AU2020443584B2 - Low-temperature high-manganese austenitic steel rapid alloying process - Google Patents

Low-temperature high-manganese austenitic steel rapid alloying process Download PDF

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AU2020443584B2
AU2020443584B2 AU2020443584A AU2020443584A AU2020443584B2 AU 2020443584 B2 AU2020443584 B2 AU 2020443584B2 AU 2020443584 A AU2020443584 A AU 2020443584A AU 2020443584 A AU2020443584 A AU 2020443584A AU 2020443584 B2 AU2020443584 B2 AU 2020443584B2
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ladle
alloying
manganese
steel
molten steel
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AU2020443584A1 (en
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Yuliang Cao
Pan JIA
Guoping Wu
Guangpen YUAN
Guicheng Zhou
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Nanjing Iron and Steel Co Ltd
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Nanjing Iron and Steel Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/04Making ferrous alloys by melting
    • C22C33/06Making ferrous alloys by melting using master alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
    • C21C5/30Regulating or controlling the blowing
    • C21C5/34Blowing through the bath
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/072Treatment with gases
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27BFURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20Details, accessories, or equipment peculiar to rotary-drum furnaces
    • F27B7/22Rotary drums; Supports therefor
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/001Austenite
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • General Engineering & Computer Science (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)

Abstract

A low-temperature high-manganese austenitic steel rapid alloying process, comprising manganese alloy baking→converter tapping and tapping alloying→LF slag alloying, and specifically: (1) preparing a ladle the ladle age of which is in an early stage; (2) preparing a ladle support piece and transporting the manganese alloy that requires baking into the ladle; (3) ladle alloy baking; (4) controlling the tapping amount and tapping temperature of a converter; (5) LF refining furnace temperature rise alloying process; and (6) LF refining furnace large argon stirring, cooling and alloying process. The alloying process reduces the manganese alloying time of high-manganese austenitic steel from eight hours to within three hours, improving production efficiency and molten steel quality.

