Steel for high-cleanliness track shoe and preparation method thereof

Abstract

The invention provides steel for a high-cleanliness track shoe and a preparation method thereof. The steel for the high-cleanliness track shoe comprises the following chemical components in percentage by mass: 0.24%-0.26% of C, 0.22%-0.26% of Si, 1.18%-1.22% of Mn, less than or equal to 0.018% of P, less than or equal to 0.004% of S, 0.35%-0.39% of Cr, 0.0017%-0.0023% of B, 0.022%-0.032% of Ti, less than or equal to 0.30% of Ni, less than or equal to 0.08% of Mo, less than or equal to 0.35% of Cu, 0.018%-0.025% of Al, less than or equal to 0.0015% of H, less than or equal to 0.02% of Pb, less than or equal to 0.03% of Sn, less than or equal to 0.03% According to the method, the gas content and the non-metallic inclusion grade are controlled, the high-cleanliness steel for the track shoe is prepared, and the service life of the track shoe is greatly prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to high-cleanliness track plate steel and a preparation method thereof. Background Art

[0002] Track shoes are vulnerable parts on construction machinery. Harsh working conditions, heavy loads, and intense impacts can easily lead to failures such as rib wear, plate deformation, and plate fracture. Therefore, track shoe steel requires excellent hardenability, high purity, and fracture resistance. Commonly used track shoe steel grades are 40SiMn2 and 35MnTiB. However, due to their high carbon content, they are prone to fine cracks after quenching. Medium-carbon MnB steel is currently used to manufacture track shoes to meet customer requirements. However, the low purity leads to large inclusions, which can cause fatigue cracks and ultimately failure.

[0003] CN102618792A discloses a high-strength wear-resistant steel for engineering machinery and a preparation method thereof. The steel comprises the following components by weight: C: 0.15-0.30%, Si: 0.20-0.65%, Mn: 1.20-1.60%, S≤0.010%, P≤0.020%, B: 0.0010-0.0040%, Cr: 0.30-1.00%, V: 0.030-0.080%, Al: 0.015-0.050%, [N]: 80-200×10 -6 、[H]≤2×10 -6 , [O]≤40×10 -6 The wear-resistant steel has a surface Brinell hardness of not less than 395 HBW, a tensile strength of not less than 1220 MPa, an elongation after fracture of not less than 13%, an impact absorption energy of not less than 70 J at -20°C, and is low in cost.

[0004] CN107619906A discloses a method for preparing aluminum-deoxidized steel billets, comprising the following steps: molten steel in a converter, deoxidation and alloying, steel refining, and continuous casting to produce a steel billet with a T[O] content of 0.0003 to 0.0005%. During the refining process, active lime and refining slag are added to the molten steel for refining. This method can ideally control the desulfurization rate of the molten steel between 25 and 85%, and the T[O] content of the continuously cast billet between 0.0003 and 0.0005%. This method not only improves the desulfurization rate of the molten steel, but also reduces the content of non-metallic inclusions in the steel, thereby improving the cleanliness of the molten steel.

[0005] CN108480579A discloses a low-silicon and ultra-low-carbon coating agent specifically designed for automotive sheet steel and its preparation method. The coating agent comprises the following components by mass percentage: SiO₂≤3.0%, CaO 40.0-50.0%, C ≤1.0%, Al₂O₃ 20.0-30.0%, MgO 6.0-14.0%, Fe₂O₃≤3.0%, and S ≤0.04%, with the remainder being unavoidable impurities. This coating agent effectively addresses the problem of automotive sheet steel being prone to carbon accumulation. By incorporating new materials and optimizing the formulation, it effectively improves the absorption of inclusions in molten steel, further reducing the impurity content of the billet and improving the cleanliness of the molten steel.

