Steel for engineering machine track link and manufacturing process thereof

Abstract

This invention relates to the field of iron and steel metallurgy, particularly to a steel for track links in engineering machinery and its manufacturing process. The steel contains C, Si, Mn, Ca, Cr, Al, Ti, Nb, B, Mo, and N. The production process includes electric furnace smelting, LF ladle refining, RH vacuum treatment, continuous casting, heating, rolling, and cooling. Based on 15B36Cr steel, this invention increases the Cr content to 1.00%–1.20% to improve its wear resistance and increase the hardenability of the core of large-size track links. It also incorporates 0.020%–0.035% Nb to form a “B-Nb-Ti-Al” synergistic microalloying system. Simultaneously, it optimizes inclusion control by controlling Ca and sulfur content to ensure a calcium-sulfur ratio ≥1.5, thereby enhancing the steel's corrosion resistance and avoiding or reducing the risk of fracture.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and in particular to a type of steel for track links in engineering machinery and its manufacturing process. Background Technology

[0002] Tracked construction machinery is widely used in harsh working conditions such as mining, construction, and earthmoving. The tracked walking mechanism is the load-bearing and transmission component of the entire machine, and the track links, as key load-bearing parts, are subjected to impact, bending, wear, and alternating tensile and compressive loads over long periods of time, requiring extremely high strength, toughness, wear resistance, and fatigue resistance. Complex working conditions can easily cause premature failure of the track links, directly affecting the reliability and service life of the equipment.

[0003] From the perspective of commonalities in heavy-duty chain steel, both marine mooring chain steel and track chain link steel need to meet the requirements of large cross-section, high strength and toughness, high hardenability, and corrosion resistance. Existing mooring chain steels mostly use a medium-carbon Mn-Cr-Ni-Mo composition, relying on expensive alloys to improve performance. This results in problems such as high carbon equivalent, high risk of quenching cracking, difficulty in controlling the yield strength ratio, and high production costs. Although process improvements have been made, defects such as compositional segregation, unbalanced microstructure, and insufficient stability of large cross-section performance still exist.

[0004] Currently, the steel used in engineering machinery track links is still mainly medium carbon boron steel such as 40MnB and 35MnB, which is strengthened by adding Cr and Mo elements. However, there are two common problems in practical applications: First, the hardenability stability is poor. Fluctuations in the nitrogen and oxygen content in the steel make it difficult to control the effective boron, resulting in uneven hardenability bandwidth and hardness at the end, and discrete performance after heat treatment. Second, there is insufficient inclusion and corrosion resistance. The inclusion level in the steel is relatively high, which easily forms crack initiation and corrosion weak points, making it prone to fracture failure during long-term service.

[0005] For example, 15B36Cr steel has a Cr content of about 0.54% and does not contain Nb. The grain size of the finished steel plate is only 6.5 to 7.5 grade, and the end hardenability J1.5 fluctuates to 51 to 57 HRC and J20 fluctuates to 41.5 to 52 HRC. The hardenability stability is insufficient and cannot meet the requirements of high-end engineering machinery for long service life and high reliability of track links. Summary of the Invention

[0006] This invention provides a steel for track links in engineering machinery and its manufacturing process. Based on 15B36Cr steel, the Cr content is increased to 1.00%–1.20% to improve its wear resistance and increase the hardenability of the core of large-size track links. 0.020%–0.035% Nb is added to form a “B-Nb-Ti-Al” synergistic microalloying system. Simultaneously, inclusion control is optimized, and by controlling Ca and sulfur content, the calcium-sulfur ratio is ensured to be ≥1.5, enhancing the steel's corrosion resistance and avoiding or reducing the risk of fracture.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A type of steel for engineering machinery track links, wherein the chemical composition of the steel, by mass percentage, is: C: 0.32%–0.36%, Si: 0.15%–0.35%, Mn: 1.10%–1.25%, P≤0.030%, Ca≥0.0045%, S≤0.003%, Cr: 1.00%–1.20%, Al: 0.020%–0.050%, V≤0.01%, Ti: 0.020%–0.050%, Nb: 0.020%–0.035%, B: 0.0008%–0.0030%, Mo: 0.08%–0.13%, N: 0.0066%–0.0120%, Ni≤0.25%, Cu≤0.25%, [O]≤12ppm, with the remainder being Fe and unavoidable impurities.

