A method for removing oxygen pressure defects on high temperature surface of Fe-Si alloy steel

Abstract

The present invention relates to a method for removing oxygen pressure defects on a high-temperature surface of a Fe-Si alloy steel, comprising: manufacturing a 1-3 mm thick ordinary carbon steel isolation layer on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet before the Fe-Si alloy steel continuous casting billet enters a heating furnace, filling a 0.5-1 mm thick high-purity iron powder in the gap between the ordinary carbon steel isolation layer and the surface of the Fe-Si alloy steel casting billet, and forming a composite billet with the Fe-Si alloy steel continuous casting billet, the high-purity iron powder and the ordinary carbon steel isolation layer. The present invention utilizes the advantage that the ordinary carbon steel oxide layer is easier to remove than the silicon-containing steel oxide layer, manufactures an ordinary carbon steel isolation layer on the surface of the silicon-containing steel slab, isolates the silicon-containing steel surface from direct contact with the air during heating, and avoids the formation of iron olivine that is difficult to remove. After hot rolling and pickling, the ordinary carbon steel isolation layer is removed, completely solving the oxygen pressure problem of direct rolling of Fe-Si alloy steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel processing, and in particular relates to a method for removing oxygen pressure defects on a high-temperature surface of a Fe-Si alloy steel, and further relates to an isolation layer on the high-temperature surface of the Fe-Si alloy steel, and a preparation method and an application method thereof. Background Art

[0002] While the Si element added to Fe-Si alloy steel improves the electromagnetic properties of the strip, it also causes the Fe-Si alloy steel to produce more complex oxidation behavior at high temperatures. The complex oxidation behavior causes many problems in the production process of Fe-Si alloy steel: (1) Compared with ordinary carbon steel, Fe-Si alloy steel with a higher Si content will experience more serious oxidation and burning in the heating furnace. (2) For Fe-Si alloy steel with a higher Si content, the iron olivine formed by the oxidation of silicon in the oxide scale has a low melting point and strong adhesion to the substrate, making it difficult to remove it completely by high-pressure water descaling. In the subsequent rolling process, the unpeeled oxide layer will be pressed into the surface of the strip to form oxygen pressure defects. Oxygen pressure defects not only affect the surface quality of the strip, but will also be inherited to the pickling and cold rolling stages. Strips with more serious oxygen pressure problems may even have pits after pickling. (3) After the Fe-Si alloy steel with a high Si content is coiled and stored for a period of time, a large area of ​​reddish-brown oxide layer will appear on its surface, commonly known as the "red oxide layer". The location where the reddish-brown oxide layer appears will be under-pickled during the subsequent pickling process, resulting in residual oxide layer defects on the surface of the Fe-Si alloy steel. These defects caused by the hot rolling and pickling processes of the Fe-Si alloy steel with a high Si content seriously affect the surface quality of the Fe-Si alloy steel, reduce the lamination factor, increase the iron loss and reduce the magnetic induction intensity. Therefore, the oxygen pressure defect of the Fe-Si alloy steel during the rolling process is a technical problem that plagues enterprises.

[0003] The patent document with application number CN201711292772.7 discloses an isolation agent and a method for removing red rust from the high-temperature surface of silicon-containing steel. The isolation agent for removing red rust from the high-temperature surface of silicon-containing steel is composed of dry powder and water. The dry powder is made of vermiculite powder, nano-magnesium silicate, nano-chromium oxide, mullite powder, fly ash, iron bauxite, and cassava starch, and water accounts for 50% to 70% of the total weight of the dry powder. The above-mentioned isolation agent and method for removing red rust from the high-temperature surface of silicon-containing steel are suitable for protecting silicon-containing steel during heating, and can effectively reduce oxidation and burning, inhibit the formation of fayalite, and reduce the area of ​​red rust on the downstream hot-rolled surface; it can weaken the adhesion between the iron oxide scale and the steel matrix, and after being removed from the furnace, the iron oxide scale and the isolation agent layer can be completely removed by descaling with high-pressure water; the area of ​​red rust on the surface after hot rolling is greatly reduced by more than 50%, which can effectively improve the product qualification rate and product quality, but cannot completely solve the problem of oxygen pressure, because at high temperature, the isolation agent itself is not dense and is stratified with the silicon steel ingot, and the oxygen in the air will also oxidize the surface of the ingot.

