Patent GB-614732-A (GB)
Title: Improvements in or relating to welded components of corrosion resistant alloy steel
IPC: B23K9/00
Filed: 1946-07-23
Abstract: Corrosion resistant alloy steel parts for use with corrosive fluid at temperatures within the steel embrittlement range, (600 DEG F. to 1000 DEG F.), are welded together by depositing by fusion welding at the bottom of the welding groove corrosion resistant steel which, on quick cooling from a temperature above a given temperature higher than the higher temperature of the embrittlement range, retains its corrosion resistant property while having suitable values of hardness and ductility, and completing the weld by depositing another steel thereon which can operate within the temperature range without embrittlement and when subjected to heat treatment involving rapid cooling from a temperature at least as high as the aforesaid given temperature possesses a low value of hardness and high value of ductility, and subjecting the weld to such heat treatment.  The parts and the first weld metal may contain steel with 27 to 30 per cent of chromium and the second weld metal contains steel with 5 to 10 per cent of chromium, and the heat treatment may involve a rapid cooling from a temperature higher than 1250 DEG F. but not above 1375 DEG F., so that the second weld metal is not hardened during cooling.  The header and tube may be formed of chromium iron containing 0.2 per cent of carbon, 1.5 per cent of manganese, 0.025 per cent each of sulphur and phosphorus, 0.75 per cent of silicon, 1.02 per cent of nickel, 26 to 30 per cent of chromium, 0.12 to 0.25 per cent of nitrogen and the remainder iron.  The weld rod for forming the root beads may consist of 0.1 to 0.15 per cent of carbon, 0.6 to 0.7 per cent of manganese, 0.4 to 0.6 per cent of silicon, 28 to 30 per cent of chromium, 3.5 to 4.5 per cent of nickel, 0.15 to 0.17 per cent of nitrogen and the rest iron.  It may be coated with flux containing 20 to 35 per cent of SiO2, 2 to 8 per cent of Fe2O3.  0 to 6 per cent of Al2O3, 3 to 10 per cent of Mn3O4, 25 to 50 per cent of CaO, 0 to 5 per cent of MgO, 5 to 25 per cent of F, 11 to 22 per cent of CO2, 2 to 6 per cent of Na2O, and about 0.3 per cent of Cr2O3, the CaO being preferably in excess of 30 per cent.  The outer weld deposit is effected by a weld rod having a composition comprising up to 0.1 per cent of carbon, 0.4 to 0.6 per cent each of manganese, silicon and molybdenum, 5 to 10 per cent of Cr, up to 0.025 per cent each of sulphur and phosphorus, and the remainder iron and provided with a coating comprising 20 to 35 per cent of SiO2, 2 to 8 per cent Fe3O2 0.6 per cent of Al2O3, 3 to 10 per cent of Mn3O4, 25 to 50 per cent of CaO, 0 to 5 per cent of MgO, 5 to 25 per cent of F, 11 to 22 percent of CO2, 2 to 6 per cent of Na2O, and up to 30 per cent of TiO2, the CaO and TiO2 being preferably in excess of 30 and 3 per cent respectively.  The air hardening of the metal of the root beads is stated to be alleviated by the lime titanium flux on the second rod.  The metal of the header and tube and the beads is stated to be subject to embrittlement when cooled slowly through or held at temperatures of about 600 DEG F. to 1000 DEG F. and the outer weld heated to 1375 DEG F. and water quenched or otherwise rapidly cooled is stated to be softened and to impart to the embrittled root beads and the metal of the header and tube a relatively high degree of toughness and ductility.