摘要40CrNiMo是常用的一类优质调质钢材料，制作爬升齿轮时，因锻压力分布不均匀，锻后组织常以不均匀的形态分布，导致锻件质量不能达标，影响整体锻件质量。

课题通过工艺试验和冲击、拉伸性能测试、组织观察，讨论了40CrNiMo钢锻造后的组织均匀性对产品质量和力学性能的影响，得出以下结论。

（1）锻件中由于偏析组织的存在，导致锻件抗拉强度、屈服强度较低，特别是冲击韧性的下降。

（2）锻后热处理调质完后有回火索氏体组织存在于黑色偏析带中，且表层组织晶粒细小均匀，芯部组织晶粒粗细不均，出现混晶现象。

（3）锻件表层的应力、应变场相对芯部与小圆中部更加复杂，硬度值也最高。67691

（4）制定更好的工艺使得锻件组织更加均匀细小是保证大型锻件锻造质量的主要研究方向。

毕业论文关键词  40CrNiMo钢爬升齿轮；锻件组织；晶粒细化；组织均匀

毕业设计说明书（论文）外文摘要

study on the uniformity of the organization of large forgings

Abstract

40CrNiMo is a kind of high quality quenched and tempered steel materials.When used to make climbing gears,because of the uneven distribution of forging force,the organization often unevenly distributed,leading forging quality not up to standard,affecting the overall quality of forging pieces.

In this paper,through the forging process,impact test,tensile test and the organization observed on the test specimen,discussed the influence of organizational uniformity of 40CrNiMo steel after forging on the quality and mechanical properties of the product,draws the follwing conclusion.

(1) Due to the present of segregation in the forging,the tensile strength,yield strength of test specismen was so low,especially the impact toughness was serious down.

(2) Afer quenching and tempering heat treatment ,tempering sorbite in the black segregation band was existed,and the microstructure of the surface on climbing gear was fine,while the core part was uneven,even appear mixed crystal. 

(3) The stress yield and strain yield of forging surface was more complex than the core one cut from the large circle or from the small circle of the climbing gear .

(4) Developing a better process that  make the forging organization more uniform and grain more refinement is the main research direction to improve the quality of large forgings.

Keywords :40CrNiMo steel climbing gear; Forging Organization；Grain refinement; Uniformity of the organization

目 录

1  绪论 1

1.1 大型锻件的锻造工艺及特点 2

1.1.1  锻造的一般生产过程介绍 2

1.1.2 大型锻件的锻压成型对金属组织的影响 3

1.2  影响锻件组织不均匀性的几个主要问题 4

1.2.1  晶粒度对锻件组织质量的影响 4

1.2.2  组织分布均匀性对锻件组织质量的影响 5

1.3  国内外大型锻件金相组织均匀性的研究现状 6

1.4  本文研究的意义和主要研究内容 7

2  实验材料与研究方法 7

2.1  实验材料