25CrMnSi and 22SiMn2 Low Alloy Steel

Abstract: 25CrMnSi and 22SiMn2 are two kinds of low alloy wear-resistant steels. In order to study their wear-resistant properties, the wear morphology and microstructure of the two materials were tested and analvzed by sliding wear and impact wear tests. The results show that both the surface and the core of 25CrMnSi are more wear-resistant than 22SiMn2 under the sliding wear condition, but the wear resistance of the core of 25CrMnSi is more different than that of 22SiMn2.Under the condition of impact wear, the wear resistance of 25CrMnSi is relatively poor. Under the two wear conditions, the weight loss of 25CrMnSi is not significantly different, while that of 22SiMn2 under sliding wear conditions is almost 10 times that of impact wear. so 22SiMn2 is more suitable for impact wear conditions.Key words: 25CrMnSi: 22SiMn2; microstructure; wear morphology; friction and wear properties

Bucket teeth are the key components of the loader and are important factors affecting the efficiency of the excavator. Bucket teeth are in direct contact with hard materials such as ore and rock during work and withstand strong impact. The tip of the bucket tooth is subject to relatively strong abrasive wear, and various cutting furrow deformations often appear on its surface, causing the surface to wear or fall off. . Therefore, higher requirements are placed on the wear resistance of bucket tooth materials, and low-alloy high-strength wear-resistant steel with good comprehensive properties is a better choice for such parts. Wear-resistant steel is the most widely used type of steel. In order to reduce the amount of wear during work, domestic and foreign countries are actively developing wear-resistant steels with good performance to reduce the loss caused by wear failure. At present, there are many steel plants in China that can produce low-alloy high-strength wear-resistant steels, such as Baosteel and Anshan Iron and Steel.However, there is still a certain gap between the product’s functional stability and overall quality and foreign products. 25CrMnsi steel and 22SiMn2 steel are produced. The two low-alloy wear-resistant steels commonly used in applications have good wear resistance, but there is still a lack of theoretical guidance for the selection under different working conditions. In this paper, the micromorphology, impact properties, metallographic structure and hardness of 25CrMnSi and 22SiMn2 low alloy wear-resistant steels under sliding wear and impact wear conditions are studied in order to better guide this material under different conditions. s Choice.

1 Test Method

Take 25CrMnsi steel and 22SiMn2 steel as research objects, cut and make sliding wear samples, impact wear samples and metallographic samples, and perform specific tests on them, and analyze the performance of the two steels based on the results. Test 25CrMnsi steel 22SiMn2 steel edge and core sliding wear loss, according to GB / T 12444-2006 (metal material wear test method test ring-test block sliding wear test) related experiments. Adopt M-2000 type wear test machine, the friction matching auxiliary steel ring is bearing steel (GCr15), the speed of the steel ring is 200 r / min, the load is 600 N, and the sand is abraded. , Wear 4h, test 25CrMnSi and 22SiMn2 edges and cores for heavy impact wear loss, using MLD-10 impact wear tester, friction paired steel ring is bearing steel (GCr15), speed 200 r / min, impact energy 2.5J Adding sand to the abrasion condition, the size of the sand particles is 8-12 mesh, and the morphology of the sliding abrasion and impact abrasion samples was observed with an S-3000N scanning electron microscope for 4 hours after impact. The metallographic sample prepared in advance was ground, polished and etched with 4% nitric acid, and the metallographic structure was observed.

2 Test Results and Analysis

2.1 Chemical Composition and The Microstructure

The chemical composition w (%) of 25CrMnSi wear-resistant steel is: Cs0.28, Sis1.20, Mn1.10, S <0.035, P <0.035, Crs1.10, Ni <0.30, Cu <0.30, the balance is Fe, The chemical composition w (%) of 22SiMn2 wear-resistant steel is: Cs0.23 Sis0.81, Mns1.70, S <0.035, P <0.015, Als0.036, Tis0.039, Bs0.002, and the balance is Fe. 1 is the metallographic structure of two wear-resistant steels after quenching and tempering at low temperature. It can be seen from the figure that the microstructures of the two types of wear-resistant steel are slab-shaped martensite, and its spatial configuration is a bundle of narrow and slender strips, which are arranged inward from the austenite grain boundaries into the grain. In clusters, the slat bundles consist of parallel slats with the same habitual surface.

