A high-speed flying shear for a cast and rolled thin wide strip steel production line and a manufacturing method thereof

Abstract

The application discloses a high-speed flying shear for a cast-rolling thin wide strip steel production line, and chemical components of the high-speed flying shear are as follows in percentage by mass (wt%): C: 0.6-0.7%, Si: 0.5% or less, Mn: 0.5% or less, P: 0.025% or less, S: 0.01% or less, Cr: 5.5-6.5%, Mo: 3.0-3.8%, Ni: 2.0-2.8%, V: 1.5-2.0%, W: 0.6-0.9%, and the balance of Fe. Meanwhile, the application discloses a manufacturing method of the high-speed flying shear: vacuum induction smelting, argon protection electroslag remelting, ingot casting, forging and spheroidizing annealing, rough milling, boring and milling, drilling, quenching and three times of tempering, flat grinding and numerical control grinding. The high-speed flying shear for the cast-rolling thin wide strip steel production line obtained according to the material quality, the processing steps and the heat treatment process has high strength and toughness and high wear resistance, prolongs the shearing life, guarantees the shearing demand of the steel rolling production line and meets the shearing demand of the cast-rolling thin wide strip steel production line.

Description

Technical Field

[0001] The invention relates to a material for a long-life high-speed flying shear and a manufacturing method thereof, which is suitable for coil shearing of strip steel in a casting and rolling thin wide strip steel production line. Background Art

[0002] The high-speed flying shear is a crucial component in cast-rolled thin and wide strip steel production lines. Its primary function is to separate and shear strip steel with a thickness of 0.6-4mm. It primarily handles ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel, low-alloy high-strength steel, IF steel, duplex steel, and pipeline steel. The high-speed flying shear has a shearing width of 900-1600mm, a shearing speed of 1.33-13.33m / s, and a shearing temperature of 200-800°C.

[0003] At present, some heavy equipment in the cast and rolled thin wide strip steel production line has been domestically produced, but the core component of the high-speed flying shear for shearing steel plates is still imported. In the process of shearing steel plates, the imported high-speed flying shears often suffer from defects such as chipping, cracks, and wear, forcing the failed flying shears to be taken offline. The number of times they can shear steel plates can only reach about 400 times. In addition, due to the problems of chipping, cracks, and wear of the high-speed flying shears, a large amount of cutting edge grinding is required after they are taken offline, and the number of repeated grinding is extremely limited, resulting in a short service life. At the same time, it also restricts the production efficiency of the steel rolling line.

[0004] The following is an analysis of the reasons for the above shortcomings of imported high-speed flying shears: The main materials of imported high-speed flying shears are Cr12Mo1V1 and 7Cr7Mo3V2Si; among them, Cr12Mo1V1 material is a typical ledeburite steel. During the casting process, as the temperature decreases, carbides are very likely to aggregate, grow and angularize; due to the limitations of smelting and forging levels, the finished shear blade contains a large amount of unevenly distributed carbides, the size of which even reaches more than 100um; carbides themselves are high in hardness and brittle. Aggregated strip-shaped and angular block-shaped carbides easily cause stress concentration during the shearing process, reducing the fatigue performance and toughness of the shear blade, causing early failures such as chipping, cracks, and wear; among them, 7Cr7Mo3V2Si material is a base steel with high strength and toughness but insufficient wear resistance. In summary, the currently used high-speed flying shears are difficult to meet the shearing needs of the cast and rolled thin wide strip steel production line. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a high-speed flying shear for a cast-rolled thin wide strip steel production line, which has high strength and toughness and high wear resistance, thereby extending the service life, ensuring the shearing quality, and meeting the shearing requirements of the cast-rolled thin wide strip steel production line. At the same time, the present invention also provides a manufacturing method of the high-speed flying shear.

[0006] The invention discloses a high-speed flying shear for a cast-rolled thin wide strip steel production line, wherein the mass percentage (wt%) of the chemical composition is as follows: C: 0.6-0.7%, Si≤0.5%, Mn≤0.5%, P≤0.025%, S≤0.01%, Cr: 5.5-6.5%, Mo: 3.0-3.8%, Ni: 2.0-2.8%, V: 1.5-2.0%, W: 0.6-0.9%, and the balance is Fe.

