Home > Special steel > Alloy Structural Steel > 4130 25CrMo4 SCM430 alloy structural steel

4130 25CrMo4 SCM430 alloy structural steel

4130 alloy structural steel offers excellent strength-to-weight ratio, good hardenability, and high fatigue resistance. With good weldability and toughness, ideal for aircraft structures, pressure vessels, and automotive suspension components.

Standard: AISI 4130, DIN 25CrMo4 (1.7218), JIS SCM430, GB 30CrMo
Technique: EAF + LF + VD, forged or hot-rolled, multi-directional forging ratio ≥4, normalized and tempered or quenched and tempered as required
Shape: Round, Flat, Plates, Blocks
Heat treatment: Supplied in quenched and tempered (QT) condition with hardness 22–30 HRC typical; annealed or normalized condition available on request
Surface Treatment: Turned, milled / ground, sawn ends. Black (hot-rolled / forged surface) available for large sections
Tolerance: flat bars & plates thickness: +0.5/-0.0 mm (turned); forged blocks: ±0.2 mm
MOQ: 1 Ton

We supply AISI 4130 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S (≤)	Cr	Mo
4130	0.28–0.33	0.15–0.35	0.40–0.60	0.035	0.040	0.80–1.10	0.15–0.25
1.7218 (25CrMo4)	0.22–0.29	≤0.40	0.60–0.90	0.025	0.035	0.90–1.20	0.15–0.30
SCM430	0.28–0.33	0.15–0.35	0.60–0.85	0.030	0.030	0.90–1.20	0.15–0.30
30CrMo	0.26–0.34	0.17–0.37	0.40–0.70	0.030	0.030	0.80–1.10	0.15–0.25

Main characteristics of 4130 Alloy Steel

4130 | 25CrMo4 | SCM430 Alloy Steel applications

4130 steel for Aircraft Engine Mount

High strength-to-weight ratio and excellent weldability make 4130 ideal for critical aircraft engine mounts subjected to dynamic and vibration loads.

4130 steel for Motorsport Chassis & Roll Cage

Superb toughness and fatigue resistance ensure maximum driver safety and structural integrity under extreme racing conditions.

4130 steel for Oil & Gas Flowline Pipe

Good hardenability and resistance to high-pressure environments guarantee reliable, long-term service in demanding upstream and midstream piping systems.

Our Production Technology For 4130 (1.7218 / 25CrMo4 / SCM430) Engineering Alloy Steel

EAF
LF
VD
ESR
Forged, Hot Rolled, or Cold Drawn
Annealed / Normalized / Quenched and Tempered (as specified)
Machined surface / Peeled / Black finish

Ultrasonic testing (UT) 100% as per ASTM A388 or SEP 1921 (upon request)
Micro Cleanliness as per ASTM E45 or DIN 50602 (upon agreement)
Grain size ≥ 5 per ASTM E112 for critical applications
Delivery condition options:
Soft annealed (+A): max. 212–220 HB (easily machinable)
Normalized (+N): refined grain structure, good strength
Quenched and tempered (+QT): tensile strength ranging from 670–1040 MPa (depending on diameter and tempering temperature)
Mechanical properties as per ASTM A29 / ASTM A322 or EN 10083-3

mechanical properties & heat treatment of 4130 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1200 – 1230 °C	1200 – 1150 °C	≥ 950 °C	Pit, sand, or furnace cooling

Annealing

Annealing temperature: 680 – 860°C.
Lower range (680–720°C): for maximum softness, followed by slow furnace cooling.
Upper range (830–860°C): transfer part straight from forging to furnace at this temperature, holding for suitable time, then furnace cooling
Hold at temperature for sufficient time (minimum 2 minutes per mm of section thickness, or 2–5 hours depending on section size)
Cool slowly in the furnace to approximately 480°C (if heated to 850°C), then air cool to room temperature
Hardness after annealing: max. 212 – 220 HB
Annealing in a protective atmosphere is recommended to reduce decarburization and surface scaling

Hardening

4130 alloy steel can be hardened in oil or water, depending on section size and quenching equipment. Proper preheating and austenitizing are critical to achieve the desired hardness without cracking. The steel has excellent weldability and mild hardenability compared to higher-carbon grades like 4140
Pre-heating (recommended): Preheat to 600 – 650°C to reduce thermal shock during austenitizing
Austenitizing temperature: 815 – 870°C (1500 – 1600°F).
Lower range (815–840°C): oil quench for thinner sections
Upper range (840–870°C): water quench for heavier sections
Holding time: At least 30 minutes at austenitizing temperature (or 30 min per 25mm of section thickness)
Quenching media:
Oil (preferred for most sections) — provides good hardness with moderate distortion, suitable for thinner sections
Water (faster quench — for larger or heavier sections, but increases distortion and crack risk)
Polymer (medium quench rate — good for medium sections)
Hardness after quenching: Surface hardness approx. 40 – 55 HRC (depending on section size, quenching medium, and carbon content)

Stress relieving

Perform after rough machining, heavy stock removal or welding to reduce residual stresses and reduce distortion risk during final hardening
Heat carefully to 600 – 650°C
Hold at temperature for 1 hour per 25mm of section thickness (minimum 2 hours)
Air cool after holding
This operation reduces the risk of distortion during final heat treatment and improves dimensional stability

Tempering

Temper immediately after the workpiece cools to hand-warm temperature (approx. 50–70°C). Delayed tempering may cause cracking
Number of tempers: Minimum 1 time for standard applications; 2 times recommended for critical components requiring maximum toughness and property stability
Holding time: 1 hour per 25mm of section thickness (minimum 2 hours)
Cooling method: Air cool after each tempering cycle
Tempering temperature range: 400 – 680°C, depending on final hardness requirement

Why Choose NSPM as Your 4130 Alloy Steel Supplier

Source Direct

Direct mill cooperation ensures stable supply, competitive pricing, and consistent quality. Global resource integration and strong supply chain management guarantee reliable material sourcing and long-term availability.

Stock Ready

50,000+ tons inventory across 11 warehouses enables fast delivery. Flexible cutting, short lead times, and ready stock support urgent demands and improve customers’ production efficiency.

Expert Team

600+ professionals, including R&D specialists and technical engineers, provide application-driven support. Fast response and deep tooling knowledge ensure accurate solutions for diverse industrial needs.

Fully Inspected

Strict quality control system with full traceability, UT testing, and heat treatment records. Certified standards (ISO, CE) ensure every material meets high-performance and reliability requirements.

Full-Chain Machining

From steel supply to precision machining, heat treatment, and equipment manufacturing, NSPM offers integrated solutions that enhance accuracy, efficiency, and overall tooling performance.