Smelting method of medium-thickness plate low-alloy steel
By using converter smelting, VD refining, calcium treatment, soft blowing and continuous casting of slabs during the smelting of medium-thick plate low-alloy steel, the LF refining process was cancelled, and the high power consumption and inclusions during the LF refining process was solved. The difficult-to-remove problems achieve cost reduction and inclusion level control, ensuring the quality of the steel plate.
Patent Information
- Application Number
- CN202411592194.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-02-21
AI Technical Summary
During the smelting of medium-thick plate low-alloy steel, the power consumption of the LF refining process is high, resulting in high cost. At the same time, after LF refining, Al2O3 inclusions in the steel water are denaturated and difficult to completely remove, resulting in the inclusion level exceeding the standard during the rolling process of steel plates.
Using converter smelting, VD refining, calcium treatment, soft blowing and slab continuous casting, the process of controlling the end point temperature of the converter, adding aluminum blocks to deoxygenate, slag making and alloying, VD vacuum refining removes solid inclusions, and calcium treatment of denaturation inclusions Remove inclusions by soft blowing, and cancel the LF refining process.
It realizes that the medium-thick plate low-alloy steel does not require LF refining during the smelting process, reduces production costs, and controls the Class A and Class B inclusions in the steel plate below level 2.0. At the same time, the steel plate can be guaranteed to pass the flaw detection without stacking and cooling after rolling. .
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a smelting method for medium and thick plate low alloy steel. Background Art
[0002] Medium and thick plate low alloy steel is widely used in shipbuilding, bridges, containers, buildings, steel structures and other fields, and has strict requirements on the strength, toughness, plasticity, weldability, internal quality and inclusion rating of the steel plate. Medium and thick plate low alloy steel generally requires a relatively low S content in the steel, so it needs to be desulfurized by LF refining. At the same time, in order to ensure that the steel plate is qualified for flaw detection, vacuum treatment (RH refining or VD refining) is required, or the rolled steel plate is subjected to stack cold treatment. The domestic smelting route of medium and thick plate low-alloy steel is generally (molten iron pretreatment-) converter-LF refining-RH refining (or VD refining)-CC; the LF refining process in this smelting route has high power consumption, resulting in high cost. At the same time, the Als content in the LF refining process is generally controlled at 0.025-0.045%. The long-term interaction between molten steel and slag will cause the Al2O3 inclusions in the molten steel to be denatured, resulting in a large part of the molten steel inclusions entering the CaO-Al2O3-MgO low melting point area; since liquid inclusions are not easy to remove from the molten steel, even after vacuum refining and subsequent calcium treatment and soft blowing processes, some low-melting point inclusions will remain in the molten steel, thereby deforming and extending during the steel plate rolling process, making the Class B inclusion level exceed Level 2.0. Summary of the invention
[0003] The object of the present invention is to provide a smelting method for medium and thick plate low alloy steel, which does not require LF refining process and can control the A and B inclusions of the rolled steel plate below level 2.0. At the same time, the steel plate can be guaranteed to pass the flaw detection without cooling after rolling.
[0004] To achieve the above purpose, the technical solution provided by the present invention is as follows: A smelting method for medium and thick plate low-alloy steel comprises converter smelting, VD refining, calcium treatment, soft blowing and slab continuous casting processes; the converter smelting process comprises: controlling the S content of raw materials and scrap steel entering the furnace, controlling the S content of molten steel after the converter is less than or equal to 0.025%, controlling the final temperature of the converter at 1680-1710°C, adding aluminum blocks for deoxidation after 1 / 4 of the converter is tapped, adding 5-8 kg / t of lime and 3-5 kg / t of pre-melted slag for slagging, adding silicon-manganese alloy, ferromanganese, ferroniobium and ferrotitanium for alloying, and controlling the Als content of the molten steel sample after the converter is tapped at 0.040-0.065%.
[0005] Furthermore, in the smelting method of medium and thick plate low alloy steel described in the present invention, in the converter smelting process, the sulfur content of the raw and auxiliary materials entering the furnace is controlled to be less than 0.05%, and the sulfur content of the scrap steel is controlled to be less than 0.02%.
[0006] Furthermore, in the smelting method of medium and thick plate low alloy steel described in the present invention, if the S content of the finished product is required to be ≤0.003%, molten iron pretreatment is required before converter smelting, and the S content of the molten iron is required to be ≤0.005% after pretreatment, and more than 90% of the molten iron pretreatment slag is removed; if the S content of the finished product is required to be >0.003%, molten iron pretreatment is not required.
