Steel SCM430 QT+NIT
Finish state
JIS SCM430 · AISI/SAE 4130 · GB 30CrMo
QT+NIT = q&T + gas/plasma nitrided surface
Use when a wear/fatigue-resistant hard skin is needed on an already tough Q&T core (shafts, spindles).
Values for the QT+NIT condition
Other SCM430 tempers and conditions
SCM430 is listed in 9 conditions; see the grade overview at SCM430.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for deep machining, cold forming or as a pre-heat-treat blank. | 360 | 560 | 28 | 163 HB | — |
Hot rolled | Cheapest mill condition for forging stock or parts that will be heat treated after machining. | 390 | 620 | 22 | 11 HRC | 7.7 % IACS |
Normalized | Uniform fine-grain structure with good toughness; standard condition for 4130/SCM430 welded tubing and weldments. | 435 | 670 | 25 | 197 HB | — |
Cold drawn | Bright, close-tolerance bar with raised strength; good for shafts machined without further heat treatment. | 580 | 700 | 15 | 14 HRC | 7.7 % IACS |
Q&T 22–26 HRC (high-temper, sour/bolting service) | Soft-tempered condition for maximum toughness and NACE-type sulphide stress cracking limits. | 690 | 830 | 22 | 24 HRC | 7.7 % IACS |
QT-JISDefault Q&T | Standard supply condition: oil quench from ~860 °C, temper ~570–650 °C, for shafts, gears and high-strength bolts. | 760 | 900 | 20 | 27 HRC | — |
QT+NITThis page Q&T + gas/plasma nitrided surface | Use when a wear/fatigue-resistant hard skin is needed on an already tough Q&T core (shafts, spindles). | 760 | 900 | 18 | 28 HRC | 7.7 % IACS |
Q&T 28–32 HRC | Common machined-part hardness band balancing strength, toughness and tool life. | 830 | 960 | 18 | 30 HRC | — |
Q&T 32–36 HRC (low temper, high strength) | Choose when higher strength/wear is needed in thin sections; toughness and machinability drop. | 970 | 1,100 | 16 | 34 HRC | — |
What is SCM430 QT+NIT?
SCM430 QT+NIT is SCM430 supplied in the QT+NIT condition — use when a wear/fatigue-resistant hard skin is needed on an already tough Q&T core (shafts, spindles). SCM430 QT+NIT has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). SCM430 QT+NIT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). QT-JIS is the default condition FabDigit quotes; QT+NIT is available on request or by drawing note.
Advantages
- Good corrosion resistance — 24/100, better than 91% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- High strength — 760 MPa (110 ksi), better than 85% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
SCM430 QT+NIT properties
Typical room-temperature values for SCM430 QT+NIT; 22 are specific to this condition. Other listed values are SCM430 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCM430 QT+NIT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
SCM430 QT+NIT has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SCM430 QT+NIT is rated for continuous service to 450°C (842 °F). It conducts heat at 42.7 W/m·K (24.7 BTU/hr·ft·°F), better than 50% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
SCM430 QT+NIT conducts electricity at 7.7 % IACS, worse than 65% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (24/100), better than 91% of steel grades.
Sustainability4
Producing a kilogram of SCM430 QT+NIT takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
SCM430 QT+NIT's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (5/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCM430 QT+NIT
Is SCM430 easy to machine?
Best machined annealed or ≤30 HRC; use rigid setups, carbide inserts at 90–140 m/min and finish-grind after heat treatment for tight tolerance.
Can SCM430 be welded?
Weldable by TIG/MIG/SMAW with low-hydrogen 4130/ER80S-D2 filler; preheat 150–260 °C for thick sections and post-weld temper to avoid martensitic cold cracking.
Can SCM430 be formed, bent or molded?
Cold bend only in the annealed/normalized condition with generous radii; hot forge 1150–850 °C followed by normalizing.
What surface finishes work on SCM430?
No native corrosion protection — apply zinc/phosphate, black oxide, Cr plating or paint; nitriding or induction hardening for wear surfaces.
SCM430 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.28 – 0.33 | 0.3 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual, max | ≤ 0.25 | — |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SCM430 QT+NIT — frequently asked
What is SCM430 QT+NIT used for?
SCM430 QT+NIT is typically used for shafts, bolts and structural machine parts. In short: weldable Cr-Mo shaft steel; AISI 4130 equivalent; tougher than SCM435.
What is the yield strength of SCM430 QT+NIT?
SCM430 QT+NIT has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is SCM430 QT+NIT easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Best machined annealed or ≤30 HRC; use rigid setups, carbide inserts at 90–140 m/min and finish-grind after heat treatment for tight tolerance.
Can SCM430 QT+NIT be welded?
Not readily — weldability is rated not recommended (5/100). Weldable by TIG/MIG/SMAW with low-hydrogen 4130/ER80S-D2 filler; preheat 150–260 °C for thick sections and post-weld temper to avoid martensitic cold cracking.
What surface finishes work on SCM430 QT+NIT?
No native corrosion protection — apply zinc/phosphate, black oxide, Cr plating or paint; nitriding or induction hardening for wear surfaces.
Can SCM430 QT+NIT be formed, bent or molded?
Cold bend only in the annealed/normalized condition with generous radii; hot forge 1150–850 °C followed by normalizing.
What is the maximum service temperature of SCM430 QT+NIT?
SCM430 QT+NIT is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SCM430 QT-JIS and SCM430-A?
QT-JIS is the default condition — standard supply condition: oil quench from ~860 °C, temper ~570–650 °C, for shafts, gears and high-strength bolts. A: softest condition for deep machining, cold forming or as a pre-heat-treat blank. Yield strength is 760 MPa in QT-JIS versus 360 MPa in A.
Sources
- JIS G 4105 — Chromium molybdenum steels (SCM430) — JSA (2015)
- GB/T 3077 — Alloy structural steels (30CrMo) — SAC (2015)
- EN 10083-3 (25CrMo4) / SAE J404 (4130) — CEN / SAE (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- MMPDS-Handbook, 4130 steel property tables — Battelle/FAA (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.