[0006] However, when the finished steel obtained by the above steel preparation method is used in the manufacture of track plates, its purity still needs to be further improved. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a high-cleanliness track plate steel and a preparation method thereof, improves the purity of the 25CrMnB series track plate steel, achieves quality improvement in terms of gas content and non-metallic inclusion level, and prepares high-cleanliness track plate steel with low oxygen content and low impurities, which greatly improves the service life of the track plate.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a high-cleanliness track shoe steel, wherein the chemical composition of the high-cleanliness track shoe steel comprises, by mass percentage:

[0010] C: 0.24% to 0.26%, Si: 0.22% to 0.26%, Mn: 1.18% to 1.22%, P≤0.018%, S≤0.004%, Cr: 0.35% to 0.39%, B: 0.0017% to 0.0023%, Ti: 0.022% to 0.032%, Ni≤0.30%, Mo≤0.08%, Cu≤0.35%, Al: 0.018% to 0.025%, H≤0.0015%, Pb≤0.02%, Sn≤0.03%, As≤0.03%, the remaining components are Fe and unavoidable impurities;

[0011] The oxygen content of the high-cleanliness track plate steel is ≤12ppm; the non-metallic inclusions of Class A are ≤1.5, Class B are ≤1.0, Class C are 0, Class D are ≤1.0, and DS are ≤1.0.

[0012] The high-cleanliness track shoe steel of the present invention has an S content of ≤0.004%, which can significantly reduce the level of Class A non-metallic inclusions. The high-cleanliness track shoe steel has a low oxygen content and low contents of various non-metallic inclusions, which greatly improves the purity of the track shoe steel and thereby increases the service life of the track shoe.

[0013] The chemical composition of the high-cleanliness track shoe steel of the present invention includes, by mass percentage: C: 0.24% to 0.26%, for example, 0.24%, 0.243%, 0.245%, 0.248%, 0.25%, 0.255%, 0.257% or 0.26%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0014] Si: 0.22% to 0.26%, for example, 0.22%, 0.225%, 0.23%, 0.24%, 0.245%, 0.25%, 0.255% or 0.26%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0015] Mn: 1.18% to 1.22%, for example, 1.18%, 1.185%, 1.19%, 1.195%, 1.20%, 1.21%, 1.215%, or 1.22%, but is not limited to the listed values. Other values not listed within the range are also applicable.

[0016] P≤0.018%, for example, it can be 0.018%, 0.017%, 0.016%, 0.015%, 0.014%, 0.012%, 0.011% or 0.01%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0017] S≤0.004%, for example, it can be 0.004%, 0.0038%, 0.0035%, 0.0033%, 0.003%, 0.0025%, 0.002% or 0.001%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0018] Cr: 0.35% to 0.39%, for example, 0.35%, 0.355%, 0.36%, 0.37%, 0.38%, 0.385%, 0.388% or 0.39%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0019] B: 0.0017% to 0.0023%, for example, 0.0017%, 0.0018%, 0.0019%, 0.002%, 0.0021%, 0.00215%, 0.0022% or 0.0023%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0020] Ti: 0.022% to 0.032%, for example, 0.022%, 0.023%, 0.025%, 0.027%, 0.028%, 0.029%, 0.03% or 0.032%, but is not limited to the listed values. Other values not listed within this range are also applicable;

