Steel processing and conversion Volume 3, no. 7

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 Excerpt: ...and 100 millimetres long between punch marks, for the tensile tests. The elastic limit was determined roughly bv observing the slowing down in the rate of the rise of the mercury column. The Rrinell hardness was ascertained by means of a ball 10 millimetres in diameter at a pressure of 3000 kilogrammes and applied to the surface of the bars used for the shock tests. Roth the shock and tensile test-pieces were quenched, from a temperature of 800 deg., in oil at about 50 deg. They were kept for about half an hour at the tempering temperature, after which they were quenched in cold oil. As an exception the tensile test-piece of steel No. 15 was taken from a forged round of 20 millimetres diameter. It was completely turned down, before testing, to a diameter of 13.8 millimetres. It was cut to 100 millimetres length between punch marks and after machining was quenched from 800 deg. in oil at 150 deg. and tempered for one hour at 200 deg. The tests shown in this table show the properties of steels containing copper to be practically the same, both on quenching and tempering, as those of steels not containing copper. Reclaiming Worn-out Dies and Punches Two Methods Can Be Used--Rehardening, Shrinking and Grinding Necessary in Most Cases--Expanding of Dies Discov-ered in Grinding Recently. By JAMES Observation of the actions of steel under certain conditions coupled with some mistakes and their outcome has helped the writer not only to save a number of punches and dies from a premature place on the scrap pile but to put them in such condition as to give much service than was originally expected of them. In some shops it is common practice when a punching or trimming die gets so far worn that face grinding will no longer keep it in working condition to have it annea...