[0007] Among them, the mass percentage of the high-speed flying shear chemical composition is preferably: C: 0.65%, Si: 0.32%, Mn: 0.44%, P: 0.018%, S: 0.01%, Cr: 5.85%, Mo: 3.55%, Ni: 2.55%, V: 1.69%, W: 0.68%, and the balance is Fe.

[0008] Among them, the mass percentage of the chemical composition of the high-speed flying shear is preferably: C: 0.68%, Si: 0.35%, Mn: 0.47%, P: 0.015%, S: 0.008%, Cr: 6.35%, Mo: 3.35%, Ni: 2.32%, V: 1.84%, W: 0.83%, and the balance is Fe.

[0009] Among them, the mass percentage of the high-speed flying shear chemical composition is preferably: C: 0.62%, Si: 0.33%, Mn: 0.38%, P: 0.020%, S: 0.006%, Cr: 6.15%, Mo: 3.75%, Ni: 2.75%, V: 1.98%, W: 0.75%, and the balance is Fe.

[0010] The high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention is manufactured by the following method: vacuum induction melting → argon gas protected electroslag remelting → ingot casting → forging and spheroidizing annealing → rough milling → boring and milling → drilling → quenching + three-times tempering → flat grinding → CNC grinding.

[0011] The specific heat treatment process is as follows: (1) spheroidizing annealing: 860±10℃ holding furnace cooling + 750±10℃ holding furnace cooling to 500±10℃, and then air cooling to room temperature; (2) quenching and tempering: first holding at 1080±10℃ and then oil cooling to room temperature, then holding at 550±10℃ for the first tempering, air cooling to room temperature, then holding at 570±10℃ for the second tempering, and then air cooling to room temperature, and finally holding at 580±10℃ for the third tempering, and then air cooling to room temperature.

[0012] Among them, the heating rate is 100±20℃ / h, the spheroidizing and quenching holding time is 1-2 minutes / mm according to the effective thickness of the high-speed flying shear, and the tempering holding time is controlled at 2-4 minutes / mm.

[0013] Among them, the hardness after spheroidizing annealing treatment is 240-255HB, and the structure is granular pearlite matrix with spherical carbides distributed on it; the hardness after quenching and tempering is 56-60HRC, and the structure is tempered martensite + carbide.

[0014] The room temperature mechanical properties of the high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention are: compressive strength ≥3400MPa; tensile strength ≥2300MPa; yield strength ≥2000MPa; elongation after fracture ≥5%; cross-sectional shrinkage ≥5%; and impact energy (without notch) ≥80J.

[0015] The high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention can meet the shearing needs of the cast-rolled thin wide strip steel production line such as ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel, low alloy high-strength steel, IF steel, dual-phase steel, pipeline steel, etc. It can be ground offline after 1000 shearings in a single time, with the single grinding amount within 0.5mm, and can be ground 10 times.

[0016] The advantages of the high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention are: 1. Reasonable configuration and optimization of the alloy element ratio: the C, Cr, and Si contents in the steel are reduced, thereby reducing eutectic carbides, and at the same time, an appropriate amount of W is added to form stable carbides, and the Mo content is increased to suppress the uneven distribution of carbides and refine the grains; in addition, the Ni element is added to the high-speed flying shear material to enhance the strength and toughness of the matrix; 2. Determine the appropriate manufacturing method, especially the heat treatment process and corresponding process parameters: spheroidizing annealing, quenching + three tempering are set, and the heating time, the temperature reached, the insulation method, the insulation time, etc. of the spheroidizing annealing and quenching + three tempering are properly controlled, so that the high-speed flying shear obtains a uniform structure after the spheroidizing annealing heat treatment process, making structural preparations for the final heat treatment; the hardness of the high-speed flying shear is further improved and the matrix is ​​strengthened after quenching + three tempering, thereby improving all aspects of the high-speed flying shear performance, thereby significantly improving the service life of the shear blade and ensuring the shearing quality.

