Throught hardening steel

Chemical composition - alloy additives and subgroups

Structural alloys for improvement include in most cases additional or higher concentrations of elements such as Manganese - Mn, Chromium - Cr, Silicon - Si, Nickel - Ni, Molybdenum - Mo, and additionally Tungsten - W, Vanadium - V, and Bor - B, normally not exceeding 4.8%.

On the list of products for improvement, there are also steels for improvements without nickel and molybdenum, such as:

• Chromium-silicon steels (eg. 37HS)
• chromium steels (eg. 30H, 40H, 45H, 38HA)
• manganese steels with improved hardening capacity (eg. 20G2, 30G2, 35G2A,40G2, 45G2),
• Steel with boron addition 27MnCrB5-2, 1.7182, 33MnCrB5-2, 1.7185, 32CrB4, 1.7076, 36CrB4, 1.7077
• abrasion-resistant silico-manganese steels (eg. 37MnSi5, 1.5122 , 40GS, 45SG)
• and chromium-manganese-silicon steels (eg. 20HGS, 25HGS, 30HGSA, 35HGSA, 35HGSNA)

which also has high hardness, tensile strength, yield strength and abrasion resistance without any additional elements. A manganese content of more than 1.8% may reduce the material's ductility, so some of the grades are supplemented with a suitable silicon concentration (35SG, 30HGSA).

Other interesting facts about steel for hardening and tempering

Forging of alloy steels at too high temperatures leads to coarseness and brittleness of the product, while at low temperatures it causes harmful stresses and cracks.

Steels for improvement do not show practically no resistance to atmospheric corrosion. Quite high carbon content, low chromium concentration, and nickel will automatically appear after contact with the outside atmosphere. Products with this composition of elements and structure acts as part of heavily loaded machines and vehicles, such as shafts, gears, axles, bolts, valves, pins requiring high ductility and plasticity.

Among steels for thermal improvement there is also steel for the mining chains 23GHNMA.

Other grades for quenching and tempering: 25H2N4WA, 37HN3A, 38ChN3MFA, 30HN3A, 30ChN2MFA, 65S2WA, 30HGSNA, 35NiCrMoV12-5, 1.6959, 37HGNM

Normy

The above-described steels for thermal improvement of structural alloy steels are defined by the standards PN-72/H-84035, PN-89/H-84030-04, according to which are delivered:

• Seamless tubes for thermal improvement according to PN-70/H-74256, PN-74/H-74207, PN-PN-74/H-74209, PN-EN 10297-1,PN-EN 10305-1
• Rolled sheets for thermal improvement according to PN-75/H-92134, PN-81/H-92129, PN-81/H-92135, PN-EN 10029
• Forgings and forged bars for thermal improvement according to PN-79/H-94500, PN-54/H-94005, PN-84/H-94004, PN-EN 10250-3, PN-EN 10250-2
• Cold-rolled strips for thermal improvement according to, PN-75/H-92335, PN-84/H-92331, PN-67/H-92330, PN-93/H-92329, PN-EN 10132-3
• Rolled bars for thermal improvement according to PN-60/H-93013, PN-87/H-93200, PN-72/H-93202, PN-98/H-93237, PN-56/93223, PN-79/H-93203, Steel FE-PL2108, FEPL2108, EN 2480, PN-67/H-93225, PN-EN 10061, PN-EN 10025-6, and PN-EN 10060, PN-EN 10058, PN-EN 10059,
• Bright and drawn bars for thermal improvement according to PN-85/H-93210, PN-72/H-93208, PN-EN 10278, PN-EN 10277-5, PN-85/H-93210, PN-86/H-93209, PN-52/H-93212
• Wires for thermal improvement according to PN-70/H-92600, PN-75/H-93200, PN-70/H-92608, PN-EN 10263-4, PN-EN 10263-1