ISO 4779:2021

Overview

ISO 4779:2021 specifies requirements for forged eye hooks with point and latch - Grade 4, stainless steel, solution annealed, intended primarily as components in welded chain slings (grade 4). The standard covers material, manufacture, heat treatment, dimensions, mechanical properties, testing, marking and certificates for hooks matched to round steel sling chains with nominal diameters from 4 mm to 22 mm. Hooks manufactured to ISO 4779 are suitable for service temperatures from –100 °C to +400 °C and are solution annealed to ensure corrosion resistance.

Keywords: ISO 4779:2021, forged eye hook, grade 4, stainless steel, solution annealed, lifting chain components, working load limit (WLL).

Key topics and requirements

• Scope and application: Hooks are intended preferably for welded chain slings of grade 4; alternative uses (wire rope or textile slings) require design verification for safe use.
• Material: Austenitic stainless steels with molybdenum and resistance to intergranular corrosion (e.g., X6CrNiMoTi17-12-2 / 1.4571 / S31635) are specified.
• Manufacture and heat treatment:
  • Drop-forged in one piece, free from harmful surface defects.
  • Solution annealed (approx. 1 020 °C to 1 120 °C) and rapidly cooled; surface pickling/passivation required after heat treatment.
• Dimensions and designation: Dimension limits are given (Table 1) and calculation bases are in Annex A. Hooks are designated by nominal chain diameter and grade (e.g., 10-4).
• Mechanical properties & WLL: Working Load Limit (WLL) values correspond directly to the sling chain grade per ISO 1835; mechanical test requirements (test force, elongation, breaking force, deformation) are specified.
• Testing & inspection: Type, manufacturing and end tests include dimensional checks, surface/penetrant tests, tensile testing and inspection criteria; personnel qualification and test certification are required.
• Marking & documentation: Product body coding and certificates (type test and manufacturer’s) are required for traceability.

Applications and users

• Primary users: lifting equipment manufacturers, chain-sling fabricators, forging shops, QA/inspection teams, procurement/specification engineers, and lifting/safety officers.
• Practical applications: Components for chain slings used in material handling, offshore, chemical and food industries where corrosion resistance and high temperature performance are required.
• Practical notes: Always verify hook compatibility (geometry, WLL, attachment type) when substituting between sling types; rely on the product code/WLL for direct correlation to chain grade.

Related standards

• ISO 1835 - Round steel short link chains for lifting (Grade 4)
• ISO 1837 - Lifting hooks - Nomenclature
• ISO 16143-2 - Stainless steels - Corrosion-resistant semi-finished products
• ISO 3452-1, ISO 7500-1, ISO 8539, ISO 13385-1, EN 10228-2 - referenced for testing, NDT and calibration

For specification or procurement, reference ISO 4779:2021 to ensure forged eye hooks meet recognized international requirements for safety, corrosion resistance and traceability.