Heat Treatment Of High Speed Steel (Hss)

Product Description

DEFINITION
High Speed Steel HSS is a class of tool steel known for its ability to retain hardness and strength at high temperatures making it ideal for cutting tools drills and other applications requiring wear resistance and high temperature performance Heat treatment is critical in achieving the desired mechanical properties in HSS such as hardness toughness and wear resistance

 

OBJECTIVES OF HSS HEAT TREATMENT

Hardness Development : Achieve a high level of hardness typically 6270 HRC for cutting and machining applications

Wear Resistance : Enhance resistance to abrasion under high speed conditions

Thermal Stability : Improve performance at elevated temperatures without losing hardness

Toughness : Balance hardness with toughness to prevent brittle failure

 

KEY HEAT TREATMENT STAGES

Annealing

Purpose Soften the steel for machining and relieve internal stresses

Process Heat to 700950C and hold for several hours Cool slowly in a furnace  4080C hour to 600C then air cool

Hardening Austenitizing

Purpose Dissolve carbides and create a martensitic micro structure during quenching

Process Heat to 11501280C depending on HSS grade and hold for the required soaking time

Use vacuum or inert atmosphere furnaces to prevent oxidation Quench rapidly in oil air or high pressure gas

Tempering

Purpose Relieve stresses from quenching and enhance toughness while maintaining hardness

Process Conduct multiple tempering cycles usually 23 Heat to 500600C for each cycle and hold for 12 hours

Allow cooling to room temperature between cycles

Stress Relieving

Purpose Remove residual stresses from machining or previous treatments

Process Heat to 600700C and cool slowly

HSS Heat Treatment Techniques

Vacuum Heat Treatment Advantages

Ensures clean oxidation free surfaces

Precise temperature control for consistent properties

Commonly used for high precision tools

Heat Treatment Advantages

Provides rapid and uniform heating

Effective for small and intricately shaped tools

Requires careful handling to avoid contamination

Conventional Furnace Treatment Advantages

Cost effective for large batches

May require protective atmospheres to prevent oxidation

PROPERTIES ACHIEVED AFTER HEAT TREATMENT

Hardness :  Typical hardness ranges from 6270 HRC

Wear Resistance : Superior resistance to abrasive and adhesive wear due to carbide dispersion

Red Hardness :  Retains hardness at temperatures up to 600650C crucial for cutting tools operating at high speeds

Toughness : Improved resistance to chipping and cracking during heavy duty applications

 

Common Grades of HSS M2 High Toughness General purpose HSS for drills taps and milling cutters

M35: Cobalt Based Enhanced wear resistance and red hardness due to 5 cobalt content Ideal for high performance cutting tools

M42: High Cobalt Content Superior hot hardness and wear resistance with 810 cobalt Used in heavy duty machining and cutting applications

T1:  TungstenBased Traditional HSS with excellent toughness and wear resistance

KEY APPLICATIONS OF HEAT TREATED HSS

Cutting Tools : Drills taps milling cutters end mills and reamers

Forming Tools : Dies and punches for metal forming

Saws and Blades : Band saws and circular saws for high speed cutting

Aerospace Components : Precision tools for machining aero space grade materials