[0021] Ni≤0.30%, for example, it can be 0.30%, 0.28%, 0.25%, 0.23%, 0.2%, 0.18%, 0.15% or 0.1%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0022] Mo ≤ 0.08%, for example, it can be 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.035%, 0.03% or 0.01%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0023] Cu≤0.35%, for example, it can be 0.35%, 0.33%, 0.3%, 0.28%, 0.25%, 0.21%, 0.2% or 0.1%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0024] Al: 0.018% to 0.025%, for example, 0.018%, 0.0185%, 0.0188%, 0.019%, 0.0195%, 0.02%, 0.023% or 0.025%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0025] H≤0.0015%, for example, it can be 0.0015%, 0.0014%, 0.0013%, 0.0012%, 0.0011%, 0.001%, 0.0009% or 0.0005%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0026] Pb ≤ 0.02%, for example, it can be 0.02%, 0.018%, 0.015%, 0.013%, 0.011%, 0.01%, 0.009% or 0.005%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0027] Sn≤0.03%, for example, it can be 0.03%, 0.028%, 0.025%, 0.022%, 0.02%, 0.018%, 0.015% or 0.01%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0028] As≤0.03%, for example, it can be 0.03%, 0.028%, 0.025%, 0.023%, 0.02%, 0.018%, 0.015% or 0.01%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0029] The oxygen content in the high-cleanliness track shoe steel is ≤12ppm, for example, it can be 12ppm, 11.5ppm, 11ppm, 10ppm, 9ppm, 7ppm or 5ppm, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0030] In a second aspect, the present invention further provides a method for preparing the high-cleanliness track shoe steel as described in the first aspect, the preparation method comprising the following steps:

[0031] The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel;

[0032] The end point C of the converter smelting is above 0.08%;

[0033] The LF refining adopts a ternary high-aluminum slag system, and the components thereof include, by mass percentage, CaO: 45% to 55%, SiO2≤8%, and Al2O3: 35% to 40%.

[0034] The method for preparing high-cleanliness track plate steel described in the present invention uses vanadium-extracted semi-steel liquid as raw material, which has extremely low vanadium content, low phosphorus and sulfur contents, and is suitable for smelting high-purity steel; the vanadium-extracted semi-steel liquid is first subjected to KR pretreatment and further desulfurization by mechanical stirring; then, converter steelmaking is carried out, and high carbon drawing reduces the total oxygen content, thereby reducing the gas content in the steel and the amount of various inclusions generated; in LF refining, a ternary high-aluminum slag system is used to achieve the characteristics of low melting point, good fluidity, and strong inclusion adsorption capacity of the LF furnace final slag, thereby controlling the formation of DS-type non-metallic inclusions, and subsequently VD vacuum degassing and continuous casting are carried out to prepare high-cleanliness track plate steel with low oxygen content and few non-metallic inclusions.

[0035] The method for producing high-cleanliness track shoe steel disclosed herein reduces the total oxygen content in the track shoe steel by ensuring that the carbon content at the end point of converter smelting is above 0.08%. This prevents the formation of numerous fine Al2O3 particles after strong aluminum deoxidation at tapping, which serve as nuclei for the formation of DS inclusions. The converter carbon-oxygen product is approximately 0.0023, thus controlling the total dissolved oxygen below 230 ppm and reducing the formation of various inclusions.

[0036] The LF refining of the present invention adopts a ternary high-aluminum slag system, and the components, by mass percentage, include: CaO: 45% to 55%, for example, 45%, 48%, 50%, 52%, 53%, 54% or 55%, etc., but are not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0037] SiO2≤8%, for example, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0038] Al2O3: 35% to 40%, for example, it can be 35%, 36%, 36.5%, 37%, 37.5%, 38%, 39% or 40%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0039] Preferably, lime, fluorite and aluminum particles are added during the KR pretreatment.

[0040] Preferably, S in the vanadium-extracted semi-steel after KR pretreatment is ≤0.020%, for example, it can be 0.020%, 0.018%, 0.015%, 0.013%, 0.01%, 0.009%, 0.005% or 0.002%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0041] Preferably, the stirring speed of the KR pretreatment is 80 to 100 r / min, for example, 80 r / min, 85 r / min, 88 r / min, 90 r / min, 93 r / min, 95 r / min or 100 r / min, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0042] The stirring time is 12 to 20 minutes, for example, 12 minutes, 13 minutes, 15 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0043] Preferably, the endpoint P of the converter smelting is ≤0.012%, for example, it can be 0.012%, 0.011%, 0.01%, 0.009%, 0.008%, 0.005%, 0.003% or 0.001%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0044] When the converter end point S≤0.025%, the composition of the ternary high-alumina slag added in LF refining does not need to be adjusted; when the end point S>0.025%, lime can be added as a deoxidizer according to actual conditions.

