Steel 20HNM, 22HNM carburizing steel alloyed chromium-nickel-molybdenum structural steel PN-89/H-84030.02 20NiCrMo2-2, 1.6523, 1.6522, 1.6526, 20NiCrMo2, 21NiCrMoS2, 8620H, 20NCD2
Comparison of the chemical composition of 20HNM, 22HNM with substitutes 20NiCrMo2-2, 1.6523, 1.6522, 1.6526, 20NiCrMo2, 21NiCrMoS2, 20NCD2, 8620H
| Chemical composition in % | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Steel grade | Norma | C | Mn | Si | P | S | Cr | Ni | Mo | V | W | Cu | Other |
| 20HNM | PN | 0.17–0.23 | 0.6–0.9 | 0.17–0.37 | max 0.035 | max 0.035 | 0.35–0.65 | 0.35–0.75 | 0.15–0.25 | max 0,3 | |||
| 22HNM | PN | 0.19–0.25 | 0.6–0.9 | 0.17–0.37 | max 0.035 | max 0.035 | 0.35–0.65 | 0.35–0.75 | 0.15–0.25 | max 0,3 | |||
| 20HNMA PN-89/H-84030.8 | PN | 0.17–0.23 | 0.6–0.9 | 0.10–0.25 | max 0.030 | max 0.030 | 0.35–0.65 | 0.40–0.70 | 0.15–0.25 | max 0,2 | Al 0,02–0,05 | ||
| 20NiCrMo2-2, 21NiCrMo2, 1.6523 | EN | 0.17–0.23 | 0.65–0.95 | max 0.4 | max 0.025 | max 0.035 | 0.35–0.70 | 0.4–0.7 | 0.15–0.25 | ||||
| 20NiCrMo2F, 20NiCrMo2, 1.6522 | ISO | 0.17–0.23 | 0.60–0.95 | max 0.4 | max 0.025 | max 0.030 | 0.35–0.65 | 0.4–0.7 | 0.15–0.25 | max 0.3 | Al max 0.05 | ||
| 20NCD2, 20NCD 2 | AFNOR | 0.17–0.23 | 0.65–0.95 | 0.10–0.35 | max 0.03 | max 0.025 | 0.40–0.65 | 0.4–0.7 | 0.15–0.25 | Al max 0.02 | |||
| 20NiCrMoS2-2, 21NiCrMoS2, 1.6526 | DIN | 0.17–0.23 | 0.65–0.95 | max 0.4 | max 0.025 | 0.02–0.04 | 0.35–0.70 | 0.4–0.7 | 0.15–0.25 | ||||
| 20HGNM, 20ChGNM, 20KhGNM, 20ХГНМ | GOST | 0.18–0.23 | 0.7–1.1 | 0.17–0.37 | max 0.035 | max 0.035 | 0.4–0.7 | 0.4–0.7 | 0.15–0.25 | max 0.05 | max 0.2 | max 0.3 | N max 0.008, Ti max 0.03 |
| J1268, AISI 8620H, 8620H, UNS H86200 | SAE | 0.17–0.23 | 0.60–0.95 | 0.15–0.35 | max 0.035 | max 0.040 | 0.35–0.65 | 0.35–0.75 | 0.15–0.25 | ||||
Steel 20HNM and 22HNM – 20NiCrMo2-2, 8620H, 1.6523, 1.6522, 1.6526, 20NiCrMo2, 21NiCrMoS2, 20NCD2 – description, application and properties
20HNM steel i 22HNM are low-alloy chromium-nickel-molybdenum structural steels intended primarily for thermochemical treatment, mainly carburization, and then hardening i temperingAfter appropriate processing, these steels combine a hard, wear-resistant surface layer with a strong and ductile core.
Contained in steel chrome, nickel i molybdenum increase hardenability and enable obtaining favorable mechanical properties even in elements with larger cross-sections. Low content coal in the core allows it to maintain its ductility, while carburizing increases the carbon content in the surface layer, enabling it to achieve high hardness after hardening.
Mechanical properties after processing
- Hardness surface after carburizing and hardening: 58-62 HRC
- Tensile strength Rm core: depending on the heat treatment condition and the dimensions of the element
- Good ductility and impact strength core
- Increased hardenability due to the presence of Cr, Ni i Mo
- High resistance of the carburized layer to wear and surface pressure
Application
20HNM and 22HNM steel is used where high strength is required. very hard and wear-resistant surface and durable and ductile core.
Typical Applications:
- shafts and drive pins,
- gears, gear crowns and gear rims,
- bushings and pins,
- camshafts,
- transmission and mechanism components exposed to wear,
- parts of machines and vehicles operating under variable and impact loads.
Technological purpose
- Carburizing – basic thermochemical treatment enabling the obtaining of a surface layer enriched with carbon.
- Hardening – used after carburizing to obtain a hard martensitic layer structure.
- Letting go – carried out after hardening in order to reduce stresses and obtain the required functional properties.
- Carbonitriding – alternative surface treatment consisting in the simultaneous enrichment of the layer with carbon and nitrogen.
