不同蠕化率的蠕墨铸铁滚动磨损性能研究

发布时间：2018-05-31 04:58

本文选题：蠕墨铸铁 + 蠕化率　；参考：《江苏大学》2016年硕士论文

【摘要】：重型车辆在国民经济中扮演越来越重要的角色,对其需求量也在不断增大。现代柴油发动机要求高的功率、轻的质量以及轻薄化的体积。蠕墨铸铁具有优良的铸造性能,较高的力学性能,完全能满足复杂、厚度不均的发动机缸体的使用要求。发动机工作过程中各运动副的运动表面产生剧烈的摩擦,其中缸体缸盖磨损形式复杂,属于滚滑复合磨损形式。所以探讨蠕墨铸铁的滚动磨损性能就显得特别有意义。柴油发动机缸体缸盖形状复杂且壁厚不均,导致在铸造过程中冷却速度不一样,得到不同的蠕化率。目前学界对于蠕墨铸铁的滚动磨损性能,特别是蠕化率作为影响因素的研究报道不多,所以把蠕化率作为一个变量来研究蠕墨铸铁的滚动磨损性能具有一定的实际意义。本文研究了不同蠕化率的蠕墨铸铁的组织和力学性能,并研究了在干摩擦和油润滑两种条件下的蠕墨铸铁的滚动磨损性能,得到的主要结论如下:1.随着蠕化率的升高,蠕虫状石墨分布更加均匀。随着蠕化率的增加,蠕墨铸铁的抗拉强度、延伸率及硬度直线下降。蠕60试样抗拉强度为513MPa,延伸率为4%,硬度为272HB;蠕90试样抗拉强度为452MPa,延伸率为1%,硬度为239HB。灰铸铁试样抗拉强度为200MPa,延伸率为0.5%,硬度为220HB;球墨铸铁试样抗拉强度为547MPa,延伸率为4%,硬度为280HB。2.油润滑条件下,随着蠕化率的上升,磨损量呈直线上升趋势,蠕墨铸铁滚动磨损性能明显下降。蠕60试样与蠕90试样在400N载荷下,两者磨损量相差6.6%。二者在高载荷1000N,磨损量相差达到了17.3%。在恶劣工况条件下,蠕化率对蠕墨铸铁滚动磨损性能影响更大。油润滑条件下,蠕墨铸铁试样滚动磨损属于典型的疲劳磨损形式。3.干摩擦条件下,在一定范围内,随着蠕化率的提高,磨损量呈直线上升趋势。蠕60试样与蠕90试样在400N载荷下,两者磨损量相差2.1mg,达到7.2%,二者在高载荷1000N下,磨损量相差反而缩小到1.4mg,约为3.9%。在干摩擦严酷工况下,蠕化率对蠕墨铸铁滚动磨损性能影响降低。在干摩擦条件下,磨损产生的高温促使两摩擦表面发生粘着现象,其磨损机制为粘着磨损。4.随着蠕化率的提高,蠕墨铸铁的硬度和耐磨性能呈明显下降趋势。蠕化率低的蠕墨铸铁试样接近球墨铸铁试样;反之,蠕化率高的蠕墨铸铁试样和灰铸铁试样在硬度和耐磨性表现得更为接近。球墨铸铁试样磨损量最小,为蠕铁试样磨损量77.8%;灰铁的磨损量最大,接近蠕铁试样的2.6倍。三种铸铁亚表层由于在滚动磨损过程中受到挤压,其中灰铁中片状石墨尖端出现微裂纹,延伸到磨损表面;蠕铁、球铁中石墨无变形。灰铁亚表面出现明显变形,片状石墨尖端形成微裂纹向基体内延伸,同时石墨相发生脱落现象,其亚表面顶端磨面上出现磨损后的凹坑。5.蠕墨铸铁中石墨相虽然在磨损过程中有着自润滑的作用,但是因其本身硬度较低在循环接触应力下破碎,成为表面疲劳的裂纹源,反而加剧了蠕铁的磨损。试样表面承受高载循环应力,与大气接触比表面积增加,吸附氧的能力增强,产生氧化磨损。在摩擦过程中生成的大量的热,影响了润滑效果,形成大量的氧化层,加快磨屑的生成,使蠕墨铸铁的耐磨性能下降。
[Abstract]:Heavy vehicles are playing a more and more important role in the national economy, and their demand is increasing. Modern diesel engines require high power, light mass and light volume. Vermicular cast iron has excellent casting properties, high mechanical properties, full full of complex and uneven thickness of engine cylinder. In the process of engine work, the movement surface of the movement pairs of the engine produces violent friction, in which the wear form of the cylinder head is complicated, and it belongs to the form of rolling and sliding composite wear. So it is particularly meaningful to discuss the rolling wear performance of the vermicular cast iron. At present, there are few reports on the rolling wear properties of vermicular cast iron, especially the vermicular rate as an influencing factor, so it is of certain practical significance to study the rolling wear properties of vermicular graphite cast iron as a variable. The microstructure and mechanical properties of cast iron and the rolling wear properties of vermicular graphite cast iron under two conditions of dry friction and oil lubrication are studied. The main conclusions are as follows: 1. with the increase of vermicular rate, the distribution of vermicular graphite is more uniform. With the increase of creep rate, the tensile strength, elongation and hardness of vermicular graphite cast iron decrease linearly. Creep 60 The tensile strength of the specimen is 513MPa, the elongation is 4%, the hardness is 272HB, the tensile strength of the 90 specimen is 452MPa, the elongation is 1%, the tensile strength of the hardness is 200MPa, the elongation is 0.5%, the hardness is 220HB, the tensile strength of the spheroidal graphite cast iron is 547MPa, the elongation is 4%, the hardness is 280HB.2. oil