What is an Alloy Steel Round Bar?

Alloy steel round bar is a solid cylindrical bar stock that contains chromium, molybdenum, and nickel. These additions make the steel stronger, harder, and more resistant to wear than plain carbon steel. The alloying elements allow heat treatment to provide the material with certain mechanical properties. 4140 and EN19 are examples of chrome-moly grades that have a good combination of strength and toughness. Nickel-containing grades like 4340 and EN24 are better for critical uses as they are more resistant to fatigue. We supply alloy steel bars in multiple conditions based on your machining and performance needs.

Alloy Steel Round Bars Grades Available

AISI 4140 Round Bar

The 4140 round bar is a chrome-moly alloy with excellent hardenability and good toughness. Tensile strength reaches 655-1000 MPa (95-145 ksi) after heat treatment. This grade machines well and responds to through hardening in moderate sections. We stock 4140 alloy steel bars as one of our most requested products.

AISI 4340 Round Bar

The 4340 round bar is a Ni-Cr-Mo alloy with the highest toughness and fatigue strength among common grades. This grade handles severe stress and impact loads. Aircraft landing gear, heavy-duty shafts, and critical components use 4340 for maximum reliability.

EN19 / 42CrMo4 Round Bar

The European chrome-moly grade EN19 round bar is equivalent to AISI 4140. The chemical composition and properties are very similar, with only small differences in the allowable ranges. Machinery manufacturers in Europe and Asia use EN19 bar because it has proven performance in gears and shafts.

EN24 Round Bar

EN24 round bar is a Ni-Cr-Mo steel that is stronger than EN19. After being heat treated, this grade can reach a tensile strength of up to 1080 MPa. EN24's combination of strength and toughness makes it ideal for gears, shafts, and heavy-duty parts.

Alloy Steel Round Bars Specifications

The following alloy steel bar specifications (grades, dimensions, and standards) outline our product range.

Designation AISI 4140, AISI 4340, EN19 / 42CrMo4, EN24
Thickness 0.5 mm to 500 mm Diameter
Length 100 mm to 6000 mm
Bar Finishing Bright, Polished, Black
Form Round Bar, Square Bar, Hex Bar, Flat Bar, Rectangle Bar
Length Single Random, Double Random, Cut Length
Rods 4 mm to 350 mm dia, Wires: 0.5 mm to 10 mm dia

Alloy Steel Round Bars Chemical Composition

The chemical composition changes with each grade, and each one is designed for specific performance characteristics. Nickel makes the steel tougher, while chrome and molybdenum provide hardenability.

Standard Grade C Cr Mo Si Mn P S Ni Cu
GB 42CrMo 0.38-0.45 0.90-1.20 0.15-0.25 0.17-0.37 0.50-0.80 0.035 0.035 0.3 0.3
JIS SCM440 0.38-0.43 0.90-1.20 0.15-0.30 0.15-0.35 0.60-0.90 0.03 0.03 0.25 0.3
ASTM 4140 0.38-0.43 0.80-1.10 0.15-0.25 0.15-0.35 0.75-1.00 0.035 0.04 — —
ENISO 42CrMo4 0.38-0.45 0.90-1.20 0.15-0.30 ≤0.40 0.60-0.90 0.035 0.035 — —
1.7225

Alloy Steel Round Bars Mechanical Properties

Mechanical properties depend on heat treatment conditions. Quenched and tempered bars achieve higher strength than normalised or annealed material.

Tensile Strength Yield Strength Elongation Reduction Impacting Energy HBW
Rm,MPa Rel,MPa A,% Z,% Aku,J ≤
After annealing
≥1080 ≥930 ≥12 ≥45 ≥63 217

Applications

The alloy steel round bar is used in 3 major industries.

Automotive

Crankshafts, axles, connecting rods, and transmission components use alloy steel round bars. The combination of strength and toughness handles the cyclic loads in automotive powertrains. We supply many automotive component manufacturers in Gujarat’s industrial areas.

Machinery

Drive shafts, spindles, gears, and machine tool components rely on alloy steel bars. These parts require fatigue resistance and dimensional stability under operating loads. Hot rolled and normalised bars suit initial machining, while Q&T bars provide ready-to-use properties.

Oil & Gas

Drill collars, tool joints, and wellhead components demand high-strength alloy steel. The severe stresses in drilling operations require grades like 4145H and 4340. We stock material meeting API specifications for oil field applications.

Frequently Asked Questions

  • What is the difference between 4140 and EN19?

    AISI 4140 and EN19/42CrMo4 are equivalent grades, with almost the same composition and properties. 4140 meets American ASTM/AISI standards, and EN19 meets European EN standards. There are small differences in the ranges of allowable compositions, but they work the same in most situations. Pick based on your specification requirements.