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CPM® S90V (420V)
(AISI 420 modified with high vanadium)
CPM S90V is a unique tool steel made by the Crucible Particle Metallurgy process. It is a martensitic stainless steel to which vanadium and carbon have been added for exceptionally good wear resistance. CPM S90V offers substantial improvements in wear resistance over 440C and D2, and other high chromium steels, with corrosion resistance equal to or better than 440C. CPM S90V’s high vanadium content favors the formation of hard vanadium carbides instead of chromium carbides for wear resistance, leaving more free chromium available to provide corrosion resistance.
The wear and corrosion resistance of CPM S90V make it an excellent candidate to replace 440C, where increased wear is a primary concern. It can replace D2 or other tool steels in applications where improved corrosion resistance is also of benefit.
Typical Chemistry
Carbon 2.30%
Chromium 14.00%
Vanadium 9.00%
Molybdenum 1.00%
Typical Applications
Plastic Injection and Extrusion Feedscrews
Non-return Valve Components
Pelletizing Equipment
Gate and Nozzle Inserts Industrial Knives,
Slitters, and Cutters
Long-wearing Specialty Cutlery
Injection Molds and Inserts
Wear Components for Food and Chemical Processing
Bearings, Bushings, Valves, Rolls
Gear Pumps
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Machinability and Grindability
Due to its high vanadium carbide content, the machinability and grindability of S90V will be slightly more difficult than that of D2 or 440C. Similar grinding equipment and practices are acceptable. SG type alumina wheels or CBN wheels have generally given the best performance with the CPM steels.
Thermal Treatments
Annealing: 1650°F (900°C), hold 2 hours, slow cool no faster than 25°F (15°C) per hour to 1000°F (540°C), then furnace cool or cool in still air to room temperature.
Annealed Hardness: Approx. BHN 277.
Stress Relieving:
Annealed Parts: Heat to 1100-1300°F (595-705°C), hold 2 hours, then furnace cool or cool in still air.
Hardened Parts: Heat to 25-50°F (15-30°C) below original tempering temperature, hold 2 hours, then furnace cool or cool in still air.
Hardening:
Austenitize: 2100-2150°F (1150-1175°C) Hold time at temperature: 10-30 minutes
Quench: Salt quench, interrupted oil quench, positive pressure gas quench or air cool at a minimum cooling rate of 150°F/min (80°C)/min) to below 1000°C (540°C) followed by still air or moderately forced air cooling to below 125°F (50°C). For optimum vacuum heat treatment response, a minimum 4 bar gas quench is recommended.
Temper: For an optimum combination of hardness, wear resistance and corrosion resistance, double temper at 400-750°F (200-400°C). Hold for a minimum of 2 hours each temper. For optimum stress relieving and dimensional stability, S90V may be double tempered at 1000-1025°F (540-550°C), but tempering above 800°F (425°C) may result in some loss of corrosion resistance. A freezing treatment may be employed between the first and second tempers, if desired. Freezing treatments should always be followed by at least one temper.
PLEASE NOTE: Tempering between about 800 and 1000°F (425 and 540°C) is not recommended. All martensitic stainless steels suffer from embrittlement when tempered in this range.
Aim Hardness: HRC 56-59
Size Change: +0.03 to +0.05%
Size change shown is for a fully martensitic microstructure. The presence of retained austenite may reduce the net growth. When tempering at 400-750°F (200-400°C), freezing treatments may be necessary to minimize retained austenite.
Impact Toughness
CPM S90V offers higher impact toughness (Charpy C-Notch) than 440C at comparable hardnesses.
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Hardness (1) Impact Toughness (2)
HRC Heat
Treatment
ft-lbs (Joules)
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CPM S90V 58 (A) 19 (26)
440C 58 (B) 16 (22)
D2 59 (C) 22 (30)
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(1) A=Hardened 2050°F (1120°C), double tempered 500°F (260°C)
B=Hardened 1900°F (1040°C), double tempered 400°F (204°C)
C=Hardened 1850°F (1010°C), double tempered 600°F (315°C)
(2) Charpy C-notch impact test
Corrosion Resistance
Corrosion tests measure the amount of material lost to corrosion. Therefore, lower numbers indicate better corrosion resistance.
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Corrosion Test Results (1)
Salt Spray (2) Aqua-Regia(3)
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CPM S90V 5/15 250/500
440C 5/15 500/600
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(1) Lower numbers indicate better corrosion resistance. All grades heat treated to about HRC 56/58. Corrosion resistance depends strongly on heat treated condition and specific environment. Results should be used as a qualitative comparison only.
(2) # pits/in2, in solutions of 2% and 5% NaCI (salt water) at 95°F (35°C)
(3) mils/month, in 5% HNO3 -1% HCI (nitric+hydrochloric acids) room temperature
Surface Treatments
Because of its usual low tempering temperature, CPM S90V is not usually readily nitrided or TiN coated.
Physical Properties
Modulus of Elasticity ..........................................................31 psi x 106 (215 GPa)
Specific Gravity .....................................................................................................7.40
Density ..............................................................................0.270 lb/in3 (7400 kg/m3)
Thermal Conductivity (at room temperature)
................................ 9.7 BTU/hr/ft/°F(0.04 Cal/cm2/sec/°C)
Thermal Expansion
Temperature
Range
Coefficient of Thermal
Expansion
°F °C in/in/°Fx10-6 mm/mm/°Cx10-6
70-400 21-205 6.1 11.0
70-600 21-315 6.4 11.5
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发表于 2005-4-28 08:54
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