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本文研究了铁素体可锻铸铁件的热锻造。这种铸件可以在1050℃与700℃之间,在压缩系数(RF)高达1.5和镦粗比(UR)高达2的条件下,进行锻造而无裂纹。碳从石墨高温扩散到基体,由于基体组织的改变,显著地增加了强度(布氏硬度值自126提高到340,抗拉强度极限自35kgf/mm~2提高到75kgf/mm~2)。在1080℃和更高的温度时,材料出现过烧现象。锻件的强度随RF和UR而改变,而且随锻造温度而改善,在840℃与1040℃制造的锻件,其强度随着RF(直至1.5)和UR(直至2或1.5)的增加而增加,这是因为锻件的厚度减少了,而珠光体——铁素体的比率提高了。在840℃制造的锻件,如果RF大于1.5,或者UR大于2,其强度则随着延展性和抗冲击性的增加而降低,这是由于随着石墨间距减少有少量的碳固溶在奥氏体中,促使形成较多的铁素体的缘故;而在1040℃制造的锻件,由于基体内的铁素体数量大体上不变,所以其强度也不变。按作者建立的经验公式计算的变形,无规律地发生在锻件的整个体积内。热拔锻时引起斜断裂的裂纹,萌生于石墨与基体的交界面处存在的V型缺口,而沿着石墨团间的窄桥穿晶扩展。退火可以降低强度而改善延展性和抗冲击性能。
This article studies the hot forging of ferritic malleable iron parts. The castings can be forged from 1050 ° C to 700 ° C with a compression factor (RF) of up to 1.5 and upset ratio (UR) of up to 2 without cracking. Carbon diffuses from the graphite to the matrix at high temperatures and significantly increases its strength (Brinell value increases from 126 to 340 due to matrix modification), increasing the tensile strength from 35 kgf / mm ~ 2 to 75 kgf / mm ~ 2. At 1080 ° C and higher, the material experienced over-burning. The strength of the forgings varies with RF and UR but also with the forging temperature, the strength of forgings made at 840 ° C and 1040 ° C increases with RF (up to 1.5) and UR (up to 2 or 1.5), which increases This is because the thickness of the forgings is reduced and the pearlite-ferrite ratio is increased. Forgings made at 840 ° C have a strength that decreases with increasing ductility and impact resistance if RF is greater than 1.5 or UR is greater than 2 due to the small amount of carbon dissolved in austenite as the graphite pitch decreases Body, prompting the formation of more ferrite; and forging manufactured at 1040 ℃, the amount of ferrite in the base body substantially unchanged, so its strength is not changed. The deformation calculated according to the empirical formula established by the author occurs irregularly throughout the volume of the forging. Cracks that cause oblique fracture at hot drawing are initiated at the V-notch at the interface between the graphite and the matrix, and propagate along narrow bridges between the graphite clusters. Annealing can reduce the strength and improve ductility and impact resistance.