Novel smelting and rolling production method for rare earth welding wire steel

Abstract

The invention discloses a novel rare earth welding wire steel smelting and rolling production method which is characterized by comprising the following steps: 1) a desulfurization process; 2) converter process; (3) refining operation; 4) continuous casting control; (5) in the rolling process and the heating process, the temperature ranges of a soaking section and a heating section are 1080-1130 DEG C and are strictly prohibited to exceed 1150 DEG C, and cooling is conducted in time when rolling is stopped; the pressure of high-pressure water scale is required to be not less than 7MPa, so that the descaling effect is ensured, and visual residual scale cannot exist on the surface of the steel billet after descaling. According to the novel rare earth welding wire steel smelting and rolling production method, the drawing performance of a welding wire steel wire rod is improved through implementation of the method, and phi 0.8 mm can be drawn smoothly.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting and rolling, and in particular relates to a novel rare earth welding wire steel smelting and rolling production method. Background Art

[0002] Due to the overall upgrade and transformation of the drawing equipment of welding wire steel users, all of them have been changed to a full-process continuous high-drawing speed production line of 28m / s, and welding wire steel wire rods that adapt to low drawing speeds will withdraw from the stage of history. In order to adapt to the high-speed full-continuous drawing advanced welding wire production line of downstream users and meet the user's requirements for excellent drawing performance, targeted quality upgrade work for high-speed drawing φ6.5mm specification welding wire ER70S-6 products is proposed. Since rare earths improve the toughness of steel, the research and development of rare earth welding wire steel is proposed to improve the drawing performance and low-temperature impact performance of welding wire steel. Recently, the new type of welding wire steel product containing rare earth elements developed for the first time in the country has been successful. This innovative product provides a new material for my country's welding field with its excellent performance far higher than that of traditional welding wire steel. The successful research and development of rare earth welding wire steel provides a broad application scenario for the fields of construction and welding wire, and will play a role in more fields. It is also understood that rare earth welding wire steel will also bring good economic benefits to enterprises, showing its strong market competitiveness. Summary of the invention

[0003] In order to solve the problem that Baosteel welding wire steel cannot be drawn to Φ0.8mm, the purpose of the present invention is to provide a new rare earth welding wire steel smelting and rolling production method. Through the implementation of this method, the drawing performance of the welding wire steel coil is improved, and Φ0.8mm can be drawn in a forward direction.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a novel rare earth welding wire steel smelting and rolling production method, comprising the following steps:

[0006] 1) Desulfurization process

[0007] The molten iron output is controlled at 85-95 tons, and the S in the furnace is required to be ≤0.020%. If it exceeds the limit, the judgment will be revised;

[0008] 2) Converter process

[0009] The total loading volume of the loading system is controlled at 105±2 tons; the oxygen supply system adopts low-high-low gun position control, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the molten iron conditions, and the end point basicity is controlled at 2.7-3.5; the end point control target is to blow out steel once, the blowing time is ≤1.5min, the steel carbon is 0.03%≤C≤0.05%, T≥1610℃;

[0010] The tapping port is controlled at 50-150 times; 100-200kg of dolomite thick slag is added before tapping to avoid no slag layer during tapping; 200kg of top slag lime and 80-100kg of pre-melted slag are added during tapping; a slide plate is used to block slag during tapping, and slag is strictly prohibited; the converter must switch to nitrogen-argon mode when producing new rare earth welding wire steel; strengthen contact with the tank repair during tapping, and perform argon blowing operations according to regulations; argon control requirements: contact the tank repair for argon replacement for 15s-30s before tapping, stir with large argon in the early stage of tapping, and adjust the argon flow rate to block slag when the tapping volume is greater than 2 / 3 to ensure that the alloy does not clump and the top slag material is well melted;

