What are the top five most common questions you encounter about heat treatment fixture?

As a professional in the field of heat treatment, the five most common issues I encounter regarding heat treatment fixtures (tooling) are as follows, covering aspects such as design, usage, and maintenance:

1. High-Temperature Deformation and Service Life Issues

• Symptoms: Fixtures warp, crack, or suffer structural failure after repeated heating and cooling cycles (especially in high-temperature processes like carburizing and quenching), leading to reduced load-bearing capacity, unstable workpiece placement, or dropped parts.
• Root Causes: Insufficient high-temperature strength of materials, thermal stress concentration, poor structural design (e.g., weak weld points), or operation beyond the material’s maximum temperature limit.
• Common Scenarios: Multi-purpose furnace racks, quenching trays, carburizing furnace baskets, etc., after prolonged use at high temperatures (>900°C).

2. Material Selection and Cost-Balance Challenges

Symptoms:

• Choosing expensive alloys (e.g., 310S, RA330, nickel-based alloys) for extended lifespan, but at high cost;
• Opting for low-cost heat-resistant steels (e.g., 2520) to save money, only to face rapid oxidation and deformation under frequent thermal cycling, leading to frequent replacements and higher total costs.

Key Dilemma:

• How to balance cost and lifespan by selecting materials based on process temperature (e.g., quenching, tempering, carburizing), atmosphere (oxidizing, carburizing, nitrogen-protected), and load requirements.

3. Workpiece Sticking or Surface Damage

Symptoms:

• Diffusion bonding occurs between the workpiece and fixture at high temperatures, causing scratches or damage during separation;
• Flaking oxide scale from the fixture surface contaminates workpieces or the furnace chamber.

Common Cases:

• Stainless steel heat treatment often leads to sticking with racks; carbon buildup on fixture surfaces in high-carbon atmospheres can flake off and affect workpiece surface quality.

4. Inefficient Heating and Poor Temperature Uniformity Due to Design

Symptoms:

• Overly dense fixture structures hinder furnace atmosphere circulation or radiant heat transfer, causing uneven workpiece temperatures and inconsistent hardness;
• Excessive fixture weight (high "dead mass" ratio) increases energy consumption and reduces loading efficiency.

Design Focus:

• Strive for lightweight, open designs that ensure strength while allowing proper airflow and heat distribution.

5. Poor Fixture Management and Traceability Issues

Symptoms:

• Lack of clear identification on fixtures makes it impossible to track usage cycles and heat treatment history, leading to overuse and accidents;
• Mixing fixtures made of different materials, causing cross-contamination at high temperatures (e.g., low-melting-point metal precipitation);
• Improper maintenance (e.g., failure to remove carbon buildup or correct deformations) accelerates deterioration.

Management Pain Points:

• Absence of systematic fixture records, lifecycle predictions, and regular inspection protocols.

Recommended Solutions

1. Precision Material Selection: Choose appropriate heat-resistant steel grades based on maximum operating temperature and atmosphere; consider surface coatings (e.g., aluminosilicon diffusion coatings) to enhance oxidation resistance.
2. Optimized Structural Design: Use simulation software to analyze thermal stress distribution and avoid sharp corners; adopt modular designs for easy partial replacement.
3. Standardized Management: Establish fixture records (material, date of entry, usage cycles), set mandatory replacement intervals, or implement retirement criteria based on deformation levels.
4. Process Coordination: Adjust heating rates and loading configurations within controllable limits to reduce thermal shock.
5. Regular Maintenance: Clean carbon deposits and oxide scale, correct minor deformations, and avoid using damaged fixtures.