Shape-property integrated preparation method for high-strength and high-toughness track steel
Patent Information
- Application Number
- PCT/CN2026/075563
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-19
- Filing Date
- 2026-01-29
- Publication Date
- 2026-08-27
Smart Images
Figure CN2026075563_27082026_PF_FP_ABST
Abstract
Description
A method for integrated preparation of high-strength and high-toughness track steel Technical Field
[0001] This invention belongs to the field of steel manufacturing technology, specifically relating to a method for the integrated preparation of high-strength and high-toughness track steel. Background Technology
[0002] Currently, construction machinery is developing towards higher technology content, higher added value, higher reliability, and larger tonnage. Track plates, as a core component of tracked construction machinery, require excellent comprehensive performance, especially in terms of strength, impact toughness, and wear resistance. Track steel is an asymmetric cross-section steel, and its deformation during rolling is complex. Significant differences exist in the deformation and cooling conditions of the web, teeth, and the transition area between the teeth and web, resulting in significant variations in the microstructure and properties of different parts of the rolled track plate, making performance control extremely difficult.
[0003] Patent application CN202410823121.X describes a variable-hardness single-tooth track steel and its preparation method. During hot rolling, cooling water is used to control the final rolling temperature of different parts of the track steel. The final rolling temperature of the track web is 820~840℃, the final rolling temperature of the joint between the track web and the track teeth is 840~870℃, and the final rolling temperature of the track teeth is 680~700℃. During the quenching process, the track teeth are quenched in water, and the track web is quenched in polymer... The process involves cooling the track steel web and the joint between the track teeth in a quenching liquid, followed by air cooling. During tempering, the track teeth are heated to 180-190°C in a furnace, held for 50-60 minutes, and then air-cooled to room temperature. The track web and the joint between the track teeth are heated to 210-220°C in a furnace, held for 50-60 minutes, and then air-cooled to room temperature. The track web is heated to 240-250°C in a furnace, held for 50-60 minutes, and then air-cooled to room temperature. This patent requires different temperature controls for different parts during hot rolling, quenching, and tempering, which would make the actual operation extremely complex and impractical.
[0004] Patent application CN202010164865.7 describes a heat treatment method for track plates. The method involves heating the steel to austenitize it, followed by a first quenching. The steel is then isothermally heated to 30-50°C below the martensitic transformation initiation temperature (Ms) for 20-30 minutes, then heated to 20-30°C above Ms for another 30-50 minutes before a second quenching. Finally, the steel is cooled to room temperature. This patented method can only control the stability of the residual austenite. Once the austenitizing conditions are determined before quenching, it is difficult to effectively control the grain size, thus limiting its effectiveness in controlling the final mechanical properties, especially impact toughness.
[0005] Patent application CN202210887603.2 discloses a blanking die and hot rolling method for a single-tooth track plate. The method includes a first blanking die and a second blanking die. The first blanking die is used to extrude a rectangular continuously cast billet into a mountain-shaped intermediate billet including a right curved limb, a first central column, and a left curved limb. The second blanking die is a rear die used to extrude the mountain-shaped intermediate billet into an inverted T-shaped intermediate billet including a right flat limb, a second central column, and a left flat limb. This patented method significantly reduces the dependence on billet size, allowing the production of larger single-tooth track plates using smaller billets, resulting in better energy saving and consumption reduction. However, it uses rectangular billets.
[0006] Existing technology typically uses rectangular billets to roll track steel. Since the tooth root of the track plate corresponds to the near-center position of the rectangular billet, the deformation zone of the rectangular billet in the first rolling pass cannot reach the center of the billet, resulting in a small cumulative deformation at the tooth root and coarser grains. This leads to poor overall mechanical properties at the tooth root. In addition, the difficulty in cooling this part during quenching further deteriorates the mechanical properties. Summary of the Invention
[0007] To address the aforementioned technical problems, this invention provides a method for the integrated preparation of high-strength and high-toughness track steel. By controlling the shape of the billet, increasing the number of descaling passes, and adjusting the heat treatment parameters, the produced track steel possesses both good strength and impact toughness, with minimal performance differences between different parts.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0009] A method for the integrated preparation of high-strength and high-toughness track steel, comprising the following steps:
[0010] Step 1: Send the billet to be rolled into the heating furnace for heating;
[0011] The billet is a round billet, the diameter of which is 0.8 to 1.2 times the height of the rectangular billet used in the prior art;
[0012] The heating temperature is 1050~1250℃, the heat spread temperature is 1180~1220℃, and the heat spread time is 30~90min;
[0013] Step 2: High-pressure water descaling;
[0014] The high-pressure water descaling is performed in multiple passes, preferably 2 to 4 passes, to reduce the surface temperature of the steel billet by 100 to 200°C.