Description

LOW-TEMPERATURE HIGH-MANGANESE AUSTENITIC STEEL RAPID ALLOYING PROCESS TECHNICAL FIELD
[0001] The present disclosure relates to a low-temperature high-manganese austenitic steel rapid alloying process.
BACKGROUND
[0002] Since the manganese content in molten steel is high and manganese is easy to be oxidized, the high-manganese austenitic steel for cryogenic applications (15% [Mn] < 30%) is incapable of being added to the converter together with scrap steel. Thus, manganese may only be alloyed through the converter tapping and ladle furnace (LF) refining processes which lead to long manganese alloying time (more than 8 h) and low production efficiency, and are not conducive to the continuous casting. The long LF alloying time is likely to cause high content of hydrogen and nitrogen in the molten steel, which greatly affects the quality of continuous casting billets. To improve the production efficiency of the high-manganese austenitic steel (15% < [Mn] < 30%) and the quality of the continuous casting billets, it is urgent to develop a low-temperature high-manganese austenitic steel rapid alloying process via converter smelting.
SUMMARY
[0003] In view of the above-mentioned shortcomings in the prior art, the technical problem to be solved by the present disclosure is to provide a low-temperature high-manganese austenitic steel rapid alloying process. The process reduces manganese alloying time of the high-manganese austenitic steel from 8 h to 3 h, and improves the production efficiency and quality of molten steel. The process is capable of rapidly alloying the low-temperature high-manganese austenitic steel.
[0004] The technical solution employed by the present disclosure to solve the above-mentioned technical problem is to provide the low-temperature high-manganese austenitic steel rapid alloying process, comprising baking a manganese alloy -- tapping from a converter and alloying molten steel -- melting slag and alloying in a ladle furnace (LF). The process specifically comprises:
[0005] (1) baking the manganese alloy:
[0006] (1.1) preparing a ladle whose age is in an early stage;
[0007] (1.2) welding a grid plate into a support with the same diameter as a bottom of the ladle, and placing the support at the bottom of the ladle; then adding the manganese alloy to be baked in the ladle; wherein, an addition amount of the manganese alloy is 230-260 Kg/t of steel, and the addition amount of the manganese alloy does not exceed three-quarters of a volume of the ladle; and
[0008] (1.3) placing the ladle accommodated with the manganese alloy in a normal upline ladle baking station, and baking at 1000 °C for more than 24 h;
[0009] (2) tapping from the converter and alloying the molten steel:
[0010] (2.1) transporting the ladle accommodated with the manganese alloy after baking to a tapping station of the converter, and connecting the tapping station of the converter to a ladle bottom blowing system, and then turning on the ladle bottom blowing system for tapping at 1660 °C-1700 °C for 3-5 min; wherein, a tapping volume is = a molten steel weight accommodated by a standard ladle - a weight of the manganese alloy baked - 1/3 x the molten steel weight accommodated by the standard ladle; and
[0011] (3) melting the slag and alloying in the LF:
[0012] (3.1) heating the LF for alloying:
[0013] energizing an electrode of the LF for heating, carrying out argon stirring with an argon flow rate of 400-500 NL/min for desulfurization, and heating the molten steel to 1580 °C-1600 °C for more than 60 min via the argon stirring for alloying; and
[0014] (3.2) cooling the LF via the argon stirring for alloying:
[0015] stopping heating after the molten steel is heated to 1580 °C-1600 °C, adjusting the argon flow rate for ladle bottom blowing to 600 NL/min, closing a hood of the LF, and cooling the molten steel to 1480 °C via the argon stirring for alloying; then stopping the argon stirring after alloying, adjusting the argon flow rate for the ladle bottom blowing to 50-80 NL/min, and keeping the argon stirring for 15 min, and then transporting to a continuous casting station for casting; wherein, sampling is carried out when the molten steel is cooled via the argon stirring to measure temperature, and a composition of the molten steel is analyzed according to the sampling; when the composition of the molten steel is below composition requirements of a steel grade, alloys are added to fine-tune the composition of the molten steel to meet the composition requirements of the steel grade.
[0016] The technical solution further limited by the present disclosure is as follows:
[0017] The age of the ladle prepared is preceding one-third of a total age of the ladle.
[0018] After the manganese alloy is added to the ladle, a layer of lime for steelmaking is added on a top of the manganese alloy, and an addition amount of lime is 8-10 Kg/t of steel.
[0019] The ladle accommodated with the manganese alloy after baking is transported to the tapping station of the converter, and the tapping station of the converter is connected to the ladle bottom blowing system for the ladle bottom blowing with the argon flow rate of 600-800 NL/min.
[0020] When the molten steel is cooled via the argon stirring, lime is added in batches to accelerate the cooling, the addition amount of lime in each batch is 1.5 Kg/t of steel, and a total addition amount of lime during the cooling process is no more than 6 Kg/t of steel.