[0004] The patent document with application number CN201811139477.2 discloses "An isolating agent for removing red rust from high-temperature surface of silicon-containing steel and its application method", the components and weight percentages of which are: vermiculite powder 10-30%, nano magnesium silicate 1-5%, nano chromium oxide 1-5%, mullite 25-45%, fly ash 10-35%, iron bauxite 5%-25%, cassava starch 0.5-1%, water as diluent, the amount of water added is 50-70% of the total weight of the above components; the above components are mechanically The isolation agent with a particle size of less than 100μm is made by grinding and mixing; this high-temperature oxidation isolation agent is suitable for high-temperature protection of silicon-containing steel billets when heated at 1000~1300℃ / 1~10 hours. It is sprayed on the surface of the steel billet at room temperature. The thickness of the isolation agent is 100~400μm. It forms a glass-based protective film during the heating process. After the isolation agent is heated, it can be completely removed by washing with tap water or low-pressure water to completely remove the isolation agent and the iron oxide scale on the surface of the steel billet, reduce the area of ​​red rust on the surface of hot-rolled materials, improve the surface quality of rolled materials, and have low cost of use. Similarly, the isolation agent cannot completely solve the problem of oxygen pressure. This is because the isolation agent itself is not dense at high temperatures and is stratified with the silicon steel billet. Therefore, the oxygen in the air can also oxidize the surface of the billet to form iron olivine oxide.

[0005] In the paper "Research on High-temperature Oxidation and Oxide Layer Removal of Fe-Si Alloy Steel Plates" (Zhang Zhaoning, PhD thesis of Beijing University of Science and Technology, December 2018), the high silicon steel of a certain factory was easily exposed to oxygen pressure defects after being heated by a 1150℃ low-temperature slab heating process. The heating temperature was increased to a temperature range of 1150℃~1200℃, which improved the stripping performance of silicon-containing steel during high-pressure water dephosphorization. When pickling hot-rolled silicon-containing steel plates, adding 1% HF acid to the HCI solution can effectively reduce the H 2 SiO 3 The formation of oxygen-pressed steel is reduced and its adhesion effect is reduced, thus improving the removal effect of the surface oxide layer. In addition, the optimization of the straightening process parameters of silicon-containing strip steel improves the removal of the surface oxide layer. The traditional process optimization does not isolate the air, and the stubborn iron olivine oxide layer formed is still not easy to remove. It can only reduce the oxygen pressure defect and improve product quality, but cannot fundamentally solve the oxygen pressure problem.

[0006] As mentioned above, the existing technology can only reduce the oxygen pressure defect of Fe-Si alloy steel plate, but cannot completely eliminate the defect of steel plate, which has limited effect on improving product quality. The best method is to isolate the surface of the casting from air when the silicon-containing slab is heated at high temperature to avoid the formation of fayalite in the oxide layer. The oxide layer can be easily removed by descaling and pickling. Therefore, the produced Fe-Si alloy steel hot-rolled plate eliminates the oxygen pressure defect. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for removing oxygen pressure defects on the high-temperature surface of Fe-Si alloy steel. Taking advantage of the fact that the oxide layer of plain carbon steel is easier to remove than the oxide layer of silicon-containing steel, a plain carbon steel isolation layer is manufactured on the surface of the silicon-containing steel slab, which isolates the silicon-containing steel surface from direct contact with air during heating, thereby avoiding the formation of difficult-to-remove iron olivine. After hot rolling and pickling, the plain carbon steel isolation layer is removed, completely solving the oxygen pressure problem of direct rolling of Fe-Si alloy steel.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for removing oxygen pressure defects on a high-temperature surface of an Fe-Si alloy steel comprises: before the Fe-Si alloy steel continuous casting billet enters a heating furnace, a 1-3 mm thick ordinary carbon steel isolation layer is respectively manufactured on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet; a 0.5-1 mm thick high-purity iron powder is filled in the gap between the ordinary carbon steel isolation layer and the surface of the Fe-Si alloy steel casting billet; the Fe-Si alloy steel continuous casting billet, the high-purity iron powder and the ordinary carbon steel isolation layer form a composite billet; the specific manufacturing steps are as follows:

[0010] 1) Sand blasting is used to remove the oxide scale produced during the continuous casting process of the Fe-Si alloy steel continuous casting billet, so that the fresh metal surface of the billet is exposed;

[0011] 2) Place 1-3mm thick plain carbon steel plates symmetrically on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet, weld the bonding surface between the steel plate and the billet along the circumference, and reserve one side for filling with high-purity iron powder;

[0012] 3) Fill the reserved side with high-purity iron powder, and compact it while filling so that the gap between the bonding surfaces is filled with powder. After filling, seal and weld the reserved side to make a composite billet that is isolated from air.

[0013] The carbon content of the plain carbon steel isolation layer is less than 0.03wt%, and the silicon content is less than 0.01wt%.

[0014] The particle size of the high-purity iron powder is in the range of 53 to 100 μm, the purity is greater than 99.9%, the carbon content is less than 50 ppm, and the silicon content is less than 50 ppm.

[0015] The welding method used in step 2) and step 3) is vacuum welding or argon arc welding under non-vacuum conditions.

[0016] A method for removing oxygen compression defects on a high-temperature surface of an Fe-Si alloy steel also includes: pushing a composite billet into a heating furnace for heating and heat preservation, and preferentially oxidizing a plain carbon steel isolation layer; after the composite billet comes out of the heating furnace, removing phosphorus by high-pressure water to remove the primary oxide scale formed on the isolation layer; using high-pressure water to descale the composite billet during rough rolling and fine rolling to remove a portion of the secondary oxide scale formed on the surface of a high-purity iron powder steel layer; coiling a hot-rolled plate with a partial thickness of the powder steel layer, forming a tertiary oxide scale on the surface of the steel plate after coiling, and finally removing the tertiary oxide scale by a pickling process, that is, completely removing the oxygen compression defects on the surface of the Fe-Si alloy steel during the cold rolling process.

[0017] The heating temperature of the heating furnace is 1100-1150°C, and the insulation time is 90-120 minutes.

[0018] High-pressure water descaling is performed twice during the rough rolling process and once before the finishing rolling.

[0019] When the hot rolled plate is coiled after fine rolling, the thickness of the surface powder steel layer is controlled to be 1 to 3 μm.

[0020] The basis and considerations for the design of the isolation layer of the present invention are:

[0021] 1) When silicon-containing steel ingot is heated in a heating furnace, it is easy to form iron-containing olivine (Fe 2 SiO 4 ) has a strong adhesion to the surface of the ingot and is difficult to remove completely through subsequent descaling and pickling. However, the oxide scale formed by high-temperature oxidation of ordinary carbon steel with a carbon content of less than 0.03% and a silicon content of less than 0.01% is very easy to remove. Therefore, an isolation layer of ordinary carbon steel on the surface of the silicon-containing steel ingot is designed and manufactured before entering the heating furnace.

[0022] 2) The present invention is based on the oxidation depth of the plain carbon steel plate under the heating system of silicon-containing steel. Considering that the isolation layer is completely oxidized into iron scale in the heating furnace, and the iron scale is just removed by dephosphorization water after leaving the furnace, the thickness of the isolation layer is designed to be 1-3 mm. If the isolation layer is too thick, it cannot be oxidized in the heating furnace. If the isolation layer is too thin, it will be oxidized to the surface of the silicon-containing ingot in the heating furnace.

[0023] 3) In order to reduce the manufacturing cost of the isolation layer, the present invention uses sandblasting to simply treat the surface of the ingot to ensure that there is no oxide scale generated during the continuous casting process on the surface, and the gap formed after welding between the isolation layer and the ingot is filled with high-purity iron powder.