[0015] Step 3: Opening the round billet;
[0016] The number of passes for the round billet is the same as that for the rectangular billet, which is 1 to 4 passes.
[0017] Step 4: Slitting and rolling, the rectangular intermediate billet after the initial blanking is slid and rolled into track steel blanks;
[0018] Step 5: Final rolling, rolling the track steel blank into finished track steel product;
[0019] Step 6: Cooling. After final rolling, the finished track steel is transported to a cooling bed to cool to below 100°C. The cooling bed is equipped with a heat preservation device to control the cooling rate to below 0.5°C / s, so that the metallographic structure of the cooled track steel is ferrite + pearlite.
[0020] Step 7: Heat treatment, including: heating and holding the cooled track steel at a certain temperature and then performing a first quenching to obtain a first-quenched steel; heating and holding the first-quenched steel at a certain temperature and then performing a second quenching to obtain a second-quenched steel; and tempering the second-quenched steel to obtain a high-strength and high-toughness track steel with a uniform and refined microstructure, the microstructure of which is tempered martensite.
[0021] The heating rate of the first quenching is 5~10℃ / min, the holding temperature is 880~920℃, the holding time is 20~40min, and the cooling method is water cooling.
[0022] The second quenching process involves a heating rate of 5~10℃ / min, a holding temperature of 820~860℃, a holding time of 20~40min, and a cooling method of water cooling.
[0023] The heating rate of the tempering treatment is 5~10℃ / min, the holding temperature is 180~250℃, and the holding time is 90~150min.
[0024] The chemical composition of the high-strength and high-toughness track steel of the present invention has the following weight percentages: C: 0.22~0.33%, Si: 0.15~0.80%, Mn: 1.00~1.50%, P≤0.020%, S≤0.010%, Cr: 0.20~0.90%, B: 0.0005~0.0035%, Ti: 0.020~0.065%, Al: 0.01~0.05%, with the remainder being iron and trace impurities.
[0025] The high-strength and high-toughness track steel of the present invention has a yield strength of 1300~1500MPa, a tensile strength of 1600~1800MPa, an elongation of 12.0~15.0%, and a room temperature U-shaped impact energy of 75~100J.
[0026] Compared with the prior art, the beneficial effects of the present invention are:
[0027] Replacing rectangular billets with round billets of similar height in existing technology, without increasing the number of billet passes or reducing production efficiency, can promote the movement of the deformation zone from near the surface of the billet towards the center, increasing the deformation amount in the central region. Using multi-pass high-pressure water descaling can lower the temperature of the near-surface region of the billet by 100-200°C compared to the central region, increasing the deformation resistance near the surface and making deformation in this area more difficult. This further promotes the movement of the billet deformation zone towards the center, increasing the deformation amount in the central region. This significantly improves upon the existing technology's small cumulative deformation at the tooth root and reduced overall force. The shortcomings of poor mechanical properties; the control of the cooling bed insulation device and cooling rate can prevent the track steel from cooling too quickly and forming bainite structure, which would lead to machining cracks during subsequent machining of track plates; the design of quenching once and then quenching again below the austenitizing temperature, followed by tempering, can refine the martensite laths, increase the number of carbide precipitates and dislocation density in the martensite, reduce the performance differences between different parts of the track steel, and at the same time have a stronger ability to inhibit crack initiation and propagation. After tempering, the track steel has higher strength and impact toughness, and improves the service life of the track. Attached Figure Description
[0028] Figure 1 shows the cross-sectional view of the steel for a single-tooth track;
[0029] Figure 2 shows the cross-sectional view of the steel for the three-toothed track;
[0030] Wherein: 1-single tooth track steel, 12-teeth of single tooth track steel, 13-tooth root of single tooth track steel, 2-three tooth track steel, 22-teeth of three tooth track steel, 23-tooth root of three tooth track steel.
[0031] Figure 3 shows the cross-section of the circular billet used in this invention;
[0032] Figure 4 shows the cross-section of a rectangular billet used in the existing technology for rolling track steel;
[0033] Figure 5 shows the deformation zone range of the first pass in the rectangular billet opening process;
[0034] Wherein: 3 - the range of the rectangular billet deformation zone.
