ผลของปริมาณการรีดเย็น และอุณหภูมิการอบอ่อนต่อสมบัติเชิงกลของเหล็กกล้าความแข็งแรงสูงธาตุผสมต่ำ / อังคาร พงษ์ไพบูลย์ = Effects of cold reduction and annealing temperature on mechanical properties of the high-strength low-alloy steel / Angkan Pongpaibul
This study investigates effects of %cold reduction and annealing temperature on mechanical properties and microstructure of high-strength low-alloy steel. Specimens were reheated at temperature of 1,150 ํC, roughing rolled at the same temperature, finishing rolled at 860 ํC and coiled between temperatures of 550 ํC and 630 ํC. Mechanical properties were examined by tensile test and microstructure was investigated by optical microscope. Results show that specimens coiled at 550 ํC have better formability than those coiled at 630 ํC. This effect might be due to precipitation of particles during coiling temperature of 630 ํC while precipitation did not take place at coiling temperature of 550 ํC. Pearlite structure in specimens coiled at 550 ํC has smaller sizes and more distribution than those coiled at 630 ํC, as a result, specimens coiled at 550 ํC have lower % recrystallization than those coiled at 630 ํC. This effect causes specimens coiled at 550 ํC have higher yield strength and lower %elongation than those coiled at 630 ํC at annealing temperature of 620 ํC and 640 ํC while increase of annealing temperature between 660 ํC and 680 ํC have no effect on yield strength in specimens coiled at 550 ํC. Furthermore increase of %cold reduction from 50% to 70% and increase of annealing temperature from 620 ํC to 680 ํC results in better formability.