CSM® 420 XL
(AISI 420 Modified)
CSM 420 XL is a high-quality, double-melted stainless mold steel, designed for plastic molding applications requiring a combination of corrosion resistance and wear resistance. Due to its high internal cleanliness and homogeneity, CSM 420 XL molds are capable of highly polished finishes. CSM 420 XL is particularly suited for medical, electronic, food processing, or other clean-room type molding environments, or molding of mildly corrosive resins.
Typical Chemistry
Carbon 0.38%
Manganese 0.50%
Silicon 0.75%
Chromium 13.60%
Vanadium 0.30%
Sulfur <0.003%
Typical Applications
Injection Molds Compression Molds
Glass Molds Rubber Molds
Hardening

Critical Temperature: About 1500 F.

Preheat: 1000/1250F(540/680C), equalize,
1400/1500F(760/820C), equalize.

High Heat: 1850/1925F(1010/1050C), 30/45 minutes at temperature. Higher temperatures produce higher hardness, but result in lower toughness. 1850/1880F(1010/1030C) is the recommended austenitizing temperature for best combination of properties.

Quench: air, positive pressure vacuum, salt, or interrupted oil*. Salt bath or interrupted oil* quenches may be required to produce maximum hardness in thick sections.
*An interrupted oil quench consists of quenching in oil until just black [about 1000/1100F(540/600C)], then removing from oil and air cooling.

Temper: 400/800F(210/430C); temper twice. 550/750F(290/400C) is recommended for best results. Tempering above 800F(430C) may result in slightly increased hardness, but is not generally recommended, due to a resulting decrease in both toughness and corrosion resistance.
Hardness & Tensile Properties
Hardness after air cooling and tempering between 550F and 750F(290 &400C) will be about 49/53 HRC.
Tempering
Temperature
°F
Hardness HRC
1850F
(1010C)
1880F
(1030C)
1920F
(1050C)
550 48/51 50/52 51/53
650 48/51 50/52 51/53
750 49/52 50/53 52/54
850 50/53 51/54 52/54
950 47/49 48/50 50/53
1050 36/40 37/40 38/40
Room Temperature Properties
Hardness
HRC
Tensile
 Yield
PSI
MPa
PSI
MPa
53 265,000 1,825 220,000 1,515
51 250,000 1,725 210,000 1,445
49 235,000 1,625 200,000 1,375
Annealing/Stress Relieving
Heat treated tools may be annealed by either of the following methods:

A. Heat to 1600F(870C), equalize, hold 6 hours, cool slowly in a furnace [25F(15C) per hour maximum] to 1200F(650C), then air cool.
or
B. Heat to 1600F(870C), equalize, hold 2 hours, cool to 1300F(700C), hold 4/6 hours, then air cool.

Annealed hardness: Approx. 200/240 BHN

Stress Relieving
Annealed CSM 420 XL: Heat tools to 1100/1250F(590/680C), hold two hours, and allow to cool in still air.

Hardened CSM 420 XL: Heat tools to 25/50 F (15/30 C) below tempering temperature, hold two hours, and allow to cool in still air.

Welding
420 filler material should be used for molding surfaces. 308 or 309 stainless filler material may be used for simple joints, but will not develop heat treated properties like CSM 420 XL.

Heat Treated Tools: Preheat to about 50F (30C) below the original tempering temperature, and maintain at temperature during welding. Allow to cool to hand warm [about 150F (65C)] after welding. Temper immediately at 25/50F (15/30C) below the original tempering temperature.

Annealed Tools: Preheat to 600/800F (320/430C), and maintain above 600F (320C) during welding. Reanneal immediately after welding. Annealing procedures are detailed in Annealing section above.

Physical Properties
Density .......................................................................0.276 lb/in3............ (7640 kg/m3)
Modulus of Elasticity ..............................................29 psi x 106 ......(200 x 103 GPa)
Thermal Conductivity .......200F (95C)........ 14.4 BTU/hr/ft/°F.......... (24.9 W/m°C)
Thermal Expansion
Temperature
Range
Coefficient of Thermal
Expansion
°F
°C
in/in/°Fx10-6
mm/mm/°Cx10-6
32-212
0-100
5.7
10.3
32-600
0-320
6.0
10.8
32-1000
0-540
6.5
11.7
32-1200
0-650
6.8
12.2
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