[0017] In summary, the high-speed flying shear for the cast-rolled thin wide strip steel production line obtained according to the material, processing steps and heat treatment process of the present invention has high strength and toughness, high wear resistance, extends the shear life, ensures the shearing requirements of the steel rolling production line, and meets the shearing requirements of the cast-rolled thin wide strip steel production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a metallographic photograph of the structure of the high-speed flying shear of the cast-rolled thin wide strip steel production line of the present invention after spheroidizing annealing.

[0019] Figure 2 This is a metallographic photograph of the structure of the high-speed flying shear of the cast-rolled thin wide strip steel production line of the present invention after quenching and tempering. DETAILED DESCRIPTION

[0020] The technical solutions related to the high-speed flying shear for the thin wide strip steel production line for casting and rolling of the present invention are further described in detail below with reference to the embodiments.

[0021] The present invention provides a high-speed flying shear for a cast-rolled thin wide strip steel production line, wherein the mass percentage (wt%) of the chemical composition is: C: 0.6-0.7%, Si≤0.5%, Mn≤0.5%, P≤0.025%, S≤0.01%, Cr: 5.5-6.5%, Mo: 3.0-3.8%, Ni: 2.0-2.8%, V: 1.5-2.0%, W: 0.6-0.9%, and the balance is Fe.

[0022] Among them, the mass percentage of the high-speed flying shear chemical composition is preferably: C: 0.65%, Si: 0.32%, Mn: 0.44%, P: 0.018%, S: 0.01%, Cr: 5.85%, Mo: 3.55%, Ni: 2.55%, V: 1.69%, W: 0.68%, and the balance is Fe.

[0023] Among them, the mass percentage of the chemical composition of the high-speed flying shear is preferably: C: 0.68%, Si: 0.35%, Mn: 0.47%, P: 0.015%, S: 0.008%, Cr: 6.35%, Mo: 3.35%, Ni: 2.32%, V: 1.84%, W: 0.83%, and the balance is Fe.

[0024] Among them, the mass percentage of the high-speed flying shear chemical composition is preferably: C: 0.62%, Si: 0.33%, Mn: 0.38%, P: 0.020%, S: 0.006%, Cr: 6.15%, Mo: 3.75%, Ni: 2.75%, V: 1.98%, W: 0.75%, and the balance is Fe.

[0025] Table 1 shows a comparison of the chemical composition mass percentages of the Cr12Mo1V1 and 7Cr7Mo3V2Si materials in the above three embodiments of the present invention and the background art.

[0026] Table 1. Material composition (wt%) of high-speed flying shears used in thin wide steel casting production lines

[0027]

[0028] As can be seen from the table above, the chemical composition characteristics of the high-speed flying shear used in the cast-rolled thin wide strip steel production line of the present invention are reduced C, Cr, and Si contents in the steel, thereby reducing eutectic carbides. Simultaneously, the appropriate addition of W forms stable carbides, while the increased Mo content suppresses uneven carbide distribution and refines grain size. Furthermore, the addition of Ni to the high-speed flying shear material enhances the strength and toughness of the substrate.

[0029] The manufacturing method for the high-speed flying shear for a cast-rolled thin wide steel production line comprises the following steps: vacuum induction melting → argon-shielded electroslag remelting → ingot casting → forging and spheroidizing annealing → rough milling → boring and milling → drilling → quenching and triple tempering → flat grinding → CNC grinding. The high-speed flying shear is forged into a blank with dimensions of 2000 mm in length, 150 mm in width, and at least 100 mm in thickness.

[0030] The specific heat treatment process in the manufacturing method is as follows: (1) spheroidizing annealing: 860±10℃ holding furnace cooling + 750±10℃ holding furnace cooling to 500±10℃, and then air cooling to room temperature; (2) quenching and tempering: first holding at 1080±10℃ and then oil cooling to room temperature, then holding at 550±10℃ for the first tempering, air cooling to room temperature, then holding at 570±10℃ for the second tempering, and then air cooling to room temperature, and finally holding at 580±10℃ for the third tempering, and then air cooling to room temperature. Among them, the heating rate is 100±20℃ / h, the holding time for spheroidizing and quenching is 1-2 minutes / mm, and the holding time for tempering is controlled at 2-4 minutes / mm.

