MANUFACTURE OF INVAR STEEL PIPE FITTING

摘要

PROBLEM TO BE SOLVED: To manufacture a pipe fitting for transporting LNG and the like in which the formation of coarse grains by recrystallization and the like does not appear and the lowering of strength is not generated by machining and forming Fe-Ni base low thermal expansion steel containing a specific amount of Ni in the range of the specific temperature. SOLUTION: An invar pipe fitting is manufactured by machining and forming the invar steel which is Fe-36%Ni base low thermal expansion steel at 400-600 deg.C. From a tensile test at high temp. which is executed for the invar steel, a value lower than 20% is obtained at 600-950 deg.C in uniform elongation which is an index of hot workability and about 20% is obtained at 900-1000 deg.C. High uniform elongation of about 30% is attained at 400-600 deg.C on the lower-temp. side and it shows the high temp. tensile property which is peculiar to the invar steel. A material 10 is formed by pushing out a ball 12 while pressing the ball 12 to the material 10 placed on a side 13 with a pressing jig 11.