Alloys
On this page you will find information about commonly used heat resisting alloys. These are the most common alloys:
- St. 37 / 000
- 304 AISI (1.4301)
- 308 AISI (1.4828)
- 310 AISI (1.4841)
- 316 AISI
- 321 AISI (1.4541)
- 330 AISI (1.4864)
- 446 AISI
- 253 MA
- Inc. 601
- Inc. 800
- 302
You will find the chemical composition of the most common heat resisting alloys for refractory and furnace-internal applications below
Some of the anchors may contain alloys that are not listed here, this is because those alloys are only available for those anchors.
000
This is the code for carbon steel.
304 AISI (1.4301)
This is the most common of the stainless steel types. A general purpose alloy suited for a variety of corrosion resistant applications. It has an excellent temperature resistance; up to 750 C°, after which its oxidation and scaling resistance is drastically reduced. It suffers from several different hardening/embrittlement phenomena including "Sigma" and heavy carbide precipitation in the grain boundaries when exposed for a long period of time at temperatures around 650 C°.
It is suggested that this alloy be used for continuous or low thermal cycling applications up to 800 C°.
310 AISI (1.4841)
This is a very popular alloy type in this industry, with good strength and oxidation resistance. Although prone to SIGMA formation, it is reasonably resistant to thermal cycling breakages and oxide spalling. In high gas velocities the oxide may tend to spall-off. The oxide resistance grows weaker with increasing temperature, which becomes critical at 1000 C°.
It has a moderate sulfur resistance due primarily to its higher nickel content. It has a light resistance due to carburization or a possible carbon build-up.
This alloy may be used up to temperatures of 1200 C° when combined with a 2" cuplock. It has a remarkable performance in GAS fired furnaces.
330 AISI (1.4864)
This alloy is able to withstand temperatures up to 1250 C° in oxidising atmospheres. It has good oxide adhesion, resistance to spalling, and is totally immune to SIGMA formation. It is very suitable for metal annealing furnaces where thermal cycling may be encountered. It has good strength and thermal shock resistance.
This alloy is not suitable for applications where sulfur is present due to the alloy's high nickel content. It is well suited for oxygen depleted atmospheres.
This alloy has good carbon and nitrogen absorption resistance and offers a good alternative to Inconel 601 especially for heavy refractory anchors.
With lock washer applications this alloy is equal to or superior to Inconel 601 due to its higher melting point (1400 C).
253 MA
This alloy is based on type 308 with small additions of rare earth elements, which have given it excellent oxidation resistance for temperatures up to 1150 C°. Due to the low nickel content in the alloy, there is a good resistance to SO2 and SO3 attacks. An oxygen depleted atmospheres will corrode this alloy severely by rapid removal of the oxide scale. H2S in very small quantities will attack the oxide scale.
It has very good strength at high temperatures due to the solid solution particles formed by the Rare Earth Element additions. It is slightly susceptible to SIGMA formation and it would not be suggested for use in severe thermal cycling applications, as it may cause the anchors to break after having been in use for long periods of time. It is ideally suited for continuous high temperature applications demanding slightly better performance than type 310 AISI.
Inconel 601
This alloy is excellent in high temperatures suited for applications above 1100 C°. It may be used up to 1250 C°, although its melting point is close to 1300 C°. This alloy has proved to have superior strength right up to the melting point. It is immune to SIGMA formation and great for thermal cycling and thermal shock applications. It has excellent oxide scale adhesion to the base metal due to the addition of Aluminum. It is not suited in gasses containing traces of sulfur or vanadium oxides due to the high nickel content of the alloy. It will tend to form a eutectic at approx. 650 C°, thereby severely weakening the base metal structure. In the case of ceramic fibre it should be used in combination with 330 AISI lock washers or ceramic cuplocks.
It has superior strength compared to other alloys and should be used when applying heavier refractory above 1150 C°. In certain cases Inconel 601 may be prone to internal oxidation if the stresses on the anchor exceeds 5 - 10% creep rate in 10.000 hrs. In this case, more anchors per square meter should be applied.
302
This alloy has the following characteristics: 18/8 (0.4% C°).