[0011] 3) Refining operation

[0012] In order to accurately control the composition, the refining is heated for 8 minutes. According to the slag surface of the molten steel, the electrode adopts 8 polarized slag for 30s-50s and then gradually adjusts to the normal temperature of level 2; 10-30kg of ferrosilicon powder is added during the heating process, and fluorite spheroidizing slag agent is added according to the slag situation, and the amount of lime added is 200kg-300kg; the further heating time is estimated according to the in-situ temperature and production sequence, and the heating efficiency is calculated at 4℃ / min; after the molten steel is heated to the appropriate temperature, the slag is observed, and according to the slag viscosity, slag-forming agent or lime is added to ensure that the slag viscosity is appropriate; the heating process is adjusted The dust hood valve opening is set at 50%-80% or adjusted by the fan speed. The fan frequency is 32Hz-35Hz for night shift and 35Hz-38Hz for day shift production, to ensure that a small amount of smoke overflows from the electrode hole during heating to ensure slightly positive pressure heating; when sulfur is less than 0.015%, weak stirring of 200-400NL / min of vehicle-mounted argon is used during stirring, and the stirring time is controlled for 1-2 minutes to prevent the steel liquid from being exposed and nitrogenized; rare earth ferrocerium alloy is added in the later stage of refining, and the addition amount is more than 0.0030% to ensure the retention of rare earth in steel, and at the same time, the oxygen content of rare earth alloy should be controlled;

[0013] 4) Continuous casting control

[0014] The temperature of the first furnace of the upper stage is controlled at 1606-1616℃, and the process furnace is controlled at 1575-1595℃; the baking time of the tundish is 3-3.5h, and the baking temperature is>1250℃; asbestos bowl is used for each furnace of steel in the long nozzle of the protective pouring ladle, and argon is blown in the long nozzle, so that the T-shaped nozzle does not emit carbon flowers; covering agent is added to the tundish so that the steel liquid surface does not shine; the immersion nozzle is strictly centered, and the immersion nozzle uses a sealing ring; low-carbon steel protection slag is used; crystallizer Add less protective slag frequently, and carbon flowers are not allowed on the surface of the molten steel; the liquidus temperature of the steel grade is 1516℃, the superheat target of the first furnace is ≤50℃, and the superheat target of the second and subsequent furnaces is ≤30℃; the starting pulling speed is 0.25m / min, the pulling speed of the first furnace is controlled at 1.5~2.1m / min, and the target pulling speed of the remaining furnaces is 2.1m / min, and the pulling speed fluctuation range is ±0.1m / min; after control, the superheat of the new rare earth welding wire steel is ≤30℃;

[0015] The water flow rate of each crystallizer is 125-130m3 / h, the water inlet pressure is ≥0.8MPa, the temperature difference between the inlet and outlet water is 4-8℃, and the secondary cooling water meter adopts aerosol strong cooling; the electromagnetic stirring current of the crystallizer is 270±5A, the frequency is 3.5Hz; the terminal electric stirring current is 100±5A, the frequency is 8.0Hz; the steel passing capacity of the crystallizer is ≤6000 tons; the insertion depth of the immersion nozzle is 70-100mm, and it should be adjusted in time; the allowable deviation of the cross-section size of the ingot is ±3mm; the allowable deviation of the fixed length is 0-+50mm; the allowable deviation of the diagonal length of the cross section is ≤5mm; the curvature shall not exceed 20mm per meter, and the total curvature shall not be greater than 1% of the total length; the cutting surface of the ingot shall be perpendicular to its axis, and the cutting slope shall not be greater than 10mm;

[0016] 5) Rolling process

[0017] Heating process: The temperature range of the soaking section and the heating section is 1080-1130℃, and it is strictly forbidden to exceed 1150℃. The temperature should be reduced in time when the rolling is stopped; the high-pressure water scale pressure should be no less than 7MPa to ensure the descaling effect. There should be no visible residual iron oxide on the surface of the billet after descaling;

[0018] (1) Rolling start temperature (℃): 1000±30, the temperature fluctuation range of the billet throughout its length is within 50℃, the ratio is ≥80%;

[0019] (2) Finishing rolling temperature (℃): 910±20, the temperature fluctuation range of the billet throughout the length is within 30℃, the ratio is ≥80%;

[0020] (3) Spinning temperature (°C): 920±20. The temperature fluctuation range of the billet throughout its length within 30°C shall be ≥80%.

