Abstract: In the thermal cracking of or heating of hydrocarbons, for example naphtha, a carbonization reaction incidentally takes place due to the fact that Ni, Fe and Co contained in, for example, the conduits of the thermal cracking apparatus have a catalytically carbonizing action. The aim of the present invention is to effectively suppress carbon deposition promoted by these elements, to provide for the incorporation of an inhibitor element, e.g. Li, Na, Ba, Be, Ca, Mg or their oxides, into the heat-resistant alloy, and to form on the surface of this alloy a carbon deposition suppressing layer which comprises an inhibitor element.

Abstract: In the thermal cracking of or heating of hydrocarbons, for example naphtha, a carbonization reaction incidentally takes place due to the fact that Ni, Fe and Co contained in, for example, the conduits of the thermal cracking apparatus have a catalytically carbonizing action. The aim of the present invention is to effectively suppress carbon deposition promoted by these elements, to provide for the incorporation of an inhibitor element, e.g. Li, Na, Ba, Be, Ca, Mg or their oxides, into the heat-resistant alloy, and to form on the surface of this alloy a carbon deposition suppressing layer which comprises an inhibitor element.

Abstract: One of the difficulties in developing a metallic material which is corrosion resistant to caustic alkaline solutions is that the corrosiveness of these solutions is different depending upon the process for producing the same. The chromium alloyed steel developed according to the present invention, contains, from 29 to 31%, of Cr; not more than 3% of Mo; not more than 0.005% of C; at least one element selected from the group of Nb and Ta in an amount, which follows the equation20.times.C(%).ltoreq.Nb(%)+0.5.times.Ta(%).ltoreq.60.times.C(%);from 0.0005 to 0.02% of Ca and; not more than 0.02% of deoxidation products being present in said chromium alloyed steel and essentially composed of CaO, SiO.sub.2 and Al.sub.2 O.sub.3.Because of the combination of the reduction of C, N and the impurities of the steel with the addition of Nb and/or Ta, the corrosion resistance of the chromium steel is excellent with regard to the caustic alkaline solution produced by every kind of processes.