A wear-resistant manganese-boron steel, a chain track link, and a preparation method and application thereof

Abstract

The present invention belongs to the technical field of alloy materials, and specifically relates to a wear-resistant manganese-boron steel, a chain track section, and a preparation method and application thereof. Based on the existing wear-resistant manganese-boron steel, the present invention increases the silicon content in the system by an appropriate amount, optimizes the carbon content, and combines the limitations of elements such as Ni, Cu, Sn, and Pb, thereby improving the hardenability of MnB series steel, refining the structure, and precipitating a uniformly dispersed hard phase, thereby improving the mechanical properties of the product and enhancing the wear resistance of the product. Compared with the prior art, the addition (or increase) of other expensive alloy components and the increase of the relatively cheap silicon dosage to obtain materials with high mechanical properties and high hardenability greatly reduce the production cost, reduce the risk of fluctuations in product quality, and have a high industrial utilization value.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and in particular relates to a wear-resistant manganese-boron steel, a chain track segment, and a preparation method and application thereof. Background Art

[0002] Crawler tracks are an important part of the traveling device of construction machinery, and are widely used in excavators, pavers, scrapers, bulldozers, etc. The main function of crawler tracks is to convert the driving torque and rotational motion transmitted from the engine to the driving wheel into the driving force required for the machine to travel, and to support the entire machine and the load. Common crawler tracks are mainly composed of crawler pins, pin bushings, chain links, and crawler shoes.

[0003] With the upgrading and development of crawler engineering machinery technology, customers have put forward higher requirements for the service life of equipment. In recent years, according to market surveys and statistics of failure cases, the main failure parts of crawlers are track links, and the average trouble-free service life is relatively low. The failure of track links begins with wear. Excessive wear will lead to a reduction in the hardened layer, which will affect the matrix, resulting in a low actual service life of the track links. Due to the limitations of the inherent characteristics of the materials used in the products, it is difficult to achieve breakthrough improvements by relying solely on forging processes and heat treatments. If other materials with better hardenability and higher mechanical properties are replaced, it is generally chosen to add elements such as Ni, Cr, and Mo to improve hardenability, and to add elements such as V and Nb to improve wear resistance. However, these elements are all relatively expensive metal elements, or the content of these metal elements is increased, which will lead to a substantial increase in the material cost of the product, which is difficult for both companies and customers to accept and recognize.

[0004] Therefore, in order to increase product life and ensure product quality, it is urgent to develop chain track products with higher cost performance and better wear resistance. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects that the wear resistance of manganese-boron steel for track links in the prior art is insufficient, and in order to improve the wear resistance, expensive metal elements are used, resulting in increased costs, etc., thereby providing a wear-resistant manganese-boron steel, track links, and their preparation method and application.

[0006] To this end, the present invention provides the following technical solutions:

[0007] The invention provides a wear-resistant manganese-boron steel, which comprises the following components in percentage by weight, calculated by elements: C 0.34-0.38wt%, Si 0.60-0.90wt%, Mn 1.10-1.40wt%, P≤0.025wt%, S≤0.025wt%, Cr0.15-0.35wt%, Ti0.02-0.03wt%, B 0.0008-0.0030wt%, Ni≤0.20wt%, Cu≤0.25wt%, Sn≤0.020wt%, Pb≤0.0100wt%, N≤0.006wt%, H≤0.0002wt%, O≤0.0018wt%, Ti / N≥5, and the rest is iron.

[0008] The present invention also provides a track link, which is composed of the above-mentioned wear-resistant manganese-boron steel or is prepared from the above-mentioned wear-resistant manganese-boron steel.

[0009] The present invention also provides a method for preparing the above-mentioned track link, comprising the following steps:

[0010] S1, prepare wear-resistant manganese boron steel;

[0011] S2, forging the wear-resistant manganese-boron steel and subjecting it to non-waste heat quenching and tempering process to obtain the chain track segment.