[0031] The heat treatment processes of the high-speed flying shear for the thin wide strip steel production line according to the three embodiments of the present invention are shown in Table 2:

[0032] Table 2. Heat treatment process of high-speed flying shear for thin wide steel production line

[0033]

[0034] After the high-speed flying shear for the cast-rolled thin wide steel production line of the present invention is subjected to the spheroidizing annealing heat treatment process, the metallographic structure is mainly granular pearlite with spherical carbides distributed on the matrix, the carbide grade is level 2, and the hardness is 240-255HB. Figure 1 shown.

[0035] After quenching and three-times tempering heat treatment, the high-speed flying shear for the cast-rolled thin wide steel production line of the present invention has a metallographic structure mainly consisting of tempered martensite + carbide, with a hardness of 56-60 HRC, as shown in Figure 2. The high-speed flying shear for the cast-rolled thin wide steel production line is then fine-machined using a high-precision surface grinder and a CNC grinder.

[0036] The room temperature mechanical properties and friction and wear tests of the samples of the high-speed flying shears obtained by processing the Cr12Mo1V1 and 7Cr7Mo3V2Si materials in the three embodiments of the present invention and the background art are shown in Tables 3 and 4.

[0037] Table 3 Mechanical properties of high-speed flying shears for thin wide strip steel production lines (23°C)

[0038]

[0039] Table 4. Friction and wear properties of high-speed flying shears used in cast-rolled thin wide steel production lines (load 300N, speed 200r / min, wear time 30min)

[0040] Original weight M0 / g Weight after wear M1 / g Weight loss ΔM / g Weight loss rate% Average friction coefficient Example 1 9.5161 9.5146 0.0015 0.016 0.6607 Example 2 9.5516 9.5502 0.0014 0.015 0.6195 Example 3 9.5825 9.5809 0.0016 0.017 0.6610 Comparative Example Cr12Mo1V1 9.5432 9.5401 0.0031 0.032 0.6876 Comparative Example 7Cr7Mo3V2Si 9.5645 9.5542 0.0103 0.108 0.8515

[0041] As shown in Table 3, the mechanical properties of three examples of high-speed flying shears for cast and rolled thin wide steel production lines, obtained according to the materials, processing steps, and heat treatment processes of the present invention, are as follows: compressive strength ≥ 3400 MPa; tensile strength ≥ 2300 MPa; yield strength ≥ 2000 MPa; elongation after fracture ≥ 5%; reduction of area ≥ 5%; and impact energy (unnotched) ≥ 80 J. Therefore, while maintaining comparable hardness, the mechanical properties of the present high-speed flying shears significantly outperform those of conventional high-speed flying shears made of Cr12Mo1V1 and 7Cr7Mo3V2Si materials. They avoid premature failures such as chipping and cracking during use, thereby extending the shear life and ensuring the shearing requirements of steel rolling production lines.

[0042] As can be seen from Table 4, under the same experimental conditions (wear time 30 min, wear speed 200 r / min, loading load 300 N), the high-speed flying shear specimen of comparative example 7Cr7Mo3V2Si material has the largest wear weight loss, the largest weight loss rate, and the largest friction coefficient, followed by the high-speed flying shear specimen of comparative example Cr12Mo1V1 material. The wear weight loss of the three embodiments of the present invention is relatively small, among which embodiment 2 has the least, indicating that the wear resistance of the high-speed flying shear of the present invention is relatively good, thereby increasing the number of shearing times and extending the service life.

[0043] In summary, the mechanical properties and wear resistance of the high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention are significantly better than those of the high-speed flying shears of Cr12Mo1V1 and 7Cr7Mo3V2Si materials in the background technology when the hardness difference is not much. The shearing use data of nine domestic cast-rolled thin wide strip steel production lines show that the high-speed flying shear for the cast-rolled thin wide strip steel production line of the present invention can be used to shear 1000 times when shearing ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel, low alloy high-strength steel, IF steel, dual-phase steel, pipeline steel and other cast-rolled thin wide strip steel production line strips; at the same time, due to the good comprehensive performance of the high-speed flying shear of the present invention, early failure problems such as chipping and cracking will not occur. In this way, after one shearing cycle, the shear is taken offline and the cutting edge is sharpened. A grinding amount of 0.5 mm can remove the fatigue layer generated by the shearing process of the previous cycle. After grinding, the shearing number can reach 1000 times, the same as that of a new shear. Within the adjustable range of the shear blade and shear installation dimensions, a pair of high-speed flying shears can be repeatedly sharpened approximately 10 times. This allows the shears to have a total shearing life of over 10,000 cycles by the time they are finally scrapped. Therefore, compared to imported flying shears in the prior art, the high-speed flying shears of the present invention significantly extend their service life, ensuring the production efficiency of steel rolling lines and thus meeting the shearing needs of cast-rolled thin and wide steel production lines.

