CN100439743C - Brake drum with biomimetic non-smooth surface - Google Patents

Abstract

The invention relates to a brake drum with high friction coefficient, wear resistance and heat fatigue resistance for vehicles, especially a brake drum with bionic non-smooth surface. It is characterized in that the working surface of the brake drum is distributed with convex and concave units with a height difference of 0.15-0.5mm from the surface of the base body. The convex and concave units are pits or convex hulls, parallel or grid-like stripes, convex and concave , The concave unit body contains alloy elements Cr, Si, Mn, Mo, W, V, B, which are higher than the corresponding element content in the matrix, and the content difference is: Cr0.5-1%, Mn0.5-5%, Si0.1-1%, Mo0.5-5%, W0.5-5%, V0.5-10%, B0.01-0.1%. Its organizational structure and chemical composition can ensure that the wear resistance and thermal fatigue resistance of the brake drum are significantly improved. At the same time, the surface contact between the brake drum surface and the friction lining is changed from point or line contact, which reduces the bonding force of the friction pair, thereby reducing the wear of the brake drum, and the service life is compared with the smooth surface brake drum of the same base material. , increased by 1.5-3 times, and the friction coefficient increased by 1 time.

Description

Brake drum with biomimetic non-smooth surface

technical field

The invention relates to a high friction coefficient, wear-resistant, thermal fatigue-resistant brake drum for vehicles.

Background technique

The device that uses the frictional resistance generated when the moving surfaces are in contact to slow down or stop the movement is called a friction brake or a mechanical brake. The chemical composition and structure of the brake drum in the process of brake friction is one of the important factors that affect the characteristics of the friction pair and the reliability of the work. Taking the automobile brake drum as an example, the brake drum is required to have good friction performance and be less affected by the environment, including low temperature (<0°C), high temperature (500-600°C), humidity (road area water), or high or low Braking initial speed, braking deceleration, occasional multiple consecutive braking, etc. These characteristics of automobile brake drums have a lot to do with the friction layer on the interface during braking. It is generally believed that the way to effectively reduce wear and improve friction coefficient is to design a brake drum whose surface should have high friction coefficient, wear resistance and thermal fatigue resistance.

From the perspective of improving safety and reliability, it is hoped that the friction coefficient of the brake drum can be improved, especially at high temperatures, it can still maintain a high friction coefficient, that is, there is sufficient braking friction torque. But generally speaking, the higher the coefficient of friction, the greater the shear resistance generated by friction, and the greater the shear stress on the surface, so the loss or damage of the friction surface material will be more serious, the greater the wear and the shorter the service life. shorter. Therefore, friction and wear are two aspects that are related and contradictory in the friction process. For the brake material, it is necessary to have a certain friction resistance without causing excessive wear. At home and abroad, improving the thermal fatigue performance of brake drums, increasing the friction coefficient of materials and increasing the life of brake drums have always been one of the most concerned topics for brake researchers. In recent years, with the increase of people's demand for brake drums, some beneficial explorations have been made in improving the single performance of brake drums, such as adding alloy elements, increasing the volume of pearlite, improving materials, etc., but the cost is correspondingly higher than before. Improvement, so far there is no way to improve these properties at the same time.

Contents of the invention

The purpose of the present invention is to solve the contradiction between improving the friction coefficient of the brake drum surface and reducing the wear of the brake pair. Through the bionic non-smooth surface modification treatment, a device that can simultaneously improve the friction coefficient, wear resistance and anti-wear of the brake drum surface is designed. Brake drums with biomimetic non-smooth surfaces for properties such as thermal fatigue.

Biomimicry is potentially the most effective route for the design and manufacture of new materials in the future. The structure of organisms has been optimized by natural selection for 2 billion years, and it is almost perfect. Through the study of the non-smooth shape theory of the biological surface, it leads to the formation of the design idea of the new brake material of the bionic non-smooth surface.

Non-smooth form is a new bionic idea proposed through the study of the structure, static and dynamic properties of biological materials. Through the study of some organisms such as dung beetles, marine shellfish, pangolins, snakes, lizards, bamboo, etc., it is found that the functions of the surface of organisms such as wear resistance, extrusion resistance, and crack resistance are related to the non-smooth shape of the body surface. Close relationship, this is the evolution and optimization of organisms for hundreds of millions of years, and gradually forms the characteristics that adapt to the living environment.