[0021] The beneficial effects of the present disclosure are as follows: The present disclosure greatly shortens the LF alloying time from 9 h to 3 h by controlling the appropriate alloys amount, appropriate baking temperature, baking time and baking batch in advance through the ladle, and optimizing the tapping temperature of the converter and the LF alloying process. Thus, the probability of increasing the gas content in the molten steel caused by the long LF heating and alloying time. The process of the present disclosure not only ensures the continuous production, but also improves the product quality.
DETAILED DESCRIPTION
[0022] Example 1
[0023] This example selects 150 t converter, 150 t LF for smelting, and 25Mn steel grade, and provides the low-temperature high-manganese austenitic steel rapid alloying process. The process includes baking the manganese alloy -- tapping from the converter and alloying the molten steel -- melting the slag and alloying in the ladle furnace (LF). Specifically, the process is described below.
[0024] (1) Baking the manganese alloy
[0025] (1.1) The ladle is prepared by selecting the No. 23 ladle with the age of 19 whose total age is 100.
[0026] (1.2) The ordinary reinforcing bar with the diameter of 10 mm is selected to be welded into two supports with the same diameter as the bottom of the ladle, and the two supports are placed into the bottom of the ladle. Then, 35 tons of the manganese alloy are added, and then 1.5 tons of lime for steelmaking are added into the ladle to prevent the manganese alloy in the upper layer of the ladle from being baked to be softened.
[0027] (1.3) The ladle accommodated with the manganese alloy and lime is transported to the normal upline ladle baking station to bake at 1000 °C for 27 h.
[0028] (2) Tapping from the converter and alloying the molten steel
[0029] (2.1) The ladle accommodated with the manganese alloy which is baked for 27 h is transported to the tapping station of the converter, and the temperature of the manganese alloy after baking is 708 °C. Then, the tapping station of the converter is connected to the ladle bottom blowing system, and the ladle bottom blowing system is turned on with the argon flow rate of 800 NL/min for tapping at 1668 °C for 3 min. The tapping volume is 100 t = 150 t - 35 t - 1/3 x 150 t.
[0030] (3) Melting the slag and alloying in the LF
[0031] (3.1) The LF is heated for alloying.
[0032] The electrode of the LF is energized for heating, and sampling is carried out. The result is shown as Table 1. The argon stirring is carried out for desulfurization, the ladle bottom blowing system is operated with the argon flow rate of 500 NL/min, and the molten steel is heated to 1593 °C via the argon stirring and alloyed for 77 min.
[0033] (3.2) The LF is cooled via the argon stirring for alloying.
[0034] The heating operation is stopped after the molten steel is heated to 1583 °C, the argon flow rate for ladle bottom blowing is adjusted to 600 NL/min, and the hood of the LF is closed to isolate the air and prevent secondary oxidation. Then, the molten steel is cooled to 1487 °C with min via the argon stirring for alloying. When the molten steel is cooled via the argon stirring, lime is added in two batches to accelerate the cooling, and the addition amount of lime in each batch is 1.5 Kg/t. Then, the argon stirring is stopped after alloying, the argon flow rate for the ladle bottom blowing is adjusted to 50 NL/min, and the argon stirring is kept for 15 min. Then, the molten steel obtained is transported to the continuous casting station for casting, and sampling is carried out during the cooling process to measure the temperature, which can be seen in Table 1 for details.
[0035] Table 1 Temperature and manganese content in the process of melting the slag and alloying in the LF
Steel grade Description of sampling code Mn(%) Temperature (°C)
First sampling after BOF blowing 0.05008 1593
First sampling after BOF tapping 3.67221 1499
First sampling during the LF heating 4.66 1483
Second sampling during the LF heating 5.95 1507 25Mn Third sampling during the LF heating 8.71 1521
Fourth sampling during the LF heating 13.05 1525
Fifth sampling during the LF heating 19.04 1569
Sixth sampling during the LF heating 23.04 1586
First sampling during the LF cooling 23.11 1557
Second sampling during the LF cooling 23.42 1531
Third sampling during the LF cooling 23.41 1487
[0036] In this example, the 25Mn steel is produced, 35 tons of the manganese alloy is added to bake for 27 h, and the temperature of the manganese alloy baked is 708 °C. The LF is heated to 1583 °C for 77 min for the manganese alloying, and the manganese content in the molten steel after heating is 23.04%. Then, the LF is cooled to 1587 °C for 65 min via the argon stirring for alloying, and the manganese content in the molten steel after cooling is 23.41%. Thus, the composition requirements of the steel grade is met. The total alloying time of the LF is controlled to 142 min, and the production efficiency is greatly improved.
[0037] In addition to the above-described example, the present disclosure may also have other examples. All technical solutions made by equivalent replacements or transformations shall fall within the protection scope of the present disclosure.