[0007] Furthermore, in the smelting method of medium and thick plate low alloy steel described in the present invention, the VD refining process includes: sampling and temperature measurement after the molten steel reaches the VD station, the VD vacuum degree is ≤100Pa, the vacuum treatment time is 8 to 20 minutes, sampling and temperature measurement are performed after the VD breaks through the air, and alloy materials are added to fine-tune the composition according to the sampling results.
[0008] Furthermore, in the smelting method of medium and thick plate low alloy steel of the present invention, the VD refining process: controls the CaO content of the slag after VD refining to be 50-60%, the Al2O3 content to be 22-30%, the SiO2 content to be less than 10%, the (MnO+FeO) content to be less than 1%, and the MgO content to be less than 8%.
[0009] Furthermore, in the smelting method of medium and thick plate low alloy steel of the present invention, in the calcium treatment step: after the VD vacuum treatment is completed, a calcium wire is fed for calcium treatment, and the total calcium content is controlled at 0.0015-0.0025%.
[0010] Furthermore, in the smelting method of medium and thick plate low alloy steel of the present invention, the soft blowing process is as follows: soft blowing of argon is performed after the calcium treatment is completed, the soft blowing time is ≥8 minutes, and the soft blowing flow rate is controlled at 50-100 NL / min.
[0011] Furthermore, in the smelting method of medium and thick plate low alloy steel of the present invention, the composition of inclusions in the molten steel after soft blowing is controlled in the CaO-CaS-Al2O3 system, and the CaO content is less than 25%.
[0012] Furthermore, the smelting method of medium and thick plate low alloy steel of the present invention, wherein the slab continuous casting process: adopts the light reduction technology at the end of solidification, with a total reduction of ≥8mm, and the medium and thick plate low alloy steel slab is obtained after subsequent treatment of the continuously cast slab.
[0013] Furthermore, the method of the present invention is applicable to the production of medium and thick plate low alloy steel within the following composition range: C: 0.09-0.18%, Si: 0.15-0.30%, Mn: 0.9-1.40%, P≤0.020%, S≤0.010%, Als: 0.015-0.03%, Ti: 0-0.02%, Nb: 0-0.04%, and the balance is iron and unavoidable impurities.
[0014] After the medium and thick plate low alloy steel slab smelted by the method of the present invention is rolled into a 16-40 mm thick steel plate, both the Class A and Class B inclusions in the steel plate can be controlled below level 2.0.
[0015] After the medium and thick plate low alloy steel slab smelted by the method of the present invention is rolled into a 16-40 mm thick steel plate, it is directly sheared and stored without cold stacking to ensure that it passes the flaw detection.
[0016] The inventive principle of the technical solution of the present invention is: The present invention controls the sulfur content of the raw materials fed into the converter and reduces the sulfur content of the molten steel to below the target value through VD vacuum refining; solid inclusions are fully removed through VD vacuum refining, inclusions in the molten steel are denatured through calcium treatment, and inclusions are promoted to float and be removed through soft blowing. After the produced slab is rolled into a 16-40mm thick steel plate, both the Class A and Class B inclusions in the steel plate can be controlled to be below Class 2.0, and the steel plate can be directly sheared and stored without cold stacking after rolling to ensure that it is qualified for flaw detection.
[0017] The beneficial effects of adopting the above technical solution are: (1) The method of the present invention eliminates the LF refining process when producing low alloy steel slabs, thereby reducing production costs. At the same time, it avoids the technical problem of excessive Class B inclusions caused by the long-term reaction of slag during LF refining to form large-sized liquid inclusions.
[0018] (2) When the method of the present invention is used to produce steel with a sulfur content of ≤0.003% in molten steel, it can be achieved through the steps of molten iron pretreatment desulfurization, converter controlled resulfurization, and VD deep desulfurization, without the need for long-term LF refining; and when the method of the present invention is used to produce steel with a sulfur content of >0.003% in molten steel, it can be achieved through the steps of converter controlled resulfurization and VD desulfurization, without the need for molten iron pretreatment and LF refining.
