Control method beneficial to removal of oxide scale of high-Si welding wire steel wire rod

Abstract

The invention discloses a control method beneficial to removal of oxide scale of a high-Si welding wire steel wire rod, the method comprises the working procedures of steel billet heating, controlled rolling and waste heat isothermal treatment, the temperature of a steel billet heating section is 850-950 DEG C, the heating time is 50-60 min, the temperature of a soaking section is 950-1000 DEG C, the soaking time is 30-40 min, the total in-furnace time is 80-100 min, and the rolling starting temperature is 970 + / -20 DEG C; the casting blank enters a high-speed wire rod rolling mill to be rolled, the overall temperature in the rolling process is 850 + / -20 DEG C, and the spinning temperature is set to be 830 + / -20 DEG C; after spinning, a wire rod is rapidly conveyed to an isothermal salt pond through a roller way, the speed of the roller way is set to be 0.5-1.0 m / s, the isothermal heat treatment temperature is set to be 570-600 DEG C, the wire rod is cooled to 570-600 DEG C at the heat exchange rate that the cooling speed is larger than or equal to 80 DEG C / s, heat preservation is conducted for 2-6 min, and the thickness of the oxide scale can be controlled to be smaller than or equal to 5 micrometers.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and more specifically to a control method for removing iron oxide scale from a high-Si welding wire steel wire rod. Background Art

[0002] Silicon is the most commonly used deoxidizing element in welding wire. It can reduce FeO in the molten pool to prevent the combination of iron and oxygen. It can also increase the fluidity of the deposited metal and the corrosion resistance of the welding wire. Therefore, a high silicon element is added to the gas shielded welding wire steel. The preparation of welding wire is generally drawn by hot-rolled wire rods of welding wire steel. The iron oxide scale on the surface of the wire rod needs to be removed before drawing. The addition of a high content of silicon to the welding wire steel can easily cause the iron oxide scale on the surface of the hot-rolled wire rod to be embedded in the matrix and form a three-layer iron oxide scale structure. At present, most users use mechanical peeling combined with sanding belt rust removal to remove the iron scale, but the iron scale is embedded in the matrix and the structure is unreasonable, which makes it difficult to remove it by mechanical stripping. The residual iron scale scratches the mold and the steel wire surface during drawing, which reduces the lubrication effect and affects the life of the wire drawing die. In severe cases, it will cause wire breakage. Therefore, improving the removal effect of the iron oxide scale of high-silicon welding wire steel wire rods is of great significance to the processing performance of the subsequent process.

[0003] At present, some manufacturers have improved the iron scale removal effect, such as CN 114733920 A, a method for controlling the scale of hot-rolled wire rod of welding wire steel ER70Sˉ6. After rolling, the main components of the scale are changed by controlled cooling, so that the main components of the scale are changed from FeO to more brittle Fe3O4; finally, after the wire rod is cooled, the scale on the surface of the wire rod is separated from the matrix by spheroidizing annealing treatment, so as to improve the mechanical stripping rate of the scale. This method requires offline annealing, has a high overall production cost, a long production cycle, and produces thicker scale, resulting in a lower final welding wire yield, and is not suitable for pickling to remove scale, and has a relatively single usage scenario.

[0004] Another part of manufacturers, such as CN 111647811 A, a welding steel wire rod and production method suitable for pickling-free peeling process, etc., through the traditional means such as the total furnace time of continuous casting billet heating and high-pressure water dephosphorization after the billet is out of the furnace, and the control of the cooling speed of the Stelmor roller, so that the thickness of the wire rod iron oxide scale is 30-40μm, and the phase ratio of FeO is 2-3 times that of Fe3O4, which is conducive to the mechanical peeling and removal of the welding steel wire rod by downstream users. This process is not suitable for welding steel wire rods with high Si content. The generated SiO2 film will significantly inhibit the formation of iron oxide scale, and it is difficult to make the iron scale thickness reach more than 30μm. In addition, the thick iron oxide scale is easy to fall off during the transportation and storage of the wire rod, and the falling position is secondary rusted. The iron scale produced by the rust is mainly Fe2O3, and the thickness is thin, which is difficult to remove in the subsequent mechanical descaling.

