High carbon steel wire rod and rolling method thereof

Abstract

The present invention provides a method for rolling high-carbon steel wire rod, wherein the high-carbon steel wire rod has a carbon content of 0.70-0.90%. The rolling method includes heating and rough rolling steps. The rough rolling step specifically includes rolling the heated billet through a six-mill continuous rolling mill, wherein the start rolling temperature is controlled to be 1040-1080°C. The six-mill continuous rolling mill includes rolling mills 1#, 2#, 3#, 4#, 5#, and 6#, and the elongation coefficients of the billet in the rolling mills 1#, 2#, 3#, 4#, 5#, and 6# are controlled to be 1.20-1.30, 1.12-1.22, 1.65-1.75, 1.21-1.31, 1.50-1.60, and 1.28-1.38, respectively. The high-carbon steel wire rod rolling method provided by the present invention utilizes high-temperature large deformation to break up the center segregation structure, effectively reducing the formation of network cementite and improving the product qualification rate.

Description

Technical Field

[0001] The present invention relates to the technical field of steel manufacturing, in particular to a high-carbon steel wire rod rolling method and the high-carbon steel wire rod. Background Art

[0002] The presence of cementite in high-carbon steel wire rod has long been a technical challenge for the deep processing industry, particularly the steel cord and stranded wire industries. This cementite network can lead to pen-point wire breakage, strand breakage, and poor torsional properties during drawing, impacting both production efficiency and the quality of the finished wire. The root cause of this cementite network is central segregation within the continuous casting billet, which results in a higher chemical composition in the center of the wire rod. This increases the Acm temperature and expands the cementite transformation temperature range, making it more likely for cementite to precipitate along austenite grain boundaries during cooling. Ultimately, this network cementite forms in the center of the wire rod, reducing product qualification and quality.

[0003] Due to their small specifications, rod and wire products are generally rolled from small square billets (cross-section ≤ 180mm×180mm). However, during the casting process, there is no light / heavy reduction equipment at the end of the liquid core of the small square billet to improve the center segregation. As a result, the high-carbon steel wire rod rolled from the small square billet has more network cementite structure than the wire rod rolled from the large square billet, making production more difficult.

[0004] Therefore, for high carbon steel wire rod produced by billet, how to reduce the center segregation of billet is the key to solving the network cementite problem. Summary of the Invention

[0005] The purpose of the present invention is to provide a rolling method for high carbon steel wire rod, which controls the deformation conditions of rolling at high temperature to break the central segregation structure, effectively reduce the generation of network cementite, improve the product qualification rate, and solve the problem of low qualification rate of high carbon steel wire rod products in the prior art.

[0006] In order to achieve one of the above-mentioned objects of the invention, an embodiment of the present invention provides a method for rolling a high-carbon steel wire rod, wherein the carbon content of the high-carbon steel wire rod is 0.70-0.90%, and the rolling method includes heating and rough rolling steps:

[0007] The rough rolling process specifically includes:

[0008] The heated billet is rolled through a six-mill continuous rolling mill, wherein the starting rolling temperature is controlled at 1040-1080°C;

[0009] The six-mill continuous rolling mill group includes 1#, 2#, 3#, 4#, 5# and 6# rolling mills, and the elongation coefficients of the billets in the 1#, 2#, 3#, 4#, 5# and 6# rolling mills are controlled to be 1.20-1.30, 1.12-1.22, 1.65-1.75, 1.21-1.31, 1.50-1.60 and 1.28-1.38 respectively.

[0010] As a further improvement of one embodiment of the present invention, the elongation coefficients of the billet in the 1#, 2#, 3#, 4#, 5# and 6# rolling mills are controlled to be 1.25, 1.17, 1.70, 1.26, 1.55 and 1.33 respectively.

[0011] As a further improvement of one embodiment of the present invention, the rolling speed of the billet is controlled to be 0.15-0.30 m / s.

[0012] As a further improvement of one embodiment of the present invention, the billet is rolled in sequence through the 1#, 2#, 3#, 4#, 5# and 6# rolling mills with hole shapes of box, box, oval, circular, oval and circular.