[0019] (3) After the medium and thick low alloy steel slab produced by the method of the present invention is rolled into a 16-40 mm thick steel plate, the Class A and Class B inclusions in the steel plate can be controlled below Level 2.0; and the steel plate is not piled up for cooling after rolling, but is directly sheared and stored, which can also ensure that it passes the flaw detection. DETAILED DESCRIPTION
[0020] The present invention will be further described in detail below in conjunction with specific embodiments. Example 1
[0021] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.16-0.18%, Si: 0.20-0.30%, Mn: 1.20-1.30%, P≤0.020%, S≤0.010%, Als: 0.015-0.03%; the smelting method includes the following steps: 1) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.03%, and the S content in the scrap steel is 0.015%; the S content in the molten steel after the converter is 0.02%, and the converter terminal temperature is controlled at 1690℃; after 1 / 4 of the converter steel is tapped, aluminum blocks are added for deoxidation, and 5kg / t of lime and 3kg / t of pre-melted slag are added for slag making; silicon-manganese alloy, ferromanganese, etc. are added for alloying according to the composition requirements, and the Als content of the molten steel sample after the converter is 0.04%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 8min. Sampling and temperature measurement are carried out after the VD breaks the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 50%, Al2O3 content: 30%, SiO2 content: 9%, (MnO+FeO) content: 0.9%, MgO content: 7.1%.
[0022] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0025%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 8 minutes, and the soft blowing flow rate is controlled at 50 NL / min; after soft blowing, the inclusion composition of the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 10% 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 8mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0023] The slab produced in this embodiment is used for rolling 16mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The Class A inclusions in the steel plate are 1.5 level and the Class B inclusions are 2.0 level. Example 2
[0024] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.16-0.18%, Si: 0.20-0.30%, Mn: 1.20-1.30%, P≤0.020%, S≤0.010%, Als: 0.015-0.03%; the smelting method includes the following steps: 1) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.040%, the S content in the scrap steel is 0.019%, the S content in the molten steel after the converter is 0.025%, the converter terminal temperature is controlled at 1695℃, and aluminum blocks are added for deoxidation after 1 / 4 of the converter is tapped. Lime 6kg / t steel and pre-melted slag 4kg / t steel are added for slag making. Silicon manganese alloy, ferromanganese, ferroniobium, ferrotitanium, etc. are added for alloying according to the composition requirements. The Als content of the molten steel sample after the converter is 0.065%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 10min. Sampling and temperature measurement are carried out after the VD breaks through the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 60%, Al2O3 content: 22%, SiO2 content: 8%, (MnO+FeO) content: 0.5%, MgO content: 7.5%.
[0025] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0020%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 10 minutes, and the soft blowing flow rate is controlled at 100 NL / min; after soft blowing, the inclusion composition in the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 15%.
[0026] 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 10 mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0027] The slab produced in this embodiment is used for rolling 40mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The Class A inclusions in the steel plate are 1.0 level and the Class B inclusions are 1.5 level. Example 3
[0028] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.13-0.15%, Si: 0.20-0.30%, Mn: 1.20-1.30%, P≤0.017%, S≤0.007%, Als: 0.015-0.03%, Ti: 0.005-0.015%, Nb: 0.015-0.025%; the smelting method includes the following steps: 1) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.020%, the S content in the scrap steel is 0.015%, the S content in the molten steel after the converter is 0.015%, the converter terminal temperature is controlled at 1695℃, and aluminum blocks are added for deoxidation after 1 / 4 of the converter is tapped. Lime 6kg / t steel and pre-melted slag 4kg / t steel are added for slag making. Silicon manganese alloy, ferromanganese, ferroniobium, ferrotitanium, etc. are added for alloying according to the composition requirements. The Als content of the molten steel sample after the converter is 0.054%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 10min. Sampling and temperature measurement are carried out after the VD breaks through the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 55%, Al2O3 content: 25%, SiO2 content: 6%, (MnO+FeO) content: 0.7%, MgO content: 7.4%.
[0029] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0018%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 10 minutes, and the soft blowing flow rate is controlled at 75 NL / min. After soft blowing, the inclusion composition in the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 17%.
[0030] 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 10 mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0031] The slab produced in this embodiment is used for rolling 25mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The A-type inclusions in the steel plate are 1.5 level and the B-type inclusions are 1.5 level. Example 4
[0032] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.13-0.15%, Si: 0.20-0.30%, Mn: 1.20-1.30%, P≤0.015%, S≤0.005%, Als: 0.015-0.03%, Ti: 0.005-0.015%, Nb: 0.025-0.035%; the smelting method includes the following steps: 1) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.020%, the S content in the scrap steel is 0.010%, the S content in the molten steel after the converter is 0.015%, the converter terminal temperature is controlled at 1700℃, and aluminum blocks are added for deoxidation after 1 / 4 of the converter is tapped. Lime 7kg / t steel and pre-melted slag 4kg / t steel are added for slag making. Silicon manganese alloy, ferromanganese, ferroniobium, ferrotitanium, etc. are added for alloying according to the composition requirements. The Als content of the molten steel sample after the converter is 0.053%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 12min. Sampling and temperature measurement are carried out after the VD breaks through the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 54%, Al2O3 content: 28%, SiO2 content: 8.5%, (MnO+FeO) content: 0.4%, MgO content: 7.5%.