[0021] Furthermore, in the step 1), the materials used must be dry and free of inclusions, and the amount of scrap steel used is 10-20 tons.

[0022] Furthermore, in step 2), the temperature of the new steel outlet, low-temperature ladle and cooling furnace is increased by 20-40°C as appropriate, or adjusted appropriately according to the iron-steel ratio control requirements and furnace conditions.

[0023] Furthermore, in step 3), the amount of refined lime is controlled to be within 200 kg as much as possible.

[0024] Furthermore, the surface of the ingot shall not have any defects such as desquaring, cracks, inclusions, joints, or pores visible to the naked eye; pitting, depressions, and scratches with a depth not exceeding 2 mm are allowed; the ingot shall not have serious desquaring, bulging, or central shrinkage. Low-magnification hot acid specimens of the ingot shall be taken from each furnace for inspection.

[0025] Furthermore, the composition of the welding wire steel by mass percentage is: C: 0.07-0.08%, Si: 0.83-0.93%, Mn: 1.43-1.53%, P: ≤0.015%, S≤0.015%, N≤0.0040%, Ce: 0.0005-0.0015% (preferably 0.0010%), and the rest is Fe and impurities.

[0026] High dimensional accuracy and small ovality can ensure that the drawing process meets the requirements of the process regulations, reduce the friction of drawing, reduce mold consumption, and improve the surface quality and uniformity of mechanical properties of steel wire. When the out-of-roundness of the wire rod exceeds the standard seriously, the wire rod is cold-drawn with a mold matching the standard raw material. Due to the severe local work hardening of the maximum compressive stress and tensile stress in the long axis direction and the size exceeding the standard, the wire rod cannot pass through the mold smoothly and is stuck at the entrance of the mold. With the increase of compressive stress and tensile stress, it will eventually break at the bite. After the wire with excessive out-of-roundness barely enters the mold, the organization is severely deformed due to the excessive compression rate in the long axis direction. At the same time, a large friction heat is generated between the contact surface of the mold, causing the metal temperature of the surface layer of the wire to exceed its critical temperature. The subsequent rapid cooling causes a martensitic phase transformation, forming a thin layer of martensitic organization. Therefore, the out-of-roundness and dimensional deviation of the wire rod must be controlled.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are:

[0028] This innovative product, with its excellent performance far superior to traditional welding wire steel, provides a new type of material for my country's welding field. After being tried by many domestic users, it can completely draw Φ0.8mm, and the low-temperature impact performance is significantly improved. DETAILED DESCRIPTION

[0029] In order to better illustrate the invention content of the patent of this invention, specific operation methods are proposed, and specific examples are analyzed. The specific implementation methods are as follows.

[0030] Through the above-mentioned desulfurization-converter-refining-continuous casting-rolling key process control, the oxygen content of the added rare earth ferrocerium alloy is controlled below 100ppm, ensuring that the rare earth Ce sampled in the tundish in the steel is above 10ppm, which can ensure continuous casting of more than 15 furnaces. The composition control of the specific example is shown in Table 1.

[0031] Table 1 Component control of specific examples / %

[0032]

[0033]

[0034] The starting pulling speed is 0.25m / min, and the pulling speed of the first furnace is controlled at 1.5~2.1m / min. The target pulling speed of the remaining furnaces is 2.1m / min, and the pulling speed fluctuation range is ±0.1m / min. After control, the superheat of the new rare earth welding wire steel is ≤30℃. The ingot is taken for low-power detection of hot acid. The maximum level of central cracks and central loose defects is 1.5. Most of the shrinkage holes in the center of the ingot are concentrated at level 0, and some are at level 0.5 and 1.0. There are no defects such as middle cracks, subcutaneous bubbles, and corner cracks. Most of the non-metallic inclusions are concentrated at level 0.5, and some are at level 1 and 0. The overall control level of the internal quality of the ingot is good.