[0035] Figure 6 shows the deformation zone range of the first pass of the round billet opening process;
[0036] Wherein: 4 - the range of the round billet deformation zone.
[0037] Figure 7 shows the deformation zone range of the round billet after multiple high-pressure water descaling passes;
[0038] Among them: 5 - the range of the deformation zone of the round billet after descaling.
[0039] Figure 8 is a schematic diagram of the heat treatment process used in this invention;
[0040] Figure 9 shows the microstructure of the tooth root region of the track steel prepared by secondary quenching in Comparative Example 1.
[0041] Figure 10 is a microstructure diagram of the tooth root region of the high-strength and tough track steel prepared by secondary quenching and tempering in Example 1. Embodiments of the present invention
[0042] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
[0043] The composition of the steel used in the embodiments of the present invention will be described as follows:
[0044] The track steel used has the following chemical composition by weight percentage: C: 0.22~0.33%, Si: 0.15~0.80%, Mn: 1.00~1.50%, P≤0.020%, S≤0.010%, Cr: 0.20~0.90%, B: 0.0005~0.0035%, Ti: 0.020~0.065%, Al: 0.01~0.05%, with the remainder being iron and trace impurities. This invention first continuously casts molten steel of this composition into round billets, and then prepares the track steel according to the following method.
[0045] It should be noted that different components can be used to prepare track steel according to different usage requirements, but it is not limited to the components used in this invention. Example 1
[0046] A method for the integrated preparation of shape and properties of single-tooth / triple-tooth track steel, as shown in Figure 1-2, includes the following steps:
[0047] Step 1: The round billet to be rolled (as shown in Figure 3) is sent into the heating furnace for heating. The diameter D of the round billet is 0.8 times the height H of the rectangular billet (as shown in Figure 3) used in the prior art. The heating temperature is 1050℃, the soaking temperature is 1180℃, and the soaking time is 30 minutes.
[0048] Step 2: Perform multiple passes (2 passes) of high-pressure water descaling on the heated billet to make the surface temperature of the billet 100°C lower than the center temperature.
[0049] Step 3: The descaled round billet is then cut into smaller passes. The number of cuts is the same as that of the rectangular billet in existing technology, both being one pass, with similar reduction per pass. Due to the different geometric characteristics of the round and rectangular billets, under similar reduction conditions, the deformation zone 3 depth of the rectangular billet is 1 / 5 of the billet height (Figure 5), while the deformation zone 4 depth of the round billet is 1 / 3 of the billet height (Figure 6). That is, the deformation zone of the round billet is closer to the center of the billet than that of the rectangular billet. Combined with the surface cooling effect of the high-pressure water descaling in Step 2, near-surface deformation of the round billet becomes more difficult, and the deformation zone further penetrates into the center 5 of the billet (Figure 7).
[0050] Step 4: Segmentation and rolling. The rectangular intermediate billet after sizing is rolled into track steel blanks.
[0051] Step 5: Final rolling, rolling the blank into finished track steel product;
[0052] Step 6: Cooling. After final rolling, the track steel is transported to a cooling bed to cool to below 100°C. The cooling bed is equipped with a heat preservation device to control the cooling rate to below 0.5°C / s, so that the metallographic structure of the cooled track steel is ferrite + pearlite.
[0053] Step 7: Heat Treatment. A schematic diagram of the heat treatment process is shown in Figure 8. The cooled track steel is heated at a rate of 5℃ / min, held at 880℃ for 20 minutes, and then quenched once using water cooling to obtain first-quenched steel. The first-quenched steel is then heated again at a rate of 5℃ / min, held at 820℃ for 20 minutes, and then quenched a second time using water cooling to obtain second-quenched steel. The second-quenched steel is then tempered at a rate of 5℃ / min, held at 180℃ for 90 minutes. The final result is a high-strength, high-toughness track steel with a uniform and refined microstructure, consisting of tempered martensite (as shown in Figure 10), a yield strength of 1300 MPa, a tensile strength of 1600 MPa, an elongation of 12.0%, and a room temperature U-shaped impact energy of 75 J. Example 2
[0054] A method for the integrated preparation of shape and properties of single-tooth / triple-tooth track steel, as shown in Figure 1-2, includes the following steps:
[0055] Step 1: The round billet to be rolled (as shown in Figure 3) is sent into the heating furnace for heating. The diameter D of the round billet is 1.2 times the height H of the rectangular billet (as shown in Figure 3) used in the prior art. The heating temperature is 1250℃, the soaking temperature is 1220℃, and the soaking time is 90min.