[0013] As a further improvement of one embodiment of the present invention, the billet is sequentially passed through the 1# rolling mill provided with a box-shaped hole with a groove width of 174-178 mm and a groove depth of 42-46 mm, the 2# rolling mill provided with a box-shaped hole with a groove width of 126-130 mm and a groove depth of 46-50 mm, the 3# rolling mill provided with an elliptical hole with a groove width of 149-153 mm and a groove depth of 25-29 mm, the 4# rolling mill provided with a circular hole with a groove width of 93-97 mm and a groove depth of 34-38 mm, the 5# rolling mill provided with an elliptical hole with a groove width of 115-119 mm and a groove depth of 17-21 mm, and the 6# rolling mill provided with a circular hole with a groove width of 64.5-68.5 mm and a groove depth of 24-28 mm.

[0014] As a further improvement of one embodiment of the present invention, the billet is sequentially passed through the No. 1 rolling mill provided with a box-shaped hole with a groove width of 176 mm and a groove depth of 44 mm, the No. 2 rolling mill provided with a box-shaped hole with a groove width of 128 mm and a groove depth of 48 mm, the No. 3 rolling mill provided with an elliptical hole with a groove width of 151 mm and a groove depth of 27 mm, the No. 4 rolling mill provided with a circular hole with a groove width of 95 mm and a groove depth of 36 mm, the No. 5 rolling mill provided with an elliptical hole with a groove width of 117 mm and a groove depth of 19 mm, and the No. 6 rolling mill provided with a circular hole with a groove width of 66.5 mm and a groove depth of 26 mm.

[0015] As a further improvement of one embodiment of the present invention, the bite angles between the 1#, 2#, 3#, 4#, 5#, and 6# rolling mills and the billet are controlled to be 20-24°, 23-27°, 19-23°, 22-26°, 21-25°, and 19-23°, respectively.

[0016] As a further improvement of one embodiment of the present invention, the bite angles between the 1#, 2#, 3#, 4#, 5#, and 6# rolling mills and the billet are controlled to be 22°, 25°, 21°, 24°, 23°, and 21° respectively.

[0017] As a further improvement of one embodiment of the present invention, the rolling method of high carbon steel wire rod also includes: rolling the billet with a cross section of (140-150) mm×(140-150) mm into the high carbon steel wire rod with a diameter of 5.0-14.0 mm.

[0018] One embodiment of the present invention further provides a high carbon steel wire rod obtained by the above-mentioned high carbon steel wire rod rolling method.

[0019] One or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0020] The rolling method of the high-carbon steel wire rod provided by the present invention starts rolling at a high temperature, and after rolling in a six-mill continuous rolling mill group, the elongation coefficient of each rolling mill is reasonably regulated, so that the billet undergoes repeated large deformation at a high temperature, the core of the billet is effectively compressed and elongated, the central segregation structure is broken, the generation of network cementite is effectively reduced, and the product qualification rate is improved. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to specific embodiments, but these embodiments do not limit the present invention. Changes in reaction conditions, reactants, or raw material amounts made by ordinary technicians in this field according to these embodiments are all included in the scope of protection of the present invention.

[0022] An embodiment of the present invention provides a method for rolling a high-carbon steel wire rod, comprising heating and rough rolling processes.

[0023] The heating process specifically includes:

[0024] A small square billet with a carbon content of 0.70-0.90% and a cross-section of (140-150) mm x (140-150) mm is placed in a heating furnace and heated for 90-120 minutes. Heating the billet for 90-120 minutes ensures uniform temperature across the billet's surface and core, while also avoiding the time-consuming and costly heating process.

[0025] The cross-section of the billet is (140-150) mm × (140-150) mm and is a commonly used size of billet. The embodiment of the present invention only takes the billet of 140 mm × 140 mm as an example, but the present invention is not limited to the cross-section of the billet being 140 mm × 140 mm, and may be a billet of other sizes.

[0026] The rough rolling process specifically includes:

[0027] The heated billet is rolled through a six-mill tandem rolling mill, wherein the starting rolling temperature is controlled at 1040-1080°C;

[0028] The six-mill continuous rolling mill includes mills 1#, 2#, 3#, 4#, 5#, and 6#. The elongation coefficients of the billet in mills 1#, 2#, 3#, 4#, 5#, and 6# are, respectively, 1.20-1.30, 1.12-1.22, 1.65-1.75, 1.21-1.31, 1.50-1.60, and 1.28-1.38. Preferably, the elongation coefficients of the billet in mills 1#, 2#, 3#, 4#, 5#, and 6# are controlled to be 1.25, 1.17, 1.70, 1.26, 1.55, and 1.33, respectively.