[0045] Preferably, the temperature of the converter smelting is ≥1620°C, for example, it can be 1620°C, 1630°C, 1650°C, 1680°C, 1700°C, 1705°C or 1710°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0046] Preferably, the sulfur solubility ratio R of the LF refining is 6 to 12, for example, 6, 7, 8, 10, 11 or 12, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0047] Preferably, the LF refining time is ≥ 48 min, for example, it can be 48 min, 49 min, 50 min, 52 min, 54 min, 55 min or 58 min, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0048] The white slag retention time is ≥15 min, for example, it can be 15 min, 17 min, 20 min, 22 min, 25 min or 30 min, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0049] Preferably, the deep vacuum holding time of the VD vacuum degassing is ≥12 min, for example, it can be 12 min, 15 min, 17 min, 20 min, 22 min, 25 min or 30 min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0050] The soft blowing time is ≥ 25 min, for example, it can be 25 min, 26 min, 27 min, 28 min, 30 min, 32 min or 35 min, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0051] The present invention preferably adopts a deep vacuum holding time of ≥12 min and a soft blowing time of ≥25 min in the VD vacuum degassing to ensure that inclusions have sufficient time to float.

[0052] Preferably, calcium wire is fed into the first furnace during the VD vacuum degassing process, and calcium wire is not fed into the continuous casting furnaces to reduce the probability of formation of DS type non-metallic inclusions.

[0053] Preferably, the feeding amount of the calcium wire is 40 to 60 m / furnace, for example, 40 m / furnace, 42 m / furnace, 45 m / furnace, 50 m / furnace, 55 m / furnace, 57 m / furnace or 60 m / furnace, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0054] Preferably, the continuous casting adopts full-degree protective pouring, and the tundish uses a high-magnesium dry material with a MgO mass content of ≥85%, for example, it can be 85%, 85.5%, 86%, 87%, 88%, 89%, 90% or 95%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0055] The argon filling pressure of the tundish is 0.25-0.35 MPa, for example, 0.25 MPa, 0.26 MPa, 0.27 MPa, 0.28 MPa, 0.29 MPa, 0.3 MPa or 0.35 MPa, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable;

[0056] The argon filling time is ≥ 4 min, for example, it can be 4 min, 4.5 min, 5 min, 6 min, 8 min, 10 min or 15 min, but is not limited to the listed values. Other values not listed within the numerical range are also applicable;

[0057] The ladle adopts the residual steel operation, and the residual steel amount of each furnace is ≥2.5t, for example, it can be 2.5t, 2.6t, 2.7t, 2.8t, 2.9t, 3t or 3.2t, etc., but it is not limited to the listed values. Other values not listed in the numerical range are also applicable.

[0058] In the present invention, continuous casting adopts full-degree protection pouring, and high-magnesium dry material is used in the tundish, which improves the corrosion resistance of the track plate steel and reduces the entry of non-metallic inclusions in the track plate steel.

[0059] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0060] The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel;

[0061] Lime, fluorite and aluminum particles are added during the KR pretreatment; S in the vanadium-extracted semi-steel water after the KR pretreatment is less than or equal to 0.020%; the stirring speed of the KR pretreatment is 80 to 100 r / min, and the stirring time is 12 to 20 min;

[0062] The end point C of the converter smelting is above 0.08%; the end point P is ≤ 0.012%; the temperature of the converter smelting is ≥ 1620°C;

[0063] The LF refining adopts a ternary high-aluminum slag system, wherein the components by mass percentage include: CaO: 45% to 55%, SiO2 ≤ 8%, Al2O3: 35% to 40%; the sulfur solubility ratio R of the LF refining is 6 to 12; the LF refining time is ≥ 48 minutes, and the white slag holding time is ≥ 15 minutes;

[0064] The deep vacuum holding time of the VD vacuum degassing is ≥12 minutes, and the soft blowing time is ≥25 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnaces. The feeding amount of the calcium wire is 40-60m / furnace.

