CN114774618A - Smelting production method for solving drawing brittle failure of gas shielded welding wire steel - Google Patents
Smelting production method for solving drawing brittle failure of gas shielded welding wire steel Download PDFInfo
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- CN114774618A CN114774618A CN202210463589.3A CN202210463589A CN114774618A CN 114774618 A CN114774618 A CN 114774618A CN 202210463589 A CN202210463589 A CN 202210463589A CN 114774618 A CN114774618 A CN 114774618A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/34—Blowing through the bath
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/116—Refining the metal
- B22D11/117—Refining the metal by treating with gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
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Abstract
The invention discloses a smelting production method for solving drawing brittle failure of gas-shielded welding wire steel, which is characterized in that the nitrogen content of gas is controlled through key processes of converter, refining, continuous casting and the like, so that the nitrogen content of the gas of the welding wire steel is obviously reduced to below 50ppm from 60ppm to 90 ppm.
Description
Technical Field
The invention relates to the technical field of metal smelting, in particular to a smelting production method for solving drawing brittle failure of gas shielded welding wire steel.
Background
ER70S-6 welding wire steel wire rod is CO2The main base material of gas shielded solid welding wire is mainly used in automobile manufacture, locomotive and chemical machineryMachinery, agricultural machinery and other industries. In order to reduce the production cost, a gas shield welding wire steel user requires not to carry out any annealing procedure in the drawing process, and directly draws from phi 6.5mm and phi 5.5mm to phi 0.8mm, phi 1.0mm and phi 1.2mm, so that the requirements of uniform chemical components, low non-metallic inclusion and uniform microstructure are required to be achieved. A brittle fracture form can appear when a user pulls the test piece, no trauma is seen at the broken wire position, the metallographic structure is observed after the failed test piece is longitudinally polished, the microstructure is normally ferrite and a small amount of pearlite structure, but obvious microcracks are found inside the failed test piece and are in a herringbone shape, the content of nitrogen in the brittle fracture sample exceeds the standard through inspection, and the defect pictures are shown in figures 1 and 2.
Production practices prove that the influence of the content of gas nitrogen on the drawing performance of the gas-shielded welding wire is critical, and the nitrogen serving as a solid solution strengthening element can improve the strength of steel, can obviously reduce the plasticity and toughness of the steel as interstitial atoms, increases the brittleness of the steel, improves the mechanical performance in the drawing process, reduces the surface shrinkage rate in the drawing process and causes brittle fracture in the drawing process. Therefore, it is very important to control the nitrogen content in the production process of the gas shielded welding wire steel.
Disclosure of Invention
The invention aims to provide a smelting production method for solving the drawing brittle failure of gas shielded welding wire steel, which controls the nitrogen content in the welding wire steel through a smelting converter and refining, reduces the drawing brittle failure rate and improves the quality of the welding wire steel.
In order to solve the technical problem, the invention adopts the following technical scheme:
a smelting production method for solving drawing brittle failure of gas shielded welding wire steel comprises the following steps:
1) nitrogen control for smelting in converter
The key process control of nitrogen control in the production of welding wire steel by a converter comprises the following steps: the converter bottom blowing ensures that the time of bottom blowing argon is more than 5 minutes after the nitrogen and argon switching, and the nitrogen content is reduced; steel tapping is avoided by peroxidation in the smelting process, and negative pressure nitrogen absorption is prevented; CO bubbles generated by decarburization provide a reaction interface for denitrification, simultaneously reduce nitrogen partial pressure, optimize the adding proportion of the steel scrap, control the steel scrap ratio of the converter to be below 20 percent, control the nitrogen content and improve the reaction of a molten pool to the maximum extent;
2) refining nitrogen control
Key process control of nitrogen control in refining production of welding wire steel: the S content of the steel in the converter and the refining furnace is controlled to be below 0.010 percent, and the refining furnace cannot be used as a main desulfurization process; the adding amount of the lime in the refining furnace is controlled to be below 200 kg; only ferrosilicon powder is added into the refining furnace, aluminum deoxidation is not used, calcium wires are prevented from being fed, and the calcium content is controlled to be less than 8 ppm; closing the side pumping of the refining furnace, establishing a micro-positive pressure environment and reducing nitrogen absorption; the refining and granulating amount is reduced from over 1000Kg to below 200Kg, or no granulating is added in refining;
3) continuous casting nitrogen control
The large ladle nozzle adopts a graphite pad, and the sealed argon forms rotary airflow at the joint part of the lower nozzle and the long nozzle, so that an argon leakage channel is prevented from being formed, air is completely isolated, and a positive pressure area is formed at the top of the long nozzle; argon is blown between the ladle nozzle and the long nozzle for sealing so as to prevent air from entering molten steel through gaps of the air, and meanwhile, a high-temperature-resistant sealant is adopted for the tundish nozzle.
