GB/T 38749-2020 in English
VALIDTechnical requirements of controlled atmosphere heat treatment
- Issued on:2020-04-28
- Implemented on:2020-11-01
- File Format:PDF
- Delivery:Via email within 5 business days
$388.00
《GB/T 38749-2020可控气氛热处理技术要求》由TC75（全国热处理标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Analysis of the core content of the standard
GB/T38749-2020 is my country's first national standard that systematically regulates controlled atmosphere heat treatment technology. It is applicable to the process control of equipment such as carburizing furnaces and nitriding furnaces. The standard defines four major categories of technical requirements:
- Atmosphere control: 9 atmosphere classifications and applicable scenarios
- Equipment specifications: 21 key equipment indicators
- Process system: Carburizing/nitriding process parameter matrix
- Quality inspection: 7 major inspection project methods
Controlled atmosphere classification and application comparison
| Atmosphere type | Code | Main components | Applicable process | Carbon potential control accuracy |
|---|---|---|---|---|
| Endothermic atmosphere | XQ | CO20-25%+H230-40% | Carburizing, Carbonitriding | ±0.05%C |
| Nitrogen-based atmosphere | DQ | N2+5-20%H2/CO | Protective heat treatment | ±0.03%C |
| Ammonia decomposition gas | AQ | 75%H2+25%N2 | Stainless steel heat treatment | - |
Technical requirements for key equipment
Core indicators of carburizing furnace
- Sealing performance: furnace pressure ≥50Pa positive pressure
- Atmosphere uniformity: ≤±0.10%C (Appendix A test)
- Temperature control: ±1.5℃ (GB/T9452)
Safety protection system
The standard requires the configuration of triple protection:
- Combustible gas leakage alarm device
- Automatic gas cut-off system below 750℃
- Continuous monitoring of waste gas combustion torch
Key points of process control
Carburizing process parameter matrix
| Deepness of hardened layer (mm) | Temperature range (℃) | Carbon potential control range (%C) | Allowance deviation |
|---|---|---|---|
| 0.5-1.5 | 880-930 | 0.8-1.2 | ±0.10mm |
| 1.5-2.5 | 900-950 | 1.0-1.4 | ±0.15mm |
Furnace sample management
The standard stipulates that three types of samples must be processed simultaneously:
- Process samples: tested every 2 hours
- Verification samples: tested after each heat
- Archived samples: retained for ≥3 months
Implementation suggestions
Enterprise application roadmap
- Equipment transformation phase: focus on upgrading the carbon potential control system and exhaust gas treatment device
- Process verification phase: Conduct effective hardening layer uniformity test according to Appendix B
- Standardization phase: Establish a quality control system based on GB/T32541
Solutions to common problems
Case: The carbon content on the surface of a carburized part of a certain company fluctuates greatly
Analysis: Carbon deposition on oxygen probe leads to delayed carbon potential feedback
Solution: Increase the frequency of steel foil carbon determination according to clause 5.3.4 of the standard (recommended once every 4 hours)
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