[0056] Step 2: Perform multiple passes (4 passes) of high-pressure water descaling on the heated billet to make the surface temperature of the billet 200°C lower than the center temperature.
[0057] Step 3: The descaled round billet is then cut into smaller blanks. The number of cutting passes is the same as that of the rectangular billet in existing technology, both being four passes, with similar reduction per pass. Due to the different geometric characteristics of the round and rectangular billets, with similar reduction, the deformation zone 3 depth of the rectangular billet is 1 / 4 of the billet height (Figure 5), while the deformation zone 4 depth of the round billet is 2 / 5 of the billet height (Figure 6). That is, the deformation zone of the round billet is closer to the center of the billet than that of the rectangular billet. Combined with the surface cooling effect of the high-pressure water descaling in Step 2, near-surface deformation of the round billet becomes more difficult, and the deformation zone further penetrates into the center 5 of the billet (Figure 7).
[0058] Step 4: Segmentation and rolling. The rectangular intermediate billet after sizing is rolled into track steel blanks.
[0059] Step 5: Final rolling, rolling the blank into finished track steel product;
[0060] Step 6: Cooling. After final rolling, the track steel is transported to a cooling bed to cool to below 100°C. The cooling bed is equipped with a heat preservation device to control the cooling rate to below 0.5°C / s, so that the metallographic structure of the cooled track steel is ferrite + pearlite.
[0061] Step 7: Heat Treatment. A schematic diagram of the heat treatment process is shown in Figure 8. The cooled track steel is heated at a rate of 10℃ / min, held at 920℃ for 40 minutes, and then quenched once using water cooling to obtain first-quenched steel. The first-quenched steel is then heated again at a rate of 10℃ / min, held at 860℃ for 40 minutes, and then quenched a second time using water cooling to obtain second-quenched steel. The second-quenched steel is then tempered at a rate of 10℃ / min, held at 250℃ for 150 minutes. The final result is a high-strength, high-toughness track steel with a uniform and refined microstructure, consisting of tempered martensite (as shown in Figure 10), a yield strength of 1500 MPa, a tensile strength of 1800 MPa, an elongation of 15.0%, and a room temperature U-shaped impact energy of 100 J. Example 3
[0062] A method for the integrated preparation of shape and properties of single-tooth / triple-tooth track steel, as shown in Figure 1-2, includes the following steps:
[0063] Step 1: The round billet to be rolled (as shown in Figure 3) is sent into the heating furnace for heating. The diameter D of the round billet is 1 time the height H of the rectangular billet (as shown in Figure 3) used in the prior art. The heating temperature is 1200℃, the soaking temperature is 1180℃, and the soaking time is 30 minutes.
[0064] Step 2: Perform multiple passes (4 passes) of high-pressure water descaling on the heated billet to make the surface temperature of the billet 150°C lower than the center temperature.
[0065] Step 3: The descaled round billet is then cut into smaller blanks. The number of cutting passes is the same as that of the rectangular billet in existing technology, both being two passes with similar reduction per pass. Due to the different geometric characteristics of the round and rectangular billets, with similar reduction, the deformation zone 3 of the rectangular billet has a depth of 1 / 5 of the billet height (Figure 5), while the deformation zone 4 of the round billet has a depth of 2 / 5 of the billet height (Figure 6). This means the deformation zone of the round billet is closer to the center of the billet than that of the rectangular billet. Combined with the surface cooling effect of the high-pressure water descaling in Step 2, near-surface deformation of the round billet becomes more difficult, and the deformation zone extends further into the center 5 of the billet (Figure 7).
[0066] Step 4: Segmentation and rolling. The rectangular intermediate billet after sizing is rolled into track steel blanks.
[0067] Step 5: Final rolling, rolling the blank into finished track steel product;
[0068] Step 6: Cooling. After final rolling, the track steel is transported to a cooling bed to cool to below 100°C. The cooling bed is equipped with a heat preservation device to control the cooling rate to below 0.5°C / s, so that the metallographic structure of the cooled track steel is ferrite + pearlite.
