1.4828 | X15CrNiSi20-12 | APFR/SI

This alloy is available from stock.

Please send enquiries to:

• phone: +49 (2133) 2706-0
• email: [email protected]

• Round EN 10060 / EN 10278
• Flat EN 10058 / EN 10278
• Square EN 10059 / EN 10278
• Hexagonal EN 10278
• Angle EN 10056
• Bar steel, bright steel, wire, wire rod, billets, ingots, semi-finished products

APFR/SI is an austenitic stainless steel with a high chromium-nickel content and excellent corrosion resistance at high temperatures. Due to its silicon content, it is more suitable for intermittent and higher temperature applications compared to APFR.

This grade offers excellent corrosion resistance at high temperatures and good creep properties. It is frequently used in the mechanical engineering and automotive industries, in furnaces, in the chemical industry, in high-temperature applications, in petrochemical plants and in refineries.

Argon-oxygen decarburization

Optimum resistance is achieved after annealing and rapid quenching. In continuous operation, APFR/SI offers good scale resistance up to temperatures of 1150 °C and about one hundred degrees less in intermittent operation. It has good resistance to oxidizing environments up to 1150 °C and up to 980 °C in the case of carburizing and high sulphur environments. It should be noted that the composition and steelmaking process of these grades are optimized to achieve the best performance at high temperatures. This means that corrosion resistance at low or room temperatures may not be as good as typical austenitic grades, and this behavior must be well considered in the formation of low PH stagnant condensate products. Further evaluation should address the consequences of high service temperatures, which can cause local microstructural transformation such as the formation of the sigma phase and other intermetallic compounds, leading to a severe reduction in corrosion resistance. APFR with a lower silicon content is less susceptible to sigma-phase embrittlement than APFR/SI. It should be noted that, as with any type of stainless steel, the surfaces of this grade should be free of impurities and scale, heat-treated and passivated for optimum corrosion resistance.

APFR/SI can be easily produced by cold forming such as cold drawing and bending, but should only be used moderately for cold heading or work hardening, as its chemical equilibrium does not allow it to obtain a soft, solidified structure after cold forming. This could lead to rapid wear of the die and tool. In the case of severe cold
working, annealing is required to reduce the microstructural hardness and restore ductility.

APFR/SI has the typical machinability of austenitic structures with high carbon and nickel content that not microresulphated, so drilling, turning, tapping and milling can be difficult as it is a work-hardened grade that also has low machinability. In terms of machining parameters, it should be noted that this grade is more work- hardened than other typical austenitic grades and therefore requires stiffer and more powerful machines as well as the correct selection of tools, carbide coatings and cooling lubricants.

APFR/SI can be welded using any welding process used with typical austenitic grades, but requires some different welding process evaluations compared to these. Proper welding procedures such as proper heat input, shielding gas and cleanliness before and after welding must be followed to achieve the best results in terms of corrosion resistance. In high-energy oxy-acetylene welding processes, there is a risk of hot cracking in the fusion zone due to a solidification process from primary ferrite to primary austenite. Preheating is not normally required. APFR/SI is not a low carbon grade, so PWHT annealing should be carried out at high temperature as this heat treatment improves intergranular corrosion resistance.

APFR/SI has good high-temperature plasticity and is suitable for processing by high-temperature extrusion or by upsetting with electrical resistance heating. However, overheating must always be avoided. When selecting the thermoforming temperature and the process parameters, the elongation rate and the associated temperature rise after thermoforming must always taken into account. High strain rates and temperatures at the upper end of the range during the extrusion and forging process can lead to internal chipping. Small forgings can be cooled quickly in air or quenched with water. However, the best corrosion resistance is achieved by annealing followed by rapid cooling.

1.4828 | X15CrNiSi20-12 | APFR/SI