[0012] Optionally, the method further comprises the steps of performing medium frequency quenching and low temperature tempering on the tread of the obtained chain track segment, wherein the operating parameters of the medium frequency quenching are: voltage of 320-360V, current of 240-330A, frequency of 3.1-3.9KHz, temperature of 850-890°C, time of 50-70s, and quenching liquid temperature of ≤40°C;

[0013] And / or, a water-based quenching liquid with a mass concentration of 3-5wt% is used, and specifically, a PAG water-based quenching liquid can be used.

[0014] Optionally, the low-temperature tempering treatment uses an induction tempering furnace, the tempering temperature is 210-250° C., and the holding time is 7-10 min;

[0015] Alternatively, the low-temperature tempering treatment adopts a box-type tempering furnace, the tempering temperature is 175-185° C., and the insulation time is 230-250 min.

[0016] Optionally, in step S2, the forging temperature is 1170-1230°C.

[0017] Optionally, in the non-waste heat quenching and tempering process in step S2, the quenching temperature is 855-865°C, the quenching holding time is 100-120 minutes, the quenching liquid temperature is controlled below 40°C, and the concentration of the water-based quenching liquid is 8-13wt%; specifically, PAG water-based quenching liquid can be used.

[0018] And / or, the quenching liquid is mechanically stirred during the quenching process, and the chain track segments are sprayed underwater.

[0019] Optionally, in the non-waste heat quenching and tempering process in step S2, the tempering temperature is 445-455° C., and the holding time is 170-190 minutes.

[0020] Optionally, in step S1, the rolling ratio of the hot rolling step is ≥10;

[0021] Optionally, the rolling ratio is 10-15.

[0022] The present invention also provides an application of the above-mentioned track link or the track link prepared by the above-mentioned preparation method in the field of engineering machinery.

[0023] In the present invention, silicon can be dissolved in the matrix in the steel to play a role of solid solution strengthening, which can improve the tempering resistance of the steel. The present invention improves the performance of the product by adjusting the silicon content. The Si content is 0.60-0.90wt%, which can inhibit the formation of brittle carbides and promote the generation of free carbon. Silicon can reduce the critical cooling rate, improve the hardenability of the product, and then increase the depth of the hardened layer and ensure the strength of the matrix, thereby improving the mechanical properties and wear resistance of the product. Silicon can prevent excessive grain growth in the steelmaking process, make the structure more uniform and dense, and play a role in refining the grains, so that the precipitated hard phase is more dispersed and uniform, increase the precipitation of the hardened phase, and help the product improve the metallographic structure and mechanical properties. The limitation of Ni, Cu, Sn and Pb elements can also improve the stability of the product and avoid large differences between different batches. The limitation of Ti / N≥5 is because the Ti element can preferentially combine with N to form a titanium nitrogen compound, avoid the B element and the N element from combining, maintain the content of free boron, and thus ensure the hardenability of the product.

[0024] In the present invention, there is no special requirement for the specific refining process of the steel, which is a conventional process, as long as the element composition of the steel meets the requirements. Typically, the steelmaking process includes roughing, LF refining, (RH / VD) vacuum degassing, continuous casting, hot rolling and other processes, and the operating parameters of each process step are conventional in the field and are not specifically limited here.

[0025] The technical solution of the present invention has the following advantages:

[0026] The wear-resistant manganese-boron steel provided by the present invention comprises the following components in percentage by weight, calculated by elements: C 0.34-0.38wt%, Si 0.60-0.90wt%, Mn 1.10-1.40wt%, P≤0.025wt%, S≤0.025wt%, Cr0.15-0.35wt%, Ti0.02-0.03wt%, B 0.0008-0.0030wt%, Ni≤0.20wt%, Cu≤0.25wt%, Sn≤0.020wt%, Pb≤0.0100wt%, N≤0.006wt%, H≤0.0002wt%, O≤0.0018wt%, and Ti / N≥5, and the rest is iron. On the basis of the existing wear-resistant manganese-boron steel, the present invention increases the silicon content in the steel appropriately, optimizes the carbon content, and combines the content of elements such as Ni, Cu, Sn, Pb and the limitation of Ti / N≥5 without adding other expensive metal elements or significantly increasing the amount of these metal elements, so as to improve the hardenability of MnB series steel, refine the organization and precipitate a uniformly dispersed hard phase, improve the mechanical properties of the product, and enhance the wear resistance of the product. Compared with adding (or increasing) other expensive alloy components, increasing the amount of relatively cheap silicon to obtain materials with high mechanical properties and high hardenability, the production cost is greatly reduced, the risk of fluctuation of product quality is reduced, and the industrial utilization value is high.

