GJB 9451-2018 (English Version)

Standard No.: GJB 9451-2018
Language: Chinese, Available in English version
Release Date: 2018
Published By: Military Standard of the People's Republic of China-General Armament Department
Latest: GJB 9451-2018

Introduction

Technical background of the standard

GJB 9451-2018 is a national military standard, led by the Metallurgical Industry Information Standards Research Institute and jointly formulated by seven units including Northeast Special Steel Group. The standard specifies the technical indicators of four special alloy steel bars, including 16Cr3NiWMoVNbE, in response to the extreme working conditions of aircraft engine gears.

Comparison of key material properties

Grade	Applicable diameter(mm)	Smelting process	Tensile strength(MPa)	Impact energy(J)
16Cr3NiWMoVNbE	≤200	Vacuum induction+Electroslag/Consumable	≥1270	≥51
16Ni3CrMoE	≤200	Vacuum induction+Electroslag/Consumable	1180-1380	≥30

Core technical requirements

3.1 Smelting control

The standard stipulates that 16Cr3NiWMoVNbE must adopt the vacuum induction + vacuum consumable dual process to ensure the purity of the material. The oxygen content must be controlled below 15ppm, and the sulfur and phosphorus content must be ≤0.010%.

3.4 Mechanical properties

Take 16CrNi4MoA as an example, after 920℃ normalizing + 650℃ tempering treatment:

Tensile strength: 1320-1520MPa
Yield strength: ≥1030MPa
Sectional shrinkage: ≥35%

Special testing requirements

3.11 Hairline testing

Use the tower test method, the total length of each step hairline is ≤10mm, and the maximum length of a single hairline is ≤6mm. For key components, hairline-free steel may be required.

3.12 Ultrasonic Testing

Diameter Range (mm)	Testing Standard	Allowable Defects
≤60	GB/T 4162 AA Grade	≤Φ1.2mm Flat Bottom Hole
>60	GB/T 4162 A Grade	≤Φ1.5mm Flat Bottom Hole

Implementation Suggestions

Melt Control: Preferentially use vacuum consumable furnace to reduce oxygen and nitrogen content
Heat Treatment Optimization: class=instrument>18CrNi4AIt is recommended to adopt a step-type tempering process
Inspection strategy: Ultrasonic testing should be combined with penetrant testing to improve the defect detection rate

GJB 9451-2018 history

2018 GJB 9451-2018 Specification for alloy structural steel rods for aero-engine gears