[0024] 4) The high-purity iron powder in the present invention has two functions: one is to remove the air in the gap between the isolation layer and the surface of the ingot to prevent oxidation of the silicon-containing ingot from the inside; the other is to form powder steel with a thickness of micrometers on the surface of the silicon-containing hot-rolled steel plate to prevent surface oxidation of the silicon-containing steel plate after hot rolling and coiling. Considering the thickness of the oxide scale during hot rolling and coiling, the thickness of the high-purity iron powder is designed to be 0.5-1mm. If the powder layer is too thick, it is difficult to remove during pickling, and if the powder layer is too thin, it will oxidize to the surface of the silicon-containing steel plate.

[0025] 5) The particle size range of high-purity powder affects the fluidity and filling capacity of the powder. In order to obtain the best tap density of the powder layer, high-purity powder with a particle size range of 53 to 100 μm is filled in the interlayer gap.

[0026] 6) Use high-purity metal powder to avoid element diffusion, especially carbon diffusion, between the powder steel layer and the silicon-containing steel plate during hot rolling, thereby ensuring the original mechanical and magnetic properties of the silicon-containing steel plate.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention utilizes the advantage that the oxide layer of plain carbon steel is easier to remove than the oxide layer of silicon-containing steel, and manufactures a plain carbon steel isolation layer and a powder steel layer on the surface of the silicon-containing steel slab, so that the entire hot rolling process completely isolates the silicon-containing steel surface from direct contact with the air, avoiding the formation of difficult-to-remove iron olivine. After the tertiary oxide skin is descaled and pickled, the isolation layer is removed, fundamentally solving the oxygen pressure problem of direct rolling of Fe-Si alloy steel, and improving the quality and magnetic properties of silicon-containing steel cold-rolled plates. In addition, the silicon-containing steel has not been oxidized and consumed throughout the production process, so the metal yield of the silicon-containing steel is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of ion diffusion during high-temperature oxidation of ordinary carbon steel.

[0030] Figure 2 This is a schematic diagram of ion diffusion during high-temperature oxidation of Fe-Si alloy steel.

[0031] Figure 3 This is a schematic diagram of ion diffusion during high-temperature oxidation of Fe-Si alloy steel-plain carbon steel composite billet.

[0032] Figure 4 Schematic diagram of the composite blank prepared by the present invention.

[0033] In the figure: 1- ordinary carbon steel isolation layer, 2- high purity iron powder, 3- Fe-Si alloy steel ingot. DETAILED DESCRIPTION

[0034] 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 embodiments. The following embodiments are used to specifically illustrate the contents of the present invention. These embodiments are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0035] like Figure 1-Figure 4 As shown, the first technical solution of the present invention is: before the Fe-Si alloy steel continuous casting billet 3 enters the heating furnace, a 1-3 mm thick ordinary carbon steel isolation layer 1 is manufactured on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet 3 respectively, and the gap between the ordinary carbon steel isolation layer 1 and the surface of the Fe-Si alloy steel casting billet 3 is filled with 0.5-1 mm thick high-purity iron powder 2, and the Fe-Si alloy steel continuous casting billet 3, the high-purity iron powder 2 and the ordinary carbon steel isolation layer 1 form a composite billet.

[0036] The second technical solution of the present invention is: the composite billet is pushed into a heating furnace for heating and heat preservation, and the ordinary carbon steel isolation layer 1 is preferentially oxidized; after the composite billet comes out of the heating furnace, the primary oxide scale formed on the isolation layer is removed by high-pressure water dephosphorization; high-pressure water is used for descaling during the rough rolling and fine rolling of the composite billet to remove part of the secondary oxide scale formed on the surface of the powder steel layer of the high-purity iron powder 2; the hot-rolled plate with a partial thickness of the powder steel layer is coiled, and a tertiary oxide scale is formed on the surface of the steel plate after coiling, and finally the tertiary oxide scale is removed by a pickling process, that is, the surface oxygen pressure defects of the Fe-Si alloy steel are completely removed during the cold rolling process.

