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AISI SAE P-20 is a pre hardened high tensile tool steel which offers ready machineability in the hardened and tempered condition, therefore does not require further heat treatment. This eliminates the risks, cost, and waiting time of heat treatment thus avoiding the associated possibility of distortion or even cracking. Subsequent component modifications can easily be carried out.

Prehardened plastic mould steel with good machinability, better than steel grade Mat. No. 1.2312, suitable for texturing. 1.2311 usually used on Plastic moulds, mould frames for plastic moulds, large injection moulds, pressure casting dies,recipient sleeves.

Forging: Heat slowly and uniformly to 1050°C. Do not forge below 930°C. After forging cool slowly.

Annealing: P20 should always be annealed after forging and before rehardening. Heat uniformly to 770/790°C. Soak well and cool slowly in the furnace.

Hardening: Heat uniformly to 840/870°C until heated through. Quench in oil. Tempering: Heat uniformly and thoroughly at the selected tempering temperatures and hold at heat for one hour per 25 millimetre of total thickness.

Nitriding:
Moulds machined from pre hardened P20 may be nitrided to give a hard surface which is very resistant to wear and erosion. A nitrided surface also increases the corrosion resistance. The surface hardness after nitriding at a temperature of 525°C in ammonia gas will be approximately 650HV.

Tufftriding:
Tufftriding at 570°C will give a surface hardness of approximately 700HV. After 2 hours treatment the hard layer will be approximately 0.01mm

Flame & Induction Hardening:
P20 can be flame or induction hardened to a hardenss of 50 to 55 HRc. Cooling in air is preferable. Smaller pieces may however require forced cooling. Hardening should be immediately followed by tempering.

Hard Chromium Plating:
After hard chromium plating the steel should be tempered for approximately 4 hours at 180°C, in order to avoid hydrogen embrittlement.

Case Hardening:
In order to maintain maximum surface hardness P20 may be case hardened. Before case hardening is carried out the steel should be annealed. To carburise, pack with carburising powder into a cast iron or heat resisting steel box and see that the articles are separated from the sides by at least two inches of carburising powder. Lute the lid with fireclay. Heat to the carburising temperature of 880°C and soak for sufficient time to give the required depth of case. Cool to 800/820°C and quench in oil. Tempering will then be necessary. Reheat to 200/300°C and allow to cool in the air to give a final  surface hardness of Rockwell C55/59

Welding:
Firstly heat to approximately 400 to 500°C. Weld at approximately 400 to 500°C and stress relieve. Use Chromium-Nickel-Molybdenum alloyed basic electrodes for welding of structural steel. Welding may also be carried out using an austenitic stainless steel electrode. In this case the stipulated increased working temperature may be modified, but the weld metal has a lower strength than the parent material.



Temperature

Time

Approximate Depth of Case

525°C

20 hours

0.30mm

525°C

30 hours

0.35mm

525°C

60 hours

0.50mm


 Chemical Composition - P20 Tool Steel

 C.

Si.

Mn. 

Cr. 

Mo. 

 0.40%

0.40% 

1.00% 

1.20% 

0.35%


Tempering °C

  100

  200

  300

   400

   500

   600

   700

HRc

 51

 50

 48

 46

 42

  36

 28

N/mm²

1730

1670

1570

1480

1330

1140

 920


Physical Properties: Temperature:    
  20°C 200°C 400°C
Density (Kg/m³) 7800 7750  7700 
Coefficient of thermal expansion (per °C from 0°C) - 12.7 x 10-6 13.6 x 10-6
Thermal conductivity (J/m.s °C) 29.0 29.5 31.0 
Specific heat (J/kg °C)  460
Modulus of elasticity:      
Kp/mm²   20 900   20 400   18 900
N/mm² 205 000 200 000 185 000

Machining:
 Turning

 Rough

Medium 

Finish 

 Carbide Tools

Turning

Turning

Turning

 Depth of cut (t) mm

 min. 10

2-10

max. 2 

 Feed (s) mm

 mm 1.0

 0.3-1.0

max. 0.3 

 ISO Machining Group

 P30-P40

P20-P30 

P10 

 Cutting Speed

 40-60

60-100 

90-160 


Milling:    
Carbide Tools &

Rough

Finish

High Speed Steel Tools

Milling

Milling

Depth of cut (t)

min. 2

max.2

Feed (s) mm/tooth

min. 0.2

max. 0.2

ISO Machining Group

P30-P40

P10-P20

  Carbide Tools:
Cutting Speed (v) m/min.

55-85

75-95

  High Speed Steel Tools:
Cutting Speed (v) m/min.

10-20

15-30


 Mechanical Properties (at room temperature)

Tensile Strength

 1000-1068 N/mm²

 Yield Stress

 861-930 N/mm²

 Reduction of Area

 45-50%

Elongation

 14-17%



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