VACCUM HARDENING PROCESS
Hot-worked Tool Steels
- Carbon-content =0.3-0.5%.These Steels are used for high temperature metal forming operation (except cutting), where the temperature is around 200-800 degree Celsius.
- These are characterized by high hot yield strength, high red hardness, wear resistance, toughness, erosion resistance, resistance to softening at elevated temperatures, good thermal conductivity.
- These are divided into 3 groups depending on the principle alloying elements:
- Chromium-based [H11-H19]
- Tungsten-based [H20-H26]
- Molybdenum-based [H41-H43]
- Contains Chromium (>=3.25%), and small amounts of vanadium, Tungsten, and molybdenum.
- These are characterized by High red Hardness & high hardenability.
- Oil quenching is required when dimensional stability is not of prime importance. Tempering temperature for these steels varies from 550-675 degree Celsius.
- Hot dies for extrusion, forging, mandrels, punches.
- Highly stressed structural parts of supersonic aircrafts.
- Hot work steels
- Contains Tungsten (=9.00%) & Chromium (2.0 -12.0%), and low carbon %.
- These are characterized by resistance to high temperature softening.
- Tempering temperature for these steels varies from 550-675 degree Celsius.
- Extrusion dies for Brass, Steel &Nickel alloys.
- Contains Molybdenum (8.00%) & Chromium (4.0-12.0%), and some tungsten and vanadium.
- These are characterized by high toughness & high heat check resistance.
- Tempering temperature for these steels varies from 550-650 degree Celsius.
Vacuum-Hardening of Hot-Work Tool Steel
Microstructure of H-13 Tool Steel (1000x)
Microstructure of Annealed H-13 Tool Steel
NADCA Specification #207-2006
Annealed Quality Microstructure chart
Heat Treatment Quality Microstructure Chart
Cold-worked Tool Steels
- These steels are used for making tools for cold work applications, when the tool surface temperature does not rise more than 200 degree Celsius.
- These are characterized by high abrasion & wear resistance, higher toughness and high impact resistance.
- These steels are also called “Non-distorting steels”, as they show little change in dimension during heat treatment.
- These are divided into 3 groups:
- Oil hardening Steels [GRADE ‘O’]
- Air hardening Steels [GRADE ‘A’]
- High Carbon, High Chromium Steels [GRADE ‘D’]
- These are hardened by oil-quenching & contain high carbon with manganese, chromium, molybdenum.
- These are characterized by high machinability, wear resistance, and non-distorting properties.
- Tempering temperature for these steels varies from 100-425 degree Celsius.
- Blanking and forging dies
- Threading dies
- Expansion reamers
- These are hardened by air-quenching & contain carbon (1.0%) with manganese, chromium, molybdenum & tungsten.
- These are characterized by high wear resistance & high hardenability, fair red hardness, good toughness and resistance to decarburization.
- Tempering temperature for these steels varies from 150-425 degree Celsius.
- Blanking and Trimming dies
- coining dies
High Carbon, High Chromium Steels
- These are hardened by oil- or air-hardening & contain carbon (1.4-2.3%) & chromium (12-14%), with molybdenum, cobalt, vanadium.
- Vanadium prevents these steels form showing grain coarsening (up to 1040 degree Celsius). Chromium imparts non-deforming properties. Tempering of these steel results in high hardness, wear & abrasion resistance.
- Tempering temperature for these steels varies from 150-375 degree Celsius.
- Mandrel for tube rolling by pilger rolls.
- Blanking and piercing dies, coining dies, drawing dies
High Speed Tool Steels
- These are highly alloyed tool steels developed initially to do high speed metal cutting. Now they used in a wide variety of machining operations.
- These are characterized by high hardness (60-65 HRC at 600-650 degree Celsius), high red hardness, wear resistance, reasonable toughness and good hardenability.
- They contain 0.6% carbon, 4% chromium, 5-12% cobalt.
- Carbon imparts hardness of at-least 60 HRC of martensite formed. Chromium increase hardenability & corrosion resistance. Cobalt increases the thermal conductivity, melting point, red hardness & wear resistance of high speed steels.
- These are divided into 2 groups depending upon the principal alloying elements & the composition:
- Molybdenum high speed steel [GRADE ‘M’]
(Contain molybdenum, tungsten, chromium, vanadium & sometimes cobalt)
- Tungsten high speed steel [GRADE ‘T’]
(Contain high amount of tungsten with chromium, vanadium and some cobalt)
- End mills, drills, lathe tools, planar tools.
- punches, reamers
- Routers, taps, saws
- Broaches, chasers, and hobs.
Typical heat treatment cycle for HSS
Note: Photographs and illustrations are more for clarity and educative purpose of the business we do and not necessarily in original form of our service centers