In the research on soil animals, it is found that soil animals go in and out of viscous feces and soil, withstand wear and tear, can move freely, and their bodies seldom adhere to feces and soil. Under the condition, the body surface can absorb energy and undergo elastic deformation. The concave part is easy to collect and retain air, which can reduce the negative pressure of the atmosphere, thereby reducing the adhesion between the body surface and feces and soil, and has the effect of reducing adhesion and desorption. The raised part is relatively hard, and contains not only the elements in the matrix, but also some other elements, and its function is mainly to withstand the extrusion and friction of feces and soil, and to resist wear and tear. It is this structure imitating the surface of soil animals that can significantly reduce the adhesion between the brake drum and the friction lining, improve the wear resistance of the brake drum surface, and reduce adhesive wear and abrasive wear.

Another example is the surface of conch, which is composed of many uneven layers with different directions. The layer orientation and unevenness are closely related to the hardness and toughness distribution of the shell surface. Studies have shown that this cross-ply structure has obvious advantages in preventing crack development. Another example is the insect skin, which is also a non-smooth structure under the microscope, and the softness and hardness of different positions on the body surface are different, which produces different stress distributions on the insect skin. This structure provides insects with the lightest, highest strength and toughness. Protect. This principle can effectively improve the thermal fatigue resistance of the brake drum surface, reduce thermal fatigue wear, and resist the initiation and expansion of thermal fatigue cracks.

On the basis of using the above principles, a new type of braking material with bionic non-smooth surface is prepared. Process the unit body with bionic non-smooth function on the surface of the brake drum. These unit bodies are regularly or randomly distributed, have a certain geometric shape, and the organizational structure is different from the parent body. According to needs, the unit body can also appear chemical composition relative to the parent body. Variety. The new brake drum can significantly improve the friction coefficient, wear resistance and thermal fatigue resistance of the mold brake drum surface.

The present invention is realized according to the following scheme based on above-mentioned thought:

A brake drum with a bionic non-smooth surface, characterized in that the working surface of the brake drum is distributed with convex and concave units with a height difference of 0.15-0.5mm from the surface of the base body, and the convex and concave units are pits Or convex hull, parallel or grid-like stripes, the convex and concave units contain alloying elements Cr, Si, Mn, Mo, W, V, B, and the content is higher than the corresponding element content in the matrix, and the content difference is: Cr0.5-1%, Mn0.5-5%, Si0.1-1%, Mo0.5-5%, W0.5-5%, V0.5-10%, B0.01-0.1%.

The pits or convex hull units are distributed in a dot matrix on the surface of the brake drum (disc), the diameter of the bottom circle of the convex hull or the diameter of the upper mouth of the pit is 0.5-4mm, and the center distance between the unit bodies is 20- 50mm.

The parallel or grid stripes have a stripe width of 0.3-3mm and a center-to-center distance of 10-40mm.

The hardness difference between the convex and concave unit body and the matrix is HB 0-450.

The technical means adopted in the present invention are: design the non-smooth unit body shape size and distribution law on the surface of the brake drum by computer, through mechanical processing, laser, corrosion, engraving and combined with spraying, chemistry, physics, sputtering, gas phase By depositing, plating and other methods, a non-smooth unit with a certain geometric shape, chemical composition and organizational structure different from the base material is processed on the surface of the brake drum. The shape, size, distribution, chemical composition, and processed structure of the non-smooth unit play an important role in improving the friction coefficient, wear resistance and thermal fatigue resistance of the brake drum surface. Finally, a bionic non-smooth brake drum with high friction coefficient, high wear resistance and high thermal fatigue resistance is obtained.

One or several elements among the seven chemical elements of Cr, Mn, Si, Mo, V, W, and B can be added to the unit body, so that the content of the element in the unit body is higher than that of the matrix material, and forms with the matrix material The chemical composition content is poor.