Further, in the step 2), if the granules are added for refining, the added granules cannot be the granules of the twisted steel, and the nitrogen content of the ordinary twisted steel is higher than 60 ppm.
Further, the pressure of the middle positive pressure zone in the step 3) is 0.6-0.8 MPa.
Furthermore, the content of the gaseous nitrogen is controlled through key processes of converter, refining and continuous casting, so that the content of the gaseous nitrogen in wire steel is obviously reduced, and is reduced to below 50ppm from 60ppm to 90 ppm.
Further, the chemical components of the gas shield welding wire steel comprise, by mass: 0.05 to 0.08 percent of C, 0.80 to 0.89 percent of Si, 1.40 to 1.49 percent of Mn, less than or equal to 0.020 percent of P, 0.006 to 0.020 percent of S, less than or equal to 0.10 percent of Ni, Cr and Cu, less than or equal to 0.006 percent of Al, and the balance of Fe and other residual elements
Compared with the prior art, the invention has the following beneficial technical effects:
the method effectively reduces the gas nitrogen content of the ER70S-6 gas shielded welding wire steel, improves the subsequent drawing performance of the wire rod and prevents drawing brittle failure.
Drawings
The invention is further illustrated in the following description with reference to the drawings.
Fig. 1 and 2 show metallographic structures observed after longitudinal polishing of a failed sample.
Fig. 3 shows the metallographic structure of the finished product produced by the present invention.
Detailed Description
The invention aims to reduce the gas nitrogen content of ER70S-6 gas shielded wire steel, improve the subsequent drawing performance of a wire rod and prevent drawing brittle failure. The ER70S-6 gas shielded welding wire steel related to the patent comprises the following components: c0.050.08%, Si 0.800.89%, Mn 1.401.49%, P not more than 0.020%, S0.0060.020%, Ni + Cr + Cu not more than 0.10%, Al not more than 0.006%, and the balance of Fe and other residual elements. Converter, refining and continuous casting are all key processes for controlling nitrogen content, but the key factors for the ER70S-6 gas shielded wire steel mainly comprise the following aspects:
1. converter procedure
From the dynamic condition, the reaction interface of the slag and the molten steel is a limiting link of nitrogen absorption. From thermodynamic calculation, the high partial pressure of nitrogen in air and the high solubility of nitrogen in molten steel determine the good nitrogen absorption condition of molten steel. During converter blowing, nitrogen in the converter is mainly carried in by molten iron, and accounts for about 76% of total nitrogen in the converter, and in converter blowing, as a molten pool generates violent carbon-oxygen reaction, a large amount of CO gas is generated, and part of nitrogen dissolved in steel can be carried away, so that the amount of CO is a key factor for influencing degassing. In the early stage of converting, pure oxygen is adopted to convert ammonia partial pressure gas into low partial pressure gas, and then the decarburization speed is reduced to a lower value in metal in the violent boiling metal in the melting bath when the melting bath carbon content in the metal is reduced in the middle stage of descending converting along with the increase of the decarburization speed. After molten steel is involved in air in the blowing process, a spontaneous nitrogen absorption phenomenon can occur, particularly, the carbon-oxygen reaction speed is increased along with the temperature rise in the middle period of blowing, the generated CO amount is increased, and the denitrification reaction is continuously intensified. If the flow of argon blown from the bottom of the steel ladle is too large, slag on the top of the steel ladle is blown away by the argon, so that the contact area between the liquid level of molten steel and the atmosphere is increased invisibly, and the nitrogen is increased in the molten steel, especially in the strongly deoxidized molten steel behind the furnace, and the nitrogen absorption is more sensitive. The carbon content in the scrap steel is far lower than that of the molten iron, so that the improvement of the proportion of the molten iron is more powerful than the improvement of the carbon content in the molten pool. However, the excessive molten iron proportion causes excessive physical thermochemical heat, the excessive temperature in the blowing process causes severe reaction, the high temperature is caused to be dry, the molten steel is exposed in the air, and nitrogen is easily absorbed when the carbon-oxygen reaction is weakened in the later period, and meanwhile, the end point composition is not suitable.