[0029] The rolling method of high carbon steel wire rod provided in an embodiment of the present invention starts rolling at a high temperature, and after rolling in a six-mill continuous rolling mill group, the elongation coefficient of the billet in each rolling mill is reasonably regulated, so that the billet undergoes repeated large deformation at a high temperature, the core of the billet is effectively compressed and elongated, the central segregation structure is broken, the generation of network cementite is effectively reduced, and the product qualification rate is improved.

[0030] Specifically, in this embodiment, the billet is rolled in a six-stand tandem mill, arranged alternately in horizontal and vertical positions, at a rolling speed of 0.15 to 0.30 m / s. This rolling speed prevents the rolling force from failing to transmit to the center of the billet, thereby preventing the center segregation structure from breaking up. It also prevents a significant temperature drop, which could hinder large deformations due to lower temperatures in the later stages of rolling, or a surge in deformation resistance, which could lead to excessive mill loads and shutdowns.

[0031] The hole types of the 1#, 2#, 3#, 4#, 5# and 6# rolling mills of the six-mill continuous rolling mill group are box-shaped, box-shaped, elliptical, circular, elliptical and circular respectively.

[0032] The rough rolling of the billet passes through rolling mills with hole shapes of box, box, oval, round, oval and round in sequence. The cross section of the billet changes from square to box-shaped, approximately square, then to oval, approximately round, and finally to round. The rough rolling process of the billet is a process in which the cross section of the billet is gradually compressed from square to round and the length of the billet is continuously extended, which can ensure the uniformity of the billet during the deformation process.

[0033] The billet is sequentially passed through the No. 1 rolling mill provided with a box-shaped hole with a groove width of 174 to 178 mm and a groove depth of 42 to 46 mm, the No. 2 rolling mill provided with a box-shaped hole with a groove width of 126 to 130 mm and a groove depth of 46 to 50 mm, the No. 3 rolling mill provided with an elliptical hole with a groove width of 149 to 153 mm and a groove depth of 25 to 29 mm, the No. 4 rolling mill provided with a circular hole with a groove width of 93 to 97 mm and a groove depth of 34 to 38 mm, the No. 5 rolling mill provided with an elliptical hole with a groove width of 115 to 119 mm and a groove depth of 17 to 21 mm, and the No. 6 rolling mill provided with a circular hole with a groove width of 64.5 to 68.5 mm and a groove depth of 24 to 28 mm.

[0034] The small square billet is rolled in a rolling mill set up alternately in horizontal and vertical directions. When passing through the No. 1 rolling mill, the rollers of the No. 1 rolling mill are set horizontally, and the upper and lower surfaces of the small square billet are squeezed. The small square billet is rolled into a box-shaped billet with a flat cross-section under the box-shaped pass. The pass area of ​​the No. 1 rolling mill is reduced, that is, the elongation coefficient is controlled to be larger, so that the small square billet is extended along its length during the rolling process, realizing the first large deformation.

[0035] When passing through the 2# rolling mill, the rollers of the 2# rolling mill are set vertically. During rolling, the left and right surfaces of the box-shaped billet are squeezed, and the cross-section of the box-shaped billet is rolled from a flat box shape to a vertical box shape. After rolling through the 2# rolling mill, the cross-sectional area continues to decrease, and the billet length continues to be extended.

[0036] When passing through the 3# rolling mill, the box-shaped billet is rolled into a nearly round shape. The rollers of the 3# rolling mill are set horizontally, squeezing the upper and lower surfaces of the billet with a vertical box-shaped cross-section. After rolling by the 3# rolling mill, the box-shaped billet becomes an elliptical billet with a flat cross-section. The reduction in the cross-sectional area of ​​the billet after rolling by the 3# rolling mill is larger than that after rolling by the 1# and 2# rolling mills. That is, the 3# rolling mill has a larger hole extension coefficient, and the deformation of the 3# rolling mill is greater than that of the 1# and 2# rolling mills, realizing the second large deformation.