[0005] In summary, the high-Si welding wire steel wire rod produced by the traditional Stelmor process or adding an offline annealing process has problems such as high production cost and single usage scenario, which seriously restricts the market competitiveness of this series of products. At the same time, the iron oxide scale formed by the high-Si welding wire steel wire rod produced by the current traditional process cannot fully meet the requirements of mechanical descaling and pickling to remove the iron scale, and the mechanical descaling effect is not ideal, which also seriously affects the final surface quality of the welding wire. Summary of the invention

[0006] In order to solve the problems raised in the above background technology, the present invention provides a control method for removing iron oxide scale from high-Si welding wire steel wire rod, which can achieve the control of iron oxide scale thickness ≤ 5μm, avoid the generation of Fe3O4 and Fe2O3 below 570℃, and achieve single-layer control of iron oxide scale.

[0007] In order to achieve the above object, the technical solution provided by the present invention is:

[0008] A control method for removing iron oxide scale from high-Si welding wire steel wire rods, the method comprising the steps of billet heating, controlled rolling, and residual heat isothermal treatment, wherein the billet heating step comprises a billet heating section temperature of 850-950°C, a heating time of 50-60 min, a soaking section temperature of 950-1000°C, a soaking time of 30-40 min, a total furnace time of 80-100 min, and a start rolling temperature of 970±20°C; in the controlled rolling step, the billet enters a high-speed wire rolling mill for rolling, and the overall temperature of the rolling process is 850±20℃, the spinning temperature is set at 830±20℃; in the process of the residual heat isothermal treatment, the wire rod is quickly conveyed to the isothermal salt pool by the roller after spinning, the roller speed is set at 0.5-1.0m / s, the isothermal heat treatment temperature is set at 570-600℃, the wire rod is cooled to 570-600℃ at a heat exchange rate of cooling rate ≥80℃ / s, and kept warm for 2-6min, which can achieve the control of the thickness of the iron oxide scale ≤5μm, avoid the formation of Fe3O4 and Fe2O3 below 570℃, and achieve the control of the single layer of the iron oxide scale.

[0009] Preferably, after the wire rod comes out of the isothermal salt pool, a layer of molten salt adheres to the surface to isolate it from the air, thereby avoiding further oxidation of the surface iron sheet during the subsequent cooling process, and quickly coiling it to ensure that the wire rod temperature is ≥300°C.

[0010] Preferably, the method further comprises a water tank cleaning step, the temperature of the coil is ≥250°C when it is transported to the C-hook, and it quickly passes through the PF line into the water washing tank to clean the surface molten salt and quickly cool down to room temperature.

[0011] Beneficial effects of the present invention:

[0012] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0013] The high-Si welding wire steel wire rod produced by the present invention passes through an online isothermal heat treatment device, and after rolling, the wire rod is cooled to 570-600°C for heat preservation at a cooling rate of ≥80°C / s, so that the thickness of the oxide scale is ≤5μm, which is conducive to pickling removal, and the molten salt is attached to the surface to avoid the generation of Fe3O4 and Fe2O3 in the low-temperature process, ensuring that the oxide scale has a single-layer FeO structure, and the overall iron scale is loose and has poor toughness, which is conducive to mechanical bending and removal;

[0014] The iron scale of the high-Si welding wire steel wire rod produced by the present invention is cooled by water at about 250°C, so that the matrix and the surface iron scale in the wire rod shrink rapidly, and the difference in shrinkage ratio between the matrix and the surface iron scale is used to form gaps or break the surface iron scale, so that the mechanical shelling efficiency of the wire rod is improved by more than 80%;

[0015] The high-Si welding wire steel wire rod produced by the present invention has excellent guaranteed performance for pickling and mechanical descaling to remove iron oxide scale, and avoids annealing treatment, etc., thereby reducing production costs and shortening the production cycle of products; at the same time, the iron oxide scale is overall thinner, which improves the yield rate of welding wire processing and meets the user's requirements for low cost, environmental protection and high quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of producing high-Si welding wire steel wire rod iron sheet (horizontally ~1000X) by the process of Example 1;

[0017] Figure 2 This is a schematic diagram of the effect of removing iron scale by bending high Si welding wire steel wire rod once in the process of Example 1;

[0018] Figure 3 Schematic diagram of producing high-Si welding wire steel wire rod iron sheet (horizontally ~1000X) by the process of Example 2;

[0019] Figure 4 This is a schematic diagram of the effect of removing iron scale by bending high Si welding wire steel wire rod once in the process of Example 2;

[0020] Figure 5 Schematic diagram of producing high-Si welding wire steel wire rod iron sheet (horizontally ~1000X) by the process of Example 3;

[0021] Figure 6 This is a schematic diagram of the effect of removing iron scale by bending high Si welding wire steel wire rod once in the process of Example 3;

[0022] Figure 7 Schematic diagram of the traditional process for producing high-Si welding wire steel wire rod iron sheet (horizontally ~1000X);

[0023] Figure 8 Schematic diagram of the iron scale removal effect of one-time bending of high-Si welding wire steel rod produced by traditional process. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Example 1

[0027] The present embodiment provides a high-Si welding wire steel wire rod and a production method suitable for both mechanical descaling and pickling and descaling processes, which sequentially include billet heating, controlled rolling, residual heat isothermal treatment, and water tank cleaning processes.