[0008] The grain size of the finished steel product shall not be less than grade 7.

[0009] A method for manufacturing steel for track links in engineering machinery, the production process includes electric furnace smelting, LF ladle refining, RH vacuum treatment, continuous casting, heating, rolling and cooling processes, and the specific control of the following processes: 1) Electric furnace smelting: The final smelting control is as follows: C content is 0.05%–0.20%, P content ≤0.023%, tapping temperature is 1600–1630℃, slag is blocked during tapping in the electric furnace, and slag feeding is strictly prohibited; 2 minutes after tapping, 0.54–0.72 kg / t steel of ferrosilicon, 6.54–7.27 kg / t steel of silicon-manganese alloy, 6.46–7.27 kg / t steel of high-carbon ferromanganese, and 14.72–15.45 kg / t steel of high-carbon ferrochrome are added for alloying; 1–2 kg / t steel of aluminum wire, 18.18–27.27 kg / t steel of active lime, and 18.18–27.27 kg / t steel of dolomite are added for deoxidation and slag formation; 2) LF Ladle Refining: Maintain a slight positive pressure of 40-70 kPa inside the furnace, using submerged arc heating to prevent arc leakage; add pre-melted slag and lime to create white slag, and add 1.63-1.90 kg / t of silicon carbide and 1.63-2.54 kg / t of alumina balls; Alloying process: After a full analysis, adjust the Al content first. After adjustment, add aluminum granules / titanium iron before ladle loading to adjust [Alt] to 0.038%-0.05% and [Ti] to 0.03%-0.05%; add 0.36-0.72 kg / t of ferroniobium to adjust the niobium content... Adjust the amount to 0.020%~0.035%; add 1.45~1.9 kg / t steel of ferromolybdenum, 1.68~2 kg / t steel of silicon manganese, 0.68~0.9 kg / t steel of high carbon ferromanganese, and 2.9~3.63 kg / t steel of high carbon ferrochrome; add 5.25~6.36 kg / t steel of manganese nitride to adjust the [N] in the steel to the target range; LF off-site temperature control: the target temperature for the first furnace is 1664~1674℃, the target temperature for the second furnace is 1639~1649℃, and the target temperature for other furnaces is 1624~1634℃; 3) RH vacuum treatment: Maintain a vacuum of 90-110 Pa for 10-15 minutes, then turn off the 5-stage pump and maintain the vacuum for another 5-10 minutes, followed by soft blowing for 15-25 minutes; Before vacuum treatment, add ferroboron to alloy boron according to the release limit, adjusting the boron content to 0.0008%-0.0030%; After vacuum treatment, add 0.54-0.72 kg / t of silicon-calcium wire to ensure Ca / S ≥ 1.5; 4) Continuous casting: A full-process protective casting process is adopted. During continuous casting, a large reduction of ≥16mm is used. The electromagnetic stirring current in the crystallizer is 300–400A, with a frequency of 1.5–2Hz, using continuous stirring mode. At the end of continuous casting, the electromagnetic stirring current is 300–420A, with a frequency of 6–8Hz, using alternating stirring mode. The ladle temperature is 1564–1574℃, the tundish temperature is 1514–1524℃, the superheat is maintained at 20–30℃, the casting speed is controlled at 0.42–0.47m / min, a constant casting speed, and the liquid level fluctuation is controlled within ±3mm. The billet is slowly cooled in an insulation pit for more than 48 hours after leaving the line. 5) Heating: The temperature of the heating section is 810~1080℃, the temperature of the soaking section is 1200~1220℃, the soaking section holding time is ≥2h, the total heating time is 240~780min, and the furnace exit temperature is 1180~1210℃. 6) Rolling: The initial rolling temperature is 1050~1200℃, the final rolling temperature for large bars with ø200mm<diameter≤ø300mm is 950~1100℃, the final rolling temperature for medium bars with ø85mm<diameter≤ø200mm is 850~1000℃, and the final rolling temperature for small bars with ø20mm≤diameter≤ø85mm is 750~950℃.