[0035] The temperature control curves in the production of welding wire steel are all checked back for each batch. During production, the main control console measures the temperature of each control point at least once every two hours, and the technical group of the operation department and the manufacturing department conduct spot checks at least once a day. All temperature control points have achieved control targets, and the temperature fluctuation range of the billet during the rolling start is within 50°C for 88%. The temperature fluctuation range of the finished rolling entrance is within 30°C for 89%. The temperature fluctuation range of the wire drawing temperature is within 30°C for 93%.

[0036] Table 2 Rolling temperature control conditions

[0037]

[0038]

[0039] This innovative product, with its excellent performance far superior to traditional welding wire steel, provides a new type of material for my country's welding field. After being tried by many domestic users, it can completely draw Φ0.8mm, and the low-temperature impact performance is significantly improved. Specific examples are shown in Table 3.

[0040]

[0041] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A novel rare earth welding wire steel smelting and rolling production method, characterized in that: The steps include: 1) Desulfurization process The molten iron output is controlled at 85-95 tons, and the S in the furnace is required to be ≤0.020%. If it exceeds the limit, the judgment will be revised; 2) Converter process The total loading volume of the loading system is controlled at 105±2 tons; the oxygen supply system adopts low-high-low gun position control, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the molten iron conditions, and the end point basicity is controlled at 2.7-3.5; the end point control target is to blow out steel once, the blowing time is ≤1.5min, the steel carbon is 0.03%≤C≤0.05%, T≥1610℃; The tapping port is controlled at 50-150 times; 100-200kg of dolomite thick slag is added before tapping to avoid no slag layer when tapping; 200kg of top slag lime and 80-100kg of pre-melted slag are added when tapping; a slide plate is used to block the slag during tapping, and slag is strictly prohibited; The converter must switch to nitrogen-argon mode when producing new rare earth welding wire steel; strengthen contact with the tank repairer during steel tapping and perform argon blowing operations according to regulations; argon control requirements: contact the tank repairer for argon replacement for 15s-30s before steel tapping, stir with large argon in the early stage of steel tapping, and reduce the argon flow rate to perform slag blocking operations when the steel tapping volume exceeds 2 / 3, to ensure that the alloy does not clump and the top slag material is well melted; 3) Refining operation In order to accurately control the composition, the refining is heated in place for 8 minutes. According to the slag surface of the molten steel in place, the electrode adopts 8-polarized slag for 30s-50s and then gradually adjusts to the normal temperature of level 2; 10-30kg of ferrosilicon powder is added during the heating process, and the fluorite slag agent is added according to the slag situation, and the amount of lime added is 200kg-300kg; the further heating time is estimated according to the in-place temperature and production sequence, and the heating efficiency is calculated at 4℃ / min; after the molten steel is heated to the appropriate temperature, the slag situation is observed, and according to the slag viscosity, slag agent or lime is added to ensure that the slag viscosity is appropriate; during the heating process, the dust hood valve opening is adjusted by 50%-80% or adjusted by the fan speed, the night shift fan frequency is 32Hz-35Hz, and the day shift production fan frequency is 35Hz-38Hz, to ensure that a small amount of smoke overflows from the electrode hole during heating to ensure micro-positive pressure heating; When sulfur is less than 0.015%, weak stirring is adopted with vehicle-mounted argon at 200-400NL / min, and the stirring time is controlled to 1-2 minutes to prevent the steel liquid from being exposed to nitrogen addition; rare earth ferrocerium alloy is added in the later stage of refining, and the addition amount is added at a level of more than 0.0030% to ensure the retention of rare earth in the steel, and at the same time, the oxygen content of the rare earth alloy should be controlled; 4) Continuous casting control The temperature of the first furnace of the upper stage is controlled at 1606-1616℃, and the process furnace is controlled at 1575-1595℃; the baking time of the tundish is 3-3.5h, and the baking temperature is>1250℃; asbestos bowl is used for each furnace of steel in the long nozzle of the protective pouring ladle, and argon is blown in the long nozzle, so that the T-shaped nozzle does not emit carbon flowers; covering agent is added to the tundish so that the steel liquid surface does not shine; the immersion nozzle is strictly centered, and the immersion nozzle uses a sealing ring; low-carbon steel protection slag is used; crystallizer Add less protective slag frequently, and carbon flowers are not allowed on the surface of the molten steel; the liquidus temperature of the steel grade is 1516℃, the superheat target of the first furnace is ≤50℃, and the superheat target of the second and subsequent furnaces is ≤30℃; the starting pulling speed is 0.25m / min, the pulling speed of the first furnace is controlled at 1.5~2.1m / min, and the target pulling speed of the remaining furnaces is 2.1m / min, and the pulling speed fluctuation range is ±0.1m / min; after control, the superheat of the new rare earth welding wire steel is ≤30℃; The water flow rate of each crystallizer is 125-130m3 / h, the water inlet pressure is ≥0.8MPa, the temperature difference between the inlet and outlet water is 4-8℃, and the secondary cooling water meter adopts aerosol strong cooling; the electromagnetic stirring current of the crystallizer is 270±5A, the frequency is 3.5Hz; the terminal electric stirring current is 100±5A, the frequency is 8.0Hz; the steel passing capacity of the crystallizer is ≤6000 tons; the insertion depth of the immersion nozzle is 70-100mm, and it should be adjusted in time; the allowable deviation of the cross-section size of the ingot is ±3mm; the allowable deviation of the fixed length is 0-+50mm; the allowable deviation of the diagonal length of the cross section is ≤5mm; the curvature shall not exceed 20mm per meter, and the total curvature shall not be greater than 1% of the total length; the cutting surface of the ingot shall be perpendicular to its axis, and the cutting slope shall not be greater than 10mm; 5) Rolling process Heating process: The temperature range of the soaking section and the heating section is 1080-1130℃, and it is strictly forbidden to exceed 1150℃. The temperature should be reduced in time when the rolling is stopped; the high-pressure water scale pressure should be no less than 7MPa to ensure the descaling effect. There should be no visible residual iron oxide on the surface of the billet after descaling; (1) Rolling start temperature (℃): 1000±30, the temperature fluctuation range of the billet throughout its length is within 50℃, the ratio is ≥80%; (2) Finishing rolling temperature (℃): 910±20, the temperature fluctuation range of the billet throughout the length is within 30℃, the ratio is ≥80%; (3) Spinning temperature (°C): 920±20. The temperature fluctuation range of the billet throughout its length within 30°C shall be ≥80%.

