JIS G4052 SCM822H Hardenability Structural Steel
SCM822H Steel (JIS G4052) – Guaranteed Hardenability Cr-Mo Alloy for Automotive & Mechanical Pipes
Comprehensive technical data for SCM822H steel according to JIS G4052, including chemical composition, mechanical properties, physical properties, equivalent grades, and application guidance for automotive and mechanical structure pipes.
Hot rolling, hot forging, carburizing, quenching and tempering, induction hardening, nitriding, machining
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JIS G4052 SCM822H Hardenability Structural Steel Introduction
SCM822H is a chromium-molybdenum alloy steel grade specified in JIS G4052 – Structural steels with specified hardenability bands. It is designed primarily for components requiring consistent heat treatment response, such as automotive transmission parts and mechanical structure pipes. The 'H' suffix indicates guaranteed hardenability, ensuring that the steel will achieve a predictable hardness profile after quenching.
- Good balance of strength, toughness, and wear resistance after carburizing or quenching and tempering.
- Excellent hardenability enables uniform core properties in larger cross-sections.
- Widely used in gear, shaft, and mechanical tubing applications where reliability under cyclic loads is critical.
JIS G4052 SCM822H Hardenability Structural Steel Chemical Composition
The chemical composition of SCM822H is controlled to meet the hardenability requirements of JIS G4052. The values below are the ladle analysis limits.
- Carbon and alloying elements are precisely balanced to ensure the specified Jominy hardenability band.
- Phosphorus and sulfur are kept low to maintain cleanliness and toughness.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.19 - 0.25 | Key for hardenability and strength |
| Silicon (Si) | 0.15 - 0.35 | Deoxidizer, improves strength |
| Manganese (Mn) | 0.55 - 0.90 | Enhances hardenability and tensile strength |
| Phosphorus (P) | ≤ 0.030 | Residual element, kept low for toughness |
| Sulfur (S) | ≤ 0.030 | Residual element, kept low for cleanliness |
| Chromium (Cr) | 0.85 - 1.25 | Major carbide former, increases hardenability and wear resistance |
| Molybdenum (Mo) | 0.15 - 0.35 | Increases high-temperature strength and hardenability |
| Nickel (Ni) | ≤ 0.25 | Residual element; not a guaranteed addition |
| Copper (Cu) | ≤ 0.30 | Residual element |
JIS G4052 SCM822H Hardenability Structural Steel Thermal and Electrical Physical Properties
These physical constants are representative for SCM822H in the normalized and annealed condition. They are derived from general data for Cr-Mo alloy steels and serve for design calculations; they are not part of the JIS G4052 standard.
- Properties may vary slightly with heat treatment and microstructure.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Elastic Modulus (E) | 206 | GPa | Ambient temperature |
| Shear Modulus (G) | 79.3 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | — | Typical for steel |
| Thermal Expansion Coefficient (α) | 12.1 | 10⁻⁶/K | 20–100°C |
| Thermal Conductivity (λ) | 42.6 | W/(m·K) | At 20°C |
| Specific Heat Capacity (c) | 477 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρₑ) | 0.22 | μΩ·m | At 20°C |
JIS G4052 SCM822H Hardenability Structural Steel Mechanical Properties
The mechanical properties below are reference values for SCM822H after the heat treatment specified in JIS G4052 (Annex). Because this is an H-steel, the main guarantee is the hardenability band; these mechanical properties are not mandatory but are achievable with proper processing.
- Heat treatment: Quench from 850–900°C in oil, temper at 550–650°C, rapid cooling.
- Test coupons are taken from the core of the normalized and tempered bar.
| Property | Standard Requirement (Reference) | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH/0.2%) | ≥ 785 | N/mm² (MPa) | After quenching and tempering as specified |
| Tensile Strength (Rm) | ≥ 930 | N/mm² (MPa) | After quenching and tempering as specified |
| Elongation (A) | ≥ 12 | % | Gauge length 5.65√S₀, after tempering |
| Reduction of Area (Z) | ≥ 45 | % | After tempering |
| Charpy Impact Energy (KV) | ≥ 59 | J/cm² | V-notch, room temperature, after tempering (typical) |
JIS G4052 SCM822H Hardenability Structural Steel Equivalent Designations and Substitutable Grades
Internationally, SCM822H can be replaced by equivalent H-type carburizing steels that guarantee identical hardenability bands. The closest complete equivalents are from EN, ISO, and GB standards. Minor compositional adjustments exist, but the processing response is nearly identical.
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| Japan | JIS G4052 | SCM822H | Original grade |
| Europe | EN 10084 | 20CrMo5H (1.7262H) | Complete equivalent with the same hardenability band |
| International | ISO 683-11 | 20CrMo5H | Identical composition and hardenability limits |
| China | GB/T 5216 | 20CrMoH | Slightly narrower carbon range (0.17-0.23%), otherwise interchangeable |
JIS G4052 SCM822H Hardenability Structural Steel Application Introduction
SCM822H is a preferred material for medium-to-high strength mechanical components that must undergo surface hardening (carburizing, carbonitriding, or induction hardening) to obtain a wear-resistant case while retaining a tough core. Its guaranteed hardenability makes it especially suitable for automotive drivetrain parts and mechanical tubing subjected to alternating and impact loads.
- Excellent machinability in spheroidized annealed state.
- Good weldability with preheating and post-weld heat treatment.
Product Applications: Seamless mechanical steel tubes used in hydraulic cylinder barrels, axle housings, Carburized transmission gears and pinions, Heavy-duty shafts and axles, Crankshafts and connecting rods (in select applications), Bearing races and rolling elements
Processed into products: Automotive differential gears and side gears, Tractor final drive shafts, Planetary gear carriers, Precision engine valve lifters, Industrial worm and bevel gears, Machined sleeves and bushings for high contact stress
Application industries: Automotive and transportation, Agricultural and construction machinery, General mechanical engineering, Oil and gas (mechanical structural pipes), Power generation (turbine components)
JIS G4052 SCM822H Hardenability Structural Steel Similar or Closely Related Grades
If exact replacement is not required, grades from other alloy steel families may be considered. These materials offer comparable mechanical strength but may differ in hardenability, heat treatment response, or alloy cost. Adjustments in heat treatment are necessary.
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| USA | SAE J1268 | 8620H | Ni-Cr-Mo steel; lower Cr and Mo content, wider availability for carburizing |
| Europe | EN 10084 | 20NiCrMo2-2 (1.6523H) | Nickel-containing grade; slightly higher core toughness |
| China | GB/T 5216 | 16CrMnH | Mn-Cr based; lower cost but different heat treatment parameters |
| Japan | JIS G4052 | SCM420H | Lower carbon (0.18-0.23%) and chromium, used for lighter sections |
Notes:
- Hardenability is verified by Jominy end-quench testing according to JIS G0561. The hardness limits at specific distances from the quenched end must fall within the JIS G4052 band for SCM822H.
- For optimal machinability, spheroidize annealing is recommended. The surface carbon content after carburizing is typically 0.7–0.9%.
- When welding mechanical pipes, preheating to 150–250°C and stress-relieving anneal after welding reduce the risk of cold cracking.
- The information provided is based on official JIS standards and typical industry data; specific procurement should be governed by the relevant standard edition and purchaser–supplier agreements.
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