[0010] Before electric furnace smelting, the sulfur content in the molten iron is controlled to be ≤0.0028% through iron pretreatment.

[0011] In the LF ladle refining process, the pre-melted slag uses active lime, with an addition amount of 4.54 to 8.18 kg / t steel, and the S content in the lime is ≤0.06%.

[0012] During the continuous casting process, the tundish is cleaned with argon gas before casting begins, and the purging time is ≥2 minutes; a low-carbon or carbon-free covering agent is used for the tundish.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) The hardenability of the steel is extremely stable: The present invention adopts a precise process of "first fixing nitrogen (Ti, Al), then adjusting nitrogen (MnN), and then adding boron", which ensures the stability of effective B and makes the hardenability band (such as the fluctuation range of J1.5 and J20) significantly narrower than that of traditional 15B36Cr steel.

[0014] (2) Significant grain refinement: The present invention actively controls the combination of a high content of N (80-120ppm) with a sufficient amount of Ti (0.020%-0.050%) to form a large number of fine TiN particles, which strongly pin the grain boundaries; the grain size of the steel is stable at grade 7 or above, while the grain size of traditional 15B36Cr steel is only about grade 6.5.

[0015] (3) Excellent and stable end-hardenability values: Under the same heat treatment regime (austenitization at 890℃), the J1.5 and J20 values ​​of the steel produced by this invention not only remain at the ideal level, but also show smaller fluctuations between heat cycles and within the same batch. This is because the fine grains (level 7) make the phase transformation structure more uniform and the quenching stress distribution more consistent; the stable effective B content can ensure the stability of the phase transformation kinetics, and the two work together to ensure excellent reproducibility of the hardened layer depth (end-hardenability curve). In addition, due to the increase in Cr content (from the conventional 0.2%~0.6% to 1.0%~1.2%), the core hardenability of large-size track links is improved, while the dependence on effective B is reduced.

[0016] (4) Improved corrosion resistance and fracture resistance: This invention uses RH vacuum treatment for deep dehydrogenation (process hydrogen control), combined with Ca / S control, inclusion control, and adjustment of Cr composition, to increase the corrosion resistance and fracture resistance of the finished steel.

[0017] (5) Controllable composition and process cost: Chemical composition design and process optimization do not require the addition of a large amount of precious alloys, making it easy to achieve industrial production; Through accurate control of nitrogen content, the addition of MnN alloy in the LF process is reduced. MnN is changed from conventional LF addition (loss ≥ 50%) to addition when adjusting vacuum degree in RH (loss ≤ 20%), saving costs while making composition control more stable. Attached Figure Description

[0018] Figure 1 This is a metallographic photograph of the steel used for engineering machinery track links manufactured in Embodiment 1 of the present invention (banded structure grade 1.0, grain size grade 7).

[0019] Figure 2 This is a metallographic photograph of the steel used for engineering machinery track links manufactured in Embodiment 2 of the present invention (banded structure grade 2.0, grain size grade 9). Detailed Implementation

[0020] The present invention discloses a type of steel for engineering machinery track links, wherein the chemical composition of the steel, by mass percentage, is as follows: C: 0.32%–0.36%, Si: 0.15%–0.35%, Mn: 1.10%–1.25%, P≤0.030%, Ca≥0.0045%, S≤0.003%, Cr: 1.00%–1.20%, Al: 0.020%–0.050%, V≤0.01%, Ti: 0.020%–0.050%, Nb: 0.020%–0.035%, B: 0.0008%–0.0030%, Mo: 0.08%–0.13%, N: 0.0066%–0.0120%, Ni≤0.25%, Cu≤0.25%, [O]≤12ppm, with the remainder being Fe and unavoidable impurities.