[0069] Step 7: Heat Treatment. A schematic diagram of the heat treatment process is shown in Figure 8. The cooled track steel is heated at a rate of 5℃ / min, held at 900℃ for 30 minutes, and then quenched once using water cooling to obtain first-quenched steel. The first-quenched steel is then heated again at a rate of 8℃ / min, held at 830℃ for 30 minutes, and then quenched a second time using water cooling to obtain second-quenched steel. The second-quenched steel is then tempered at a rate of 5℃ / min, held at 200℃ for 90 minutes. The final result is a high-strength, high-toughness track steel with a uniform and refined microstructure, consisting of tempered martensite (as shown in Figure 10), a yield strength of 1400 MPa, a tensile strength of 1700 MPa, an elongation of 14.0%, and a room temperature U-shaped impact energy of 90 J.
[0070] Comparative Example 1
[0071] The existing process for preparing track steel involves heating the steel to austenitize it at 870-900℃ for 30-60 minutes, followed by quenching at 30-50℃ below the martensitic transformation initiation temperature (Ms) for 20-30 minutes, and then tempering at 360℃ for 30 minutes. The steel composition, based on 100% by mass, includes: C: 0.23-0.27%, Si: 0.15-0.30%, Mn: 1.1-1.3%, Cr: 0.2-0.5%, B: 0.0005-0.0035%, Ti: 0.020-0.065%, Al: 0.01-0.05%, with the balance being Fe. Water quenching is used, resulting in a martensitic + bainitic microstructure (as shown in Figure 9).
[0072] Table 1 shows a performance comparison between Comparative Example 1 and Examples 1-3 of this application:
[0073]
[0074] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values of the present invention can all achieve the present invention, and examples are not listed here.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for the integrated preparation of high-strength and high-toughness track steel, characterized in that, The integrated form-property preparation method of the high-strength and high-toughness track steel includes the following steps: Step 1: Send the round billet to be cut into the heating furnace for heating; Step 2: High-pressure water descaling, wherein the high-pressure water descaling is a multi-pass high-pressure water descaling process, which reduces the surface temperature of the steel billet by 100~200℃; Step 3: Opening the round billet; Step 4: Slitting and rolling, the rectangular intermediate billet after the initial blanking is slid and rolled into track steel blanks; Step 5: Final rolling, rolling the track steel blank into finished track steel product; Step Six: Cooling. After final rolling, the finished track steel product is transported to a cooling bed to cool to below 100°C. Step 7: Heat treatment, including: heating and holding the cooled track steel at a certain temperature and then performing a first quenching to obtain a first-quenched steel; heating and holding the first-quenched steel at a certain temperature and then performing a second quenching to obtain a second-quenched steel; and tempering the second-quenched steel to obtain a high-strength and high-toughness track steel with a uniform and refined microstructure, the microstructure of which is tempered martensite.
2. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step one, the diameter of the round billet is 0.8 to 1.2 times the height of the rectangular billet used in the prior art; the heating temperature is 1050 to 1250°C, the heat spread temperature is 1180 to 1220°C, and the heat spread time is 30 to 90 minutes.
3. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step two, the number of passes is 2 to 4.
4. The integrated method for preparing high-strength and high-toughness track steel according to claim 1, characterized in that, In step three, the number of passes for the round billet is the same as that for the rectangular billet, which is 1 to 4 passes.
5. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step six, the cooling bed is equipped with a heat preservation device to control the cooling rate to below 0.5℃ / s, so that the metallographic structure of the cooled track steel is ferrite + pearlite.
6. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step seven, the heating rate of the first quenching is 5~10℃ / min, the holding temperature is 880~920℃, the holding time is 20~40min, and the cooling method is water cooling.
7. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step seven, the heating rate of the second quenching is 5~10℃ / min, the holding temperature is 820~860℃, the holding time is 20~40min, and the cooling method is water cooling.
8. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, In step seven, the heating rate of the tempering treatment is 5~10℃ / min, the holding temperature is 180~250℃, and the holding time is 90~150min.
9. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, The high-strength and high-toughness track steel has a yield strength of 1300~1500MPa, a tensile strength of 1600~1800MPa, an elongation of 12.0~15.0%, and a room temperature U-shaped impact energy of 75~100J.
10. The method for integrated preparation of high-strength and high-toughness track steel as described in claim 1, characterized in that, The chemical composition of the high-strength and high-toughness track steel by weight percentage is as follows: C: 0.22~0.33%, Si: 0.15~0.80%, Mn: 1.00~1.50%, P≤0.020%, S≤0.010%, Cr: 0.20~0.90%, B: 0.0005~0.0035%, Ti: 0.020~0.065%, Al: 0.01~0.05%, with the remainder being iron and trace impurities.