JIS SCM440H Alloy Steel Chrome Moly Bars

Product Description

JIS SCM440H is a specialized, medium-carbon chromium-molybdenum alloy steel specified under the Japanese Industrial Standard JIS G4053 / JIS G4052.

The critical differentiator for the "H" suffix in SCM440H is that it denotes a Hardenability Band (H-Band) steel. While standard SCM440 guarantees precise chemical limits, SCM440H guarantees a strict, predictable Jominy end-quench hardenability profile. This ensures that from batch to batch, the steel will transform to an identical hardness depth when heat-treated, making it indispensable for high-volume automated manufacturing where consistent core properties are vital.

Global Designation Equivalents

When sourcing material internationally or modifying engineering drawings, SCM440H aligns closely with:

• USA (AISI/SAE): AISI 4140H / UNS H41400

• Germany (DIN / WNr): 42CrMo4H / 1.7225

• Europe (EN): 42CrMo4 (+H)

• France (AFNOR): 42CD4H

• China (GB): 42CrMoH

Chemical Composition (Typical %)

The inclusion of chromium and molybdenum provides deep through-hardening capability, while tighter tracking of impurities ensures structural purity.

Carbon (C)	Chromium (Cr)	Molybdenum (Mo)	Manganese (Mn)	Silicon (Si)	Phosphorus (P)	Sulfur (S)
0.38% 0.43%	0.90% 1.20%	0.15% 0.30%	0.60% 0.85%	0.15% 0.35%	0.030%	0.030%

Mechanical Properties (Quenched & Tempered, +QT)

When properly hardened (oil quenched at $approx 830text{C} - 880text{C}$) and high-temperature tempered ($approx 530text{C} - 630text{C}$), SCM440H round bars hit a premium performance envelope:

• Ultimate Tensile Strength ($R_m$): 930 1080 MPa (N/mm)

• Yield Strength ($R_{e}$): 780 935 MPa

• Elongation ($A_5$): 12%

• Reduction of Area ($psi$): 45%

• Impact Toughness (Charpy-V): 63 J

• Hardness Profile (Hardened Core): 28 34 HRC (Up to 5255 HRC after localized surface induction hardening)

Key Engineering Advantages

• Guaranteed Heat Treat Repeatability: The Jominy H-band control eliminates the risk of "soft cores" or unexpected brittleness across different production batches, protecting automated milling and induction lines from variation.

• Excellent Torsional Rigidity: The structural matrix features high fatigue limits, making it excellent at absorbing sudden kinetic shocks and high-torque loads without twisting out of alignment.

• Surface Nitriding and Induction Match: It acts as an elite base material for nitriding or localized induction hardening, creating an ultra-hard, wear-resistant skin (5255 HRC) while retaining a high-yield core.

• Weldability Constraints: Like standard 4140, its medium carbon level makes it susceptible to cold cracking. Forging and welding require strict thermal handling, including preheating to $200text{C} - 300text{C}$ and slow, controlled cooling.

Common Industrial Applications for SCM440H Bars

SCM440H bars are specifically requested for high-fatigue, heavy-load precision components:

• Power & Drivetrains: Heavy-duty transmission shafts, high-torque engine crankshafts, drive axles, and planetary gears.

• Fasteners & Infrastructure: Grade 10.9 and 12.9 high-tensile structural anchor bolts, tie rods, and industrial studs.

• Heavy Clamping & Machinery: Specialized double-bolted industrial clamping hardware, machine tool spindles, and high-load hydraulic piston rods.

Available SCM440 / SCM440H Industrial Sourcing Options

If you are currently sourcing or procuring round bar stock for production, several verified industrial supply formats are available near major manufacturing hubs:

• 3 Kilograms Scm440H Round Bars: A standard small-batch option available for specialized structural prototyping or workshop use. It provides verified H-band mechanical performance.

• Alloy Steel Round Bar Scm 440: Large-diameter industrial round bars ranging up to 400mm in diameter, supplied in annealed condition for high-volume turning, milling, and gear cutting.

• Scm 440 Polished Alloy Steel Round Bar: Premium 100mm diameter rough-machined or polished configurations, reducing processing allowances for machine tool spindle or shaft 

High Performance Alloy Steel for Critical Applications

SCM440H Chrome Moly Bars deliver exceptional mechanical properties and resilience suited for engineering, automotive, and construction sectors. With customizable hardness levels achieved through heat treatment, these bars offer outstanding wear resistance, toughness, and machinability, making them ideal for load-bearing parts and power transmission components. Their consistent performance ensures reliability even under high stress and in severe operating conditions.


Versatile Surface Conditions & Precise Finishes

Choose from a range of surface finishes to match exact project needs, including polished, peeled, turned, and rough turned. Each bar is produced with strict dimensional tolerances (h9, h11) to ensure precision in fit and assembly. Available in bright and black finishes, the bars meet both aesthetic standards and technical requirements. Standard export packing or customized packaging guarantees safe delivery to your site.