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Features and Uses of O1 Cold Work Tool Steel
This moderately priced oil hardening tool steel hardens in oil from a low
temperature, offers pronounced non-deforming characteristics and retains its
original dimensions after oil hardening and tempering. It gives excellent wear
resistance, holds a good cutting edge and is relatively easy to machine. Due to
these properties, O1 is an excellent general-purpose tool steel often used where
the expense of a high carbon high chromium steel would not be justified.
Typical applications of O1 include medium run dies, intricate press tools,
drawing punches, broaches, bushings, lathe centres, chuck jaws, master cavity
sinking hobs, paper cutting machine knives, plug gauges, thread gauges and
precision measuring tools generally, cams, cloth cutting knives, cold taps,
reamers, collets, cutting hobs, strip slitting cutters, trimmer dies, tube
expander rolls, plastic moulds and woodworking knives.
Available Forms
Working and Heat Treatment
Forging
Heat slowly and begin forging at 980°/1000°C. Do not allow temperature to
fall below 800°C, re-heating if necessary. Slow cool.
Annealing
To anneal, heat slowly and uniformly in a closed box or tube to 740°/760°C.
Maintain at this temperature for 2 - 3 hours, cool with the furnace until the
temperature falls below 500°C. Withdraw from box or tube and allow to cool in
air to shop temperature. Annealed hardness about 229 Brinell.
Stress Relieving
when tools are heavily machined, ground or otherwise subjected to cold work,
the relief of internal strains is essential before hardening. Stress relieving
should be done after rough machining. To stress relieve, heat carefully to
670°/700°C. Soak well and allow to cool in air. The tools may then be
finish-machined before hardening.
Hardening
Heat slowly and if possible pre-heat at 300°/500°C. before raising to the
hardening temperature of 780°/820°C. Pre-heating is especially desirable for
complex sections. Soak thoroughly, allowing 30 minutes per inch of ruling
section before quenching. Light sections should be quenched in oil from the
lower end of the hardening temperature range.
Long slender sections should always be suspended in the furnace for heating
and quenched by plunging vertically into the oil bath.
Tempering is always necessary after hardening.
Martempering
Martempering is an alternative hardening procedure which may be used when
suitable salt bath equipment is available. By this method, internal strain,
distortion and risk of quench cracking are reduced to the minimum.
Pre-heat at 360°C. then heat to 800°C. for sections 1/8" thick or
less, or to 820°C. for sections over 1/8" thick. Soak according to
section, then quench into molten salt held at 210°C. Allow sufficient time for
the centre of the piece to reach bath temperature, withdraw and cool in the air.
Tempering will then be necessary.
Tempering
Temper between 150°C. and 350°C. according to the requirements of the job
and by reference to the Tempering Curve. Soak for one hour at the tempering
temperature. Where possible, use an air-circulating furnace.
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