[0037] The billet then passes through mills 4, 5, and 6, where the rollers are arranged vertically, horizontally, and finally vertically. The billet is extruded on its left and right surfaces, then its top and bottom surfaces, and finally its left and right surfaces, gradually reducing its cross-sectional area. Mill 5 experiences the greatest deformation, further deforming the billet. Rough rolling through mills 1 through 6 yields a rough-rolled billet with a diameter of 61-65 mm. After intermediate rolling, pre-finishing rolling, and finishing rolling, the billet is refined into wire rod with a diameter of 5.0 to 14.0 mm.

[0038] By controlling the size and elongation coefficient of the rolling mill pass, the deformation of the billet during the rolling process is controlled, and the core of the billet is effectively compressed and extended to achieve the purpose of breaking the center segregation structure.

[0039] Preferably, the billet is sequentially passed through the 1# rolling mill provided with a box-shaped hole with a groove width of 176 mm and a groove depth of 44 mm, the 2# rolling mill provided with a box-shaped hole with a groove width of 128 mm and a groove depth of 48 mm, the 3# rolling mill provided with an elliptical hole with a groove width of 151 mm and a groove depth of 27 mm, the 4# rolling mill provided with a circular hole with a groove width of 95 mm and a groove depth of 36 mm, the 5# rolling mill provided with an elliptical hole with a groove width of 117 mm and a groove depth of 19 mm, and the 6# rolling mill provided with a circular hole with a groove width of 66.5 mm and a groove depth of 26 mm.

[0040] Furthermore, the bite angles between the billet and the 1#, 2#, 3#, 4#, 5#, and 6# rolling mills are 20-24°, 23-27°, 19-23°, 22-26°, 21-25°, and 19-23°, respectively. The billet entering the rolling mills at these bite angles ensures that the elongation coefficient meets the aforementioned elongation coefficients during rolling in the six-stand tandem mill, avoiding rolling pauses or steel accumulation on one side during the rolling process.

[0041] Preferably, the bite angles between the 1#, 2#, 3#, 4#, 5# and 6# rolling mills and the billet are controlled to be 22°, 25°, 21°, 24°, 23° and 21° respectively.

[0042] The embodiment of the present invention further provides a high carbon steel wire rod, which is obtained by rolling the high carbon steel wire rod by the above-mentioned high carbon steel wire rod rolling method. The carbon content of the high carbon steel wire rod is 0.70-0.90%, and the diameter is 5.0-14.0 mm.

[0043] The following three embodiments and three comparative examples further introduce the specific implementation methods of the present invention.

[0044] Examples 1 to 3 and Comparative Examples 1 to 3 all adopt the BOF-LF-CC process to produce small square billets with a cross section of 140 mm×140 mm for rolling. The brands of the small square billets are LX72A, SWRH82B and LX87A respectively.

[0045] Examples 1 to 3 and Comparative Examples 1 to 3 were rough rolled under the rolling parameters shown in Table 1, with rough rolling pass parameters shown in Table 2. After rough rolling, they were finish rolled into wire rods under the same conditions.

[0046] Table 1 Rough rolling parameters

[0047] Brand Carbon content Heating time Rolling speed Rolling temperature Wire rod specifications Example 1 LX72A 0.72％ 115 minutes 0.15m / s 1055℃ 5.5mm Comparative Example 1 LX72A 0.72％ 125min 0.18m / s 1010℃ 5.5mm Example 2 SWRH82B 0.82％ 95min 0.20m / s 1080℃ 12.5mm Comparative Example 2 SWRH82B 0.82％ 110 minutes 0.32m / s 1030℃ 12.5mm Example 3 LX87A 0.87％ 102min 0.18m / s 1070℃ 8mm Comparative Example 3 LX87A 0.87％ 115 minutes 0.25m / s 1020℃ 8mm

[0048] Table 2 Hole type parameters

[0049]

[0050]

[0051] The network carburized structures of the wire rods obtained by rolling in Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the qualified rates were statistically reported in Table 3. As can be seen from Table 3, the qualified rate of the network carburized structure of the high carbon steel wire rod obtained by the rolling method of the present invention is greatly improved compared with the comparative example.