25CrMnSi and 22SiMn2 Low Alloy Steel

2.2 Sliding wear

Figure 2 is a histogram of the arithmetic mean of the weight loss of the edges and cores of the samples before and after sliding wear of the two types of wear-resistant steel. As shown in the figure, under the condition of sliding wear, the wear loss of the surface layer and the core of the 25CrMnsi steel is lower than that of the 22SiMn2 steel, which shows better wear resistance. However, the abrasion resistance of the cores of the two types of wear-resistant steels is much different. Figure 3 is a scanning electron microscope morphology of two types of wear-resistant steels. From Figure 3 (a) and (b), it can be seen that the 25CrMnsi steel has undergone plastic deformation under sliding friction conditions, and furrows and abrasive debris are present on the surface; at the same time, some areas have spalled out, which is abrasive wear and is accompanied by Certain surface fatigue and wear. This is because the sand particles penetrate the surface of the material due to the normal force. When sliding friction occurs, under the action of tangential force, the abrasive particles that penetrate the surface of the material slide laterally and shear and cut the material surface, resulting Scratches or cutting grooves; most of the metal in the grooves undergoes plastic deformation and accumulates at the front and sides of the scratches and cutting grooves, thereby forming furrows. Under cyclic stress, the material surface stress concentration area reaches the material strength limit, and the most cracks appear; after multiple high stress cycles, the plastic deformation intensifies, the cracks continue to expand to the surroundings, and the cracks are intertwined with each other, eventually leading to the material Fatigue spalling occurred in some areas of the surface, causing heavy wear loss of the material.It can be seen from Figures 3 (c) and (d) that the surface of 22SiMn2 steel has several scratches and furrows, and there is a plastic deformation layer. More serious. When sliding friction is performed, the surface of the material is plastically sheared due to the plowing effect of the raised hard points, forming abrasive particles.

2.3 Impact Wear

Figure 4 is a bar graph of the arithmetic mean of the weight loss of the edges and cores of the specimens before and after impact wear on 25CrMnSi steel and 22SiMn2 steel. As shown in the figure, under the impact wear condition, the surface weight loss of 25CrMnsi steel is the largest, followed by the core, and the weight loss of impact grinding is higher than that of 22SiMn2 steel, indicating that the wear resistance of 22SiMn2 steel is better than that of 25CrMnSi steel. It can be seen from Figures 2 and 4 that the weight loss of 25CrMnSi steel during sliding wear and impact wear is not much different, indicating that under two wear conditions, 25CrMnsi steel has almost the same wear resistance; 22SiMn2 steel has sliding wear The weight loss under conditions is almost 10 times that of impact wear, so 22SiMn2 steel is more suitable for use under impact wear. Fig. 5 is a scanning electron micrograph of two types of wear-resistant steels under impact abrasion conditions. It can be seen from the figure that the surface of 25CrMnSi steel and 22SiMn2 steel both have plastic deformation to varying degrees, and chipping pits have appeared, but the cutting pits of 25CrMnsi steel are deeper and have obvious cutting marks, indicating that the wear is more serious.

ecause the surface of both steels is a lath martensite structure, under the condition of high strength and hardness, it still has good plastic toughness, that is, it has good elongation and impact toughness, which can absorb large The impact energy will not appear serious on its surface.

Crack propagation and material spalling, but plastic deformation occurs after absorbing impact energy, resulting in deformation pits of different sizes.7 In the hardness test and tensile test, the average hardness value of 25CrMnSi steel is 49.8 HRC, which is greater than 45.8 of 22SiMn2 steel. The average tensile strength of HRC: 25CrMnSi steel is 9873 MPa, which is less than 1459 MPa of 22SiMn2 steel. When the abrasive particles impact, the 25CrMnsi steel can only absorb the plastic deformation due to its higher hardness and lower plastic toughness. Less impact energy, so more energy left will cause cutting and peeling of the material surface, causing greater impact grinding loss.

3 Conclusions

  • The microstructures of 25CrMnsi steel and 22SiMn2 steel after quenching and tempering at low temperature are both lath martensite.
  • Under the condition of sliding wear, the surface and core of 25CrMnsi steel are more wear-resistant than 22SiMn2 steel; under the condition of impact wear, the wear performance of 25CrMnSi steel is worse than that of 22SiMn2 steel.
  • Under the conditions of sliding wear and impact wear, the wear resistance of 25CrMns steel is similar; the weight loss of 22SiMn2 steel under sliding wear conditions is almost 10 times the impact wear, so 22SiMn2 steel is suitable for use under impact wear.

 

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