CSM® 21
(AISI 17Cr-4Ni Modified)
CSM 21 is a precipitation hardening stainless mold steel, providing outstanding corrosion resistance and toughness, good polishability, and moderate wear resistance, combined with simple heat treatment. CSM 21 is supplied in the solution treated condition at about 32 HRC, but is intended to be aged prior to use.
Typical Chemistry
Carbon 0.02%
Manganese 0.60%
Silicon 0.50%
Chromium 15.25%
Nickel 4.75%
Copper 3.50%
Typical Applications
Injection Molds
Injection/Extrusion Screws
Plastic Extrusion Dies
Zinc Die Casting Dies
Hardening

CSM 21 is a precipitation hardening (age-hardening) alloy, and normal quenching and tempering is not required. Hardening is accomplished by simply holding at temperature between 925F and 1150F for one hour per inch of thickness (4 hours minimum) and cooling to room temperature. CSM 21 must be aged prior to service for any application involving steel temperatures over 400F.

Some CSM 21 stock is supplied pre-aged. Check with your local service center for details.
Age Hardened Conditions and
Resultant Properties
Condition
Temp.
°F
Hardness
HRC
Toughness,
Ft-lbs. "V"
H1150 1150 33 66
H1100 1100 34 55
H1025 1025 39 34
H975 975 40 31
H925 925 43 10
Sol. Ttd. 1900 32 50
Size Change

CSM 21 shrinks during aging. The shrinkage is uniform and predictable. Contraction will range from about .0004/.0006 inches per inch when aged at 925/975, to about .0006/.001 inches per inch when aged at 1100/1150F.

Surface Treatments
Gas or ion nitriding decreases the corrosion resistance of stainless steels, and is not recommended. In certain aged conditions, CSM 21 may be coated using titanium nitride or similar coatings.

Annealing
Heat to 1900F, hold 30 minutes after reaching temperature, air cool to room temperature.

Annealed hardness: Approx. 32 HRC

Stress Relieving
Annealed Material: Aging procedure also serves as stress relief. Holding at temperature between 400F and 900F may result in improper aging, and should be avoided.

Age Hardened Material: Heat to 25/50F below aging temperature, hold two hours, air cool.

Welding
Use 630 type filler material (17-4 or 15-5 also acceptable).

Annealed Material: Preheat and Postheat not required.

Age Hardened Materials: Preheat not required. Cool to room temperature (<90F) after welding. Age to 25F below original aging temperature (900F minimum).

Texturing
CSM 21 offers outstanding resistance to corrosion in service. Light texturers may be readily applied. The high corrosion resistance may cause difficulty in achieving uniform deep textures (>.005" metal removal). Crucible recommends discussing individual patterns with textures prior to texturing.

Corrosion Resistance
CSM 21 provides excellent resistance to corrosive environments in any condition. For maximum corrosion resistance in severe environments, CSM 21 should be used in the aged condition (900/1150F aging temperature).

Physical Properties
Modulus of Elasticity ...........................................................28.5 psi x 106
Density .......................................................................................0.282 lb/in3
Thermal Conductivity .....................200F....................... 10 BTU/hr/ft/°F)
Thermal Expansion
x10-6 in./in./F
Cond A. H900 Cond. H1150
RT-200F 6.0 6.7
RT-400F 6.0 6.9
RT-600F 6.2 7.1
RT-800F 6.3 7.3

Note: Thermal expansion characteristics vary as a function of aging temperature between
the values given for conditions H900 and H1150. For instance, values for H1025 condition
will be about midway between H900 and H1150 values.
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