lubrication condition, with vermicular rate under the 280HB.2. oil lubrication condition. The wear amount is rising in a straight line, and the rolling wear performance of vermicular graphite cast iron is obviously decreased. Under the load of 400N and 90 specimens, the difference between the 60 specimens and the wriggling specimens is 6.6%. two at high load 1000N, the difference of the wear amount is up to 17.3%. in the bad condition, and the creep rate has a greater influence on the rolling wear properties of the vermicular cast iron. The rolling wear of vermicular graphite cast iron specimen is a typical fatigue wear form.3. dry friction condition. In a certain range, with the increase of creep rate, the wear amount is rising in a straight line. Under the load of 400N, the difference between the 60 specimens and the creep 90 specimens is 2.1mg, up to 7.2%, and the difference of the wear amount is narrowed down under the high load 1000N. To 1.4mg, the effect of creep rate on the rolling wear properties of vermicular graphite cast iron is reduced under the dry friction condition of 3.9%.. Under dry friction, the high temperature caused by wear leads to the adhesion of two friction surfaces. The wear mechanism is that the hardness and wear resistance of the vermicular cast iron are obviously decreased with the increase of the creep rate of the adhesive wear.4.. The vermicular graphite cast iron specimen with low creep rate is close to the spheroidal graphite cast iron sample; conversely, the vermicular graphite cast iron specimen and gray cast iron specimen with high vermicular rate are closer to the hardness and wear resistance. The wear quantity of the ductile iron specimen is the least, the wear quantity of the vermicular iron specimen is 77.8%, the gray iron wear is the largest, close to the 2.6 times of the vermicular iron sample. Three kinds of cast iron submeters. As the layer is squeezed during the rolling wear process, there is a micro crack in the tip of flake graphite in the gray iron, which extends to the worn surface, and the graphite iron has no deformation in the ductile iron. The subsurface of the gray iron appears to be deformed, and the tip of the flake graphite forms a micro crack to the inside of the matrix. At the same time, Shi Moxiang falls off, and the top surface of the subsurface is out of the surface. In the.5. vermicular cast iron after wear, although Shi Moxiang has the function of self lubrication in the process of wear, it is broken under the cyclic contact stress because of its low hardness. It becomes the source of surface fatigue crack. Instead, it aggravates the wear of the vermicular iron. The surface of the specimen is subjected to high load cycle stress, and the surface area of the atmosphere increases. The capacity of oxygen increases and produces oxidation wear. A large amount of heat generated in the process of friction affects the lubrication effect, forms a large number of oxidation layers, speeds up the formation of the debris, and reduces the wear resistance of the vermicular cast iron.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG250

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