The addition rules are: for non-smooth unit body, if you want to improve its strength and toughness, you can add Si, Mn, Cr elements to the unit body; if you want to improve wear resistance, you can add Mo, V, W elements; if you want to improve its thermal fatigue resistance Cr, Mo, B elements can be added.

The performance index achieved by the brake drum manufactured by the invention is: its service life is increased by 1.5-3 times compared with the smooth surface brake drum with the same base material, the production cost is increased by 5%-15%, and the friction coefficient is increased by 1 time. The thermal fatigue resistance has been greatly improved.

The beneficial effect of the brake drum produced by the invention is: the bionic non-smooth surface can significantly improve the friction coefficient of the brake drum surface, significantly improve the wear resistance of the brake material, and is not easy to scratch the brake drum surface and the friction lining Produces severe adhesion, has sufficient mechanical strength, and has good thermal fatigue resistance. Through strengthening treatment on the surface of the brake drum, uneven and patchwork bionic non-smooth units are formed on the surface, and its structure and chemical composition can ensure that the wear resistance and thermal fatigue resistance of the brake drum are significantly improved. . At the same time, the surface contact between the brake drum surface and the friction lining is changed from point or line contact, which reduces the bonding force of the friction pair, thereby reducing the wear of the brake drum, and the service life is compared with the smooth surface brake drum of the same base material. , increased by 1.5-3 times, and the friction coefficient increased by 1 time. The technology has strong personalization characteristics. According to different requirements, non-smooth bionic patterns with different shapes, sizes and distribution rules can be selected to obtain different performances. The invention has the advantages of simple processing, reliable performance, low cost, high performance-price ratio and the like.

Description of drawings:

Fig. 1 is a schematic diagram of the surface structure of a non-smooth surface brake drum with spherical crown convex hull;

Fig. 2 is a schematic diagram of the surface structure of a non-smooth surface brake drum with spherical crown dimples;

Fig. 3 is a schematic view of the surface structure of a non-smooth surface brake drum with parallel stripes;

Fig. 4 is a schematic diagram of the surface structure of a non-smooth surface brake drum with grid-like stripes;

Fig. 5 is a comparison test result diagram of the influence of different surface states of the brake drum on the amount of wear;

Fig. 6 is a comparison test result diagram of the influence of different surface states of the brake drum on the coefficient of friction;

Fig. 7 is a relationship diagram between brake drum surface hardness and friction coefficient;

Fig. 8 is a relationship diagram between brake drum hardness and wear amount;

Fig. 9 is a graph showing the influence of temperature on the amount of wear of different surface shapes;

Fig. 10 is a graph showing the influence of temperature on the coefficient of friction of different surface shapes;

Fig. 11 is a microstructure diagram of the bionic non-smooth unit body generated by laser processing on the surface of the brake drum;

Fig. 12 is a microstructure diagram of a bionic non-smooth unit body on the surface of a laser-processed high-speed steel brake drum;

Figure 13 is a graph of the energy spectrum analysis results of the bionic non-smooth unit;

Fig. 14 is the morphology microstructure diagram of thermal fatigue crack propagation on the non-smooth surface;

Figure 15 is a diagram of the propagation curves (a-N curves) of thermal fatigue main cracks on three different surface samples.

Detailed ways

The following embodiments are given in conjunction with the accompanying drawings to further describe the brake drum with bionic non-smooth surface of the present invention in detail.

Example 1

Fabrication of heavy duty truck brake drums with convex non-smooth morphology on the surface.

Referring to Figure 1, the surface of the brake drum is processed with a laser to have a convex-hull non-smooth surface, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.5mm, the diameter d of the bottom circle is 4mm, and the center of the unit body The distance s is 50mm. The material of the brake drum is HT250 gray iron, the friction coefficient is 0.37, and the hardness is HB 175.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.67, hardness: HB 520, friction coefficient increased by 0.30, hardness increased by HB 345, and the service life of the brake drum with bionic non-smooth surface is longer than that of the smooth surface of the same substrate The brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 2

Manufacture of heavy duty truck brake drums with dimpled non-smooth morphology on the surface.

