Heat treatment of tool steelsCase studies

1. High Speed Steel (HS 6-5-2)

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General overview

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Comparison of properties

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Heat treatment (1)

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Heat treatment (2)

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Heat treatment (3)

Heat treatment sequence

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Immersiontime as

function ofsize and

austenisingtime

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Temperingfor optimum hardness.Precipita-tion ofcarbides.

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CCT diagram of HS 6-5-2

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Isothermal TTT diagram of HS 6-5-2

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2. Cold working tool steel (K11)

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Generaloverview

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Comparison of properties

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Heat treatment (1)

Heat treatment (2)

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Heat treatment (3)

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Heat treatment sequence

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CCT diagram of K11

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Isothermal TTT diagram of K11

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3. Powder metallurgical (PM)cold working steel

(K390 MICROCLEAN)

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Comparison of conventional andPM steel structure

Comparison of toughness andwear resistance

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Powder metallurgy

• Production of metal powder• Mixing and blending• Compacting• Sintering• Forming• Final treatment• Tool production

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Powder processing

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Shape and size of powders

• Shape and size of powders depend on the method of production

• Particle size range: 0,001…1 mm• Shapes (one-, two, three dimensional):

– spherical– elongated– irregular– porous

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Blending metal powders

• Screening by screens of various meshsizes

• Mixing by size and by material to uniform distribution of components

• Lubrication• Objective:

– Favourable composition– Better properties– Lower friction at compaction

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Compaction• Blended powders are

pressed into shapes indies

• The pressed powder is known as greencompact (rigid, lowstrength)

• Tooling:– Single acting punch– Floating container– Two counteracting

punches

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Sintering (process)

• Compressed powder is heated in controlled atmosphere

• Variables: temperature, atmosphere and time

• Result: increasing strength and toughness, lowering porosity.

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Sintering (microstructure)

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Sintering (furnace)

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Heat treatment (1)

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Heat treatment (2)

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CCT diagram of K390

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Applications (forming tools)

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Application: cutting tools

W- and Ti-carbide plates for high-speed cutting