[0027] The track link provided by the present invention has the same composition as the wear-resistant manganese-boron steel. By limiting the composition, the wear resistance of the track link is improved.

[0028] The method for preparing the track link provided by the present invention further improves the toughness of the product matrix and the wear resistance of the tread by optimizing the non-waste heat quenching and tempering process and the medium frequency quenching + low temperature tempering process parameters of the tread. Compared with adding other expensive alloy components, adding relatively cheap silicon to obtain materials with high mechanical properties and high hardenability greatly reduces production costs and reduces the risk of fluctuations in product quality, and has a high industrial utilization value.

[0029] The method for preparing the track link provided by the present invention can avoid coarse grains of residual heat quenching structure caused by too high temperature and forging cracking caused by too low temperature by limiting the forging temperature.

[0030] The method for preparing the chain track segment provided by the present invention can avoid the problems of quenching cracks caused by too low concentration and incomplete quenching caused by too high concentration by limiting the concentration of the water-based quenching liquid.

[0031] The preparation method of the chain track segment provided by the present invention can further improve the grain size grade of the steel and eliminate the defects generated in the continuous casting and casting processes by limiting the rolling ratio. The higher the rolling ratio, the more beneficial it is to improving the performance of the steel. Considering the production cost or actual production situation, it is more appropriate to control the rolling ratio to 10-15. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 Schematic diagram of sampling for wear resistance test in the test example of the present invention;

[0034] Figure 2 is a comparison chart of the steel end face quenching test results of Example 2 of the present invention and Comparative Example 1;

[0035] Figure 3 This is a photo of the austenite grain size detection of the product provided in Example 2;

[0036] Figure 4 This is a photo of the austenite grain size detection of the product provided in Example 1. DETAILED DESCRIPTION

[0037] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0038] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0039] Examples 1-3

[0040] A chain track segment, the composition and preparation method thereof are as follows:

[0041] The chain track link has the following elemental composition by mass percentage: C 0.34-0.38wt%, Si 0.6-0.9wt%, Mn1.10-1.40wt%, P≤0.025wt%, S≤0.025wt%, Cr0.15-0.35wt%, Ti0.02-0.03wt%, B 0.0008-0.0030wt%, Ni≤0.20wt%, Cu≤0.25wt%, Sn≤0.020wt%, Pb≤0.0100wt%, N≤0.006wt%, H≤0.0002wt%, O≤0.0018wt%, and Ti / N≥5, and the rest is iron.

[0042] The present invention adopts the method of adding a proper amount of silicon and optimizing the carbon content to improve the hardenability of the MnB series steel, refine the structure and precipitate a uniformly dispersed hard phase, thereby improving the mechanical properties of the product and enhancing the wear resistance of the product.

[0043] The method for preparing the track link comprises the following steps:

[0044] (1) The wear-resistant manganese-boron steel in this embodiment is provided by a cooperating steel mill, and the element composition is within the above range. The specific composition of the steel in each embodiment is shown in Table 1, and the specific steelmaking steps are not described in detail here.

[0045] The addition of appropriate amount of silicon will prevent the grains in the steel from growing too large, play a role in refining the grains, thus making the steel structure more uniform and dense, and precipitating a dispersed and uniform hard phase; the addition of silicon can also inhibit brittle carbides, promote the formation of free carbon, and improve hardenability. The rolling ratio of this steel from continuous casting billet to finished product size should be not less than 10.