[0065] The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content ≥85%, the argon filling pressure of the middle ladle is 0.25-0.35MPa, and the argon filling time is ≥4min; the large ladle adopts leftover steel operation, and the leftover steel amount of each furnace is ≥2.5t.

[0066] Compared with the prior art, the present invention has at least the following beneficial effects:

[0067] The preparation method of high-cleanliness track plate steel provided by the present invention achieves improved purity of track plate steel in terms of gas content and non-metallic inclusions through the coordination of KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting process stages, thereby extending the service life of the track plate and being suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a flow chart of a method for preparing high-cleanliness track plate steel in Example 1 of the present invention. DETAILED DESCRIPTION

[0069] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0070] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0071] Example 1

[0072] This embodiment provides a high-cleanliness track shoe steel, the chemical composition of the high-cleanliness track shoe steel includes, by mass percentage:

[0073] C: 0.25%, Si: 0.24%, Mn: 1.2%, P: 0.018%, S: 0.003%, Cr: 0.38%, B: 0.002%, Ti: 0.025%, Ni: 0.20%, Mo: 0.06%, Cu: 0.3%, Al: 0.022%, H: 0.001%, Pb: 0.01%, Sn: 0.01%, As: 0.02%, and the remaining components are Fe and inevitable impurities.

[0074] This embodiment also provides a method for preparing the high-cleanliness track plate steel, the flow chart of which is as follows: Figure 1 shown.

[0075] The preparation method comprises the following steps:

[0076] The vanadium-extracted semi-steel liquid is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting, and then sequentially subjected to stack cooling and storage finishing to obtain the high-cleanliness track plate steel;

[0077] Lime, fluorite and aluminum particles are added during the KR pretreatment; the sulfur content of the vanadium-extracted semi-steel water after the KR pretreatment is 0.01%; the stirring speed of the KR pretreatment is 90 r / min and the stirring time is 15 min;

[0078] The end point C of the converter smelting is 0.1%; the end point P is 0.01%; the temperature of the converter smelting is 1650°C;

[0079] The LF refining uses a ternary high-aluminum slag system, the components of which are calculated by mass percentage as follows: CaO: 53%, SiO2: 8%, Al2O3: 39%; the sulfur solubility ratio R of the LF refining is 8; the LF refining time is 50 minutes, and the white slag holding time is 20 minutes;

[0080] The deep vacuum holding time of the VD vacuum degassing is 15 minutes, and the soft blowing time is 28 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnace. The feeding amount of the calcium wire is 50m / furnace.

[0081] The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content of 88%, the middle ladle is filled with argon pressure of 0.27MPa, and the argon filling time is 8min; the large ladle adopts leftover steel operation, and the leftover steel volume of each furnace is 2.5t.

[0082] Example 2

[0083] This embodiment provides a high-cleanliness track shoe steel, the chemical composition of the high-cleanliness track shoe steel includes, by mass percentage:

[0084] C: 0.24%, Si: 0.26%, Mn: 1.18%, P: 0.012%, S: 0.002%, Cr: 0.35%, B: 0.0017%, Ti: 0.032%, Ni: 0.130%, Mo: 0.03%, Cu: 0.15%, Al: 0.018%, H: 0.0011%, Pb: 0.012%, Sn: 0.003%, As: 0.013%, and the remaining components are Fe and inevitable impurities.

