溶接用諸鋼材の冷却時間と脆性(第6報)

60および90kg/mm²高張力鋼について

抄録

In former reports the authors described on many mild steels and Mn-Si type high tensile steels, of which tensile strengths are below about 57kg/mm². In the present report, the authors describe on high tensile steels YF and YG which have the tensile strength of about 60 kg/mm² and contain small amounts of Ni, Cr, Ti and V besides Mn and Si, on the heat-treated Mn-Si type steel "2HA" which has been water-quenched and tempered and has tensile sterngth of about 60 kg/mm², and furthermore on a heattreated steel "DT" made on trial, which has the tensile strength of about 90kg/mm² and containing small amounts of various alloying elements and is analogous to the steel T-1 in U.S.A.
(1) On the non-notch bending tests of the steels as received, the steel of which tensile strength is higher, has generally the larger absorbed energy as in the report 5.
(2) On the specimens which have been subjected to thermal cycles of maximum heating temperature 1350°C, the bended angle by impact and slow bending becomes lower in the case of shorter cooling times for all steels used. The absorbed energy by impact bending test at 0°C tends to become higher with the decrease of cooling time for all steels used.
(3) The bad effects of carbon on the non-notch bending test are relaxed by addition of a small amount of suitable alloying elements.
(4) The reduction of area by tensile test began to lower in the case of steel specimen cooled with about C'f cooling time, but the elongation began to lower from the case of a longer cooling time and lowered slowly with the decrease of cooling time to about 8% at the neighbourhood of C'f.