When an American automotive components manufacturer reviewed its scrap and rework data, one pattern stood out: too many parts were being rejected after heat treatment. Hardness variation across batches, inconsistent case depth and microstructure, and customer complaints about unpredictable performance were all traced back to an aging box-type furnace at the center of the line.

To solve this, the plant invested in a 580kW Tube Type Heat Treatment Furnace with a maximum operating temperature of 1100°C, designed specifically for gears, shafts and other safety-critical components.

Hardness scatter and microstructure inconsistency: where the old furnace failed

Before the upgrade, the main problems were:

• Batch-to-batch hardness variation that exceeded customer limits, forcing costly 100% inspection and rework.

• Uneven temperature distribution in the furnace chamber, leading to inconsistent microstructure even when cycle times were theoretically correct.

• Limited temperature headroom, making it risky to run higher-temperature cycles for new alloy grades.

In other words, even with good process recipes on paper, the old heat treatment furnace could not physically hold the required uniformity at the work zone.

Tube type design and multi-zone control: stabilizing 1100°C processes

The new Tube Type Heat Treatment Furnace was built around several quality-focused features:

• Multi-zone tubular chamber with independently controlled zones to shape the temperature profile along the furnace length.

• High-precision thermocouples and PID control, allowing tight control around 1100°C for demanding cycles.

• Optimized loading fixtures and part spacing, so each batch sees similar gas flow, temperature exposure and quench timing.

By combining the furnace design with updated process validation, the plant was able to tighten its control over hardness and case depth for key components.

Results: fewer surprises, more predictable quality

Within months of running production through the new furnace, the plant recorded:

• A significant reduction in rework due to hardness out-of-tolerance.

• More consistent microstructure across the load, improving fatigue and wear performance.

• Higher confidence when approving new heat treatment recipes for advanced steels.

For this US auto parts plant, the 580kW, 1100°C Tube Type Heat Treatment Furnace turned heat treatment from a chronic risk point into a controlled, predictable core process.