Heat Treatment of Steel

Heat Treatmentn of Steel

August 22, 2023

What is heat treatment?

Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. 
And what is the heat treatment of steel? In order to be made appropriate for various uses and applications, steel undergoes various procedures such as quenching, tempering, and annealing. Those procedures of heat treatment change the microstructure, hardness, and tensile strength of steel.

What are the various classifications of heat treatment for steel?

No. The Types of Heat Treatment The Characteristics of the Heat Treatment Process The Main Methods of the Heat Treatment
1 Overall Heat Treatment This heat treatment process heats the workpiece as a whole and then cools it at an appropriate rate to obtain the required metallographic structure to change its overall mechanical properties. Annealing, Normalizing,Quenching, Tempering,Quenching and Tempering,Stabilizing Treatment,Solution Treatment / Water Toughening,Solution Treatment + Aging Treatment.
2 Surface Heat Treatment This process only heats the surface of the workpiece to change the mechanical properties of the surface. Surface Quenching and Tempering, Physical Vapor Deposition(PVD),Chemical Vapor Deposition(CVD),Plasma-enhanced Chemical Vapor Deposition (PECVD),Ion Implantation.
3 Chemical Heat Treatment This metal heat treatment process is able to change the chemical composition, structure and properties of the workpiece surface. Carburizing,Carbonitriding,Nitriding,Nitrocarburizing,Other Non-metallic Infiltration, Metallic,Cementation,Multicomponent Thermochemical Treatment.

Comparison Table of Heat Treatment Hardness and Tensile Strength

The hardness and tensile strength poses an important parameters as regards the heat treatment of steel, so that various types of steel can be produced, depending on their future use.
If you want to find the tensile strength of steel that is equivalent to their hardness in China Standard, please go to the following table depicting the hardness to tensile strength conversion chart (GB/T 1172-1999).