Referring to Figure 2, the surface of the brake drum is processed into a pit-shaped non-smooth surface by laser. The center distance s is 50mm. The material of the brake drum is HT250 gray iron, the friction coefficient is 0.37, and the hardness is HB 175.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.67, hardness: HB 518, friction coefficient increased by 0.30, hardness increased by HB 343, and the service life of the brake drum with bionic non-smooth surface is longer than that of the smooth surface of the same substrate The brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 3

Manufacture of heavy duty truck brake drums with striated non-smooth morphology on the surface.

Referring to Figure 3, the surface of the brake drum is processed into a striped non-smooth surface by laser, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.5 mm, the width w is 3 mm, and the center distance s of the unit body is 40 mm. The inclination α is about 45°. The material of the brake drum is HT250 gray iron, the friction coefficient is 0.37, and the hardness is HB 175.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.70, hardness: HB 532, friction coefficient increased by 0.33, hardness increased by HB 357, and the service life of the brake drum with bionic non-smooth surface is longer than that of the smooth surface of the same substrate The brake drum is 1.2 times higher, while the cost of processing bionic non-smooth surfaces is only 8% higher.

Example 4

Manufacture of brake drums for heavy duty trucks with grid-type non-smooth morphology on the surface.

Referring to Figure 4, the surface of the brake drum is processed into a grid non-smooth surface by laser, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.5 mm, the width w is 3 mm, and the center distance s of the unit body is 40 mm , the inclination angle α is 0° (parallel stripes) and 90° (vertical stripes) alternately distributed. The material of the brake drum is HT250 gray iron, the friction coefficient is 0.37, and the hardness is HB 175.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.73, hardness: HB 545, friction coefficient increased by 0.36, hardness increased by HB 370, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is 1.5 times higher, while the cost of processing biomimetic non-smooth surfaces is only 10% higher.

Example 5

Manufacture the Jiefang truck brake drum with a convex-hull non-smooth shape on the surface.

Referring to Figure 1, the surface of the brake drum is processed into a convex-hull non-smooth surface with a laser. The height difference between the non-smooth unit body and the surface of the brake drum base is 0.5mm, the diameter of the bottom circle is 4mm, and the center distance of the unit body is 50mm. The brake drum material is HT200 cast iron, the friction coefficient is 0.33, and the hardness is HB 190.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.63, hardness: HB 535, friction coefficient increased by 0.30, hardness increased by HB 345, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 6

Manufacture Jiefang truck brake drums with dimpled non-smooth morphology on the surface.

Referring to Figure 2, the surface of the brake drum is processed into a pit-shaped non-smooth surface with a laser. The distance is 50mm. The brake drum material is HT200 cast iron, the friction coefficient is 0.33, and the hardness is HB 190.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.63, hardness: HB 532, friction coefficient increased by 0.30, hardness increased by HB 342, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 7

Manufacture Jiefang truck brake drums with striated non-smooth morphology on the surface.

Referring to Figure 3, laser is used to process the surface of the brake drum into a striped non-smooth surface. The height difference between the non-smooth unit body and the surface of the brake drum base is 0.5mm, the width is 3mm, the center distance of the unit body is 40mm, and the inclination angle α is about 45°. The brake drum material is HT200 cast iron, the friction coefficient is 0.33, and the hardness is HB 190.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.68, hardness: HB 548, friction coefficient increased by 0.35, hardness increased by HB 358, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is 1.2 times higher, while the cost of processing biomimetic non-smooth surfaces is only 8% higher.

Example 8

Manufacture of Jiefang truck brake drums with grid-type non-smooth morphology on the surface.

Referring to Figure 4, the surface of the brake drum is processed into a grid-type non-smooth surface with a laser. The unevenness between the non-smooth unit body and the surface of the brake drum base is 0.5 mm, the width is 3 mm, and the center distance of the unit body is 40 mm. The inclination angle α is 0° (parallel stripes) and 90° (vertical stripes) alternately distributed. The brake drum material is HT200 cast iron, the friction coefficient is 0.33, and the hardness is HB 190.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.70, hardness: HB 562, friction coefficient increased by 0.37, hardness increased by HB 372, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is 1.5 times higher, while the cost of processing biomimetic non-smooth surfaces is only 10% higher.

Example 9

A Jetta car brake drum with a convex-hull non-smooth shape on the surface was manufactured.