[0085] This embodiment also provides a method for preparing the high-cleanliness track plate steel, the method comprising the following steps:

[0086] The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel;

[0087] Lime, fluorite and aluminum particles are added during the KR pretreatment; the S content of the vanadium-extracted semi-steel water after the KR pretreatment is 0.012%; the stirring speed of the KR pretreatment is 80 r / min and the stirring time is 20 min;

[0088] The end point C of the converter smelting is 0.2%; the end point P is 0.0102%; the temperature of the converter smelting is 1680°C;

[0089] The LF refining uses a ternary high-alumina slag system, the components of which, by mass percentage, include: CaO: 55%, SiO2: 7%, Al2O3: 38%; the sulfur solubility ratio R of the LF refining is 12; the LF refining time is 52 minutes, and the white slag holding time is 18.5 minutes;

[0090] The deep vacuum holding time of the VD vacuum degassing is 16 minutes, and the soft blowing time is 29 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnace. The feeding amount of the calcium wire is 40m / furnace.

[0091] The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content of 91%, the middle ladle is filled with argon pressure of 0.35MPa, and the argon filling time is 7min; the large ladle adopts leftover steel operation, and the leftover steel volume of each furnace is 3.5t.

[0092] Example 3

[0093] This embodiment provides a high-cleanliness track shoe steel, the chemical composition of the high-cleanliness track shoe steel includes, by mass percentage:

[0094] C: 0.26%, Si: 0.22%, Mn: 1.22%, P: 0.0018%, S: 0.0022%, Cr: 0.39%, B: 0.0023%, Ti: 0.022%, Ni: 0.03%, Mo: 0.02%, Cu: 0.035%, Al: 0.025%, H: 0.0013%, Pb: 0.012%, Sn: 0.003%, As: 0.003%, and the remaining components are Fe and inevitable impurities.

[0095] This embodiment also provides a method for preparing the high-cleanliness track plate steel, the method comprising the following steps:

[0096] The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel;

[0097] Lime, fluorite and aluminum particles are added during the KR pretreatment; the sulfur content in the vanadium-extracted semi-steel water after the KR pretreatment is 0.010%; the stirring speed of the KR pretreatment is 100 r / min and the stirring time is 12 min;

[0098] The end point C of the converter smelting is 0.09%; the end point P is 0.0012%; the temperature of the converter smelting is 1660°C;

[0099] The LF refining uses a ternary high-alumina slag system, the components of which, by mass percentage, include: CaO: 55%, SiO2: 5%, Al2O3: 40%; the sulfur solubility ratio R of the LF refining is 6; the LF refining time is 55 minutes, and the white slag holding time is 24.5 minutes;

[0100] The deep vacuum holding time of the VD vacuum degassing is 12.8 minutes, and the soft blowing time is 25.5 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnace. The feeding amount of the calcium wire is 60m / furnace.

[0101] The continuous casting adopts full-degree protective pouring, the middle ladle uses high-magnesium dry material with a MgO mass content of 85.8%, the middle ladle is filled with argon at a pressure of 0.25 MPa, and the argon filling time is 8.8 minutes; the large ladle adopts leftover steel operation, and the leftover steel volume of each furnace is 3.6 tons.

[0102] Example 4

[0103] This embodiment provides a high-cleanliness track shoe steel, the chemical composition of the high-cleanliness track shoe steel includes, by mass percentage:

[0104] C: 0.248, Si: 0.223%, Mn: 1.186%, P: 0.0118%, S: 0.0024%, Cr: 0.355%, B: 0.00176%, Ti: 0.0223%, Ni: 0.03%, Mo: 0.008%, Cu: 0.035%, Al: 0.0188%, H: 0.001%, Pb: 0.012%, Sn: 0.003%, As: 0.003%, and the remaining components are Fe and inevitable impurities.