[0033] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0017%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 10 minutes, and the soft blowing flow rate is controlled at 60 NL / min. After soft blowing, the inclusion composition in the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 21%.
[0034] 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 10 mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0035] The slab produced in this embodiment is used for rolling 35mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The A-type inclusions in the steel plate are 1.0 level and the B-type inclusions are 1.0 level. Example 5
[0036] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.09-0.12%, Si: 0.20-0.30%, Mn: 1.25-1.35%, P≤0.015%, S≤0.005%, Als: 0.015-0.03%, Ti: 0.010-0.020%, Nb: 0.025-0.035%; the smelting method includes the following steps: 1) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.021%, the S content in the scrap steel is 0.017%, the S content in the molten steel after the converter is 0.018%, the converter terminal temperature is controlled at 1700℃, and aluminum blocks are added for deoxidation after 1 / 4 of the converter is tapped. Lime 7kg / t steel and pre-melted slag 4kg / t steel are added for slag making. Silicon manganese alloy, ferromanganese, ferroniobium, ferrotitanium, etc. are added for alloying according to the composition requirements. The Als content of the molten steel sample after the converter is 0.057%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 15min. Sampling and temperature measurement are carried out after the VD breaks the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 58%, Al2O3 content: 24%, SiO2 content: 7%, (MnO+FeO) content: 0.4%, MgO content: 7%.
[0037] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0015%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 10 minutes, and the soft blowing flow rate is controlled at 80 NL / min; after soft blowing, the inclusion composition in the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 20%.
[0038] 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 10 mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0039] The slab produced in this embodiment is used for rolling 25mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The A-type inclusions in the steel plate are 1.0 level and the B-type inclusions are 1.0 level. Example 6
[0040] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.09-0.12%, Si: 0.20-0.30%, Mn: 1.30-1.40%, P≤0.013%, S≤0.003%, Als: 0.015-0.03%, Ti: 0.010-0.020%, Nb: 0.030-0.040%; the smelting method includes the following steps: 1) Hot metal pretreatment: First, hot metal pretreatment is performed. After pretreatment, the sulfur content of hot metal is 0.005%, and 95% of the hot metal pretreatment slag is removed; 2) Converter smelting: The S content in the raw and auxiliary materials entering the furnace is 0.02%, the S content in the scrap steel is 0.015%, the S content in the molten steel after the converter is 0.010%, the converter terminal temperature is controlled at 1710℃, and aluminum blocks are added for deoxidation after 1 / 4 of the converter is tapped. Lime 8kg / t steel and pre-melted slag 5kg / t steel are added for slag making. Silicon manganese alloy, ferromanganese, ferroniobium, ferrotitanium, etc. are added for alloying according to the composition requirements. The Als content of the molten steel sample after the converter is 0.063%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 20min. Sampling and temperature measurement are carried out after the VD breaks through the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 57%, Al2O3 content: 27%, SiO2 content: 6%, (MnO+FeO) content: 0.4%, MgO content: 6.8%.
[0041] 3) Calcium treatment: After the VD vacuum treatment, the steel is fed into the calcium line for calcium treatment, and the total calcium content is controlled at 0.0016%; the inclusion composition in the molten steel after soft blowing is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 24%.
[0042] 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 10 minutes, and the soft blowing flow rate is controlled at 70 NL / min; 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 10 mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0043] The slab produced in this embodiment is used for rolling 35mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The A-type inclusions in the steel plate are 0.5 level and the B-type inclusions are 1.0 level. Example 7
[0044] The chemical composition of the thick plate low alloy steel in this embodiment is: C: 0.16-0.18%, Si: 0.15-0.25%, Mn: 0.9-1.0%, P≤0.020%, S≤0.010%, Als: 0.015-0.025%; the smelting method thereof comprises the following steps: 1) Converter smelting: Control the S content of the raw and auxiliary materials entering the furnace to 0.040% and the S content of the scrap steel to 0.018%, control the S content of the molten steel after the converter to 0.025%, control the converter terminal temperature at 1680℃, add aluminum blocks for deoxidation after 1 / 4 of the converter is tapped, add 5kg / t of lime and 3kg / t of pre-melted slag for slagging, add silicon-manganese alloy, ferromanganese, etc. for alloying according to the composition requirements, and control the Als content of the molten steel sample after the converter to 0.055%; 2) VD refining: After the molten steel reaches the VD station, sampling and temperature measurement are carried out. The VD vacuum degree is ≤100Pa, and the vacuum treatment time is 8min. Sampling and temperature measurement are carried out after the VD breaks the air. Silicon manganese alloy and ferromanganese are added according to the sampling results to fine-tune the composition; the CaO content of the slag after VD refining is: 52%, Al2O3 content: 29%, SiO2 content: 6%, (MnO+FeO) content: 0.7%, and MgO content: 7.8%.
