42CrMo Steel Round Bar | GB/T 3077 Alloy Structural Steel Bar Supplier

Overview

42CrMo (GB/T 3077) is a medium-carbon, chromium-molybdenum alloy structural steel widely used for high-strength machine components requiring good toughness, hardenability, and wear resistance. With 0.38–0.45% carbon, 0.90–1.20% chromium, and 0.15–0.25% molybdenum, it responds well to quenching and tempering (Q&T), achieving tensile strengths of 980–1,200 MPa with good ductility. 42CrMo round bar is one of the most commonly specified alloy steel bars in Chinese mechanical engineering, serving as the domestic equivalent of AISI 4140 / 42CrMo4 (EN). It is supplied in spheroidize-annealed, normalized, or quenched-and-tempered condition for machining into shafts, gears, bolts, and pressure-bearing components.

Description (English)

Vertex 42CrMo steel round bar is a medium-carbon chromium-molybdenum alloy structural steel conforming to GB/T 3077, equivalent to AISI 4140 / EN 42CrMo4 (1.7225) / JIS SCM440. With 0.38–0.45% carbon, 0.90–1.20% chromium, and 0.15–0.25% molybdenum, it delivers excellent hardenability, high tensile strength (980–1,200 MPa after quenching and tempering), good toughness, and superior wear resistance. The molybdenum addition effectively prevents temper embrittlement, making it suitable for high-stress applications. Available in hot-rolled, forged, peeled, and cold-drawn finishes, 42CrMo round bar is supplied in annealed, normalized, or quenched-and-tempered condition, with diameter ranges from 10 mm to 800 mm. It responds well to induction hardening, nitriding, and standard machining operations. Widely used in automotive, heavy machinery, oil & gas, power generation, and industrial fastener manufacturing for crankshafts, gears, drill collars, high-strength bolts (Grade 10.9/12.9), hydraulic cylinder rods, and pressure-bearing components. FAQ: Q: What are the equivalent grades of 42CrMo? A:42CrMo is equivalent to AISI 4140 (USA, UNS G41400), EN 42CrMo4 / 1.7225 (Europe), JIS SCM440 (Japan), BS 708M40 / En19 (UK), and DIN 1.7225 (Germany).

Applications

42CrMo Steel Round Bar | GB/T 3077 Alloy Structural Steel Bar Supplier is supplied for demanding applications such as Automotive & Transportation, Heavy Machinery & Mining, Oil & Gas, Power Generation, Aerospace & Defense, Industrial Fasteners, Tooling & Dies, and General Engineering. These application areas rely on a carefully specified metal product that can be selected by grade, form, dimensions, and service requirements rather than by a generic material description. The listed applications provide practical context for engineers and purchasing teams reviewing this product: they indicate where corrosion resistance, strength, fabrication performance, or dimensional consistency may matter. Final suitability depends on the operating environment, design code, temperature, media, joining method, and applicable inspection requirements. Buyers can use the application information together with the grade and property data below to request a technically appropriate specification, finish, tolerance, and quantity from Vertex Alloy.

Key Mechanical & Physical Properties

42CrMo Steel Round Bar | GB/T 3077 Alloy Structural Steel Bar Supplier is described using the available technical records rather than an assumed specification. The supplied data includes mechanical data including key 2141d88c99d7, type mech_item, property Tensile Strength, Rm (MPa), value 980, mechanical data including key 73d13bcc31a0, type mech_item, property Yield Strength, Rp₀.₂ (MPa), value 835, mechanical data including key 2c03404a2e5d, type mech_item, property Elongation, A₅ (%), value 12, mechanical data including key c4d8f7c0c86c, type mech_item, property Reduction of Area, Z (%), value 45, mechanical data including key faef77ab0968, type mech_item, property Impact Energy, Charpy V-Notch (J), value 47, mechanical data including key c52ff6ab6a65, type mech_item, property Hardness (HB), value 285 – 330, mechanical data including key 980f881bd2c5, type mech_item, property Hardness (HRC), value —, physical data including key ec7c8a726d9c, type phys_item, property Density, value 7.85 g/cm³ (0.283 lb/in³), composition data including key 924bb9251155, type composition_item, element C, value 0.38 – 0.45, composition data including key a1a25e1f8add, type composition_item, element Si, value 0.17 – 0.37, composition data including key 7811290cb718, type composition_item, element Mn, value 0.50 – 0.80, composition data including key 6c6bf434769d, type composition_item, element P, value ≤ 0.030, composition data including key 0512940436af, type composition_item, element S, value ≤ 0.030, composition data including key 75dbdadfc1a4, type composition_item, element Cr, value 0.90 – 1.20, composition data including key 59a7d681338b, type composition_item, element Mo, value 0.15 – 0.25, composition data including key 235486c6a434, type composition_item, element Ni, value ≤ 0.30, composition data including key ee14626bc152, type composition_item, element Cu, value ≤ 0.25, composition data including key c87cd1e2de5f, type composition_item, element W, value ≤ 0.15, composition data including key 10bf12788863, type composition_item, element V, value ≤ 0.07, composition data including key 482efb1ac8bc, type composition_item, element Ti, value ≤ 0.03, composition data including key 6903d4e0544c, type composition_item, element Al, value ≤ 0.05, and composition data including key 20cce5825d23, type composition_item, element Fe, value Remainder. Keeping these values visible helps a technical buyer compare the product with a drawing, purchase specification, or applicable standard before requesting a quotation. Mechanical values can guide early checks for strength and forming requirements, while physical values and composition details help with material identification, process planning, and service-environment review. Values should be confirmed against the latest mill certificate, heat or lot documentation, product condition, test method, and governing standard before production use. Vertex Alloy can review the required performance range and clarify which supplied values apply to the requested size and delivery condition.

