Welding structure of tube stubs and tube header

Abstract

In order to provide a welding structure of a tube header and tube stubs which successfully improves the durability thereof against creep and fatigue damage of the tube stubs without interposing a component of a different material between the tube header and the tube stubs, i.e. requiring additional components, a welding structure of the present invention comprises: a tube header ( 2 ) being made of ferritic heat resisting steel; a plurality of tube stubs ( 4 ) which are welded onto an outer surface of the tube header, each of the tube stubs having a bended section, in which the plurality of tube stubs ( 4 ) are made of austenite stainless steel, and welded to the tube header ( 2 ) by using nickel base alloy as a welding material. Moreover annular chases ( 10 ) are respectively formed on the outer surface of the tube header ( 2 ) to surround welding portions of the tube header ( 2 ); joining portions ( 14 ) are formed on an inner side of the annular chases ( 10 ); butt grooves are formed by joining surfaces of the tube stubs ( 4 ) and the joining portions ( 14 ) in a continuous manner and welded by using the nickel base alloy as a welding material, the tube stubs having a diameter substantially same as those of the joining portions.

1 . A welding structure of a tube header and tube stubs, comprising:
 a tube header being made of ferritic heat resisting steel; and   a plurality of tube stubs which are welded onto an outer surface of the tube header, each of the tube stubs having a bended section,   wherein the plurality of tube stubs are made of austenite stainless steel, and welded to the tube header by using nickel base alloy as a welding material.   
     
     
         2 . The welding structure of the tube heater and the tube stubs according to  claim 1 , wherein:
 annular chases are respectively formed on the outer surface of the tube header to surround welding portions of the tube header onto which the tube stubs are to be welded;   joining portions are formed on an inner side of the annular chases;   butt grooves are formed between the tube stubs and the joining portions by joining surfaces of the tube stubs and the joining portions in a continuous manner, the tube stubs having a diameter that is substantially same as those of the joining portions; and   the butt grooves formed between the tube stubs and the joining portions are welded by using the nickel base alloy as a welding material.   
     
     
         3 . The welding structure of the tube heater and the tube stubs according to  claim 1 , wherein:
 through-holes are formed on the outer surface of the tube header;   ends of the tube stubs are respectively inserted in the through-holes; and   the ends of the tube stubs inserted in the through-holes are welded to an inner surface of the tube header by using the nickel base alloy as a welding material.