Conversion of Hardness to Tensile Strength Values for Steel
Rockwell Hardness Superficial
Rockwell Hardness		 Vickers Hardness Brinell Hardness(F/D²=30） Tensile Strength (Rm/MPa)
HRC HRA HR15N HR30N HR45N HV HBW Carbon Steel Chrome Steel Chromium-Vanadium Steel Chrome-Nickel Steel Chrome-Molybdenum Steel Chrome-Nickel-Molybdenum steel Chromium-Manganese-Silicon Steel Ultrahigh Strength Steel Stainless Steel
20.0 60.2 68.8 40.7 19.2 226 225 774 742 736 782 747   781   740
20.5 60.4 69.0 41.2 19.8 228 227 784 751 744 787 753   788   749
21.0 60.7 69.3 41.7 20.4 230 229 793 760 753 792 760   794   758
21.5 61.0 69.5 42.2 21.0 233 232 803 769 761 797 767   801   767
22.0 61.2 69.8 42.6 21.5 235 234 813 779 770 803 774   809   777
22.5 61.5 70.0 43.1 22.1 238 237 823 788 779 809 781   816   786
23.0 61.7 70.3 43.6 22.7 241 240 833 798 788 815 789   824   796
23.5 62.0 70.6 44.0 23.3 244 242 843 808 797 822 797   832   806
24.0 62.2 70.8 44.5 23.9 247 245 854 818 807 829 805   840   816
24.5 62.5 71.1 45.0 24.5 250 248 864 828 816 836 813   848   826
25.0 62.8 71.4 45.5 25.1 253 251 875 838 826 843 822   856   837
25.5 63.0 71.6 45.9 25.7 256 254 886 848 837 851 831 850 865   847
26.0 63.3 71.9 46.4 26.3 259 257 897 859 847 859 840 859 874   858
26.5 63.5 72.2 46.9 26.9 262 260 908 870 858 867 850 869 883   868
27.0 63.8 72.4 47.3 27.5 266 263 919 880 869 876 860 879 893   879
27.5 64.0 72.7 47.8 28.1 269 266 930 891 880 885 870 890 902   890
28.0 64.3 73.0 48.3 28.7 273 269 942 902 892 894 880 901 912   901
28.5 64.6 73.3 48.7 29.3 276 273 954 914 903 904 891 912 922   913
29.0 64.8 73.5 49.2 29.9 280 276 965 925 915 914 902 923 933   924
29.5 65.1 73.8 49.7 30.5 284 280 977 937 928 924 913 935 943   936
30.0 65.3 74.1 50.2 31.1 288 283 989 948 940 935 924 947 954   947
30.5 65.6 74.4 50.6 31.7 292 287 1002 960 953 946 936 959 965   959
31.0 65.8 74.7 51.1 32.3 296 291 1014 972 966 957 948 972 977   971
31.5 66.1 74.9 51.6 32.9 300 294 1027 984 980 969 961 985 989   983
32.0 66.4 75.2 52.0 33.5 304 298 1039 996 993 981 974 999 1001   996
32.5 66.6 75.5 52.5 34.1 308 302 1052 1009 1007 994 987 1012 1013   1008
33.0 66.9 75.8 53.0 34.7 313 306 1065 1022 1022 1007 1001 1027 1026   1021
33.5 67.1 76.1 53.4 35.3 317 310 1078 1034 1036 1020 1015 1041 1039   1034
34.0 67.4 76.4 53.9 35.9 321 314 1092 1048 1051 1034 1029 1056 1052   1047
34.5 67.7 76.7 54.4 36.5 326 318 1105 1061 1067 1048 1043 1071 1066   1060
35.0 67.9 77.0 54.8 37.0 331 323 1119 1074 1082 1063 1058 1087 1079   1074
35.5 68.2 77.2 55.3 37.6 335 327 1133 1088 1098 1078 1074 1103 1094   1087
36.0 68.4 77.5 55.8 38.2 340 332 1147 1102 1114 1093 1090 1119 1108   1101
36.5 68.7 77.8 56.2 38.8 345 336 1162 1116 1131 1109 1106 1136 1123   1116
37.0 69.0 78.1 56.7 39.4 350 341 1177 1131 1148 1125 1122 1153 1139   1130
37.5 69.2 78.4 57.2 40.0 355 345 1192 1146 1165 1142 1139 1171 1155   1145
38.0 69.5 78.7 57.6 40.6 360 350 1207 1161 1183 1159 1157 1189 1171   1161
38.5 69.7 79..0 58.1 41.2 365 355 1222 1176 1201 1177 1174 1207 1187 1170 1176
39.0 70.0 79.3 58.6 41.8 371 360 1238 1192 1219 1195 1192 1226 1204 1195 1193
39.5 70.3 79.6 59.0 42.4 376 365 1254 1208 1238 1214 1211 1245 1222 1219 1209
40.0 70.5 79.9 59.5 43.0 381 370 1271 1225 1257 1233 1230 1265 1240 1243 1226
40.5 70.8 80.2 60.0 43.6 387 375 1288 1242 1276 1252 1249 1285 1258 1267 1244
