JP2017128795A5

JP2017128795A5 -

Info

Publication number: JP2017128795A5
Application number: JP2016219905A
Authority: JP
Filing date: 2016-11-10
Publication date: 2019-11-07

Description

［評価方法］
表１及び表３に示す組成を有し、所定の平均ラス幅（表１及び表３に示す平均ラス幅）を有するＮｏ．１〜Ｎｏ．１５、Ｎｏ．３５〜Ｎｏ．４２及びＮｏ．５１〜Ｎｏ．６７の４５０ｍｍ厚の板状の鍛鋼について後述する評価を行った。平均ラス幅は、鍛鋼のｔ／４位置（ｔ：板厚）から採取したサンプルを用いて、倍率：１，０００倍にて走査型顕微鏡（ＳＥＭ）観察を行い、３視野の平均値をその鋼種の平均ラス幅とした。また、Ｎｏ．５１〜Ｎｏ．５８の鍛鋼については、表４に示す冷却温度でサブゼロ処理を実施し、平均ブロック幅を決定した。平均ブロック幅は、鍛鋼のｔ／４位置（ｔ：板厚）から採取したサンプルを用いて、倍率：４００倍にてＥＢＳＤ測定を行い、得られた結晶方位マップ上でラス断面の長手方向と垂直に線を引き、１５°以上の方位差を持つ境界との交点の数を数え、その平均切片長さを平均ブロック幅とした。なお、表３の平均ブロック幅に記した×は、鍛鋼に割れが発生して平均ブロック幅を決定できなかったことを示す。 [Evaluation methods]
No. 1 having the composition shown in Tables 1 and 3 and having a predetermined average lath width (average lath width shown in Tables 1 and 3). 1-No. 15, no. 35-No. 42 and no. 51-No. 67, a plate-like forged steel having a thickness of 450 mm, was evaluated later. The average lath width was measured with a scanning microscope (SEM) at a magnification of 1,000 times using a sample taken from the t / 4 position (t: plate thickness) of the forged steel. The average lath width of the steel type was used. No. 51-No. For 58 forged steels, subzero treatment was performed at the cooling temperatures shown in Table 4 to determine the average block width. The average block width was determined by performing EBSD measurement at a magnification of 400 times using a sample taken from a t / 4 position (t: plate thickness) of forged steel, and the longitudinal direction of the lath cross section on the obtained crystal orientation map. A line was drawn vertically, the number of intersections with a boundary having an orientation difference of 15 ° or more was counted, and the average intercept length was defined as the average block width. In addition, x described in the average block width of Table 3 indicates that cracking occurred in the forged steel and the average block width could not be determined.

一方、Ｎｏ．３５〜Ｎｏ．４２の比較例の鍛造用鋼は、平均冷却速度を１℃／ｍｉｎとした鍛造用鋼の引張強さ、平均冷却速度を１０℃／ｍｉｎとした鍛造用鋼の引張強さ、耐久性、靭性及びガス切断性の少なくとも一つが良好でないことが確認された。以下、各比較例について検討する。
On the other hand, no. 35-No. The forging steel of 42 comparative examples has the tensile strength of forging steel with an average cooling rate of 1 ° C./min, the tensile strength, durability, and toughness of the forging steel with an average cooling rate of 10 ° C./min. It was also confirmed that at least one of the gas cutting properties was not good. Hereinafter, each comparative example will be examined.