CARRS P20

BS EN ISO 4957 - 40CrMnNiMo8-6-4

BS 4659 - BP20, DIN - ~1.2311, ~1.2738

TYPICAL ANALYSIS

C	0.40		Mn	1.50
Cr	1.90		Mo	0.20

SECTIONS OVER 400mm²
Material stocked in an initial form with a cross sectional area greater than 400mm² will contain 1.05% Nickel (typical) to ensure consistent through hardness.

CHARACTERISTICS
The principal advantage of this steel is that it does not require further heat treatment thus avoiding the associated risk of distortion or even cracking. Carr's P.20 is a Chromium-Molybdenum alloy steel, pre-hardened to approximately 300 B.H. No.(65 t.s.i.) but still capable of being readily machined and giving a good polished finish.
Colour Code: GREY.

TYPICAL APPLICATIONS
P.20 is specially suited for the production of plastic moulds and can also be used for die holders, backers, bolsters, etc. This is a versatile steel which can be used for a variety of other applications such as shafts, rails and wear strips.

GUARANTEE
This material carries the Carrs Guarantee against metallurgical defects.

HEAT TREATMENT graph

It is advisable to stress relieve when heavy machining has been carried out, and in certain instances customers may require to heat treat tools to a higher hardness or to carry out carburising or nitriding treatments, the details for which are as follows:-

ANNEALING
Heat to 760^oC, soak for 2 to 3 hours.Cool slowly in furnace

STRESS RELIEVING
Heat uniformly to 500^oC, soak for approximately 2 hours and air cool

HARDENING
Pre-heat uniformly at 400/450^oC and soak thoroughly. Raise heat to 830/850^oC allow to equalise and soak for 10/30 mins. according to size. Quench in oil. Cool in still air.

TEMPERING
Temper to your requirements as follows, allowing 1 hour per inch of ruling section or 2 hours whichever is longer.
Temperature: 200^oC 300^oC 400^oC 500^oC 600^oC
Hardness (Rockwell 'C') 48/49 46/47 44/45 39/41 34/36

CASE HARDENING
Carburise at 800^oC for sufficient time to give the required case (see graph right). Cool to 800/820^oC and quench in oil. Tempering at 200/300^oC will give a surface hardness of 59/55 Rc.

NITRIDING
After finish machining P.20 can be conventionally nitrided in the supplied condition to give a hard, abrasion-resistant surface skin to a depth of up to 0.40m (0.015").

FLAME & INDUCTION HARDENING
This steel is suitable for local flame or induction hardening to about 50/55 Rc.