160 



REPORTS ON THE STATE OP SCIENCE. — 1915. 



The material, which is from a single melting, shows the influence 

 of the subsequent roHing as may be observed from some prehminary 

 tensile tests furnished by Mr. Cook, Table I. 



Tensile Tests oj B.A. Mild Steel as received from the makers. 



Table I. 



Professor Dalby has also investigated the properties of a specimen 

 of this steel, cut from a rod liV in. diameter, with an appai'atus^ in 

 which the load and extension are recorded automatically upon a photo- 

 graphic plate. The diagram so obtained is shown in fig. 1, together 

 with the numerical results of the test. 



Table of Data. 



Original diameter of specimen . . 0-564 in. Area = 0-25 sq. in. 

 Diameter at fracture .... 0-324 in. Area=0-0825 „ 



Stress at yield point =18 tons per sq. in. 



Ultimate stress reckoned on original section . . =248 ,, 



Actual stress of fracture =53-8 ,, 



Percentage reduction of area =67-4 



Distance between gauge points =5-00 in. 



Extension on length of 5 in =1-53 in. 



Elongation on length of 5 in =30-6 per cent. 



Corresponding elongation for a standaid length of 



10 diameters = 5-64 in =29-7 per cent. 



Young's Modulus (E) in pound and inch units. . =30-3x10'^ 



Photomicrographs made by Professor Dalby and Dr. B. P. Haigh 

 show that the structure is of a usual type for steel of this composition. 

 The experiments prove that the influence of rolling is considei'able and 

 that comparable results cannot be obtained without annealing by some 

 standard method which will bring the material to a uniform molecular 

 structure for all sizes of bars. 



It has been suggested that the bars should be heated at a tempera- 

 ture of 900° C, and cooled in the air. Mr. W. A. Scoble has made an 

 investigation of one of the sizes of bars after heating to 900° C. in an 

 electric furnace, and allowing them to cool in position. An account 

 of his results is given in Appendix A. 



An investigation of the effects of alternating stress has also been 

 made by Dr. B. P. Haigh and is described in Appendix B. 



> An optical load-extension indicator, together with some diagrams obtained 

 therewith. Proc. B. S. 1912. Lead-extension diagrams taken with the optical 

 load-extension indicator. Proc. B. S. 1913. 



