1.4828, DIN X15CrNiSi20-12, AISI 309

1.4828, DIN X15CrNiSi20-12, AISI 309

Designation by Standards

 

Chemical Composition (in weight %)

Description
PK15 is a heat resistant austenitic steel grade characterized by good high temperature strength at elevetaed temperatures. This alloy is known for good strength and oxidation resistance in continuous service temperatures up to 1000^oC. It can thus primarily be used wherever high mechanical stress occour. It is superior to 304 stainless in both strength and corrosion resistance.

Applications
Oven linings, boiler baffles, fire box sheets, furnace components and other high temperature containers, parts for steam boilers and furnaces like: linings, supports, pipes for air preheaters, covers, vessels for case-hardening.

Physical properties (avarage values) at ambient temperature
Modulus of elasticity [10³ x N/mm²]: 210
Density [g/cm³]: 7.9
Thermal conductivity [W/m.K]: 15.0, 21 (500^oC)
Electric resistivity [Ohm mm²/m]: 0.85
Specific heat capacity[J/g.K]: 0.50
Magnetisable: No

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

Stress Relieving
Stress relieving to remove machining stresses should be carried out by heating to approx. 650^oC, holding for 1-2 hours at heat, followed by air cooling. This operation is performed to reduce distortion during heat treatment.

Quenching + AT
Harden from a temperature of 1050-1150^oC followed by water or air (sufficienty fast) quenching. Structure after quenching is austenite.

Mechanical properties at room temperature in solution-annealed condition
For size range: <=160 mm and solution-annealed condition + AT
Hardnees: Approx. 223 HB
0.2 % proof stress: 230 N/mm²
1.0 % proof stress: 270 N/mm²
Tensile strength: 550-750 N/mm²
Elongation after fracture AT min: 30%

Approximate data on long-term high temperature resistance + AT condition

1% Creep Limit in N/mm² vs. Temperature in ^oC

Forging
Hot forming temperature: 1150-800^oC, cooling in air.

Machinability
This alloy machines similarly to type 304 stainless. Its chips are stringy and it will work harden rapidly. It is necessary to keep the tool cutting at all times and use chip breakers.

Corrosion Resistance
Steel is resistant to scaling in oxidizing atmospheres at up to 1050^oC. Steel is sensitive to SO₂, and particularly gases containing H₂S at temperatures in excess of 650^oC. It is also displays a certain sensitivity to carburising gases, especially at temperatures above 900^oC. PK15 displays a tendency towards embrittlement due to Sigma-phase formation during continuous operation in the temperature range between 600 and 850^oC.

Welding
Most of the austenitic stainless steels can be readily welded using fusion or resistance methods. Oxyacetylene welding is not recommended. Filler metal should be AWS E/ER 309 or 309L.

Cold working
Although this alloy has a high work hardening rate, it can be drawn, headed, upset, and stamped. Full annealing is required after cold work to remove internal stress.