A method for improving the edge quality of hot-rolled strip of grain-oriented silicon steel

Abstract

The present invention relates to a method for improving the edge quality of hot-rolled oriented silicon steel strips, comprising: 1) setting the steel gap between two adjacent oriented silicon steel slabs in a heating furnace to be: ΔW = W × (T1-T2) × 0.000012; wherein T1 is the maximum heating temperature, T2 is the furnace charging temperature, and W is the width of the slab at 20°C; and maintaining a steel gap of 30 to 50 mm for every five slabs; 2) rapidly heating the oriented silicon steel slabs when the temperature of the heating furnace reaches 900 to 950°C, with the heating rate controlled at 32 to 45°C / min; 3) controlling the width reduction of the roughing vertical rolls of the oriented silicon steel during rough rolling to not more than 30 mm; 4) controlling the outlet temperature of the final rough rolling pass of the oriented silicon steel to be ≥1050°C; and 5) performing temperature compensation on the edge of the intermediate slab of the oriented silicon steel before finish rolling, with the temperature compensation controlled at. The present invention can improve the edge quality of hot-rolled oriented silicon steel strips heated at low temperatures, is conducive to the production of oriented silicon steel in a cold rolling process without trimming, and improves the yield rate of the cold rolling process.

Description

Technical Field

[0001] The present invention relates to the technical field of steel rolling technology, and in particular to a method for improving the edge quality of a hot-rolled oriented silicon steel strip. Background Art

[0002] Since the heating temperature of low-temperature oriented silicon steel is significantly reduced during the hot rolling process, the heating energy consumption is greatly reduced, the loss to the heating furnace is also greatly reduced, and the yield rate of oriented silicon steel hot coil is greatly improved, which has a huge advantage over the high-temperature and high-magnetic induction oriented silicon steel process. Although oriented silicon steel adopts a low-temperature heating process, edge quality defects still exist in the hot-rolled steel strip of oriented silicon steel. The severity of the defects is reduced compared with the oriented silicon steel strip produced by the high-temperature heating process, but it still has a relatively large impact on the production of the cold rolling process and the yield rate of the process.

[0003] Patent document CN 103484643 A, "A Method for Preventing Edge Cracks in Hot-Rolled Grain-Oriented Silicon Steel," addresses this issue by controlling the temperature of the corners of the slab before entering the heating furnace to no less than 550°C; controlling the preheating section temperature in the heating furnace to 950-1050°C, the first heating section temperature to 1050-1150°C; controlling the finishing rolling entrance temperature to 1050-1150°C, and the finishing rolling temperature to 900-1000°C. The theory is that by controlling the slab's corner entry temperature and the first heating temperature, thermal stress at the corners during heating is reduced, preventing internal cracks. Furthermore, by controlling the finishing rolling entrance and finishing rolling temperatures of the continuous rolling mill and properly setting the inter-stand tension, the hot-rolling edge cracking defect is prevented. However, this method fails to address the underlying cause of edge cracking. The cause of edge cracking is prolonged heating and holding of the slab, leading to abnormal grain growth, grain boundary oxidation, and decarburization, which in turn cause edge cracking after rolling. Therefore, this method is ineffective.

[0004] Patent document CN 108193037 A, "A process for preventing edge cracks in hot-rolled oriented silicon steel," adopts process control measures to prevent edge cracks in oriented silicon steel, including controlling the heating temperature of the second heating section and the soaking section, as well as the corresponding heating time and rolling rhythm. The furnace gas temperature exceeds 1300°C, which falls within the category of edge cracks in oriented silicon steel heated at high temperatures. For oriented silicon steel heated at low temperatures, the measures can only alleviate the problem, and the improvement effect is not obvious. Summary of the Invention

[0005] The present invention provides a method for improving the edge quality of hot-rolled oriented silicon steel strips, which can improve the edge quality of hot-rolled oriented silicon steel strips heated at low temperatures, is beneficial to the production of oriented silicon steel in the cold rolling process without trimming, and improves the yield rate of the cold rolling process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for improving the edge quality of oriented silicon steel hot-rolled strip, comprising:

[0008] 1) The non-gapped steel burning method is adopted for grain-oriented silicon steel in the heating furnace. The heating temperature of the heating furnace in the hot rolling process of low-temperature grain-oriented silicon steel slabs is generally in the range of 1130 - 1170 °C, and its charging temperature is generally ≥300 °C. Since the size of the slab will increase with the increase of temperature due to thermal expansion during the heating process, in order to avoid the mutual extrusion and deformation of the grain-oriented silicon steel slabs caused by thermal expansion when heated to a high temperature, a certain gap should be left between the grain-oriented silicon steel slabs during charging. The coefficient of thermal expansion of grain-oriented silicon steel is 0.000012 mm / °C. Then the width increase of the grain-oriented silicon steel slab when heated to the highest temperature after charging is:

[0009] W×(T1 - T2)×0.000012, where T1 is the highest heating temperature, T2 is the charging temperature, and W is the width of the slab at room temperature.