[0028] In the billet heating process, the temperature of the billet heating section is 880-930°C, the heating time is 54-57min, the temperature of the soaking section is 970-980°C, the soaking time is 33-37min, the total time in the furnace is 88-94min, and the rolling start temperature is 970°C.

[0029] The rolling process is controlled, and the ingot enters the high-speed wire rolling mill for rolling. The overall rolling process temperature is 850℃, and the wire drawing temperature is set at 830℃.

[0030] In the residual heat isothermal treatment process, after spinning, the wire rod is quickly transported to the isothermal salt pool by the roller, and the roller speed is set at 0.7-0.9m / s. It enters the reducing isothermal heat treatment tank, and the isothermal heat treatment temperature is set at 580-590℃. The wire rod is cooled to 580-590℃ at a heat exchange rate of ≥80℃ / s, and kept warm for 3-5min. After the wire rod comes out of the salt tank, a layer of molten salt is attached to the surface to isolate it from the air, and it is quickly rolled up to ensure that the wire rod temperature is ≥300℃.

[0031] In the water tank cleaning process, the temperature of the coil is ≥250℃ when it is transferred to the C-hook, and it quickly passes through the PF line into the water washing tank to wash the surface molten salt and quickly cool down to room temperature.

[0032] The finished wire rod structure obtained in this embodiment is ferrite + dispersed cementite, the overall oxide scale thickness is ≤5μm, the oxide scale is a single-layer structure, and the scale is in a broken state. After a slight bending, the oxide scale peeling effect is better, as shown in the effect diagram Figure 1 , Figure 2 .

[0033] Example 2

[0034] The present embodiment provides a high-Si welding wire steel wire rod and a production method suitable for both mechanical descaling and pickling and descaling processes, which sequentially include billet heating, controlled rolling, residual heat isothermal treatment, and water tank cleaning processes.

[0035] In the billet heating process, the temperature of the billet heating section is 850-880°C, the heating time is 50-54min, the temperature of the soaking section is 950-970°C, the soaking time is 30-33min, the total time in the furnace is 80-88min, and the rolling start temperature is 950°C.

[0036] The rolling process is controlled, and the ingot enters the high-speed wire rolling mill for rolling. The overall rolling process temperature is 830℃, and the wire drawing temperature is set at 810℃.

[0037] In the residual heat isothermal treatment process, after spinning, the wire rod is quickly transported to the isothermal salt pool by the roller, and the roller speed is set at 0.5-0.7m / s. It enters the reducing isothermal heat treatment tank, and the isothermal heat treatment temperature is set at 570-580℃. The wire rod is cooled to 570-580℃ at a heat exchange rate of ≥80℃ / s, and kept warm for 2-3min. After the wire rod comes out of the salt tank, a layer of molten salt is attached to the surface to isolate it from the air, and it is quickly rolled up to ensure that the wire rod temperature is ≥300℃.

[0038] In the water tank cleaning process, the temperature of the coil is ≥250℃ when it is transferred to the C-hook, and it quickly passes through the PF line into the water washing tank to wash the surface molten salt and quickly cool down to room temperature.

[0039] The finished wire rod structure obtained in this embodiment is ferrite + dispersed cementite, the overall oxide scale thickness is ≤5μm, the oxide scale is a single-layer structure, and the scale is in a broken state. After a slight bending, the oxide scale peeling effect is better, as shown in the effect diagram Figure 3 , Figure 4 .

[0040] Example 3

[0041] The present embodiment provides a high-Si welding wire steel wire rod and a production method suitable for both mechanical descaling and pickling and descaling processes, which sequentially include billet heating, controlled rolling, residual heat isothermal treatment, and water tank cleaning processes.

[0042] In the billet heating process, the temperature of the billet heating section is 930-950°C, the heating time is 57-60 min, the temperature of the soaking section is 980-1000°C, the soaking time is 37-40 min, the total time in the furnace is 88-100 min, and the starting rolling temperature is 990°C.

[0043] The rolling process is controlled, and the ingot enters the high-speed wire rolling mill for rolling. The overall rolling process temperature is 870℃, and the wire drawing temperature is set at 850℃.