General mechanical properties of 20HNM steel and equivalents 22HNM, 20NiCrMo2-2, 1.6523, 8620H, 1.6522, 1.6526, 20NiCrMo2, 21NiCrMoS2, 20NCD2
20HNM steel is characterized by a favorable combination of strength and ductility, making it suitable for critical machine parts subjected to variable and impact loads. Mechanical property values depend on the component diameter, delivery condition, and heat treatment applied.
| Parameter | Value range |
|---|---|
| Tensile strength Rm | 660–1160MPa |
| Yield strength Re | 470–560MPa |
| Breaking work KU2 | 25–30 days |
| Relative elongation A | 9-11% |
| Hardness in annealed condition | max 229 HB |
| Density | 7,85 g / cm³ |
Heat treatment of 20HNM steel – processes, temperatures and cooling
| Process | Temperature (° C) | Cooling | Technological goal |
|---|---|---|---|
| Normalizing annealing | 860–900 | air | Obtaining a fine-grained and more homogeneous structure |
| Soft annealing | 650–700 | slow cooling | Reducing hardness and improving workability |
| Carburizing | 880–950 | depending on the adopted technological cycle | Enrichment of the surface layer in carbon |
| Carbonitriding | depending on the technology used | depending on the cycle | Simultaneous enrichment of the surface in carbon i nitrogen |
| Hardening after carburizing | selected according to the cycle used and the condition of the layer | most often, a properly selected hardening medium | Obtaining a martensitic structure of the carburized layer |
| Letting go | usually low tempering after hardening of the layer | air | Reducing stresses and stabilizing the required layer properties |
Properties after carburizing, hardening and tempering of 20HNM steel
After a properly conducted carburizing , hardening and tempering cycle , 20HNM steel combines a hard and wear-resistant surface with a ductile and durable core.
| Technical parameter | Typical characteristics |
|---|---|
| Hardness of the carburized layer | possible values of 58–62 HRC after appropriately selected carburizing, hardening and tempering |
| Depth of the carburized layer | technologically selected to suit the component requirements and operating conditions |
| Microstructure of the surface layer | mainly high-carbon martensite with possible addition of retained austenite and carbides |
| Core microstructure | depending on the heat treatment cycle, element cross-section and cooling rate |
| Abrasion resistance | high after proper carburizing and hardening |
| Core resistance to impact loads | advantageous due to the low carbon content in the core and additives Ni, Cr i Mo |
The influence of alloying elements on the properties of 20HNM and 22HNM steels
| Element | Impact on steel |
|---|---|
| Carbon C | It determines the possibility of increasing hardness. Low content in the core promotes ductility, while carburization increases its content in the surface layer. |
| Chromium Cr | It increases hardenability, influences properties after hardening and participates in the formation of carbides. |
| Nickel Ni | It improves ductility and impact strength and helps to obtain a strong core. |
| Molybdenum Mo | Increases hardenability and has a beneficial effect on the properties of steel after heat treatment. |
| Manganese Mn | Increases hardenability and influences the course of transformations during heat treatment. |
| Silicon Si | Among other things, it performs a deoxidizing function during steel production and influences the properties of the matrix. |
| Phosphorus P | The element is restricted due to its unfavorable effect on ductility and impact strength when present in excessive amounts. |
| Sulfur S | Usually limited; in certain steel grades it may be deliberately adjusted to improve machinability. |
| Copper Cu | In these steels it occurs primarily as an element with a limited permissible content. |
| Aluminum Al | It can be used to deoxidize and regulate the structure of steel. |
| Nitrogen N | It occurs in small amounts and is also important in thermochemical processes involving the saturation of surfaces with nitrogen. |
| Titanium Ti | A strong carbide- and nitride-forming element that can affect grain size and precipitation stability. |
Assortment of 20HNM steels and equivalents 1.6523, 1.6522, 1.6526, 20NiCrMo2-2
Alloyed carburizing structural steels such as 20HNM, 22HNM, 20NiCrMo2-2, 1.6523, 1.6522, 1.6526, 20NiCrMo2, 21NiCrMoS2, 8620H and 20NCD2 can be offered in various metallurgical forms and processing conditions.
| Product type | Description |
|---|---|
| Rolled bars | Hot-rolled round bars |
| Forged bars | Forged bars intended, among others, for elements with larger cross-sections |
| Flat bars | Rolled or forged flat bars |
| Forgings | Shafts, rings, bushings and other components made as forgings |
Other case-hardening steels
12HN3A – chromium-nickel carburizing steel, 1.5752, 12H2N4A, 15NiCr13, 16NiCrMo12
12H2N4A – chromium-nickel case-hardening steel
15HN – chrome-nickel case-hardening steel, 15CrNi6, 1.5919, 1.5918
17HNM – chromium-nickel-molybdenum carburizing structural steel, 18CrNiMo7-6, 1.6587
18HGT – chromium-manganese-titanium carburizing structural steel, 18ChGT, 18KHGT
18H2N2 – chromium-nickel carburizing steel, 18CrNi8, 1.5920
18H2N4WA, 18H2N4MA – carburizing structural steel, X19NiCrMo4, 1.2764
20H2N4A – chromium-nickel carburizing steel, 20KH2N4A, 20Ch2N4A
20HNM – chrome-nickel-molybdenum steel, 22HNM, 20NiCrMo2-2, 1.6523, 1.6522, 1.6526
Other structural alloy steels
Alloy structural steels for carburizing
Structural alloy steels for nitriding
Structural alloy spring steels
Structural alloy bearing steels
Structural alloy steels for heat treatment
Alloy structural steels for operation at elevated temperatures – boiler steels