Available Sizes & Forms

42CrMo Steel Round Bar | GB/T 3077 Alloy Structural Steel Bar Supplier is listed in bar form with size information including Diameter — Hot-Rolled (mm):10 – 350, Diameter — Forged (mm):80 – 800, Diameter — Peeled / Turned (mm):20 – 400, Diameter — Cold-Drawn (mm):4 – 80, Length:3,000 – 9,000 mm (standard 6,000 mm), Standard Lengths (m):3 / 4 / 5 / 6 / 7 / 8 / 9, Surface Finish:Hot-rolled (black), peeled (bright), ground, polished, Tolerance — Hot-Rolled (d ≤ 50 mm):h11 (±0.15 mm), Tolerance — Hot-Rolled (50 < d ≤ 120 mm):h11 (±0.22 mm), Tolerance — Peeled (h9):±0.05 mm (d ≤ 50); ±0.07 mm (50–100), Tolerance — Cold-Drawn (h8/h9):±0.02 – ±0.04 mm, Tolerance — Ground (h7/h8):±0.015 – ±0.025 mm, Straightness:≤ 2 mm/m (hot-rolled); ≤ 1 mm/m (peeled); ≤ 0.5 mm/m (ground), Out-of-Roundness:≤ 50% of diameter tolerance, Decarburization Depth:≤ 0.8 mm (hot-rolled); ≤ 0.3 mm (peeled), Surface Roughness (Ra):0.4 µm (ground), 1.6 µm (peeled), 6.3 µm (hot-rolled), and Weight Tolerance:±5% individual, ±3% batch. The size range is intended to help buyers screen availability and prepare an enquiry; it is not a substitute for a confirmed production schedule or tolerance agreement. When requesting this product, include thickness or diameter, width or length, cut-to-size needs, edge condition, surface finish, straightness, tolerance, quantity, and preferred packing. Dimensions may vary with grade, processing route, minimum order quantity, and mill capacity. Sharing the complete requirement allows Vertex Alloy to check whether the requested size can be supplied directly, cut from stock, or produced to order. The final commercial confirmation should state the agreed form, dimensions, tolerances, condition, inspection documents, and delivery terms.

Grade Compliance

42CrMo Steel Round Bar | GB/T 3077 Alloy Structural Steel Bar Supplier carries the recorded grade references Material 42CrMo (Cr-Mo Alloy Structural Steel), Standard GB/T 3077, GB/T 17107, GB/T 18248, EN 10083-3, UNS G41400, EN 42CrMo4 (EN 1.7225), DIN 1.7225 / 42CrMo4, JIS SCM 440, AISI/SAE 4140, Product Form Hot-rolled, forged, peeled, cold-drawn round bar, Common Delivery Conditions Annealed, Normalized, Q&T (Quenched & Tempered), and GOST 38ChM (38ХМ). These references give engineering and procurement teams a starting point for checking material identity, equivalent designations, and documentation requirements. A grade reference should always be read together with its applicable standard, product form, dimensional range, delivery condition, heat treatment, testing requirements, and revision level. Equivalent designations are not automatically interchangeable in every service, so the governing project specification remains controlling. Before order placement, confirm the required standard and certificate format, including chemical, mechanical, visual, dimensional, and any special testing requirements. Vertex Alloy can help compare the requested designation with the available product record and identify details that need confirmation from the producing mill.

Size Range

• Diameter — Hot-Rolled (mm):10 – 350
• Diameter — Forged (mm):80 – 800
• Diameter — Peeled / Turned (mm):20 – 400
• Diameter — Cold-Drawn (mm):4 – 80
• Length:3,000 – 9,000 mm (standard 6,000 mm)
• Standard Lengths (m):3 / 4 / 5 / 6 / 7 / 8 / 9
• Surface Finish:Hot-rolled (black), peeled (bright), ground, polished
• Tolerance — Hot-Rolled (d ≤ 50 mm):h11 (±0.15 mm)
• Tolerance — Hot-Rolled (50 < d ≤ 120 mm):h11 (±0.22 mm)
• Tolerance — Peeled (h9):±0.05 mm (d ≤ 50); ±0.07 mm (50–100)
• Tolerance — Cold-Drawn (h8/h9):±0.02 – ±0.04 mm
• Tolerance — Ground (h7/h8):±0.015 – ±0.025 mm
• Straightness:≤ 2 mm/m (hot-rolled); ≤ 1 mm/m (peeled); ≤ 0.5 mm/m (ground)
• Out-of-Roundness:≤ 50% of diameter tolerance
• Decarburization Depth:≤ 0.8 mm (hot-rolled); ≤ 0.3 mm (peeled)
• Surface Roughness (Ra):0.4 µm (ground), 1.6 µm (peeled), 6.3 µm (hot-rolled)
• Weight Tolerance:±5% individual, ±3% batch

Grade Specification

Chemical Composition

Mechanical Properties

Physical Properties

Applications

• Automotive & Transportation
• Heavy Machinery & Mining
• Oil & Gas
• Power Generation
• Aerospace & Defense
• Industrial Fasteners
• Tooling & Dies
• General Engineering