2. Refining procedure
When the refining LF furnace is electrified, as the local temperature of an arc area reaches more than 2100 ℃, the influence of the surface activity effect of oxygen and sulfur on the inhibition of nitrogen absorption disappears, the solubility of nitrogen is increased, and the nitrogen can be absorbed as long as molten steel is exposed. The molten steel in the steel ladle enters an LF station to carry out full-stroke bottom blowing argon stirring, lime and fluorite are added, line A is fed for strengthening deoxidation, fine adjustment of alloy components, Si-Ca line feeding for calcium treatment of the molten steel and other process steps. In the early stage of refining in the LF furnace, the content of nitrogen in molten steel is low, no matter how high the partial pressure of nitrogen in atmosphere is, the nitrogen in atmosphere can not penetrate through a slag layer and enter the molten steel, but after tapping of the converter, a deoxidizer is added for deoxidation, and w (N) in steel is rapidly reduced, so that the ammonia absorption tendency of the molten steel is obviously increased. As the added carburant and ferroalloy are continuously melted into the molten steel, the w (N) in the molten steel is continuously increased. The oxidizing molten steel does not increase nitrogen, while the deoxidizing molten steel obviously absorbs nitrogen. In the early stage of refining, a large amount of slag is added, and because the added slag is not melted to form a larger gap to form a nitrogen-absorbing channel of molten steel, the amount of argon is larger in the process of melting slag, so that the molten steel with good deoxidation is continuously contacted with air. On the premise of ensuring the refining effect, the electrifying time is shortened, low voltage and low current are adopted to stabilize the arc in the earlier stage of electrifying, air electrolysis is reduced, and a rapid heating mode is adopted after the formation of the flowing slag, so that the nitrogen increase amount is further reduced; aiming at different steel types, an interaction mode is selected when a deoxidizing agent is adopted, foam slag is produced, excessive deoxidation is avoided, a small amount of carbide slag is added in the middle and later stages of aluminum deoxidized steel, so that the carbide slag is diluted and isolated from nitrogen, and nitrogen absorption is slowed down; in the LF electrifying process, micro-positive pressure operation is realized by adjusting the rotating speed of the fan and the opening degree of the air door, so that smoke is slightly emitted outwards from the periphery of the furnace mouth and the electrode hole, and the phenomenon that the surrounding air is pumped into the furnace by negative pressure operation and is contacted with molten steel is avoided. In addition, the proper bottom argon blowing flow is selected, so that the liquid steel surface is prevented from being exposed on the premise of stirring.
3. Continuous casting procedure
The nitrogen increase in the continuous casting process is mainly caused by poor protection and casting of the tundish. In the continuous casting process, the molten steel is well deoxidized,
nitrogen will be absorbed as long as the protection is not good in contact with the atmosphere. The high-speed flow of the molten steel in the long nozzle enables the space around the long nozzle to generate negative pressure, and argon is blown between the ladle nozzle and the long nozzle for sealing, so that air is prevented from entering the molten steel through a gap between the ladle nozzle and the long nozzle. Therefore, the key of argon blowing sealing is to make up gas carried away by molten steel by blowing argon so as to prevent air from entering and causing nitrogen absorption. Therefore, the sealing mode of the long nozzle is improved. Before improvement, argon directly vertically contacts molten steel, partial area generates negative pressure, argon dead angles exist, and the argon sealing effect is poor.