[0052] Table 3 Qualified rate of network cementite

[0053] Brand Qualified rate of network cementite Example 1 LX72A 98.5％ Comparative Example 1 LX72A 93.7％ Example 2 SWRH82B 99.05％ Comparative Example 2 SWRH82B 95.28％ Example 3 LX87A 97.2％ Comparative Example 3 LX87A 92.3％

[0054] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0055] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for rolling high carbon steel wire rod, characterized in that: The carbon content of the high carbon steel wire rod is 0.70-0.90%, and the rolling method includes heating and rough rolling steps: The rough rolling process specifically includes: The heated billet is rolled through a six-mill continuous rolling mill, wherein the starting rolling temperature is controlled to be 1040-1080° C., and the rolling speed of the billet is controlled to be 0.15-0.30 m / s; The six-mill continuous rolling mill group includes 1#, 2#, 3#, 4#, 5#, and 6# rolling mills, and the elongation coefficients of the billets in the 1#, 2#, 3#, 4#, 5#, and 6# rolling mills are controlled to be 1.20-1.30, 1.12-1.22, 1.65-1.75, 1.21-1.31, 1.50-1.60, and 1.28-1.38, respectively; The pass shapes of the 1#, 2#, 3#, 4#, 5# and 6# rolling mills are box-shaped, box-shaped, oval, round, oval and round respectively; Among them, the groove width of the box-shaped hole of the No. 1 rolling mill is 174~178mm, and the groove depth is 42~46mm; the groove width of the box-shaped hole of the No. 2 rolling mill is 126~130mm, and the groove depth is 46~50mm; the groove width of the elliptical hole of the No. 3 rolling mill is 149~153mm, and the groove depth is 25~29mm; the groove width of the circular hole of the No. 4 rolling mill is 93~97mm, and the groove depth is 34~38mm; the groove width of the elliptical hole of the No. 5 rolling mill is 115~119mm, and the groove depth is 17~21mm; the groove width of the circular hole of the No. 6 rolling mill is 64.5~68.5mm, and the groove depth is 24~28mm.

2. The method for rolling high carbon steel wire rod according to claim 1, characterized in that: The elongation coefficients of the billet in the 1#, 2#, 3#, 4#, 5# and 6# rolling mills are controlled in sequence as follows: 1.25、1.17、1.70、1.26、1.55、1.33。 3. The method for rolling high carbon steel wire rod according to claim 1, characterized in that: The billet is sequentially passed through the No. 1 rolling mill provided with a box-shaped hole with a groove width of 176 mm and a groove depth of 44 mm, the No. 2 rolling mill provided with a box-shaped hole with a groove width of 128 mm and a groove depth of 48 mm, the No. 3 rolling mill provided with an elliptical hole with a groove width of 151 mm and a groove depth of 27 mm, the No. 4 rolling mill provided with a circular hole with a groove width of 95 mm and a groove depth of 36 mm, the No. 5 rolling mill provided with an elliptical hole with a groove width of 117 mm and a groove depth of 19 mm, and the No. 6 rolling mill provided with a circular hole with a groove width of 66.5 mm and a groove depth of 26 mm.

4. The method for rolling high carbon steel wire rod according to claim 1, wherein: The bite angles between the 1#, 2#, 3#, 4#, 5# and 6# rolling mills and the billet are controlled to be 20~24°, 23~27°, 19~23°, 22~26°, 21~25° and 19~23° respectively.

5. The method for rolling high carbon steel wire rod according to claim 4, characterized in that: The bite angles between the 1#, 2#, 3#, 4#, 5# and 6# rolling mills and the billet are controlled to be 22°, 25°, 21°, 24°, 23° and 21° respectively.

6. The method for rolling high carbon steel wire rod according to claim 1, characterized in that: The rolling methods of high carbon steel wire rod also include: The billet with a cross section of (140-150) mm×(140-150) mm is rolled into the high carbon steel wire rod with a diameter of 5.0-14.0 mm.

7. A high carbon steel wire rod, characterized in that: The high carbon steel wire rod is obtained by the high carbon steel wire rod rolling method according to any one of claims 1 to 6.

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