[0105] This embodiment also provides a method for preparing the high-cleanliness track plate steel, the method comprising the following steps:

[0106] The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel;

[0107] Lime, fluorite and aluminum particles are added during the KR pretreatment; S in the vanadium-extracted semi-steel water after the KR pretreatment is 0.002%; the stirring speed of the KR pretreatment is 88 r / min and the stirring time is 12.3 min;

[0108] The end point C of the converter smelting is 0.088%; the end point P is 0.0012%; the temperature of the converter smelting is 1680°C;

[0109] The LF refining uses a ternary high-alumina slag system, the components of which, by mass percentage, include: CaO: 52%, SiO2: 8%, Al2O3: 40%; the sulfur solubility ratio R of the LF refining is 6.6; the LF refining time is 48.8 minutes, and the white slag holding time is 15.5 minutes;

[0110] The deep vacuum holding time of the VD vacuum degassing is 12.5 minutes, and the soft blowing time is 25.5 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnace. The feeding amount of the calcium wire is 40.6m / furnace.

[0111] The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content of 85.5%, the middle ladle is filled with argon pressure of 0.258MPa, and the argon filling time is 4.8min; the large ladle adopts leftover steel operation, and the leftover steel volume of each furnace is 2.58t.

[0112] From Examples 1 to 4, it can be seen that the method for preparing high-cleanliness track shoe steel provided by the present invention, through specific process control, has an oxygen content of ≤12ppm; non-metallic inclusions of Class A ≤1.5, Class B ≤1.0, Class C 0, Class D ≤1.0, DS ≤1.0, high cleanliness and long service life.

[0113] Example 5

[0114] This embodiment provides a high-cleanliness track shoe steel, which is the same as that in Example 1.

[0115] This embodiment also provides a preparation method for the high-cleanliness track plate steel. The preparation method is the same as that of Example 1 except that the soft blowing time of the VD vacuum degassing is 20 minutes.

[0116] In this embodiment, since the soft blowing time of VD vacuum degassing is short, the inclusions do not have sufficient time to float up, and the purity of the track plate steel finally prepared is lower than that of the embodiment, which in turn leads to a shorter service life of the track plate.

[0117] Example 6

[0118] This embodiment provides a high-cleanliness track shoe steel, which is the same as that in Example 1.

[0119] This embodiment also provides a preparation method for the high-cleanliness track plate steel. The preparation method is the same as that of Example 1 except that a high-magnesium dry material with a MgO mass content of 80% is used in the continuous casting tundish.

[0120] In this embodiment, due to the low MgO mass content in the high-magnesium dry material in the continuous casting tundish, the corrosion resistance of the track plate steel is low, which in turn leads to the entry of non-metallic inclusions in the track plate steel, affecting the purity of the track plate steel finally prepared.

[0121] Comparative Example 1

[0122] This comparative example provides a high-cleanliness track shoe steel. The high-cleanliness track shoe steel is the same as Example 1 except that the S content is 0.008%.

[0123] This comparative example also provides a preparation method of the high-cleanliness track shoe steel, which is the same as that in Example 1.

[0124] In this comparative example, due to the high S content in the high-cleanliness track shoe steel, more Class A non-metallic inclusions will be present, and the cleanliness of the prepared track shoe steel will be reduced, thereby shortening the service life of the track shoe.

[0125] Comparative Example 2

[0126] This comparative example provides a high-cleanliness track shoe steel, which is the same as that in Example 1.

[0127] This comparative example also provides a preparation method for the high-cleanliness track plate steel. The preparation method is the same as that of Example 1 except that the end point C of the converter smelting is 0.05%.

[0128] In this comparative example, due to the high C content at the end point of converter smelting, the total oxygen content in the track shoe steel increases, which in turn leads to the formation of a large number of fine Al2O3 particles after the steel is strongly deoxidized by aluminum, and the content of DS-type inclusions greatly increases. The cleanliness of the track shoe steel finally prepared is reduced, which in turn shortens the service life of the track shoe.

