ZG40Cr25Ni20Si2钢合金化组织与性能

发布时间：2018-07-22 15:00

【摘要】：奥氏体耐热钢ZG40Cr25Ni20Si2具有良好的高温力学性能和抗氧化性、耐蚀性及组织稳定性,在汽车排气歧管、涡轮增压器壳体等零部件上的应用日趋广泛。然而铸态合金中粗大的树枝晶使其产生严重的偏析,即使通过热处理也无法消除,导致合金性能下降、使用寿命缩短。本文旨在探索单一元素合金化和双元素合金化对ZG40Cr25Ni20Si2钢微观组织及力学性能的作用规律,揭示合金化处理的强化机制。研究表明:ZG40Cr25Ni20Si2钢中碳化物数量为8.49%。对其进行单一元素合金化处理后,合金中碳化物的量随着合金元素含量的增加而增多。同时,Ti、V、Nb的加入可以改善合金中碳化物的形貌以及其在晶界分布的状态,致使晶间碳化物形态由最初连续的网状分布向细小的断续状分布转化。ZG40Cr25Ni20Si2钢的二次枝晶臂间距及一次枝晶直径分别为13.99μm和174.73μm,其硬度为174HB。当对其进行单一元素合金化处理时,Ti、V、Nb的添加使合金的二次枝晶臂间距及一次枝晶直径均有不同程度的减小,并且合金的硬度也得到了提升。随着合金元素Ti、V、Nb添加量的增加,二次枝晶臂间距及一次枝晶直径先减小后增大,而合金硬度则表现为先增大后减小。当Ti含量为0.15%时,二次枝晶臂间距及一次枝晶直径分别达到最小值11.15μm及93.05μm,合金硬度达到最大值184HB;在V含量为0.05%时,二次枝晶臂间距及一次枝晶直径分别达到最小值10.63μm及75.11μm,合金硬度达到最大的186HB;当Nb含量为0.05%时,二次枝晶臂间距及一次枝晶直径分别达到最小值10.21μm及73.43μm,合金硬度达到最大值198HB。Nb和V在ZG40Cr25Ni20Si2钢中细化枝晶的能力稍强于Ti,Nb对ZG40Cr25Ni20Si2钢的强化作用大于Ti和V。经过双元素合金化处理之后,合金中基体微观组织显著细化,碳化物析出量有所增多,合金硬度升高。当复合添加0.05%Ti和0.05%V时,二次枝晶臂间距及一次枝晶直径分别达到最小值12.07μm及99.36μm,碳化物的量高达14.56%,合金硬度达到195HB;当复合添加0.10%Nb和0.05%V时,合金的二次枝晶臂间距及一次枝晶直径分别达到最小值10.59μm和86.93μm,合金中碳化物的量达到15.09%,合金硬度达到202HB。并且合金中碳化物的形貌及其在晶界的分布状态同样得到了改善。尽管不同组配的双元素合金化处理对合金微观组织的细化作用基本相似,但Nb、V复合合金化对ZG40Cr25Ni20Si2钢的强化效果明显优于Ti、V复合合金化。此外,经单一元素Ti合金化和双元素Ti、V合金化处理的合金,基体中存在弥散分布的第二相颗粒,具有第二相强化作用。
[Abstract]:Austenitic heat-resistant steel ZG40Cr25Ni20Si2 has good high temperature mechanical properties, oxidation resistance, corrosion resistance and microstructure stability. It is widely used in automobile exhaust manifold, turbocharger shell and other parts. However, the coarse dendrites in the as-cast alloy cause serious segregation, which can not be eliminated even by heat treatment, which leads to the deterioration of the properties and the shortening of the service life of the as-cast alloys. The purpose of this paper is to explore the effect of single element alloying and double element alloying on microstructure and mechanical properties of ZG40Cr25Ni20Si2 steel, and to reveal the strengthening mechanism of alloying treatment. The results show that the amount of carbides in the 20% ZG40Cr25Ni20Si2 steel is 8.49. After single element alloying, the amount of carbides in the alloy increases with the increase of alloy element content. At the same time, the addition of TiNb can improve the morphology of carbides and the distribution of carbides at grain boundaries. As a result, the morphology of intergranular carbides changed from the initial continuous network distribution to the fine discontinuous distribution. The secondary dendritic arm spacing and primary dendritic diameter of steel ZG40Cr25Ni20Si2 were 13.99 渭 m and 174.73 渭 m, respectively, and the hardness was 174HB. When the alloy was alloyed with single element, the secondary dendritic arm spacing and the primary dendritic diameter of the alloy were decreased to some extent, and the hardness of the alloy was also improved. With the increase of the content of TiNb, the secondary dendritic arm spacing and primary dendritic diameter decrease first and then increase, while the hardness of the alloy increases first and then decreases. When Ti content is 0.15, the secondary dendritic arm spacing and primary dendritic diameter reach the minimum values of 11.15 渭 m and 93.05 渭 m, respectively. The second dendritic arm spacing and the primary dendritic diameter reached the minimum values of 10.63 渭 m and 75.11 渭 m, respectively, and the hardness of the alloy reached the maximum value of 186HB.The NB content was 0.05 渭 m. The secondary dendritic arm spacing and the primary dendrite diameter reached the minimum values of 10.21 渭 m and 73.43 渭 m, respectively. The alloy hardness reached the maximum value 198HB.Nb and V in ZG40Cr25Ni20Si2 steel, the ability to refine the dendrite in ZG40Cr25Ni20Si2 steel was slightly stronger than that of TiG40Cr25Ni20Si2 steel. After double element alloying, the microstructure of the alloy was refined, the amount of carbide precipitated increased and the hardness of the alloy increased. With the addition of 0.05 Ti and 0.05 V, the secondary dendritic arm spacing and primary dendritic diameter reached the minimum values of 12.07 渭 m and 99.36 渭 m, respectively, the amount of carbides reached 14.56 and the hardness of the alloy reached 195HB.When the composite was added 0.10Nb and 0.05V, The secondary dendritic arm spacing and the primary dendritic diameter of the alloy reach the minimum values of 10.59 渭 m and 86.93 渭 m, respectively. The amount of carbide in the alloy reaches 15.09 and the hardness of the alloy reaches 20HB. The morphology and distribution of carbides in the alloy were also improved. Although the effect of different alloying treatments on microstructure refinement is similar, the strengthening effect of NbAV composite alloying on ZG40Cr25Ni20Si2 steel is better than that of TiG40Cr25Ni20Si2 steel. In addition, after Ti alloying and Ti V alloying, the second phase particles are dispersed in the matrix, which has the effect of strengthening the second phase.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

【参考文献】