Tool tempering furnace

The tool tempering furnace is a specialized heat treatment equipment designed for tool materials such as high-speed steel and tool steel. Its core function is to optimize the hardness, toughness, and red hardness of the tool by precisely controlling the temperature and time. The following analysis will be conducted from three aspects: technical characteristics, process matching, and operational points:

1. Technical characteristics and selection criteria
temperature control accuracy
Requirement: The tool tempering furnace must have a temperature control accuracy within ± 2 ℃ to ensure the uniformity of martensite decomposition. For example, W18Cr4V high-speed steel needs to be tempered three times at 560 ℃± 2 ℃ to ensure that its hardness remains ≥ HRC60 at 600 ℃.
Configuration: Priority should be given to devices equipped with intelligent temperature control modules (such as PID regulation) and multi-point thermocouple monitoring to avoid uneven hardness caused by local overheating.
Atmosphere control ability
Vacuum tempering furnace: suitable for high-precision cutting tools (such as aviation cutting tools), can eliminate oxide scale and improve fatigue life. For example, TC4 titanium alloy cutting tools can increase fatigue strength by 15% when tempered at 500 ℃ under vacuum.
Protective atmosphere furnace: Nitrogen or argon atmosphere can prevent decarburization on the surface of stainless steel cutting tools (such as M2 high-speed steel) and maintain a smoothness Ra ≤ 0.4 μ m.
Heating efficiency and uniformity
Heating method: Resistance wire heating is suitable for medium and low temperature tempering (≤ 650 ℃), while molybdenum wire heater (up to 1100 ℃) is more suitable for high temperature tempering requirements.
Circulating system: Forced convection fans can eliminate furnace temperature differences, for example, the temperature difference within a 2-meter furnace should be ≤± 5 ℃ to avoid tool deformation.

2. Process matching and case studies
Tempering of high-speed steel cutting tools
Process: After quenching at 1270 ℃, it needs to be tempered three times for 1 hour at 560 ℃.
Effect: After three rounds of tempering, the residual austenite content decreased from 30% to below 5%, the red hardness (600 ℃) was ≥ HRC60, and the tool life was doubled.
Cold work mold steel tempering
Process: Cr12MoV steel is quenched at 1020 ℃ and then tempered at 180-220 ℃ with a hardness of HRC58-62.
Effect: The impact toughness has been increased from 3J/cm ² in the quenched state to 15J/cm ², making it suitable for cold stamping molds.
Stress relief tempering of stainless steel cutting tools
Process: The 316L stainless steel welding tool is tempered in a nitrogen atmosphere at 250 ℃ for 2 hours.
Effect: Residual stress reduced by 60%, corrosion resistance improved by 15%, suitable for medical cutting tools.

3. Operation points and safety regulations
Furnace loading requirements
The cutting tools should be hung vertically or laid flat, with a spacing of ≥ 50mm, to avoid uneven heat conduction. For example, when tempering a milling cutter, the handle and blade need to be misaligned.
Heating and cooling rates
Heating rate ≤ 10 ℃/min to prevent thermal stress cracking. For example, large-sized cutting tools (diameter>50mm) need to be heated in sections below 400 ℃.
The cooling method needs to be matched with the material: high-speed steel is tempered and air-cooled, while aluminum alloy cutting tools (such as 7075-T6) need to be quickly water-cooled to fix the structure.
Safety and Maintenance
Nitrogen introduction: When starting the furnace, first introduce nitrogen gas (flow rate 1.6m ³/h) to eliminate moisture, and then reduce the flow rate to 0.5m ³/h after 400 ℃.
Regular calibration: Verify the furnace temperature with a standard thermocouple every month, and adjust the temperature control parameters if the deviation exceeds ± 3 ℃.
Troubleshooting: When the circuit catches fire, immediately cut off the power and open the door to cool down. Do not use water to extinguish the fire.