[0037] Embodiment 1:

[0038] 1) Raw material preparation

[0039] Prepare the raw materials and chemical composition as follows: Fe-Si alloy steel ingot 3 has a size of 1.5m×5m×230mm, and its chemical composition (mass fraction, %) is: 0.015C, 0.49Si, 0.21Al, 0.22Mn, 0.01P, 0.0015S, and the rest is Fe; the size of ordinary carbon steel plate is 1.5m×5m×1mm, and its chemical composition (mass fraction, %) is: 0.023C, 0.004Si, 0.0009Al, 0.018Mn, 0.002P, 0.0016S, and the rest is Fe; the high-purity iron powder 2 with a screening particle size range of 53-100μm, its chemical composition (mass fraction, %) is 0.004C, 0.003Si, 0.0008Al, 0.018Mn, 0.002P, 0.0016S, 0.0035Ni, 0.007Cr, 0.0052Cu, 0.0003Nb, 0.0001V, 0.0001Ti, 0.0023As, and the rest is Fe.

[0040] 2) Composite billet preparation process

[0041] Firstly, the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet 3 are sandblasted to remove the oxide scale generated during the continuous casting process; secondly, ordinary carbon steel plates with the same composite area are placed symmetrically on the upper and lower surfaces of the ingot, and after the composite billet is fixed by spot welding, the bonding surface between the steel plate and the ingot is welded around the circumference by argon arc welding, and one side is reserved for filling with high-purity iron powder 2. The gap between the bonding surfaces is 0.5 mm after ultrasonic testing; finally, high-purity iron powder is filled from the reserved side, and the filling is vibrated while filling to fill the gap between the bonding surfaces with powder. After filling, the reserved side is sealed and welded to make a composite billet that is isolated from air.

[0042] 3) Hot rolling and pickling of composite billet

[0043] The composite billet was heated to 1100℃ and held for 90min. The composite billet was descaled once with high pressure water after leaving the heating furnace, descaled twice with high pressure water after rough rolling by the first rough rolling mill, and descaled three times with high pressure water after rough rolling by the second rough rolling mill. The intermediate billet was descaled four times with high pressure water before finishing rolling. The thickness of the hot rolled sheet powder steel layer was measured to be 1μm before coiling. After testing, there was no oxygen pressure defect on the upper and lower surfaces of the silicon-containing cold rolled sheet after pickling and cold rolling.

[0044] Embodiment 2:

[0045] 1) Raw material preparation

[0046] Prepare the raw materials and chemical composition as follows: Fe-Si alloy steel ingot 3 has a size of 1.5m×5m×230mm, and its chemical composition (mass fraction, %) is: 0.012C, 1.39Si, 0.41Al, 0.23Mn, 0.011P, 0.0012S, and the rest is Fe; the size of ordinary carbon steel plate is 1.5m×5m×2mm, and its chemical composition (mass fraction, %) is: 0.023C, 0.004Si, 0.0009Al, 0.018Mn, 0.002P, 0.0016S, and the rest is Fe; the high-purity iron powder 2 with a screening particle size range of 53-100μm, its chemical composition (mass fraction, %) is 0.004C, 0.003Si, 0.0008Al, 0.018Mn, 0.002P, 0.0016S, 0.0035Ni, 0.007Cr, 0.0052Cu, 0.0003Nb, 0.0001V, 0.0001Ti, 0.0023As, and the rest is Fe.

[0047] 2) Composite billet preparation process

[0048] Firstly, the upper and lower surfaces of the Fe-Si alloy steel ingot 3 are sandblasted to remove the oxide scale produced during the continuous casting process; secondly, ordinary carbon steel plates with the same composite area are placed symmetrically on the upper and lower surfaces of the ingot, and after the composite ingot is fixed by spot welding, the bonding surface between the steel plate and the ingot is welded around the circumference by argon arc welding, and one side is reserved for filling with high-purity iron powder 2. The gap between the bonding surfaces is 0.72 mm after ultrasonic testing; finally, high-purity iron powder 2 is filled from the reserved side, and the filling is vibrated while the filling is performed to fill the gap between the bonding surfaces with powder. After filling, the reserved side is sealed and welded to form a composite ingot that is isolated from air.