[0010] Then the charging gap between two adjacent grain-oriented silicon steel slabs is △W = W×(T1 - T2)×0.000012.

[0011] Where T1 is the highest heating temperature, with the unit of °C; T2 is the charging temperature, with the unit of °C; W is the width of the slab at room temperature, with the unit of mm; the unit of the charging gap △W is mm;

[0012] In this way, there will be no gap after the slabs are heated to a high temperature. However, in order to ensure the steel burning effect of the grain-oriented silicon steel slabs, a certain gap still needs to be left for every 5 slabs during charging, and the size is to leave a gap of 30 - 50 mm when charging the slab steel.

[0013] This measure can achieve non-gapped steel burning for grain-oriented silicon steel slabs during the heating process, avoid the erosion of the slab edge by the heat flow in the high-temperature heating section, and avoid decarburization and grain boundary oxidation at the edge.

[0014] 2) When the temperature of the grain-oriented silicon steel slab in the heating furnace reaches 900 - 950 °C, it needs to be heated up rapidly, and the heating rate is controlled at 32 - 45 °C / min; accelerating the heating rate of the grain-oriented silicon steel slab at a higher temperature is because there is still a gap between the slabs before the slab reaches the highest heating temperature. In order to minimize the erosion of the slab edge by the high-temperature heat flow, the heating rate needs to be accelerated to reach the target heating temperature of the slab. After the slabs are in full contact, continue heating, and the heat flow will not cause erosion to the slab edge.

[0015] 3) In the rough rolling process of grain-oriented silicon steel, a small width reduction design is adopted, and the width reduction of the rough rolling vertical roll does not exceed 30 mm; the purpose is to reduce the friction of the vertical roll on the slab edge and help reduce the difference in the metal flow rate at the edge. Process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge.

[0016] 4) The rough rolling shall not exceed 5 passes, and the rolling speed shall be increased, the cooling water input shall be controlled, and the outlet temperature of the last pass of rough rolling of oriented silicon steel shall be controlled to be ≥1050℃, so as to provide good rolling conditions for finishing rolling.

[0017] 5) Before finishing rolling, the edge of the oriented silicon steel intermediate billet is temperature compensated and the temperature compensation is controlled at 85-130℃.

[0018] 6) Finishing rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled within the range of 15-30mm to prevent the strip from scraping the side guides. During finishing rolling, the strip is rolled at a high speed and the temperature drops, which increases its brittleness. Scratching the side guides will cause friction between the strip and the side guides, resulting in damage to the edge quality.

[0019] 7) After the strip head coiler is rolled up, the coiling side guide plate adopts a position control method, and the distance between the edge of the strip and the side guide plates on both sides is controlled within the range of 10-20mm to avoid scratching the side guide plates.

[0020] The heating temperature of the heating furnace in the hot rolling process of oriented silicon steel slabs is generally in the range of 1130-1170℃.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] After applying the production measures of the present invention, the edge quality of low-temperature oriented silicon steel is fundamentally improved, the cold-rolled silicon steel process realizes the production of hot-rolled oriented silicon steel strips without trimming, and greatly improves the yield rate of the cold-rolling process. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0024] Example 1:

[0025] The width of the room-temperature slab of low-temperature grain-oriented silicon steel is 900 mm, the charging temperature T2 is 638 °C, the heating temperature T1 is 1148 °C. When the grain-oriented silicon steel slab is heated to a high temperature after charging, the width increases by 5.5 mm. Then, the charging gap △W between two grain-oriented silicon steel slabs is 5.5 mm. To ensure the steel burning effect, a gap is left between every five slabs, and the size of the gap is 40 mm reserved when the slab steel is charged. When the temperature of the grain-oriented silicon steel slab in the heating furnace reaches 900 °C, it is rapidly heated, and the heating rate should be controlled at 35 °C / min. In the rough rolling process of grain-oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 20 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 4 rough rolling passes, and the rolling speed is increased, and the cooling water input is controlled. The exit temperature of the last rough rolling pass of grain-oriented silicon steel is 1064 °C. Before finish rolling, temperature compensation is carried out on the edge of the grain-oriented silicon steel intermediate billet, and the temperature compensation is 90 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 20 mm to avoid the strip rubbing against the side guides. After the strip head is coiled by the coiler, the coiling side guides adopt a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 15 mm, so as to avoid rubbing against the side guides. After implementation, the edge quality of the hot-rolled grain-oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

