Abstract: In a process such as the preparation of sulphuric acid wherein a wrought or cast material or a welding filler is contacted with hot concentrated sulphuric acid or oleum of up to 10 wt-%, the improvement which comprises forming the contact portion of said wrought or cast material or said filler of an austenitic iron-nickel-chromimum-silicon alloy comprising about15.5 to 17.5 wt-% nickel10 to 12 wt-% chromium5.7 to 6.5 wt-% siliconup to max. 0.06 wt-% carbonup to max. 1.5 wt-% manganeseup to max. 0.03 wt-% phosphorusup to max. 0.03 wt-% sulphurup to max. 0.15 wt-% titaniumup to max. 0.8 wt-% zirconiumup to max. 0.2 wt-% nitrogen andup to max. 0.3 wt-% molybdenumand the remainder iron,together with minimal quantities of normally present impurities, including the deoxidizing elements magnesium, aluminum and calcium.

Abstract: In the processing of hot concentrated sulfuric acid or oleum in steel apparatus, the improvement wherein said apparatus is formed of an alloyed material comprising an iron-chrome-nickel-silicon alloy containing 13 to 32% by weight Cr, 5 to 25% by weight nickel and 4 to 9% by weight Si and having a structure containing more than 10% delta-ferrite.

Abstract: In the processing of hot concentrated sulfuric acid or oleum in steel apparatus, the improvement wherein said apparatus is formed of an alloyed material comprising an iron-chrome-nickel-silicon alloy containing 13 to 32% by weight Cr, 5 to 25% by weight nickel and 4 to 9% by weight Si and having a structure containing more than 10% delta-ferrite.