[0021] The roles of key chemical components in the steel used for track links in engineering machinery described in this invention are as follows: N (0.0066%~0.0120%): One of the core elements in the steel of this invention. This invention elevates nitrogen from a conventional residual element (<80ppm) to an actively controlled alloying element. Its functions are: ① It combines with Ti, a strong nitride-forming element, to generate fine TiN particles, which pin the austenite grain boundaries and significantly refine the original austenite grains (see grain size comparison in the examples); ② Sufficient TiN can "fix" free nitrogen in the steel, protecting the subsequently added B element from nitriding and ensuring the stability of the solid solution B (effective B) content, which is the fundamental way to achieve high and stable hardenability; ③ TiN particles can act as irreversible hydrogen traps, capturing hydrogen atoms and improving resistance to hydrogen-induced cracking.

[0022] Ti (0.020%~0.050%): In this invention, the Ti content must match the N content to ensure that Ti / N≥3.0 (mass ratio) in order to fully fix N and form sufficient TiN.

[0023] Nb (0.020%~0.035%): used to form Nb(C,N), further refine the grains, and together with TiN, form a hydrogen trap network.

[0024] Cr (1.00%–1.20%): If the Cr content is below 1.0%, track links with large pitch (pitch ≥ 190 mm) cannot achieve uniform performance across the entire cross-section. This invention increases the Cr content from the conventional 0.2%–0.6% to 1.0%–1.2%, significantly improving the core hardenability of large-diameter track links and reducing dependence on effective B. The role of Cr in steel is as follows: (1) Deeply enhances hardenability, solving the technical bottleneck of "large cross-section steel core not being hardened": The larger the size of the track link, the slower the core cooling rate during quenching; if only the composition design of "boron + trace chromium (0.25%~0.40%)" is used, although it can meet the hardenability requirements of small cross-section parts, when the effective thickness exceeds 50mm, the core of medium carbon boron steel is prone to "ferrite + pearlite" mixed structure, and the hardness will drop sharply. The steel of this invention adds more than 1.0% Cr, the purpose of which is to significantly shift the CCT curve to the right, delay the pearlite transformation, and enable the core of large cross-section steel to obtain martensite or lower bainite structure. In addition, this composition design and the added Mo (0.08%~0.13%) can also form "Cr-Mo composite strengthening", Cr reduces the critical cooling rate, and Mo inhibits high temperature transformation and prevents temper brittleness.

[0025] (2) Compensating for the inherent defects of boron and solving the technical problem of "poor stability of effective boron": Boron steel has a well-known inherent defect, namely, the effective boron content is extremely unstable. This is because the contribution of boron to hardenability is significantly affected by the N and O content in the steel and the fluctuation of the alloying process, which leads to a large difference in hardenability between different batches of steel. However, the addition of Cr element to the steel of this invention can compensate for the loss of hardenability caused by the fluctuation of effective boron. Even if the effective boron of a certain batch of steel is low, the Cr content of 1.00% to 1.20% can still ensure that the lower limit of hardenability meets the requirements.

[0026] (3) Significantly improve the wear resistance and corrosion fatigue resistance of steel: The present invention adopts a high chromium (1.00%~1.20%) design, which can significantly improve the wear resistance and corrosion fatigue resistance of steel, so that the performance of steel is highly matched with the harsh working conditions of track links.

[0027] The present invention discloses a method for manufacturing steel for engineering machinery track links. The production process includes electric furnace smelting, LF ladle refining, RH vacuum treatment, continuous casting, heating, rolling, and cooling. The specific control of the process is as follows: 1) Electric furnace smelting: Preferred raw materials for smelting: 0-45% molten iron, 20-25% heavy scrap steel, and the remainder is baled automotive steel sheets. Before smelting in the electric furnace, the sulfur content in the molten iron is controlled to be ≤0.0028% through pretreatment (sulfur has a significant negative impact on the corrosion resistance of steel).

[0028] The final control of smelting is to keep the carbon content at 0.05% to 0.20%, the phosphorus content at ≤0.023%, and the tapping temperature at 1600 to 1630℃. Slag must be blocked during tapping in the electric furnace, and slag feeding is strictly prohibited.

