JIS G 4051-2023 PDF

Full title and description

JIS G 4051:2023 — "Carbon steels for machine structural use" (Japanese title: 機械構造用炭素鋼鋼材). This Japanese Industrial Standard specifies grades, chemical composition, mechanical properties and delivery conditions for carbon steels produced by hot forming (hot rolling, hot forging, hot extruding) intended for machine-structural applications.

Abstract

JIS G 4051:2023 defines requirements for non-alloy carbon steels commonly used to manufacture machine components that will undergo further machining, forging and heat treatment. The standard lists material designations (for example S35C, S45C, S50C), composition limits, mechanical property requirements, inspection and testing provisions, and delivery conditions for bars, rods and sections produced by hot forming. It excludes steel tubes and refers to related international standards for correspondence.

General information

• Status: Active standard (current edition).
• Publication date: 2023 (publicly noted 22 May 2023 in JIS listings).
• Publisher: Japanese Industrial Standards (JIS) / Japanese Standards Association (JSA).
• ICS / categories: Iron and steel products (ICS 77.140 — heat-treatable, non-alloy and related steel product categories).
• Edition / version: 2023 edition (latest revision of JIS G 4051 series).
• Number of pages: Format-dependent; published electronic/print editions typically range in the low tens of pages (examples cited: ~21–29 pages depending on distributor/format).

Scope

This standard applies to carbon steels for machine structural use manufactured by hot forming (hot rolling, hot forging and hot extruding), supplied as bars, rods or uniform cross‑section sections and ordinarily intended for further processing such as forging, cutting and heat treatment. JIS G 4051 does not apply to steel tubes; provisions for hot‑extruded sections may be given in annexes. The standard also indicates correspondence (where applicable) with related ISO/EN specifications for heat‑treatable and case‑hardening steels.

Key topics and requirements

• Material designations and grade system for carbon steels intended for machine structural use (examples: S35C, S45C, S50C).
• Chemical composition limits for each grade (carbon, silicon, manganese, phosphorus, sulfur, and any other specified elements).
• Mechanical property requirements (tensile strength, yield or proof strength where specified, elongation) and hardness guidance.
• Delivery conditions and permissible heat‑treatment states (normalized, quenched and tempered, etc.).
• Dimensional and surface condition requirements for bars and sections, plus inspection and sampling rules.
• Annex(es) giving special provisions (for example, for hot‑extruded sections) and references to corresponding international standards.

Typical use and users

Used by metallurgists, materials engineers, procurement specialists, forging and bar‑stock manufacturers, machine‑building OEMs, and test/quality engineers. Typical applications include shafts, gears, rollers, pins, bolts and other machined or forged machine components where defined composition and mechanical performance of carbon steels are required. Suppliers use the standard to specify delivery conditions and to declare conformity of product batches.

Related standards

JIS G 4051 is associated with other JIS and international standards for steel products and testing. The standard notes correspondence with parts of ISO/EN heat‑treatable steel standards (for example ISO 683 series for heat‑treatable and case‑hardening steels) and cross‑references other JIS such as those covering test methods, general technical delivery requirements and steel product documentation. Earlier and superseded editions in the JIS G 4051 series (2005, 2009, 2016, etc.) form the revision history.

Keywords

JIS G 4051, carbon steel, machine structural steel, S45C, S50C, hot‑rolled bar, hot‑forged bar, heat treatment, mechanical properties, JIS, Japanese Industrial Standard.

FAQ

Q: What is this standard?

A: JIS G 4051:2023 is the Japanese Industrial Standard that specifies carbon steels for machine structural use — defining grades, composition, mechanical properties and delivery conditions for hot‑formed bars and sections used in machine components.

Q: What does it cover?

A: It covers non‑alloy carbon steels produced by hot forming intended for further processing (machining, forging, heat treatment), including chemical and mechanical requirements, inspection and delivery conditions; it excludes steel tubes.

Q: Who typically uses it?

A: Materials and design engineers, manufacturers and suppliers of bars/rods/sections, quality and inspection personnel, and purchasers specifying machine‑structure steel for components such as shafts, gears and fasteners.

Q: Is it current or superseded?

A: The 2023 edition is the current active edition of JIS G 4051 (it updates earlier editions from 2016, 2009, 2005, etc.). For historical traceability, previous editions and amendments are listed in JIS publication records.

Q: Is it part of a series?

A: Yes — it belongs to the JIS G family covering ferrous materials and steels; JIS G 4051 is the specific series entry for carbon steels for machine structural use and sits alongside other JIS G standards that cover related steel product types, test methods and delivery requirements.

Q: What are the key keywords?

A: Carbon steel, machine structural use, S‑grades (S35C/S45C/S50C), hot‑rolling, hot‑forging, heat treatment, mechanical properties, JIS G 4051.