Abstract: A tube for a steam cracking furnace comprising: at least one downstream tubular segment of circular section having a main diameter; at least one twisted tubular segment having a length less than a quarter of the length of the tube, and comprising: a central part with an elliptical or lobed section, having a helical pitch between one times and ten times the main diameter, and an aspect ratio of the elliptical or lobed section between 0.5 and 0.8; an upstream transition part establishing a geometric transition between the central part and a tubular segment of circular section; a downstream transition part establishing a geometric transition between the central part and the downstream tubular segment, with a fluid being intended to flow from the upstream transition part to the downstream transition part.

Abstract: An austenitic alloy based on nickel and having a high chromium content, intended to be used at a given operating temperature between 900° C. and 1150° C., comprises the following elements by mass percentage: chromium between 40% and 45%; iron between 10% and 14%; carbon between 0.4% and 0.6%; titanium between 0.05% and 0.2%; niobium between 0.5% and 1.5%; at least one reactive element, selected from rare earths or hafnium, between 0.002% and 0.1%; silicon between 0% and 1%; manganese between 0% and 0.5%; nickel to balance the alloy elements. In addition, the alloy has a molar fraction of more than 0.1% of secondary carbo-nitrides rich in niobium and/or titanium, after the operating temperature has been applied thereto. The disclosure also relates to a method for designing such an alloy and to a method for validating such an alloy.

Abstract: An austenitic alloy based on nickel, chromium and iron, and having a high aluminum content, intended for use at a given operating temperature (Ts) between 900° C. and 1200° C., the alloy comprising the following elements, in weight percent: chromium between 20% and 32%, nickel between 30% and 60%, aluminum between 3.5% and 6%, carbon between 0.4% and 0.7%, titanium between 0.05% and 0.3%, niobium and/or tantalum between 0.6% and 2%, an element, composed of at least one rare earth and/or hafnium, between 0.002% and 0.1%, silicon between 0 and 0.5%, manganese between 0 and 0.5%, tungsten between 0 and 2%, and iron as the balance of the elements in the alloy. The alloy has less than 1% by volume of an intermetallic B2-NiAl phase and less than 1% by volume of an alpha prime phase rich in chromium, after subjecting the alloy to an operating temperature (Ts).

Abstract: An austenitic alloy based on nickel and having a high chromium content, intended to be used at a given operating temperature between 900° C. and 1150° C., comprises the following elements by mass percentage: chromium between 40% and 45%; iron between 10% and 14%; carbon between 0.4% and 0.6%; titanium between 0.05% and 0.2%; niobium between 0.5% and 1.5%; at least one reactive element, selected from rare earths or hafnium, between 0.002% and 0.1%; silicon between 0% and 1%; manganese between 0% and 0.5%; nickel to balance the alloy elements. In addition, the alloy has a molar fraction of more than 0.1% of secondary carbo-nitrides rich in niobium and/or titanium, after the operating temperature has been applied thereto. The disclosure also relates to a method for designing such an alloy and to a method for validating such an alloy.

Abstract: A tube for a steam cracking furnace comprising: at least one downstream tubular segment of circular section having a main diameter; at least one twisted tubular segment having a length less than a quarter of the length of the tube, and comprising: a central part with an elliptical or lobed section, having a helical pitch between one times and ten times the main diameter, and an aspect ratio of the elliptical or lobed section between 0.5 and 0.8; an upstream transition part establishing a geometric transition between the central part and a tubular segment of circular section; a downstream transition part establishing a geometric transition between the central part and the downstream tubular segment, with a fluid being intended to flow from the upstream transition part to the downstream transition part.

Abstract: An austenitic alloy based on nickel, chromium and iron, and having a high aluminum content, intended for use at a given operating temperature (Ts) between 900° C. and 1200° C., the alloy comprising the following elements, in weight percent: chromium between 20% and 32%, nickel between 30% and 60%, aluminum between 3.5% and 6%, carbon between 0.4% and 0.7%, titanium between 0.05% and 0.3%, niobium and/or tantalum between 0.6% and 2%, an element, composed of at least one rare earth and/or hafnium, between 0.002% and 0.1%, silicon between 0 and 0.5%, manganese between 0 and 0.5%, tungsten between 0 and 2%, and iron as the balance of the elements in the alloy. The alloy has less than 1% by volume of an intermetallic B2-NiAl phase and less than 1% by volume of an alpha prime phase rich in chromium, after subjecting the alloy to an operating temperature (Ts).