[0045] 3) Calcium treatment: After the VD vacuum treatment, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0023%; 4) Soft blowing: After the calcium treatment, soft blowing of argon is carried out for 8 minutes, and the soft blowing flow rate is controlled at 80 NL / min. After soft blowing, the inclusion composition in the molten steel is controlled in the CaO-CaS-Al2O3 system, and the CaO content is 16%.
[0046] 5) Slab continuous casting: The light reduction technology at the end of solidification is adopted, with a total reduction of 8mm. After subsequent processing, the continuous casting billet is obtained to obtain medium and thick plate low alloy steel slab.
[0047] The slab produced in this embodiment is used for rolling 25mm low alloy steel plate. The steel plate is qualified by cold flaw detection without stacking after rolling. The A-type inclusions in the steel plate are 1.5 level and the B-type inclusions are 1.5 level.
[0048] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.
Claims
1. A method for smelting medium and thick plate low alloy steel, characterized in that: The invention comprises the steps of converter smelting, VD refining, calcium treatment, soft blowing and slab continuous casting; the converter smelting step comprises: controlling the S content of the raw materials and scrap steel entering the furnace, controlling the S content of the molten steel after the converter furnace to be ≤0.025%, controlling the final temperature of the converter to be within 1680-1710°C, adding aluminum blocks for deoxidation after 1 / 4 of the steel is tapped from the converter, adding 5-8kg / t of lime and 3-5kg / t of pre-melted slag for slag making, adding silicon-manganese alloy, ferromanganese, ferroniobium and ferrotitanium for alloying, and controlling the Als content of the molten steel sample after the converter furnace to be within 0.040-0.065%.
2. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: In the converter smelting process, the sulfur content of the raw and auxiliary materials entering the converter is controlled to be less than 0.05%, and the sulfur content of the scrap steel is controlled to be less than 0.02%.
3. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The VD refining process: sampling and temperature measurement are carried out after the molten steel reaches the VD station, the VD vacuum degree is ≤100Pa, the vacuum treatment time is 8-20min, sampling and temperature measurement are carried out after the VD breaks the air, and alloy materials are added according to the sampling results to fine-tune the composition.
4. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The VD refining process: Control the CaO content of the slag after VD refining to be 50-60%, the Al2O3 content to be 22-30%, the SiO2 content to be less than 10%, the (MnO+FeO) content to be less than 1%, and the MgO content to be less than 8%.
5. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The calcium treatment process: after the VD vacuum treatment is completed, the calcium line is fed for calcium treatment, and the total calcium content is controlled at 0.0015-0.0025%.
6. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The soft blowing process: after the calcium treatment is completed, soft blowing of argon is performed, the soft blowing time is ≥8 minutes, and the soft blowing flow rate is controlled at 50-100 NL / min.
7. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The slab continuous casting process adopts the light reduction technology at the end of solidification, with a total reduction of ≥8mm. The continuous casting slab is subsequently processed to obtain a medium and thick plate low alloy steel slab.
8. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The method is suitable for the production of medium and thick plate low alloy steel with the following composition range: C: 0.09-0.18%, Si: 0.15-0.30%, Mn: 0.9-1.40%, P≤0.020%, S≤0.010%, Als: 0.015-0.03%, Ti: 0-0.02%, Nb: 0-0.04%, and the balance is iron and unavoidable impurities.
9. The method for smelting medium and thick plate low alloy steel according to claim 1, characterized in that: The medium and thick plate low alloy steel slab produced by the method can control the A and B inclusions in the steel plate below level 2.0 after being rolled into 16-40 mm thick steel plates; and the steel plates are not piled up for cooling after rolling, but are directly sheared and stored, which can also ensure that they pass the flaw detection.