Examples
A smelting production method for solving drawing brittle failure of gas shielded welding wire steel comprises the following steps:
1) nitrogen control in converter smelting
The key process control of nitrogen control in the production of welding wire steel by a converter comprises the following steps: the converter bottom blowing ensures that the time of bottom blowing argon is more than 5 minutes after the nitrogen and argon switching, and the nitrogen content is reduced; the steel is prevented from being oxidized and discharged in the smelting process, and the nitrogen is prevented from being absorbed by negative pressure; CO bubbles generated by decarburization provide a reaction interface for denitrification, simultaneously reduce nitrogen partial pressure, optimize the adding proportion of the steel scrap, control the steel scrap ratio of the converter to be below 20 percent, control the nitrogen content and improve the reaction of a molten pool to the maximum extent.
2) Refining nitrogen control
The key process control of nitrogen control in refining production of welding wire steel comprises the following steps: the S content of the steel in the converter and the refining furnace is controlled to be below 0.010 percent, and the refining furnace cannot be used as a main desulfurization process; the lime adding amount of the refining furnace is controlled to be below 200 kg; the lime adding amount of the refining furnace is controlled to be below 200kg, and the calcium content is controlled; only ferrosilicon powder is added into the refining furnace without aluminum deoxidation, calcium wires are prevented from being fed, and the calcium content is controlled to be less than 8 ppm; closing the side pumping of the refining furnace, establishing a micro-positive pressure environment, and reducing nitrogen absorption; the refining grain adding amount is reduced, and the added grain can not be twisted steel.
3) Continuous casting nitrogen control
The big package mouth of a river adopts the graphite pad after improving, and sealed argon gas forms rotatory air current at the mouth of a river and the long mouth of a river linking position under, prevents to form the argon gas passageway that leaks, thoroughly isolated air to make long mouth of a river top form the positive pressure district, about 0.7 MPa. Argon is blown between the ladle nozzle and the long nozzle for sealing so as to prevent air from entering molten steel through gaps of the air, and meanwhile, a high-temperature-resistant sealant is adopted for the tundish nozzle.
The nitrogen content in the molten steel is mainly dissolved in the steel through the contact of the molten steel and nitrogen in the air, and the nitrogen content is easy to control after the measures are taken. The test results show that: the gas nitrogen content is controlled through key procedures of converter, refining and continuous casting, so that the gas nitrogen content of the welding wire steel is obviously reduced, the nitrogen content of the welding wire steel is 60ppm-90ppm before measures are implemented, and is reduced to below 50ppm after measures are implemented, and specific examples are shown in the table below.