[0129] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A high-cleanliness track shoe steel, characterized in that: The chemical composition of the high-cleanliness track shoe steel includes, by mass percentage: C: 0.24% to 0.26%, Si: 0.22% to 0.26%, Mn: 1.18% to 1.22%, P≤0.018%, S≤0.004%, Cr: 0.35% to 0.39%, B: 0.0017% to 0.0023%, Ti: 0.022% to 0.032%, Ni≤0.30%, Mo≤0.08%, Cu≤0.35%, Al: 0.018% to 0.025%, H≤0.0015%, Pb≤0.02%, Sn≤0.03%, As≤0.03%, the remaining components are Fe and unavoidable impurities; The oxygen content of the high-cleanliness track plate steel is ≤12ppm; the non-metallic inclusions of Class A are ≤1.5, Class B are ≤1.0, Class C are 0, Class D are ≤1.0, and DS are ≤1.

0.

2. A method for preparing high-cleanliness track shoe steel according to claim 1, characterized in that: The preparation method comprises the following steps: The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel; The end point C of the converter smelting is above 0.08%; The LF refining adopts a ternary high-aluminum slag system, and the components thereof include, by mass percentage, CaO: 45% to 55%, SiO2≤8%, and Al2O3: 35% to 40%.

3. The preparation method according to claim 2, characterized in that Lime, fluorite and aluminum particles are added during the KR pretreatment; Preferably, the S content in the vanadium-extracted semi-steel after KR pretreatment is ≤ 0.020%; Preferably, the stirring speed of the KR pretreatment is 80-100 r / min, and the stirring time is 12-20 min.

4. The preparation method according to claim 2 or 3, characterized in that The end point P of the converter smelting is ≤ 0.012%; Preferably, the temperature of the converter smelting is ≥1620°C.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The sulfur solubility ratio R of the LF refining is 6-12.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The LF refining time is ≥48 min, and the white slag holding time is ≥15 min.

7. The preparation method according to any one of claims 2 to 6, characterized in that: The deep vacuum holding time of the VD vacuum degassing is ≥12 min, and the soft blowing time is ≥25 min.

8. The preparation method according to any one of claims 2 to 7, characterized in that During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnaces; Preferably, the feeding amount of the calcium wire is 40 to 60 m / furnace.

9. The preparation method according to any one of claims 2 to 8, characterized in that The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content ≥85%, the argon filling pressure of the middle ladle is 0.25-0.35MPa, and the argon filling time is ≥4min; the large ladle adopts leftover steel operation, and the leftover steel amount of each furnace is ≥2.5t.

10. The preparation method according to any one of claims 2 to 9, characterized in that: The preparation method comprises the following steps: The vanadium-extracted semi-molten steel is sequentially subjected to KR pretreatment, converter smelting, LF refining, VD vacuum degassing and continuous casting to obtain the high-cleanliness track plate steel; Lime, fluorite and aluminum particles are added during the KR pretreatment; S in the vanadium-extracted semi-steel water after the KR pretreatment is less than or equal to 0.020%; the stirring speed of the KR pretreatment is 80 to 100 r / min, and the stirring time is 12 to 20 min; The end point C of the converter smelting is above 0.08%; the end point P is ≤ 0.012%; the temperature of the converter smelting is ≥ 1620°C; The LF refining adopts a ternary high-aluminum slag system, wherein the components by mass percentage include: CaO: 45% to 55%, SiO2 ≤ 8%, Al2O3: 35% to 40%; the sulfur solubility ratio R of the LF refining is 6 to 12; the LF refining time is ≥ 48 minutes, and the white slag holding time is ≥ 15 minutes; The deep vacuum holding time of the VD vacuum degassing is ≥12 minutes, and the soft blowing time is ≥25 minutes. During the VD vacuum degassing process, calcium wire is fed into the first furnace, and no calcium wire is fed into the continuous casting furnaces. The feeding amount of the calcium wire is 40-60m / furnace. The continuous casting adopts full-degree protection pouring, the middle ladle uses high-magnesium dry material with MgO mass content ≥85%, the argon filling pressure of the middle ladle is 0.25-0.35MPa, and the argon filling time is ≥4min; the large ladle adopts leftover steel operation, and the leftover steel amount of each furnace is ≥2.5t.

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