[0044] In the residual heat isothermal treatment process, after spinning, the wire rod is quickly transported to the isothermal salt pool by the roller, and the roller speed is set at 0.9-1.0m / s. It enters the reducing isothermal heat treatment tank, and the isothermal heat treatment temperature is set at 590-600℃. The wire rod is cooled to 590-600℃ at a heat exchange rate of ≥80℃ / s, and kept warm for 5-6min. After the wire rod comes out of the salt tank, a layer of molten salt is attached to the surface to isolate it from the air, and it is quickly rolled up to ensure that the wire rod temperature is ≥300℃.

[0045] In the water tank cleaning process, the temperature of the coil is ≥250℃ when it is transferred to the C-hook, and it quickly passes through the PF line into the water washing tank to wash the surface molten salt and quickly cool down to room temperature.

[0046] The finished wire rod structure obtained in this embodiment is ferrite + dispersed cementite, the overall oxide scale thickness is ≤5μm, the oxide scale is a single-layer structure, and the scale is in a broken state. After a slight bending, the oxide scale peeling effect is better, as shown in the effect diagram Figure 5 , Figure 6 .

[0047] Comparative Example

[0048] This embodiment adopts the traditional process to produce high-Si welding wire steel wire rod. In the steel billet heating stage, the heating section temperature is 1050-1100°C, the soaking section temperature is 1090-1110°C, and the heating time is 2-3h. During this period, the residual oxygen in the furnace is required to be ≤3%. Then, the iron oxide scale is removed by high-pressure water descaling before rolling.

[0049] In the wire rolling process, the wire billet temperature is controlled at 900-950℃, the finishing mill temperature is controlled at 880-920℃, and the wire drawing temperature is controlled at 850-880℃.

[0050] After rolling is completed, controlled cooling is carried out. The wire rod is slowly cooled on the Stelmor roller table by covering it with an insulation cover. The main speed of the roller table is set at 0.15-0.25m / s. After the wire rod is off the line, a wind shield is set around it to extend the insulation time after the wire rod is off the line, so that the iron oxide can stay near 500℃ for a longer time.

[0051] By lowering the spinning temperature and the subsequent controlled cooling process, the composition and thickness of the oxide scale of the hot-rolled wire rod can be controlled.

[0052] The finished wire rod obtained in the comparative example has a ferrite + pearlite structure, the overall oxide scale thickness is about 10μm, the oxide scale has a three-layer structure, and the iron scale is tightly combined with the matrix. After a slight bending, the peeling effect of the oxide scale and the matrix is ​​poor. Figure 7 , Figure 8 shown.

[0053] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A control method for removing iron oxide scale from high-Si welding wire steel wire rod, characterized in that: The method comprises the steps of heating the steel billet, controlled rolling and isothermal treatment with residual heat. In the steel billet heating step, the temperature of the steel billet heating section is 850-950°C, the heating time is 50-60min, the temperature of the soaking section is 950-1000°C, the soaking time is 30-40min, the total time in the furnace is 80-100min, and the rolling start temperature is 970±20°C; in the controlled rolling step, the cast billet enters the high-speed wire rolling mill for rolling, the overall temperature of the rolling process is 850±20°C, and the wire laying temperature is 100-150°C. Set to 830±20℃; in the process of the waste heat isothermal treatment, the wire rod is quickly conveyed to the isothermal salt pool by the roller after spinning, the roller speed is set to 0.5-1.0m / s, the isothermal heat treatment temperature is set to 570-600℃, and the wire rod is cooled to 570-600℃ at a heat exchange rate of cooling rate ≥80℃ / s, and kept warm for 2-6min, which can achieve the control of iron oxide thickness ≤5μm, and avoid the formation of Fe3O4 and Fe2O3 below 570℃, so as to achieve the control of iron oxide single layer.

2. A control method for removing oxide scale from high-Si welding wire steel wire rod according to claim 1, characterized in that: After the wire rod comes out of the isothermal salt pool, a layer of molten salt adheres to the surface to isolate it from the air, thereby preventing further oxidation of the surface iron sheet during the subsequent cooling process, and quickly coiling it to ensure that the wire rod temperature is ≥300°C.

3. A control method for removing oxide scale from high-Si welding wire steel wire rod according to claim 1, characterized in that: The method also includes a water tank cleaning process. When the coil is transferred to the C-hook, the temperature is ≥250°C, and it quickly passes through the PF line into the water washing tank to clean the surface molten salt and quickly cool down to room temperature.

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