Referring to Figure 1, the surface of the brake drum is processed into a convex-hull non-smooth surface by laser. 20mm. The brake drum material is HT200 cast iron, the friction coefficient is 0.32, and the hardness is 195.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.62, hardness: HB 539, friction coefficient increased by 0.30, hardness increased by HB 344, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 10

Manufacture Jetta car brake drums with dimpled non-smooth morphology on the surface.

Referring to Figure 2, the surface of the brake drum is machined into a pit-shaped non-smooth surface with a laser. The center distance is 20mm. The brake drum material is HT200 cast iron, the friction coefficient is 0.32, and the hardness is 195.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.61, hardness: HB 536, friction coefficient increased by 0.29, hardness increased by HB 341, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is doubled, while the cost of processing bionic non-smooth surfaces is only increased by 5%.

Example 11

Manufacture Jetta car brake drums with striated non-smooth morphology on the surface.

Referring to Figure 3, the surface of the brake drum is processed into a striped non-smooth surface with a laser. The height difference between the non-smooth unit body and the surface of the brake drum base is 0.15 mm, the width is 0.3 mm, and the center distance of the unit body is 10 mm. The inclination α is about 45°. The brake drum material is HT200 cast iron, the friction coefficient is 0.32, and the hardness is 195.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.65, hardness: HB 552, friction coefficient increased by 0.33, hardness increased by HB 357, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is 1.2 times higher, while the cost of processing biomimetic non-smooth surfaces is only 8% higher.

Example 12

Fabrication of Jetta car brake drums with gridded non-smooth morphology on the surface.

Referring to Figure 4, the surface of the brake drum is processed into a grid-type non-smooth surface with a laser. The height difference between the non-smooth unit body and the surface of the brake drum base is 0.15 mm, the width is 0.3 mm, and the center distance of the unit body is 10 mm. . The inclination angle α is 0° (parallel stripes) and 90° (vertical stripes) alternately distributed. The brake drum material is HT200 cast iron, the friction coefficient is 0.32, and the hardness is 195.

After processing, the indicators of the non-smooth unit body are tested as friction coefficient: 0.68, hardness: HB 569, friction coefficient increased by 0.36, hardness increased by HB 374, and the service life of the brake drum with bionic non-smooth surface is longer than that of the same base material. The surface brake drum is 1.5 times higher, while the cost of processing biomimetic non-smooth surfaces is only 10% higher.

Example 13

Fabrication of heavy duty truck brake drums with convex non-smooth morphology on the surface.

Referring to Fig. 1, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.5 mm, the diameter of the bottom circle is 4 mm, and the center distance of the unit body is 50 mm. The matrix material contains Cr0.3%, V0.3%, Si1.8%, Mn0.8%. Using powder spraying device, alloy coating and laser infiltration technology, the alloy elements are melted into the unit body, and the coating alloy mixture contains 4.5% metal Mn, 1.7% metal Cr, 5.9% V-Fe powder, 38.6% Mo-Fe powder, the coating alloy thickness is 0.03mm, the burning loss rate is 5%, and 5% Mo is added to the unit body after treatment, 0.1% Cr, V, Mn element content increased to 0.5%, 1.3%, respectively, Mo, Cr, V, Mn element content difference is 5%, 0.1%, 0.5%, 0.5%, with bionic non-smooth surface brake drum The service life of the brake drum is 1.6 times higher than that of the smooth surface brake drum of the same base material, and the cost of processing the bionic non-smooth surface is only increased by 12%.

Example 14

Manufacture of heavy duty truck brake drums with dimpled non-smooth patterns on the surface.

Referring to Fig. 2, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.5 mm, the diameter of the upper opening of the pit is 4 mm, and the center distance of the unit body is 50 mm. The base material contains 0.3% Cr, 1.8% Si, 0.8% Mn, and 0.3% V. Using powder spraying device, alloy coating, and laser infiltration technology to melt alloy elements into the unit body, the 4.7% metal A mixture of Cr, 14.8% Si-Fe powder, 14.4% metal Mn, 39.2% V-Fe powder, the coating alloy thickness is 0.08mm, the burning loss rate is 5%, Si, V, Cr, The content of Mn element increases to 1.9%, 10%, 1.3%, 5.8%, respectively, and the difference of Si, V, Cr, Mn element content is 0.1%, 10%, 1%, 5%. Under the same working conditions, it has bionic The service life of the non-smooth surface brake drum is 1.6 times higher than that of the smooth surface brake drum of the same base material, and the cost of processing the bionic non-smooth surface is only increased by 12%.