[0029] Two minutes after tapping, 0.54–0.72 kg / t of ferrosilicon, 6.54–7.27 kg / t of ferrosilicon-manganese alloy, 6.46–7.27 kg / t of high-carbon ferromanganese, and 14.72–15.45 kg / t of high-carbon ferrochrome are added for alloying. 1–2 kg / t of aluminum wire, 18.18–27.27 kg / t of active lime, and 18.18–27.27 kg / t of dolomite are added for deoxidation and slag formation.

[0030] 2) LF Ladle Refining: Maintain a slight positive pressure of 40-70 kPa inside the furnace, using submerged arc heating to prevent arc leakage; add pre-melted slag and lime to create white slag (the pre-melted slag uses active lime, added at a rate of 4.54-8.18 kg / t steel, with an S content ≤0.06%). Additionally, add 1.63-1.90 kg / t steel of silicon carbide and 1.63-2.54 kg / t steel of alumina spheres; Alloying process: After a full analysis, adjust the Al content first. After adjustment, add aluminum granules / ferrotitanium before ladle loading to adjust [Alt] to 0.038%-0.05% and [Ti] to 0.03%-0.05%; add 0.36-0.72 kg / t steel of ferroniobium to adjust the niobium content to 0.020%-0.035%; add 1.4 kg / t steel of ferromolybdenum. 5-1.9 kg / t steel, 1.68-2 kg / t steel of silicon manganese, 0.68-0.9 kg / t steel of high-carbon ferromanganese, and 2.9-3.63 kg / t steel of high-carbon ferrochrome; add 5.25-6.36 kg / t steel of manganese nitride to adjust the [N] in the steel to the target range; LF off-site temperature control: the target temperature for the first furnace is 1664-1674℃, the target temperature for the second furnace is 1639-1649℃, and the target temperature for other furnaces is 1624-1634℃; 3) RH Vacuum Treatment: Maintain a vacuum of 90–110 Pa for 10–15 minutes, then turn off the 5-stage pump and maintain the vacuum for another 5–10 minutes. Soft blowing time is 15–25 minutes. This method results in lower nitrogen content loss. If RH vacuum treatment is performed at a vacuum of 67 Pa for more than 15 minutes, the nitrogen content needs to be increased to 0.00160%–0.0200%, and bottom blowing nitrogen is required. This increases the amount of alloying elements added and makes nitrogen content control unstable. Based on the calculation that each 100 kg of nitrogen alloy can increase the nitrogen content by 10 ppm, this invention can save at least 3.63 kg of nitrogen alloy per t of steel.

[0031] Before vacuum treatment, ferroboron is added to alloy B according to the upper limit of release, and the B content is adjusted to 0.0008%~0.0030%; after vacuum treatment, 0.54~0.72kg / t steel of silicon-calcium wire is added to ensure Ca / S≥1.5.

[0032] 4) Continuous Casting: Before casting begins, the tundish is cleaned with argon gas for ≥2 minutes; a low-carbon or carbon-free covering agent is used in the tundish. A full-process protective casting process is adopted. To increase grain size and reduce banded structures, a large reduction of ≥16mm is used during continuous casting. To reduce segregation, the electromagnetic stirring current in the crystallizer is 300–400A, with a frequency of 1.5–2Hz, using continuous stirring mode; at the end of continuous casting, the electromagnetic stirring current is 300–420A, with a frequency of 6–8Hz, using alternating stirring mode (e.g., 20s-5s-20s); the ladle temperature is 1564–1574℃, the tundish temperature is 1514–1524℃, the superheat is maintained at 20–30℃, the casting speed is controlled at 0.42–0.47m / min, a constant casting speed, and the liquid level fluctuation is controlled within ±3mm; the billet is slowly cooled in an insulation pit for at least 48 hours after leaving the line.

[0033] 5) Heating: The temperature of the heating section is 810~1080℃, the temperature of the soaking section is 1200~1220℃, the soaking section is kept warm for ≥2h (to reduce the banded tissue), the total heating time is 240~780min, and the furnace exit temperature is 1180~1210℃.

