ASM Tool Steel Type-6F4

A.I.S.I.-S.A.E. Tool Steel Type-None

Composite Forgings Ltd. PRESTEM is a low Carbon, high Molybdenum, high Nickel precipitation hardening Die Steel developed especially for hot working of ferrous and non-ferrous metals in presses and upsetting machines. PRESTEM has excellent wear in applications where the die temperatures are high. In addition to wear the resistance to impact at elevated temperatures is excellent. It is recommended that in order to obtain the best results from PRESTEM, dies and inserts should be preheated to 350-500°F. before forging.

Note: PRESTEM is not recommended for use as dies for Drop Hammer Forgings.

RECOMMENDED APPLICATIONS

GENERAL CHARACTERISTICS

A distinctive characteristic of PRESTEM is its ability to increase its "as quenched" hardness by the application of heat either by a tempering treatment or by the transfer of heat from the hot metal being worked. This process of hardening takes place through the phenomenon of precipitation hardening and accounts in great measure for the excellent resistance to abrasion at the hot working temperatures encountered in press and upsetting operations.

A remarkable feature of PRESTEM is that an increased hardness beyond commercial machinability can be obtained from a prehardened and machinable die block by a simple aging operation (950 to 1050°F) without the hazards of cracking, scaling, decarburization, distortion and warpage that usually attend the hardening of annealed alloy die steels. Another distinct advantage is the ability of PRESTEM to be water cooled (actually flooded) in service without the hazards which usually attend such a practice in ordinary hot work die steels. These advantages make PRESTEM an efficient and substantially, a cost-saving hot work die steel.

QUENCHING

After the steel is thoroughly soaked, cool in still air, permitting as rapid and uniform cooling as possible, to 200°F. Do not water quench as faster cooling rates produces a lower hardness.

AGING

During the aging cycle PRESTEM undergoes a pronounced precipitation secondary hardening which makes it unique among hot work die steels. It should always be aged prior to use. For aging temperatures up to 1020°F., hold at temperature for four (4) hours for thicknesses up to and including one inch, increasing one hour for each one inch of increase in thickness. Air cool to room temperature.

However, when aging temperatures are in the range of 1040°F-IO60°F, precipitation hardening takes place rapidly, and the total time on temperature should not be more than three to five hours. Longer aging times result in softening below the maximum attainable hardness.

In general, maximum attainable hardness (i.e., approximately 48 Rockwell-C can be obtained at temperatures lower than 1040°F-IO60°F provided the times temperatures are appreciably longer than indicated above. In practice however, it is usually advantageous to temper to less than maximum hardness allowing for the development of further hardness in service.

PRESTEM is furnished prehardened in two commercially machinable standard ranges of hardness and ready for use by the customer.

PRESTEM A = Hardness-Rc 41/45

PRESTEM B = Hardness-Rc 36/40

Note: When increased hardness up to a maximum of 47-48 Rockwell "C" is required, it may be obtained

by a simple aging operation performed on the standard prehardened and machinable die block (generally

PRESTEM B) after the impression has been machined.

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