Example 15

Manufacture of Jiefang truck brake drum with striated non-smooth surface

Referring to Fig. 3, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.3 mm, the width is 4 mm, and the center distance of the unit body is 40 mm. The base material contains 1.9% Si, 0.8% Mn, and 0.3% Cr. Using powder spraying device, alloy coating, and laser infiltration technology to melt alloy elements into the unit body, the coating alloy mixture contains 3.8% Mo-Fe Powder 0.2% B-Fe powder, 20.3% W-Fe powder, coating alloy thickness is 0.03mm, burning loss rate is 5%, after treatment, 0.5% Mo, 5% W, 0.01% B are added to the unit body, The content difference of Mo element is 0.5%, the difference of W element content is 5%, and the difference of B element content is 0.01%. Under the same conditions, the service life of the brake drum with bionic non-smooth surface is longer than that of the smooth brake drum with the same base material 1.8 times, while the cost of processing bionic non-smooth surfaces is only increased by 12%.

Example 16

Manufacture of Jetta Brake Drum with Mesh Non-smooth Surface

Referring to Fig. 4, the height difference between the non-smooth unit body and the surface of the brake drum base is 0.3 mm, the width is 4 mm, and the center distance of the unit body is 40 mm. The matrix material contains Cr0.5%, V0.3%, Si1.7%, Mn0.8%. The alloy elements are melted into the unit body by powder spraying device, alloy coating and laser infiltration technology, and the coating alloy mixture contains 2.6% W-Fe powder, 57.2% Si-Fe powder, 2% B-Fe powder, the coating alloy thickness is 0.07mm, the burning loss rate is 5%, and 0.1% B, W, Si are added to the unit body after treatment The contents are 0.5%, 2.7%, B element content difference is 0.1%, W element content difference is 0.5%, Si element content difference is 1%, under the same conditions, the brake drum with bionic non-smooth surface has a service life ratio of The smooth surface brake drum of the same substrate is 1.8 times higher, while the cost of processing the bionic non-smooth surface is 12% higher.

Through the microscopic analysis and detection of the bionic non-smooth unit body of the brake drum, it can be found that its organizational structure and chemical composition are obviously different from those of the matrix. According to the basic principles of bionics, the uneven and patchwork bionic shape, tissue structure and chemical composition on the non-smooth surface make the friction pairs change from surface contact to point or line contact, which can reduce adhesion and withstand extrusion. And friction, wear resistance, reduce thermal fatigue wear, and resist the initiation and expansion of thermal fatigue cracks. Therefore, the non-smooth brake drum developed on the basis of bionic theory can ensure that the friction coefficient, wear resistance and thermal fatigue resistance of the surface of the brake material are significantly improved. Therefore, the wear resistance is also significantly improved under the premise of ensuring that the brake material has a sufficiently high friction coefficient. The following is the relationship between the surface morphology, hardness, and temperature of the non-smooth surface unit body, the amount of wear and the coefficient of friction. (Refer to Figure 5-Figure 10)

Figure 11 is the microstructure of the bionic non-smooth unit body formed by laser processing on the surface of the brake drum. It can be seen that the grain size of the crystals in the treated area changes significantly. The grain size of the tissue in the lower untreated area is grade 6, while that in the upper treated area reaches grade 11-12. Grain refinement is a strengthening method that increases strength without sacrificing toughness, and even slightly improves toughness. The particles after laser treatment are smaller and fragmented, and have a higher dislocation structure than conventional heat treatment, increasing dislocation The number of movement disorders, not only the strength has been greatly improved, but also the toughness has been greatly improved. Therefore, this type of organization is conducive to the improvement of wear resistance and thermal fatigue resistance.