[0034] 6) Rolling: The initial rolling temperature is 1050~1200℃, the final rolling temperature for large bars with ø200mm<diameter≤ø300mm is 950~1100℃, the final rolling temperature for medium bars with ø85mm<diameter≤ø200mm is 850~1000℃, and the final rolling temperature for small bars with ø20mm≤diameter≤ø85mm is 750~950℃.

[0035] The grain size of the finished steel product shall not be less than grade 7.

[0036] In this invention, unless otherwise specified, the content refers to the mass content, and unless otherwise specified, the ratio refers to the mass ratio.

[0037] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0038] Example: The chemical composition of the steel in each embodiment and comparative example is shown in Table 1. The main production process parameters of the steel in each embodiment and comparative example are shown in Table 2. The end hardenability test results of the finished steel in each embodiment and comparative example are shown in Table 3. The low magnification structural defect test results of the finished steel in each embodiment and comparative example are shown in Table 4. The non-metallic inclusion test results of each embodiment and comparative example are shown in Table 5.

[0039] Table 1 - Chemical composition of steel (wt%): Table 2 - Main production process parameters for steel: Table 3 - Results of end-hardenability test of finished steel products: As shown in Table 3, under the same test conditions, the end hardenability of the finished steel products in each embodiment is J1.5 = 50~53 HRC and J20 = 46~48.5 HRC. The data indicate that the hardened layer depth (J20 value) of the steel manufactured by this invention is significantly higher than that of the comparative example, and the stability of the end hardenability over multiple heats is better than that of the comparative example (J20 value is distributed between 32.5 and 40.5 HRC, with greater fluctuation than the embodiments).

[0040] Table 4 - Inspection results of microstructural defects in finished steel products under low magnification: Table 5 - Inspection Results of Inclusion Defects in Finished Steel Products: The banded structure grade of the finished steel in each embodiment is ≤2.0, and the banded structure grade of the finished steel in the comparative example is ≥2.5; the grain size of the finished steel in each embodiment is ≥7, and the grain size of the finished steel in the comparative example is ≤6.5. Figure 1 The image shows the metallographic structure of the steel used for the engineering machinery track links manufactured in Example 1 (banded structure grade 1.0, grain size grade 7). Figure 2 The image shows the metallographic structure of the steel used for the track links of engineering machinery manufactured in Example 2 (banded structure grade 2.0, grain size grade 9).

[0041] Compared with the comparative example, the amount of nitrogen-containing alloy added in each embodiment was reduced by 400 kg / furnace, and the nitrogen content of the embodiments was higher and the nitrogen content recovery rate was higher than that of the comparative example.

[0042] As can be seen from the above examples and comparative examples, the grain size, end-hardenability stability, corrosion resistance, wear resistance, and fracture resistance of traditional 15B36Cr steel are all inferior to those of steel manufactured using the method described in this invention.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A type of steel for track links in engineering machinery, characterized in that, The chemical composition of the steel, by mass percentage, is as follows: C: 0.32%–0.36%, Si: 0.15%–0.35%, Mn: 1.10%–1.25%, P≤0.030%, Ca≥0.0045%, S≤0.003%, Cr: 1.00%–1.20%, Al: 0.020%–0.050%, V≤0.01%, Ti: 0.020%–0.050%, Nb: 0.020%–0.035%, B: 0.0008%–0.0030%, Mo: 0.08%–0.13%, N: 0.0066%–0.0120%, Ni≤0.25%, Cu≤0.25%, [O]≤12ppm, with the remainder being Fe and unavoidable impurities.

2. The steel for track links in engineering machinery according to claim 1, characterized in that, The grain size of the finished steel product shall not be less than grade 7.