41.0 71.1 80.5 60.4 44.2 393 381 1305 1260 1296 1273 1269 1306 1277 1290 1262
41.5 71.3 80.8 60.9 44.8 398 386 1322 1278 1317 1293 1289 1327 1296 1313 1280
42.0 71.6 81.1 61.3 45.4 404 392 1340 1296 1337 1314 1310 1348 1316 1336 1299
42.5 71.8 81.4 61.8 45.9 410 397 1359 1315 1358 1336 1331 1370 1336 1359 1319
43.0 72.1 81.7 62.3 46.5 416 403 1378 1335 1380 1358 1353 1392 1357 1381 1339
43.5 72.4 82.0 62.7 47.1 422 409 1397 1355 1401 1380 1375 1415 1378 1404 1361
44.0 72.6 82.3 63.2 47.7 428 415 1417 1376 1424 1404 1397 1439 1400 1427 1383
44.5 72.9 82.6 63.6 48.3 435 422 1438 1398 1446 1427 1420 1462 1422 1450 1405
45.0 73.2 82.9 64.1 48.9 441 428 1459 1420 1469 1451 1444 1487 1445 1473 1429
45.5 73.4 83.2 64.6 49.5 448 435 1481 1444 1493 1476 1468 1512 1469 1496 1453
46.0 73.7 83.5 65.0 50.1 454 441 1503 1468 1517 1502 1492 1537 1493 1520 1479
46.5 73.9 83.7 65.5 50.7 461 448 1526 1493 1541 1527 1517 1563 1517 1544 1505
47.0 74.2 84.0 65.9 51.2 468 455 1550 1519 1566 1554 1542 1589 1543 1569 1533
47.5 74.5 84.3 66.4 51.8 475 463 1575 1546 1591 1581 1568 1616 1569 1594 1562
48.0 74.7 84.6 66.8 52.4 482 470 1600 1574 1617 1608 1595 1643 1595 1620 1592
48.5 75.0 84.9 67.3 53.0 489 478 1626 1603 1643 1636 1622 1671 1623 1646 1623
49.0 75.3 85.2 67.7 53.6 497 486 1653 1633 1670 1665 1649 1699 1651 1674 1655
49.5 75.5 85.5 68.2 54.2 504 494 1681 1665 1697 1695 1677 1728 1679 1702 1689
50.0 75.8 85.7 68.6 54.7 512 502 1710 1698 1724 1724 1706 1758 1709 1731 1725
50.5 76.1 86.0 69.1 55.3 520 510   1732 1752 1755 1735 1788 1739 1761  
51.0 76.3 86.3 69.5 55.9 527 518   1768 1780 1786 1764 1819 1770 1792  
51.5 76.6 86.6 70.0 56.5 535 527   1806 1809 1818 1794 1850 1801 1824  
52.0 76.9 86.8 70.4 57.1 544 535   1845 1839 1850 1825 1881 1834 1857  
52.5 77.1 87.1 70.9 57.6 552 544     1869 1883 1856 1914 1867 1892  
53.0 77.4 87.4 71.3 58.2 561 552     1899 1917 1888 1947 1901 1929  
53.5 77.7 87.6 71.8 58.8 569 561     1930 1951     1936 1966  
54.0 77.9 87.9 72.2 59.4 578 569     1961 1986     1971 2006  
54.5 78.2 88.1 72.6 59.9 587 577     1993 2022     2008 2047  
55.0 78.5 88.4 73.1 60.5 596 585     2026 2058     2045 2090  
55.5 78.7 88.6 73.5 61.1 606 593               2135  
56.0 79.0 88.9 73.9 61.7 615 601               2181  
56.5 79.3 89.1 74.4 62.2 625 608               2230  
57.0 79.5 89.4 74.8 62.8 635 616               2281  
57.5 79.8 89.6 75.2 63.4 645 622               2334  
58.0 80.1 89.8 75.6 63.9 655 628               2390  
58.5 80.3 90.0 76.1 64.5 666 634               2448  
59.0 80.6 90.2 76.5 65.1 676 639               2509  
59.5 80.9 90.4 76.9 65.6 687 643               2572  
60.0 81.2 90.6 77.3 66.2 698 647               2639  
60.5 81.4 90.8 77.7 66.8 710 650                  
61.0 81.7 91.0 78.1 67.3 721                    
61.5 82.0 91.2 78.6 67.9 733                    
62.0 82.2 91.4 79.0 68.4 745                    
62.5 82.5 91.5 79.4 69.0 757                    
63.0 82.8 91.7 79.8 69.5 770                    
63.5 83.1 91.8 80.2 70.1 782                    
64.0 83.3 91.9 80.6 70.6 795                    
64.5 83.6 92.1 81.0 71.2 809                    
65.0 83.9 92.2 81.3 71.7 822                    
65.5 84.1       836                    
66.0 84.4       850                    
66.5 84.7       865                    
67.0 85.0       879                    
67.5 85.2       894                    
68.0 85.5       909