Skip to main content

Sulphidation resistance of stainless steels

By Materials & Welding

Introduction

For practical considerations, sulphidation in relation to high temperature attack of stainless steels, is more a consideration of the effects of sulphur containing atmospheres, rather than a specific attack mechanism. Both oxides and sulphides may be formed depending on the atmosphere, but generally the resistance to sulphur containing gasses is related to chromium content, in the same way as oxidation.

The combustion of high sulphur level fuel oils is not normally considered hazardous to stainless steels, provided there is sufficient oxygen present to make conditions sufficiently oxidising.

Affect of sulphur containing gas conditions-sulphur dioxide

Dry sulphur dioxide is normally not considered a hazard to stainless steels, although the scaling rates are higher for a given temperature than in dry air.
Damp sulphur dioxide is more aggressive, which may be similar to the comparison of dry and damp air oxidation.
Higher levels of chromium are beneficial in resisting attack. Although there may be little difference between grades like 1.4301 (304), 1.4401 (316) and 1.4845 (310) at around 700 °C in damp sulphur dioxide, these conditions can be expected to compromise the resistance of 1.4301 (304) at 850 °C. Generally grades 1.4016 (430), 1.4301(304) and 1.4541 (321) can be considered up to 800 °C in sulphur dioxide. Ferritic 1.4749 (446) and austenitic 1.4845 (310) heat resisting grades can be considered up to 1025 °C and 1050 °C, respectively.

Affect of sulphur containing gas conditions-hydrogen and hydrogen sulphide

Stainless steels with less than 20% chromium may form less stable chromium sulphide 'scales'. The 1.4845(310) grade (24-26% Cr in BS EN 10095) can be considered for hydrogen sulphide environments.

Combustion atmospheres with sulphur

The sulphur levels in fuels such as natural gas are low and so the combustion products of these fuels are not a hazard to stainless steels, from the point of view of sulphur content. High sulphur oil combustion products may be a hazard and it is not sensible to generalize on these.

Liquid sulphur and sulphur vapour

Liquid sulphur at up to 240 °C should not attack stainless steels, but at its boiling point (445 °C), liquid sulphur is very aggressive to 1.4301 (304) type. Grades such as 1.4401(316) have some resistance and may be useful under certain conditions.
Sulphur vapour is very aggressive to stainless steels but the higher chromium 1.4845(310) grade may be worth considering.

 

Source: http://www.bssa.org.uk/

Comments

Post a Comment

Popular posts from this blog

Re: [MW:34105] SA266 GR4N 4 Cycle SPWHT

By Materials & Welding
Hi,  You are correct, Minimum refers to the one cycle for which this part will expose until final work shop PWHT. hence mill test certificate shall include this.  Max. SPWHT, refers to additional cycles of heat treatment that are reserved for future repairs during equipment lifetime.  Again, these simulated no. Of cycles shall be specified in MTC.  The idea is we need to make sure that steel mechanical properties are not compromised upon exposure to multiple repairs (i e 4 cycles in your case).  One could say, if steel is subjected to 4 cycles and is ok, then it should by defacto be good for one cycle, yet, this is wrong assumption cause mechanical problems and microstructure of materials varies accordingly based on no. Of cycles for which material will expose. This is apparent in alloy steel and especially for impact test values as an example.  In your case, this forged CS with properties before PWHT can be understood to be " as forged" condition (i.e. Wit...
Post a Comment
Read more

Materails FAQs

By Materials & Welding
Q: What are equivalents for standard Q 235 B (and Q 235 A) for U-channels? (asked by: boris.vielhaber@vait.com) A: DIN Nr. = 2393 T.2, 2394 T.2, EN 10025 W. Nr. DIN 17007 = 1.0038 Design DIN 17006 = RSt 37-2, S235JRG2 (Fe 360 B) Q: What is St DIN 2391 BK material? (asked by: dmcandrews@automaticstamp.com) A: Precision steel tubes, cold-finished/hard. Q: What is C.D.W. Boiler Tube? (asked by: montydude123@yahoo.com) A: Cold Drawn Welded Boiler Tube. Q: WHAT IS W.Nr. 1.4301? PLS TELL US IN EASY LANGUAGUE (asked...
21 comments
Read more

Heat tint (temper) colours on stainless steel surfaces heated in air // Heat tint

By Materials & Welding
Introduction The colour formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds, is dependent on several factors that are related to the oxidation resistance of the steel. The heat tint or temper colour formed is caused by the progressive thickening of the surface oxide layer and so, as temperature is increased, the colours change.   Oxidation resistance of stainless steels However, there are several factors that affect the degree of colour change and so there is no a single table of colour and temperature that represents all cases. The colours formed can only be used as an indication of the temperature to which the steel has been heated. Factors affecting the heat tint colours formed Steel composition The chromium content is the most important single factor affecting oxidation resistance. The higher the chromium, the more heat resistant the steel and so the development of the heat tint colou...
Post a Comment
Read more