78,7
495 155 147  
510 160 152 81,7
530 165 156  
545 170 162 85
560 175 166  
575 180 171 87,1
595 185 176  
610 190 181 89,5
625 195 185  
640 200 190 91,5
660 205 195 92,5
675 210 199 93,5
690 215 204 94
705 220 209 95
720 225 214 96
740 230 219 96,7
755 235 223  
770 240 228 98,1
785 245 233  
800 250 238 99,5
820 255 242  
835 260 247 101
850 265 252  
865 270 257 102
880 275 261  
900 280 266 104
915 285 271  
930 290 276 105

 

Vickers: F ≥ 98 N, diamond pyramid (HV)
Brinell: F = 29.421 N, ball ø 10 mm (HB)
Rockwell: F = 980 N, ball 1/16" (HRB)

 

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