256 



HANDBOOK OF MECHANICAL DESIGN 



WELDING S.A.E. 4340 STEEL 



By welding, quenching, and tempering after gas welding, S.A.E. 4340 tubes can 

 be butt-welded to give a tensile strength of more than 180,000 lb. per sq. in. with a 

 Rockwell hardness of C 46. It is considered that a minimum tensile strength of 

 125,000 lb. per sq. in. can be safely specified for parts made by gas welding S.A.E. 

 4340 steel tubes and normahzing. 



As shown in the accompanying table, butt-welded specimens of S.A.E. 4340 

 tubes can be heat-treated to develop a maximum tensile strength of 217,000 lb. per 

 sq. in. as compared with a maximum tensUe strength of 252,800 lb. per sq. in. for the 

 unwelded tube. The gas-welding characteristics of this material are equal to or bet- 

 ter than those of S.A.E. 4130 steel tubes. 



RESULTS OF TENSION TESTS, 

 BUTT-WELDED 4340 STEEL TUBES 



2H in. O.D. X 0.12.5-in. wall 



Specimen 

 No. 



Tensile strength, 

 lb. per sq. m. 



Rockwell 



hardness, 



(base metal) 



As Welded 



Welded and Normalized 



9 

 10 

 11 

 12 



Average . 



135,000 

 125,700 

 130,800 

 133,900 

 134,800 

 137,500 



132,900 



40.5 

 36.5 

 42.5 

 38.0 

 43.5 

 38.5 



C 40.0 



Notes: Longitudinal bead welded on specimens 7 and 8. 

 All specimens broke in the weld. 



RESULTS OF TENSION TESTS, 

 BUTT-WELDED 4340 STEEL TUBES 



13^ in. O.D. X 0.65-in. wall 



Note: All specimens except 19 

 adjacent to the weld. 



and 20 broke in or 