[0049] 3) Hot rolling and pickling of composite billet

[0050] The heating temperature of the composite billet is 1120℃, and the holding time is 100min. The composite billet is descaled once with high pressure water after leaving the heating furnace, descaled twice with high pressure water after rough rolling by the first rough rolling mill, and descaled three times with high pressure water after rough rolling by the second rough rolling mill. The intermediate billet is descaled four times with high pressure water before finishing rolling. The thickness of the powder steel layer of the hot-rolled plate is measured to be 1.53μm before coiling. After testing, there is no oxygen pressure defect on the upper and lower surfaces of the silicon-containing cold-rolled plate after pickling and cold rolling.

[0051] Embodiment 3:

[0052] 1) Raw material preparation

[0053] Prepare the raw materials and their chemical composition as follows: the size of the Fe-Si alloy steel ingot 3 is 1.5m×5m×230mm, and its chemical composition (mass fraction, %) is: 0.012C, 2.22Si, 0.96Al, 0.20Mn, 0.009P, 0.0012S, and the rest is Fe; the size of the ordinary carbon steel plate is 1.5m×5m×2.5mm, and its chemical composition (mass fraction, %) is: 0.023C, 0.004Si, 0.0009Al, 0.018Mn , 0.002P, 0.0016S, and the rest is Fe; the high-purity iron powder 2 with a screening particle size range of 53-100μm, its chemical composition (mass fraction, %) is 0.004C, 0.003Si, 0.0008Al, 0.018Mn, 0.002P, 0.0016S, 0.0035Ni, 0.007Cr, 0.0052Cu, 0.0003Nb, 0.0001V, 0.0001Ti, 0.0023As, and the rest is Fe.

[0054] 2) Composite billet preparation process

[0055] Firstly, the upper and lower surfaces of the Fe-Si alloy steel ingot 3 are sandblasted to remove the oxide scale produced during the continuous casting process; secondly, ordinary carbon steel plates with the same composite area are placed symmetrically on the upper and lower surfaces of the ingot, and after the composite ingot is fixed by spot welding, the bonding surface between the steel plate and the ingot is welded around the circumference by argon arc welding, and one side is reserved for filling with high-purity iron powder 2. The gap between the bonding surfaces is 0.84 mm after ultrasonic testing; finally, high-purity iron powder 2 is filled from the reserved side, and the filling is vibrated while the filling is performed to fill the gap between the bonding surfaces with powder. After filling, the reserved side is sealed and welded to form a composite ingot that is isolated from air.

[0056] 3) Hot rolling and pickling of composite billet

[0057] The heating temperature of the composite billet is 1140℃, and the holding time is 110min. The composite billet is descaled once with high pressure water after leaving the heating furnace, descaled twice with high pressure water after rough rolling by the first rough rolling mill, and descaled three times with high pressure water after rough rolling by the second rough rolling mill. The intermediate billet is descaled four times with high pressure water before finishing rolling. The thickness of the powder steel layer of the hot-rolled plate is measured to be 2.2μm before coiling. After testing, there is no oxygen pressure defect on the upper and lower surfaces of the silicon-containing cold-rolled plate after pickling and cold rolling.

[0058] Embodiment 4:

[0059] 1) Raw material preparation

[0060] Prepare the raw materials and chemical composition as follows: Fe-Si alloy steel ingot 3 has a size of 1.5m×5m×230mm, and its chemical composition (mass fraction, %) is: 0.010C, 3.11Si, 1.02Al, 0.24Mn, 0.008P, 0.0011S, and the rest is Fe; the size of ordinary carbon steel plate is 1.5m×5m×3mm, and its chemical composition (mass fraction, %) is: 0.023C, 0.004Si, 0.0009Al, 0.018Mn, 0.002P, 0.0016S, and the rest is Fe; the high-purity iron powder 2 with a screening particle size range of 53-100μm, its chemical composition (mass fraction, %) is 0.004C, 0.003Si, 0.0008Al, 0.018Mn, 0.002P, 0.0016S, 0.0035Ni, 0.007Cr, 0.0052Cu, 0.0003Nb, 0.0001V, 0.0001Ti, 0.0023As, and the rest is Fe.