[0046] (2) The round steel provided by the steel plant and having the element composition meeting the above requirements is cut into the required length of the track segment, and after cutting, it is heated at 1170-1230°C and forged into track segments, and then a mesh belt furnace is used for non-waste heat quenching and tempering process. Among them, the quenching heating temperature is 855-865°C, the quenching holding time is 100-120 minutes, the quenching liquid temperature is controlled below 40°C, the PAG water-based quenching liquid concentration is 8-13wt% (the concentration in this embodiment is 10wt%), mechanical stirring is used in the quenching liquid, and underwater spraying is performed on the track segment during quenching. The tempering process uses 445-455°C tempering, and the holding time is 170-190 minutes. Then the track segment is machined.

[0047] (3) After machining, the chain track segment tread is also subjected to heat treatment hardening by medium frequency quenching + low temperature tempering. The hardness after tempering is 52-54HRC. The operating parameters of medium frequency quenching are: voltage of 320-360V (the voltage in the embodiment is 340V), current of 240-330A (the current in this embodiment is 270A), frequency of 3.1-3.9KHz (the frequency in this embodiment is 3.5KHz), temperature of 850-890℃, time of 50-70s, and quenching liquid temperature of ≤40℃. After medium frequency quenching, the chain track segment is tempered by an induction tempering furnace or a box-type tempering furnace, and the production of high wear-resistant chain track segment is finally completed.

[0048] In Examples 1-3 of the present invention, the chemical elements of the chain track segment composition are controlled as shown in the following table:

[0049] Table 1

[0050] C Si Mn P S Cr Ti B Ni Cu Sn Pb N H O Example 1 0.33 0.76 1.25 0.005 0.0049 0.25 0.025 0.002 0.0017 0.010 0.001 0.0025 0.005 0.00013 0.001 Example 2 0.36 0.84 1.26 0.012 0.009 0.242 0.028 0.0025 0.0011 0.015 0.0012 0.002 0.0043 0.0001 0.0012 Example 3 0.38 0.72 1.249 0.011 0.006 0.246 0.023 0.003 0.022 0.013 0.0016 0.0021 0.0043 0.00016 0.0008

[0051] The control of process parameters of each step is shown in the following table:

[0052] Table 2

[0053]

[0054]

[0055] Comparative Example 1

[0056] This comparative example provides a 35MnB steel, whose elemental composition is: C 0.35wt%, Si 0.28wt%, Mn1.25wt%, P0.015wt%, S≤0.0025wt%, Cr0.192wt%, Ti0.025wt%, B 0.0025wt%, Ni0.0061wt%, Cu0.025wt%, and its preparation process is the same as that of Example 1.

[0057] Test Case

[0058] The steel materials or track links provided in the embodiments of the present invention and the comparative examples were tested, and the specific testing methods are as follows:

[0059] Chain link wear resistance test: Test according to JB / T 7506-94. The sampling diagram and test structure diagram are as follows: Figure 1As shown, a round pin with a diameter of φ6.35mm, a length of 15mm, and a chamfer of 0.5×45° is used on the tread of the chain track section. Test parameters: disc speed: 60r / min; radial feed speed of the sample: 4mm / r; radial reciprocating stroke: 80mm; speed: 60m / s; reciprocating times: 5; test time: 4min; number of rotations: 105; load: 40N; sandpaper mesh: 240 mesh.

[0060] Grain grade: Refer to GB_T 6394-2017 Method for Determination of Average Grain Size of Metals and make ratings according to the grain size rating chart.

[0061] Hardness test: GB / T 230 metal Rockwell test method.

[0062] Hardenability test of steel: Tested according to standard GB255-1988 (Jominy test method), sample size During the test, the heating temperature is 850℃, the heating time is 20 minutes, and the water spraying time is 10 minutes for cooling. After cooling, the hardness is tested along the axial direction with the end face as the reference, and a curve is drawn with the distance from the end face as the horizontal axis and the hardness as the vertical axis, which is called the Jominy curve.