Claims

1. A high-speed flying shear for a cast and rolled thin wide steel production line, characterized by: The mass percentage (wt%) of the chemical composition is: C: 0.6-0.7%, Si≤0.5%, Mn≤0.5%, P≤0.025%, S≤0.01%, Cr: 5.5-6.5%, Mo: 3.0-3.8%, Ni: 2.32-2.8%, V: 1.5-2.0%, W: 0.6-0.9%, and the balance is Fe.

2. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to claim 1, characterized in that: The chemical composition is preferably composed of 0.65% by mass of C, 0.32% by mass of Si, 0.44% by mass of Mn, 0.018% by mass of P, 0.01% by mass of S, 5.85% by mass of Cr, 3.55% by mass of Mo, 2.55% by mass of Ni, 1.69% by mass of V, 0.68% by mass of W, and the remainder being Fe.

3. The high-speed flying shear for a cast-rolled thin wide steel production line according to claim 1, characterized in that: The chemical composition is preferably composed of 0.68% by mass of C, 0.35% by mass of Si, 0.47% by mass of Mn, 0.015% by mass of P, 0.008% by mass of S, 6.35% by mass of Cr, 3.35% by mass of Mo, 2.32% by mass of Ni, 1.84% by mass of V, 0.83% by mass of W, and the balance being Fe.

4. The high-speed flying shear for a cast-rolled thin wide steel production line according to claim 1, characterized in that: The chemical composition is preferably composed of 0.62% by mass of C, 0.33% by mass of Si, 0.38% by mass of Mn, 0.020% by mass of P, 0.006% by mass of S, 6.15% by mass of Cr, 3.75% by mass of Mo, 2.75% by mass of Ni, 1.98% by mass of V, 0.75% by mass of W, and the balance being Fe.

5. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to any one of claims 1 to 4, characterized in that: The manufacturing method is: vacuum induction melting → argon protection electroslag remelting → ingot casting → forging and spheroidizing annealing → rough milling → boring and milling → drilling → quenching + three tempering → flat grinding → CNC grinding; the heat treatment process is as follows: (1) Spheroidizing annealing: 860±10℃ holding furnace cooling + 750±10℃ holding furnace cooling to 500±10℃, then air cooling to room temperature; (2) Quenching and tempering: First, keep the temperature at 1080±10℃ and then oil cool to room temperature. Then, keep the temperature at 550±10℃ for the first tempering and air cool to room temperature. Then, keep the temperature at 570±10℃ for the second tempering and air cool to room temperature. Finally, keep the temperature at 580±10℃ for the third tempering and air cool to room temperature.

6. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to claim 5, characterized in that: The heating rate is 100±20℃ / h, the spheroidizing and quenching holding time is 1-2 minutes / mm according to the effective thickness of the high-speed flying shear, and the tempering holding time is controlled at 2-4 minutes / mm.

7. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to claim 5, characterized in that: After spheroidizing annealing, the hardness is 240-255HB, and the structure is granular pearlite with spherical carbides distributed on the matrix; after quenching and tempering, the hardness is 56-60HRC, and the structure is tempered martensite + carbide.

8. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to any one of claim 6, characterized in that: The room temperature mechanical properties are: compressive strength ≥3400MPa; tensile strength ≥2300MPa; yield strength ≥2000MPa; elongation after fracture ≥5%; cross-sectional shrinkage ≥5%; unnotched impact energy ≥80J.

9. The high-speed flying shear for a cast-rolled thin wide strip steel production line according to any one of claim 6, characterized in that: This high-speed flying shear can be reground after 1000 shearing cycles. The single grinding amount is within 0.5mm and the number of regrinding cycles is 10.

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