| Specific examples | Nitrogen content in steel/ppm |
| Specific example 1 | 35 |
| Specific example 2 | 48 |
| Specific example 3 | 32 |
| Specific example 4 | 25 |
| Specific example 5 | 27 |
| Specific example 6 | 26 |
| Specific example 7 | 25 |
| Specific example 8 | 38 |
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (5)
1. A smelting production method for solving drawing brittle failure of gas shielded welding wire steel is characterized by comprising the following steps:
1) nitrogen control in converter smelting
The key process control of nitrogen control in the production of welding wire steel by a converter comprises the following steps: the converter bottom blowing ensures that the time of bottom blowing argon is more than 5 minutes after nitrogen and argon switching, and reduces the nitrogen content; the steel is prevented from being oxidized and discharged in the smelting process, and the nitrogen is prevented from being absorbed by negative pressure; CO bubbles generated by decarburization provide a reaction interface for denitrification, simultaneously reduce nitrogen partial pressure, optimize the adding proportion of the steel scrap, control the steel scrap ratio of the converter to be below 20 percent, control the nitrogen content and improve the reaction of a molten pool to the maximum extent;
2) refining nitrogen control
Key process control of nitrogen control in refining production of welding wire steel: the S content of the steel in the converter and the refining furnace is controlled to be below 0.010 percent, and the refining furnace cannot be used as a main desulfurization process; the adding amount of the lime in the refining furnace is controlled to be below 200 kg; only ferrosilicon powder is added into the refining furnace, aluminum deoxidation is not used, calcium wires are prevented from being fed, and the calcium content is controlled to be less than 8 ppm; closing the side pumping of the refining furnace, establishing a micro-positive pressure environment and reducing nitrogen absorption; reducing the refining and granulating amount from over 1000Kg to below 200Kg, or not adding granules in refining;
3) continuous casting nitrogen control
The large ladle nozzle adopts a graphite pad, and the sealed argon forms rotary airflow at the joint part of the lower nozzle and the long nozzle, so that an argon leakage channel is prevented from being formed, air is completely isolated, and a positive pressure area is formed at the top of the long nozzle; argon is blown between the ladle lower nozzle and the long nozzle for sealing so as to prevent air from entering molten steel through gaps of the argon and the long nozzle, and meanwhile, the tundish nozzle adopts high-temperature-resistant sealant.
2. The smelting production method for solving the problem of the drawing brittle failure of the gas shielded welding wire steel according to claim 1, wherein in the step 2), the added granules cannot be twisted steel.
3. The smelting production method for solving the problem of drawing brittle failure of the gas shielded wire steel according to claim 1, wherein the pressure in the positive pressure area in the step 3) is 0.6-0.8 MPa.
4. The smelting production method for solving the problem of the drawing brittle failure of the gas-shielded wire steel according to claim 1, wherein the content of the gaseous nitrogen is controlled through key processes of converter, refining and continuous casting, so that the content of the gaseous nitrogen in wire steel is obviously reduced to below 50ppm from 60ppm to 90 ppm.
5. The smelting production method for solving the problem of drawing brittle failure of the gas-shielded wire steel according to claim 1, wherein the chemical components of the gas-shielded wire steel comprise the following components in percentage by mass: 0.05 to 0.08 percent of C, 0.80 to 0.89 percent of Si, 1.40 to 1.49 percent of Mn, less than or equal to 0.020 percent of P, 0.006 to 0.020 percent of S, less than or equal to 0.10 percent of Ni, Cr and Cu, less than or equal to 0.006 percent of Al, and the balance of Fe and other residual elements.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115637309A (en) * | 2022-10-28 | 2023-01-24 | 包头钢铁（集团）有限责任公司 | Smelting production method for stably controlling continuous casting nitrogen content of welding wire steel |
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| JP2002012908A (en) * | 2000-06-28 | 2002-01-15 | Kawasaki Steel Corp | Method for smelting nitrogen-containing steel |
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| CN112553527A (en) * | 2020-11-27 | 2021-03-26 | 中天钢铁集团有限公司 | Method for controlling nitrogen content of 20CrMnTi series gear steel with high scrap steel ratio produced by electric furnace process |
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| JP2002012908A (en) * | 2000-06-28 | 2002-01-15 | Kawasaki Steel Corp | Method for smelting nitrogen-containing steel |
| KR20030089955A (en) * | 2002-05-20 | 2003-11-28 | 주식회사 포스코 | The method of decreasing nitrogen in deoxidized molten steel |
| CN112553527A (en) * | 2020-11-27 | 2021-03-26 | 中天钢铁集团有限公司 | Method for controlling nitrogen content of 20CrMnTi series gear steel with high scrap steel ratio produced by electric furnace process |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115637309A (en) * | 2022-10-28 | 2023-01-24 | 包头钢铁（集团）有限责任公司 | Smelting production method for stably controlling continuous casting nitrogen content of welding wire steel |
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