[0063] The specific test results are shown in the table below:

[0064] Table 4

[0065]

[0066] It can be seen from the data in the above table that the wear resistance is significantly improved by adjusting the composition and process. The wear resistance of Example 1, Example 2, Example 3 and Comparative Example 1 are respectively improved by 28.61%, 28.71% and 28.99%. Figure 2 is a comparison chart of the steel end face quenching test results of Example 2 of the present invention and Comparative Example 1. Figure 2 It can be seen that the hardness tends to be highest at the end face, and the hardness gradually decreases as it moves away from the end face. In the area of ​​hardness value HRC>45, the curve of Example 2 is further to the right, indicating better hardenability; Figure 3 This is a photo of the austenite grain size detection of the product provided in Example 2 (×500 times), Figure 4 This is a photo of the austenite grain size detection of the product provided in Example 1 (×500 times). It can be seen from the figure that the structure of Example 2 is denser and more uniform, with a grain size grade of 8.5-9, and the grain size of Comparative Example 1 is 6-7. The grain size grade of the embodiment is higher, and the grains are finer, which is more beneficial to the toughness, fatigue and wear resistance of the product.

[0067] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a track link, characterized in that: The steps include: S1, prepare wear-resistant manganese-boron steel; the wear-resistant manganese-boron steel, in terms of elements, includes the following components in percentage by weight: C 0.34-0.38wt%, Si 0.60-0.90wt%, Mn 1.10-1.26wt%, P≤0.025wt%, S≤0.025wt%, Cr 0.242-0.35wt%, Ti 0.02-0.03wt%, B 0.0008-0.0030wt%, Ni≤0.20wt%, Cu≤0.25wt%, Sn≤0.020wt%, Pb≤0.0100wt%, N≤0.006wt%, H≤0.0002wt%, O≤0.0018wt%, and Ti / N≥5, and the rest is iron; S2, forging the wear-resistant manganese-boron steel and subjecting it to non-waste heat quenching and tempering process to obtain the chain track segment; The method also includes the steps of medium frequency quenching and low temperature tempering of the tread of the obtained chain track segment, wherein the operating parameters of the medium frequency quenching are: voltage of 320-360V, current of 240-330A, frequency of 3.1-3.9KHz, temperature of 850-890°C, time of 50-70s, and quenching liquid temperature of ≤40°C.

2. The method for preparing a track link according to claim 1, characterized in that: A water-based quenching liquid with a concentration of 3-5wt% is used.

3. The method for preparing a track link according to claim 1, characterized in that: The low temperature tempering treatment adopts an induction tempering furnace, the tempering temperature is 210-250°C, and the holding time is 7-10min; Alternatively, the low-temperature tempering treatment is carried out in a box-type furnace, the tempering temperature is 175-185° C., and the holding time is 230-250 min.

4. The method for preparing a track link according to any one of claims 1 to 3, characterized in that: In step S2, the forging temperature is 1170-1230°C.

5. The method for preparing a track link according to any one of claims 1 to 3, characterized in that: In the non-waste heat quenching and tempering process in step S2, the quenching temperature is 855-865°C, the quenching holding time is 100-120 minutes, the quenching liquid temperature is controlled below 40°C, and the concentration of the water-based quenching liquid is 8-13wt%; And / or, the quenching liquid is mechanically stirred during the quenching process, and the chain track segments are sprayed underwater.

6. The method for preparing a track link according to claim 5, characterized in that: In the non-waste heat quenching and tempering process in step S2, the tempering temperature is 445-455° C. and the holding time is 170-190 minutes.

7. The method for preparing a track link according to any one of claims 1 to 3, characterized in that: In step S1 , the rolling ratio of the hot rolling step is ≥10.

8. The method for preparing a track link according to claim 7, characterized in that: The rolling ratio is 10-15.

9. Application of a track link prepared by the preparation method according to any one of claims 1 to 8 in the field of engineering machinery.

Images