[0026] Example 2:

[0027] The width of the room-temperature slab of low-temperature grain-oriented silicon steel is 1000 mm, the charging temperature T2 is 305 °C, the heating temperature T1 is 1169 °C. When the grain-oriented silicon steel slab is heated to a high temperature after charging, the width increases by 10.4 mm. Then, the charging gap △W between two grain-oriented silicon steel slabs is 10.4 mm. To ensure the steel burning effect, a gap is left between every five slabs, and the size of the gap is 30 mm reserved when the slab steel is charged. When the temperature of the grain-oriented silicon steel slab in the heating furnace reaches 912 °C, it is rapidly heated, and the heating rate should be controlled at 45 °C / min. In the rough rolling process of grain-oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 10 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 4 rough rolling passes, and the rolling speed is increased, and the cooling water input is controlled. The exit temperature of the last rough rolling pass of grain-oriented silicon steel is 1050 °C. Before finish rolling, temperature compensation is carried out on the edge of the grain-oriented silicon steel intermediate billet, and the temperature compensation is 100 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 25 mm to avoid the strip rubbing against the side guides. After the strip head is coiled by the coiler, the coiling side guides adopt a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 10 mm, so as to avoid rubbing against the side guides. After implementation, the edge quality of the hot-rolled grain-oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

[0028] Example 3:

[0029] The width of the room-temperature slab of low-temperature oriented silicon steel is 1100 mm, the charging temperature T2 is 501 °C, and the heating temperature T1 is 1143 °C. When the oriented silicon steel slab is heated to a high temperature after charging, the width increases by 8.5 mm. Then, the charging gap △W between two oriented silicon steel slabs is 8.5 mm. To ensure the steel burning effect, a gap is left between every five slabs, and the size of the gap is 50 mm reserved when the slab steel is charged. When the temperature of the oriented silicon steel slab in the heating furnace reaches 950 °C, it is rapidly heated, and the heating rate should be controlled at 32 °C / min. In the rough rolling process of oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 30 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 3 rough rolling passes, the rolling speed is increased, and the cooling water input is controlled. The outlet temperature of the last rough rolling pass of the oriented silicon steel is 1068 °C. Before finish rolling, temperature compensation is carried out on the edge of the oriented silicon steel intermediate slab, and the temperature compensation is 100 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 30 mm to avoid the strip scraping the side guides. After the strip head is coiled by the coiler, the coiling side guide adopts a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 20 mm to avoid scraping the side guides. After implementation, the edge quality of the hot-rolled oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

[0030] Example 4:

[0031] The width of the room-temperature slab of low-temperature oriented silicon steel is 1200 mm, the charging temperature T2 is 454 °C, and the heating temperature T1 is 1132 °C. When the oriented silicon steel slab is heated to a high temperature after charging, the width increases by 9.8 mm. Then, the charging gap for the oriented silicon steel is △W = 9.8 mm. To ensure the steel burning effect, a gap is left between every five slabs, and the size of the gap is 35 mm reserved when the slab steel is charged. When the temperature of the oriented silicon steel slab in the heating furnace reaches 927 °C, it is rapidly heated, and the heating rate should be controlled at 40 °C / min. In the rough rolling process of oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 5 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 5 rough rolling passes, the rolling speed is increased, and the cooling water input is controlled. The outlet temperature of the last rough rolling pass of the oriented silicon steel is 1055 °C. Before finish rolling, temperature compensation is carried out on the edge of the oriented silicon steel intermediate slab, and the temperature compensation is 110 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 15 mm to avoid the strip scraping the side guides. After the strip head is coiled by the coiler, the coiling side guide adopts a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 13 mm to avoid scraping the side guides. After implementation, the edge quality of the hot-rolled oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

[0032] Example 5:

[0033] The width of the room temperature slab of low-temperature oriented silicon steel is 1250 mm, the charging temperature T2 is 547 °C, the heating temperature T1 is 1155 °C. When the oriented silicon steel slab is heated to a high temperature after charging, the width increases by 9.1 mm. Then the charging gap △W between two oriented silicon steel slabs is 9.1 mm. To ensure the steel burning effect, a gap is left between every 5 slabs, and the size of the gap is 45 mm reserved when the slab steel is charged. When the temperature of the oriented silicon steel slab in the heating furnace reaches 946 °C, it is rapidly heated, and the heating rate should be controlled at 38 °C / min. In the rough rolling process of oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 15 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 4 rough rolling passes, the rolling speed is increased, and the cooling water input is controlled. The outlet temperature of the last rough rolling pass of oriented silicon steel is 1064 °C. Before finish rolling, temperature compensation is carried out on the edge of the oriented silicon steel intermediate slab, and the temperature compensation is 90 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 22 mm to avoid the strip rubbing against the side guides. After the strip head is coiled by the coiler, the coiling side guides adopt a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 13 mm, so as to avoid rubbing against the side guides. After implementation, the edge quality of the hot-rolled oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

[0034] Example 6:

[0035] The width of the room temperature slab of low-temperature oriented silicon steel is 1300 mm, the charging temperature T2 is 386 °C, the heating temperature T1 is 1161 °C. When the oriented silicon steel slab is heated to a high temperature after charging, the width increases by 12.1 mm. Then the charging gap △W between two oriented silicon steel slabs is 12.1 mm. To ensure the steel burning effect, a gap is left between every 5 slabs, and the size of the gap is 42 reserved when the slab steel is charged. When the temperature of the oriented silicon steel slab in the heating furnace reaches 935 °C, it is rapidly heated, and the heating rate should be controlled at 42 °C / min. In the rough rolling process of oriented silicon steel, a small width reduction design is adopted. The width reduction of the rough rolling vertical roll is 25 mm, and process lubrication measures are taken for the rough rolling vertical roll to further reduce the friction of the vertical roll on the slab edge. It is rolled in 4 rough rolling passes, the rolling speed is increased, and the cooling water input is controlled. The outlet temperature of the last rough rolling pass of oriented silicon steel is 1071 °C. Before finish rolling, temperature compensation is carried out on the edge of the oriented silicon steel intermediate slab, and the temperature compensation is 130 °C. Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled at 27 mm to avoid the strip rubbing against the side guides. After the strip head is coiled by the coiler, the coiling side guides adopt a position control method, and the distance between the strip edge and the side guides on both sides is controlled at 18 mm, so as to avoid rubbing against the side guides. After implementation, the edge quality of the hot-rolled oriented silicon steel strip is good, and untrimmed rolling is realized in the cold rolling process.

Claims

1. A method for improving the edge quality of hot-rolled oriented silicon steel strips, characterized in that, including 1) The steel loading gap between two adjacent slabs of grain-oriented silicon steel in the reheating furnace is: △W = W×(T1 - T2)×0.000012; where T1 is the maximum heating temperature in °C; T2 is the furnace charging temperature in °C; W is the width of the slab at room temperature in mm; and the unit of the steel loading gap △W is mm; and a steel loading gap of 30 - 50 mm is reserved for every 5 slabs; 2) When the temperature of the grain-oriented silicon steel slab in the reheating furnace reaches 900 - 950 °C, it is rapidly heated, and the heating rate is controlled at 32 - 45 °C / min; 3) During rough rolling of grain-oriented silicon steel, the width reduction of the roughing vertical roll does not exceed 30 mm; 4) Control the exit temperature of the last pass of rough rolling of grain-oriented silicon steel ≥1050 °C; 5) Before finish rolling, temperature compensation is performed on the edges of the intermediate billet of grain-oriented silicon steel, and the temperature compensation is controlled at 85 - 130 °C.

2. A method for improving the edge quality of hot-rolled oriented silicon steel strips according to claim 1, characterized in that, The rough rolling is carried out in no more than 5 passes.

3. A method for improving the edge quality of hot-rolled oriented silicon steel strips according to claim 1, characterized in that, Finish rolling adopts centerline rolling, and the distance between the strip edge and the side guides on both sides is controlled within the range of 15 - 30 mm.

4. A method for improving the edge quality of hot-rolled oriented silicon steel strips according to claim 1, characterized in that, After the strip head is coiled by the coiler, the coiling side guides adopt a position control method, and the distance between the strip edge and the side guides on both sides is controlled within the range of 10 - 20 mm.

5. A method for improving the edge quality of hot-rolled oriented silicon steel strips according to claim 1, characterized in that, The heating temperature of the reheating furnace in the hot rolling process of the grain-oriented silicon steel slab is within the range of 1130 - 1170 °C.