1.4120, DIN X20CrMo13

1.4120, DIN X20CrMo13

Designation by Standards

 

Chemical Composition (in weight %)

Description
PK320 is stainless, heat resistant steel up to temperature of 550^oC. Steel is resistant to water with a low chlorine content in fine-machined or, better still, polished condition.

Applications
Owing to its greater high-temperature strength and corrosion resistance - resulting from the addition of molybdenum - PK320 is used for shafts and blades in water and steam turbine systems. One special field of application is for bedknives in the cellulose industry.

Physical properties (avarage values) at ambient temperature
Modulus of elasticity [10³ x N/mm²]: Approx. 210
Density [g/cm³]: 7.7
Thermal conductivity [W/m.K]: 25.0
Electric resistivity [Ohm mm²/m]: 0.60
Specific heat capacity[J/g.K]: 0.43
Magnetisable: Yes

Coefficient of Linear Thermal Expansion 10^{-6 o}C^-1

Annealing
Heat to 750-850^oC, cool slowly in furnace. Tensile strength is max. 770 N/mm². Structure is ferrite with spherical carbides.

Quenching
Harden from a temperature of 950-1000^oC followed by oil quenching.

Tempering
Tempering temperature: 650-750^oC, them air cooling. Structure is transformation structure with ferrite.

Mechanical properties at at ambient temperature
Condition: Quenched, d<=160 mm
Hardness: max. 220-280 HB
0.2 % proof stress: 550 N/mm²
Tensile strength: 750-900 N/mm²
Elongation: 14%
Charpy notch (ISO-V): 28 J (Longit.)

0.2 % Proof Stress in N/mm² vs. Tempering Temperature in ^oC

Forging
Hot forming temperature: 1100-800^oC, slow cooling.

Machinability
Metal cutting machining is teh same as that for special engineering steel grades of corresponding strength.

Welding
Only limted weldability using the manual arc, resistance and TIG welding process, as hardening occurs in the heat-affected zone. Filler material is Themanit or 1520.

Note: PK320 is primarily supplied in quenched and tempered condition. It can be set to other strength ranges. Is must be borne in mind in this context that the temperature range between 420 and 520 must be avoided owing to embrittlemnent at 475^oC.

Note: Optimum corrosion resistance is only ensured with a bright metallic surface.