Figure 12 is the microstructure of the bionic non-smooth unit body on the surface of the laser processed high-speed steel brake drum. Alloy elements and carbides are evenly distributed in the treatment layer, and the crystal grain size is refined from the original 7 grades to 10-11 grades, and its wear resistance and thermal fatigue resistance are improved.

Figure 13 is the energy spectrum analysis results of the bionic non-smooth unit. It describes the distribution of alloying elements and carbon in the unit body. Through the bionic non-smooth preparation technology, the alloying elements are uniformly dissolved into the bionic non-smooth unit body, forming a solid solution, compound or multi-phase coexistence in the unit body. By controlling the chemical composition of the unit body to form different concentration gradients with the chemical composition of the matrix, so as to obtain different mechanical properties from the matrix, so that the non-smooth brake drum surface has wear resistance, thermal fatigue resistance, and adhesion resistance. improve. For example, elements such as Cr, Mn, and Si in the figure provide the necessary composition conditions for the formation of fine and dispersed second-phase particles. When the moving dislocation encounters the second-phase particles on the slip surface, it either cuts through or bypasses, and the slip deformation can continue. This process will undoubtedly consume extra energy and cause strengthening. Mo element can inhibit the segregation of the second phase or other solute atoms at the grain boundary, which makes it difficult for cracks to form and expand at the grain boundary, and improves the toughness of the surface.

Figure 14 shows the morphology of thermal fatigue crack propagation on a non-smooth surface, and it is found that the bionic non-smooth unit can block the crack propagation. At the junction of the fatigue crack and the unit body, the crack cannot pass through the bionic non-smooth unit body, or terminates at the unit body, or bypasses the unit body, and the crack has multiple branches, and the path of propagation becomes more tortuous. It reflects that the crack is more hindered in the process of expansion, so it has to change direction frequently, which also shows that the bionic non-smooth unit has greater thermal fatigue resistance, and the crack must consume more energy to expand. The non-smooth unit body with a certain distribution law is pinned on the surface of the mold like a peg, effectively retarding the initiation and expansion of thermal fatigue cracks, and significantly improving the overall thermal fatigue resistance of the brake drum surface.

Figure 15 shows the propagation curves (a-N curves) of thermal fatigue main cracks on three different surface samples. Thermal fatigue cracks appeared in the smooth surface sample between 1600-1800 cycles, and the crack length was 1mm. The cracks of the striped samples with a parallel interval of 4 mm appeared later than that of the smooth surface samples, and the crack length was 0.8 mm between 2200 and 2400 cycles. There were no cracks on the surface of the striped sample with a parallel interval of 2 mm from the beginning to the end. This shows that samples with non-smooth surface have higher resistance to crack initiation than samples with smooth surface, and thus have a higher thermal fatigue life. The slope of the L-N curve of the smooth surface sample is larger, indicating that the crack growth rate is faster, which is basically consistent with the crack distribution on the sample surface.

Claims (4)

1. brake drum with bionic non-smooth surface, be distributed with protruding, the recessed cell cube that is the 0.15-0.5mm height difference with matrix surface on its working surface, this protruding, recessed cell cube is pit or convex closure, parallel or latticed striped, it is characterized in that described protruding, recessed cell cube contains one or more elements among alloying elements cr, Si, Mn, Mo, W, V, the B, and be higher than constituent content corresponding in the matrix, its content difference is: Cr0.5-1%, Mn0.5-5%, Si0.1-1%, Mo0.5-5%, W0.5-5%, V0.5-10%, B0.01-0.1%.

2. the brake drum with bionic non-smooth surface according to claim 1, it is characterized in that described pit or convex closure cell cube are dot matrix and distribute on brake drum surface, circular diameter or pit back cut diameter are 0.5-4mm at the bottom of its convex closure, and centre distance is 20-50mm between cell cube.

3. the brake drum with bionic non-smooth surface according to claim 1 is characterized in that described parallel or latticed striped, and its width of fringe is 0.3-3mm, and centre distance is 10-40mm between striped.

4. the brake drum with bionic non-smooth surface according to claim 1 is characterized in that the difference of hardness between described protruding, recessed cell cube and the matrix is HB 0-450.

Images