[0061] 2) Composite billet preparation process

[0062] Firstly, the upper and lower surfaces of the Fe-Si alloy steel ingot 3 are sandblasted to remove the oxide scale produced during the continuous casting process; secondly, ordinary carbon steel plates with the same composite area are placed symmetrically on the upper and lower surfaces of the ingot, and after the composite ingot is fixed by spot welding, the bonding surface between the steel plate and the ingot is welded around the circumference by vacuum welding, and one side is reserved for filling with high-purity iron powder 2. The gap between the bonding surfaces is 0.998 mm after ultrasonic testing; finally, high-purity iron powder 2 is filled from the reserved side, and the filling is vibrated while the filling is performed to fill the gap between the bonding surfaces with powder. After filling, the reserved side is sealed and welded to form a composite ingot that is isolated from air.

[0063] 3) Hot rolling and pickling of composite billet

[0064] The heating temperature of the composite billet is 1150℃, and the holding time is 120min. The composite billet is descaled once with high pressure water after leaving the heating furnace, descaled twice with high pressure water after rough rolling by the first rough rolling mill, and descaled three times with high pressure water after rough rolling by the second rough rolling mill. The intermediate billet is descaled four times with high pressure water before finishing rolling. The thickness of the powder steel layer of the hot-rolled plate is measured to be 2.98μm before coiling. After testing, there is no oxygen pressure defect on the upper and lower surfaces of the silicon-containing cold-rolled plate after pickling and cold rolling.

Claims

1. A method for removing oxygen pressure defects on the high temperature surface of Fe-Si alloy steel, characterized in that: The method comprises the following steps: before the Fe-Si alloy steel continuous casting billet enters the heating furnace, a 1-3 mm thick ordinary carbon steel isolation layer is respectively manufactured on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet; a 0.5-1 mm thick high-purity iron powder is filled in the gap between the ordinary carbon steel isolation layer and the surface of the Fe-Si alloy steel casting billet; the Fe-Si alloy steel continuous casting billet, the high-purity iron powder and the ordinary carbon steel isolation layer form a composite billet; the specific manufacturing steps are as follows: 1) Remove the oxide scale produced during the continuous casting process of Fe-Si alloy steel continuous casting billet, so that the billet exposes the fresh metal surface; 2) Place 1-3mm thick plain carbon steel plates symmetrically on the upper and lower surfaces of the Fe-Si alloy steel continuous casting billet, weld the bonding surface between the steel plate and the billet along the circumference, and reserve one side for filling with high-purity iron powder; 3) Fill the reserved side with high-purity iron powder, and compact it while filling so that the gap between the bonding surfaces is filled with powder. After filling, seal and weld the reserved side to make a composite blank that isolates air; The process also includes: pushing the composite billet into a heating furnace for heating and heat preservation, and preferentially oxidizing the ordinary carbon steel isolation layer; after the composite billet leaves the heating furnace, removing the primary oxide scale formed on the isolation layer by high-pressure water dephosphorization; using high-pressure water descaling during the rough rolling and fine rolling of the composite billet to remove part of the secondary oxide scale formed on the surface of the high-purity iron powder steel layer; coiling the hot-rolled plate with a partial thickness of the powder steel layer, forming a tertiary oxide scale on the surface of the steel plate after coiling, and finally removing the tertiary oxide scale through a pickling process, that is, completely removing the surface oxygen pressure defects of the Fe-Si alloy steel during the cold rolling process.

2. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: The carbon content of the plain carbon steel isolation layer is less than 0.03wt%, and the silicon content is less than 0.01wt%.

3. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: The particle size of the high-purity iron powder is in the range of 53 to 100 μm, the purity is greater than 99.9%, the carbon content is less than 50 ppm, and the silicon content is less than 50 ppm.

4. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: The welding method used in step 2) and step 3) is vacuum welding or argon arc welding under non-vacuum conditions.

5. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: The heating temperature of the heating furnace is 1100-1150°C, and the insulation time is 90-120 minutes.

6. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: High-pressure water descaling is performed twice during the rough rolling process and once before the finishing rolling.

7. The method for removing oxygen pressure defects on a high temperature surface of a Fe-Si alloy steel according to claim 1, characterized in that: When the hot rolled plate is coiled after fine rolling, the thickness of the surface powder steel layer is controlled to be 1 to 3 μm.

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