高应力作用下高速钢能量吸收效应及组织演变

发布时间：2018-08-28 07:20

【摘要】：轧辊是钢材生产过程中主要的消耗部件,轧辊的好坏决定了轧钢企业的经济效益,为提高轧辊的使用寿命,轧辊材料不断革新,含有大量高硬度高耐磨性碳化物的高速钢已成为轧辊材料的发展趋势。高速钢轧辊在轧制过程中直接与轧件相接触迫使轧件产生塑性变形,因此受到轧件很高的轧制应力作用,在高应力作用下高速钢不断的吸收、释放能量,必然对高速钢的组织及性能造成一定影响。本文通过砂型铸造的方法制备了三种用于冷轧过程中轧辊材料用的高速钢,通过静载荷压缩实验、微纳米压痕实验研究了高应力作用下高速钢宏观能量吸收行为及高速钢中不同碳化物与基体组织的能量吸收行为。利用XRD、SEM、TEM分析高应力作用下能量吸收后对高速钢组织的影响。研究成果如下:V10、W10、Mo10三种高速钢热处理后均为碳化物+马氏体+残余奥氏体的组织;V10高速钢中碳化物为球状MC型,W10高速钢碳化物为鱼骨状M6C型,Mo10高速钢碳化物为板条状M2C型;高速钢基体上弥散分布着大量二次析出碳化物。高速钢中的碳化物作为强化相,它的种类、形状、尺寸大小、结构及在基体中的位置分布等因素都影响到材料的性能。V10高速钢中MC碳化物为球状,增大了碳化物与基体的接触面积,结合程度好,并且MC碳化物粒径比其它碳化物更小,分布更均匀。V10、W10、Mo10高速钢及对比试样Cr20在1000 MPa应力作用下吸收的能量值都随着应力的增大沿二次方关系曲线形式增加;随压缩次数的增加,各种材料吸收的能量减少,当材料不再能够吸收更多能量而外在应力继续施加,则会产生变形、萌生裂纹或发生断裂等失效。实际工况要求轧辊受到周期性的高应力作用,W10高速钢吸收的能量值最高,V10高速钢与Mo10高速钢次之,均高于Cr20吸收的能量,故三种高速钢能够承受更多次的循环应力,具有更长的使用寿命。与W10、Mo10高速钢及Cr20相比,V10高速钢中MC型碳化物与基体在能量吸收方面具有良好的匹配性,分析认为MC型碳化物硬度高,载荷卸载后弹性恢复大,具有良好的能量耗散能力,而基体吸收能量后诱发了马氏体相变,基体吸收的能量被马氏体相变过程消耗掉,V10高速钢碳化物与基体能量吸收能力相差不大,高应力作用下V10高速钢吸收的能量被MC碳化物和基体吸收、耗散,能够有效的延缓裂纹的萌生。纳米蠕变性能检测表明:V10高速钢蠕变位移最小,V10、W10、Mo10高速钢及Cr20中碳化物的蠕变应变率敏感指数依次为0.01296、0.01549、0.01556、0.01937,即V10、W10、Mo10高速钢中碳化物的蠕变应变率敏感指数均小于Cr20,V10高速钢中碳化物蠕变应变率敏感指数最小,应力作用下不易变形,更有利于在高应力作用下长时间使用。高应力作用下高速钢吸收能量,诱发V10、W10、Mo10高速钢中马氏体相变,残余奥氏体向马氏体转变过程中吸收大量能量,对裂纹的萌生及扩展均有一定抑制作用;高速钢中碳化物对阻碍裂纹的扩展具有良好的作用。
[Abstract]:Roller is the main consuming part in the process of steel production. The quality of roll determines the economic benefit of steel rolling enterprises. In order to improve the service life of roll, the material of roll is innovated constantly. High speed steel containing a large number of high hardness and high wear resistance carbides has become the development trend of roll materials. High speed steel rolls are directly related to the rolls in the rolling process. Phase contact forces the rolled piece to produce plastic deformation, so the high-speed steel is subjected to high rolling stress. Under high stress, the high-speed steel continuously absorbs and releases energy, which will inevitably affect the microstructure and properties of the high-speed steel. The macroscopic energy absorption behavior of high-speed steel under high stress and the energy absorption behavior of different carbides and matrix structures in high-speed steel were studied by static compression test and micro-nanoindentation test. The effects of energy absorption on Microstructure of high-speed steel under high stress were analyzed by XRD, SEM and TEM. After heat treatment, the microstructure of HSS is carbide + martensite + retained austenite; the carbide of V10 HSS is spherical MC type, the carbide of W10 HSS is fishbone M6C type, and the carbide of Mo10 HSS is lath M2C type; the matrix of HSS is dispersed with a large number of secondary precipitated carbides. Variety, shape, size, structure and position distribution of the matrix affect the properties of the material. The MC carbide in V10 high speed steel is spherical, which enlarges the contact area between the carbide and the matrix. The bonding degree is good, and the particle size of MC carbide is smaller and more uniform than other carbides. The energy absorbed by various materials decreases with the increase of compression times. When the material can no longer absorb more energy and the external stress continues to exert, it will cause deformation, crack initiation or fracture. It is required that the roll is subjected to periodic high stress, and the energy absorbed by W10 high speed steel is the highest, followed by V10 high speed steel and Mo10 high speed steel, which are higher than that absorbed by Cr20. Therefore, the three high speed steels can withstand more cyclic stresses and have longer service life. The results show that MC carbide has high hardness and elastic recovery after unloading, and has good energy dissipation ability. The matrix absorbs energy and induces martensitic transformation. The energy absorbed by the matrix is consumed by the martensitic transformation process, and the energy absorbed by the carbide and the matrix of V10 high speed steel is consumed by the martensitic transformation process. The results of nano-creep tests show that the creep displacement of V10 high speed steel is the smallest, and the creep strain rate sensitivity index of carbide in V10, W10, Mo10 high speed steel and Cr20 is 0.01296, 0.01549, 0.01556 respectively. The creep strain rate sensitive index of carbide in V10, W10 and Mo10 high speed steel is lower than that of Cr20. The carbide creep strain rate sensitive index in V10 high speed steel is the smallest, and it is not easy to deform under stress, which is more conducive to long-term use under high stress. During the transformation of retained austenite to martensite, a large amount of energy is absorbed, which inhibits the initiation and propagation of cracks to some extent.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1;TG333.17

【共引文献】