Heat Treatment

Explore the advanced cooling and heating cycles we use to refine every material’s internal grain structure.
Contact info
  • kushal@kushalmetal.net
  • kushalmetal09@gmail.com
Scroll to Explore

INTRODUCTION

Heat Treatment is a very important process in developing a tool steel die. The mechanical properties (hardness, toughness, wear resistence ect) are achieved only after proper heat treatment is done after machining. Normal procedures adapted in making tool steel die are as under :

  • Rough machining

  • Stress relieving

  • Machining with grinding tolerances

  • Heat treatment including tempering

  • Final machining and grinding

  • Production

The main steps involved in Heat treatment are Quenching and Tempering.

QUENCHING

Process Effects Control Measures
Heating Deformation cracking Hardness,
Hot strength Toughness Oxidation 		Preheating Higher quenching temperature
Lower quenching temperature. Vacuum furnace
Cooling Toughness
Deformation cracking 		Rapid cooling Uniform quenching,
Salt bath quenching

QUENCHING

Hardness / Wear Resistance Low temperature tempering
High temperature tempering
Hot Strength High temperature tempering
Toughness Higher temperature tempering
Cracking Uniform mild cooling
Stabilization / Residual Stress Multiple tempering cycles

COMMON QUENCHING PROBLEMS

Problem Possible Causes Remedy
Distortion / Dimensional Changes Sharp corners, notches Thin sections or fins Abrupt section changes Improper marking Well-balanced design Chamfering Proper support during heating
Overheating / Underheating Improper furnace operation Poor part arrangement Inaccurate thermocouples Proper loading arrangement Regular furnace calibration Temperature control checks
Decarburization Improper furnace atmosphere Controlled atmosphere Vacuum furnace Allow machining allowance for removal
Improper Cooling Incorrect quenching medium Delay in tempering Use less severe quench Immediate tempering Control material temperature
Microstructure Issues Inadequate spheroidized carbides Non-uniform carbide distribution Spheroidizing annealing Normalize before quenching

COMMON PROBLEM IN HARDING

Problem Possible Causes Remedy
Quenching Temperature Too Low Improper furnace operation Poor part arrangement Inaccurate thermocouples Use recommended temperature Proper loading arrangement Furnace control check
Quenching Temperature Too High Improper furnace operation Inaccurate thermocouples Use recommended temperature Furnace control check
Inadequate Cooling Delay in cooling after removal from furnace Incorrect quenching medium Excess oxidation Improper quench bath temperature Poor agitation Incorrect interruption temperature Improve facility layout Use more severe quenching medium Apply protective coating or controlled atmosphere Maintain proper quench temperatures (Oil: 60–80°C, Water: ~80°C) Review procedures and equipment Interrupt cooling at Ms + 50°C
Tempering Start Temperature Tempering started before material reaches Ms temperature Monitor and control material temperature carefully
Decarburization Improper furnace atmosphere Controlled atmosphere Vacuum furnace Provide machining allowance for removal

COMPARISON BETWEEN SEVERAL COOLING METHODS

Quenching Method Advantages Disadvantages Key Considerations
Fan Cooling Low cost
Easy to operate
Good control of distortion 		Inadequate cooling rate Enhance airflow
Use cooled air
Salt Bath Uniform cooling
High heat transfer rate 		Salt entrapment in holes
Water pollution
Furnace contamination 		Salt recovery systems
Proper waste management
Oil Quenching Low cost
Adjustable cooling rate (oil type & temperature) 		Fire hazard
Risk of localized overcooling 		Step quenching
Use of preheated (semi-hot) oil
Pressurized Gas Clean, bright surface finish
No contamination 		High cost
Difficult to control distortion
Limited cooling for large parts 		Increase gas pressure (up to ~20 bar)
Improve heat exchange system
Polymer Quenching Adjustable cooling rate via concentration Risk of localized overcooling Less common for die quenching applications

Enquiry

If you have any questions or would like to enquire please contact us.