高張力鋼の熔接性に及ぼすニッケルおよびクロムの影響(第1報)

Abstract

Effects of nickel and chromium contents on weldability of high tensile manganese-silicon steels were investigated. Fourteen experimental ingots which contained 0.06 to 0.93% nickel and 0.03 to 0.91% chromium added to a base composition of 0.16% carbon, 1.10% manganess, and 0.45% silicon, were made by melting in an approximately 700kg acid-lined, high frequency furnace and rolled into 20mm plate. Four commercial heats which were made in a 40ton capacity basic open hearth were tested together for comparison.Various weldability tests ; namely, tensile test, V-Charpy impact tests, Weld-maximum hardness test, Jominy test, kommerell test, Kinzel test, Slit-type cracking type, CTS cracking test, Gas cut bend test, and Fillet-weld break test were used.From the results of tensile and V-Carpy test described in the present paper, the following conclusions have been obtained ;1. The tensile strength increased at a rate of approximately 3kg/m2 per 1% increase of nickel both in as rolled and normalized conditions, and 3kg/mm2 in as rolled condition anp 6kg/mm2 in as normalized condition per 1% increase of chromium.2. Nickel increased the yield strength at a rate of approximately 4 to 5kg/mm2 per 1% increase while chromium showed no effect.3. The energy transition temperature in V-Charpy test was lowered by nickel addition, but was raised by chromium. However, distinct relationships were not found between the 15ft-lb transition temperatures and those alloying contents.4. The effect of nickel or chromium content on the tensile and yield strengths was very slight, provided the contents were limited in a range of nickel less than 0.25% and chromium less than 0.10%. However, the 15ft-lb transition temperature seems to be lowered slightly and the tensile elongation to be increased appreciably when the contents of nickel and chromium were reduced extremely, but the energy or shear fracture transition temperature is not affected.