2. The novel rare earth welding wire steel smelting and rolling production method according to claim 1 is characterized in that: In the step 1), the materials used must be dry and free of inclusions, and the amount of scrap steel used is 10-20 tons.

3. The novel rare earth welding wire steel smelting and rolling production method according to claim 1 is characterized in that: In the step 2), the temperature of the new steel outlet, the low-temperature ladle and the cooling furnace is increased by 20-40°C as appropriate, or adjusted appropriately according to the iron-steel ratio control requirements and the furnace conditions.

4. The novel rare earth welding wire steel smelting and rolling production method according to claim 1 is characterized in that: In the step 3), the amount of refined lime is controlled to be within 200 kg as much as possible.

5. The novel rare earth welding wire steel smelting and rolling production method according to claim 1 is characterized in that: The surface of the ingot shall not have visible defects such as desquamation, cracks, inclusions, joints, and pores; pitting, depressions, and scratches with a depth not exceeding 2mm are allowed; the ingot shall not have serious desquamation, bulging, or central shrinkage. Low-magnification hot acid specimens of the ingot shall be taken from each furnace for inspection.

6. The novel rare earth welding wire steel smelting and rolling production method according to claim 1 is characterized in that: The welding wire steel has the following components in percentage by mass: C: 0.07-0.08%, Si: 0.83-0.93%, Mn: 1.43-1.53%, P: ≤0.015%, S≤0.015%, N≤0.0040%, Ce: 0.0005-0.0015%, and the rest is Fe and impurities.

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