Hardness and tensile strength of steel pipe

2021-11-12
Relationship between hardness and tensile strength of steel pipe

 
1, the relationship between hardness and tensile strength
When the hardness of steel is below 500HB, the tensile strength is proportional to the hardness, kg/mm2(óB)=1/3 X HB=3.2 X HRC=2.1 X HS, but the above relationship is not in any occasion. In the heat treatment aspect, when the tempering temperature is low, the correlation between kg/mm2 and HRC may be destroyed. The relationship between the tempering temperature, hardness and tensile strength of the steel is shown in the figure.
 
 
 
As shown in the figure, the hardness decreases with the increase of the tempering temperature, but the relationship between the hardness and the tensile strength is difficult to establish in the quenched state and the low temperature tempering below 300 °C. When the tempering temperature is around 300 °C, kg/mm2 has a correlation with HRC, that is, the hardness is high, the tensile strength is high, the hardness is low, and the tensile strength is low. It is difficult to find the value of kg/mm2 in the low temperature tempering state because the distribution of the tensile strength values ​​is very discrete.

 
 
Since the kg/mm2 of the low-temperature tempering member is unstable and cannot be determined, it is also tested in the Japanese Industrial Standard (JIS) to measure the tensile properties of the temperature tempering member above 400 ° C (there is also a tempered workpiece at 300 ° C). In other words, the tensile test is only performed on the tempering part (quenching + 400 ° C tempering). Low temperature tempering members are used in the industry only when anti-rotation bending fatigue and wear resistance are required. Induction hardening and carburizing quenching are examples of this application. Tensile parts are not subjected to low temperature tempering. However, in low carbon steel, but quenching M can occur self-tempering (so Ms point is high), there are also users in the quenched state. The slab martensite structure of low carbon steel is self-tempered and can be applied industrially, but at this time, hardenability and mass effect must be considered (metal elements such as B, Cr, Mn should be added if necessary).




2, the hardness and tensile strength comparison table (for reference only):

Vickers hardness Brinell hardness Knoop hardness Rockwell ruler Shore hardness Tensile Strength
HV HB HK HRA HRB HRC HS Kg/m㎡
528 496 558 76.3 　 51 67.6 264
513 481 542 75.9 　 50 66.2 255
498 469 526 75.2 　 49 64.7 246
484 455 510 74.7 　 48 63.4 238
471 443 495 74.1 　 47 62.1 229
458 432 480 73.6 　 46 60.8 221
446 421 466 73.1 　 45 59.6 215
434 409 452 72.5 　 44 58.4 208
423 400 438 72.0 　 43 57.2 201
412 390 426 71.5 　 42 56.1 194
402 381 414 70.9 　 41 55.0 188
392 371 402 70.4 　 40 53.9 182
382 362 391 69.9 　 39 52.9 177
372 353 380 69.4 　 38 51.8 171
363 344 370 68.9 　 37 50.7 166
354 336 360 68.4 　 36 49.7 161
345 327 351 67.9 　 35 48.7 156
336 319 342 67.4 　 34 47.7 152
327 311 334 66.8 　 33 46.6 149
318 301 326 66.3 　 32 45.6 146
310 294 318 65.8 　 31 44.6 141
302 286 311 65.3 　 30 43.6 138
294 279 304 64.6 　 29 42.7 135
286 271 297 64.3 　 28 41.7 131
279 264 290 63.8 　 27 40.8 128
272 258 284 63.3 　 26 39.9 125
266 253 278 62.8 　 25 39.2 123
260 247 272 62.4 　 24 38.4 119
254 243 266 62.0 100 23 37.7 117
248 237 261 61.5 99.0 22 36.9 115
243 231 256 61.0 98.5 21 36.3 112
238 226 251 60.5 97.8 20 35.6 110
230 219 243 60.2 96.7 　 34.6 109
222 212 236 59.5 96.3 　 33.5 104
213 203 229 58.9 96.0 　 32.3 102
204 194 220 58.3 95.0 　 31.1 100
196 187 212 57.6 94.0 　 30.0 98
188 179 204 57.0 93.0 　 　 94
180 171 196 56.4 92 　 　 92
173 165 189 55.8 91 　 　 90

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