3. A method for manufacturing steel for engineering machinery track links as described in claim 1 or 2, characterized in that, The production process includes electric furnace smelting, LF ladle refining, RH vacuum treatment, continuous casting, heating, rolling and cooling, with specific control measures implemented for the following processes: 1) Electric furnace smelting: The final smelting control is as follows: C content is 0.05%–0.20%, P content ≤0.023%, tapping temperature is 1600–1630℃, slag is blocked during tapping in the electric furnace, and slag feeding is strictly prohibited; 2 minutes after tapping, 0.54–0.72 kg / t steel of ferrosilicon, 6.54–7.27 kg / t steel of silicon-manganese alloy, 6.46–7.27 kg / t steel of high-carbon ferromanganese, and 14.72–15.45 kg / t steel of high-carbon ferrochrome are added for alloying; 1–2 kg / t steel of aluminum wire, 18.18–27.27 kg / t steel of active lime, and 18.18–27.27 kg / t steel of dolomite are added for deoxidation and slag formation; 2) LF Ladle Refining: Maintain a slight positive pressure of 40-70 kPa inside the furnace, using submerged arc heating to prevent arc leakage; add pre-melted slag and lime to create white slag, and add 1.63-1.90 kg / t of silicon carbide and 1.63-2.54 kg / t of alumina balls; Alloying process: After a full analysis, adjust the Al content first. After adjustment, add aluminum granules / titanium iron before ladle loading to adjust [Alt] to 0.038%-0.05% and [Ti] to 0.03%-0.05%; add 0.36-0.72 kg / t of ferroniobium to adjust the niobium content... Adjust the amount to 0.020%~0.035%; add 1.45~1.9 kg / t steel of ferromolybdenum, 1.68~2 kg / t steel of silicon manganese, 0.68~0.9 kg / t steel of high carbon ferromanganese, and 2.9~3.63 kg / t steel of high carbon ferrochrome; add 5.25~6.36 kg / t steel of manganese nitride to adjust the [N] in the steel to the target range; LF off-site temperature control: the target temperature for the first furnace is 1664~1674℃, the target temperature for the second furnace is 1639~1649℃, and the target temperature for other furnaces is 1624~1634℃; 3) RH vacuum treatment: Maintain a vacuum of 90-110 Pa for 10-15 minutes, then turn off the 5-stage pump and maintain the vacuum for another 5-10 minutes, followed by soft blowing for 15-25 minutes; Before vacuum treatment, add ferroboron to alloy boron according to the release limit, adjusting the boron content to 0.0008%-0.0030%; After vacuum treatment, add 0.54-0.72 kg / t of silicon-calcium wire to ensure Ca / S ≥ 1.5; 4) Continuous casting: A full-process protective casting process is adopted. During continuous casting, a large reduction of ≥16mm is used. The electromagnetic stirring current in the crystallizer is 300–400A, with a frequency of 1.5–2Hz, using continuous stirring mode. At the end of continuous casting, the electromagnetic stirring current is 300–420A, with a frequency of 6–8Hz, using alternating stirring mode. The ladle temperature is 1564–1574℃, the tundish temperature is 1514–1524℃, the superheat is maintained at 20–30℃, the casting speed is controlled at 0.42–0.47m / min, a constant casting speed, and the liquid level fluctuation is controlled within ±3mm. The billet is slowly cooled in an insulation pit for more than 48 hours after leaving the line. 5) Heating: The temperature of the heating section is 810~1080℃, the temperature of the soaking section is 1200~1220℃, the soaking section holding time is ≥2h, the total heating time is 240~780min, and the furnace exit temperature is 1180~1210℃. 6) Rolling: The initial rolling temperature is 1050~1200℃, the final rolling temperature for large bars with ø200mm<diameter≤ø300mm is 950~1100℃, the final rolling temperature for medium bars with ø85mm<diameter≤ø200mm is 850~1000℃, and the final rolling temperature for small bars with ø20mm≤diameter≤ø85mm is 750~950℃.

4. A method for manufacturing steel for engineering machinery track links according to claim 3, characterized in that, Before electric furnace smelting, the sulfur content in the molten iron is controlled to be ≤0.0028% through iron pretreatment.

5. A method for manufacturing steel for engineering machinery track links according to claim 3, characterized in that, In the LF ladle refining process, the pre-melted slag uses active lime, with an addition amount of 4.54 to 8.18 kg / t steel, and the S content in the lime is ≤0.06%.

6. A method for manufacturing steel for engineering machinery track links according to claim 3, characterized in that, During the continuous casting process, the tundish is cleaned with argon gas before casting begins, and the purging time is ≥2 minutes; a low-carbon or carbon-free covering agent is used for the tundish.

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