Claims (5)

Claims WHAT IS CLAIMED IS:
1. A low-temperature high-manganese austenitic steel rapid alloying process, comprising baking a manganese alloy -- tapping from a converter and alloying molten steel -- melting slag and alloying in a ladle furnace (LF); wherein, the process specifically comprises: (1) baking the manganese alloy: (1.1) preparing a ladle whose age is in an early stage; (1.2) welding a grid plate into a support with the same diameter as a bottom of the ladle, and placing the support at the bottom of the ladle; then adding the manganese alloy to be baked in the ladle; wherein, an addition amount of the manganese alloy is 230-260 Kg/t of steel, and the addition amount of the manganese alloy does not exceed three-quarters of a volume of the ladle; and (1.3) placing the ladle accommodated with the manganese alloy in a normal upline ladle baking station, and baking at 1000 °C for more than 24 h; (2) tapping from the converter and alloying the molten steel: (2.1) transporting the ladle accommodated with the manganese alloy after baking to a tapping station of the converter, and connecting the tapping station of the converter to a ladle bottom blowing system, and then turning on the ladle bottom blowing system for tapping at 1660 °C-1700 °C for 3-5 min; wherein, a tapping volume is = a molten steel weight accommodated by a standard ladle - a weight of the manganese alloy baked - 1/3 x the molten steel weight accommodated by the standard ladle; and (3) melting the slag and alloying in the LF: (3.1) heating the LF for alloying: energizing an electrode of the LF for heating, carrying out argon stirring with an argon flow rate of 400-500 NL/min for desulfurization, and heating the molten steel to 1580 °C-1600 °C for more than 60 min via the argon stirring for alloying; and (3.2) cooling the LF via the argon stirring for alloying: stopping heating after the molten steel is heated to 1580 °C-1600 °C, adjusting the argon flow rate for ladle bottom blowing to 600 NL/min, closing a hood of the LF, and cooling the molten steel to 1480 °C via the argon stirring for alloying; then stopping the argon stirring after alloying, adjusting the argon flow rate for the ladle bottom blowing to 50-80 NL/min, and keeping the argon stirring for 15 min, and then transporting to a continuous casting station for casting; wherein, sampling is carried out when the molten steel is cooled via the argon stirring to measure temperature, and a composition of the molten steel is analyzed according to the sampling; when the composition of the molten steel is below composition requirements of a steel grade, alloys are added to fine-tune the composition of the molten steel to meet the composition requirements of the steel grade.
2. The low-temperature high-manganese austenitic steel rapid alloying process according to claim 1, wherein, the age of the ladle prepared is preceding one-third of a total age of the ladle.
3. The low-temperature high-manganese austenitic steel rapid alloying process according to claim 1, wherein, after the manganese alloy is added to the ladle, a layer of lime for steelmaking is added on a top of the manganese alloy, and an addition amount of lime is 8-10 Kg/t of steel.
4. The low-temperature high-manganese austenitic steel rapid alloying process according to claim 1, wherein, the ladle accommodated with the manganese alloy after baking is transported to the tapping station of the converter, and the tapping station of the converter is connected to the ladle bottom blowing system for the ladle bottom blowing with the argon flow rate of 600-800 NL/min. 5. The low-temperature high-manganese austenitic steel rapid alloying process according to claim 1, wherein, when the molten steel is cooled via the argon stirring, lime is added in batches to accelerate the cooling, the addition amount of lime in each batch is 1.
5 Kg/t of steel, and a total addition amount of lime during the cooling process is no more than 6 Kg/t of steel.
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CN114032473B (en) * 2021-11-29 2022-04-22 东北大学 Alloy adding method of coating-free hot forming steel
CN114317882A (en) * 2021-12-21 2022-04-12 中车长江铜陵车辆有限公司 Alloy baking method for duplex smelting
CN114686784A (en) * 2022-04-02 2022-07-01 四川罡宸不锈钢有限责任公司 Nickel-saving austenitic stainless steel material and preparation method thereof
CN114908208B (en) * 2022-04-18 2023-09-26 包头钢铁(集团)有限责任公司 Method for smelting high alloy steel with Mn content of more than 12% by utilizing converter end temperature
CN117089667A (en) * 2023-09-05 2023-11-21 湖南华菱涟源钢铁有限公司 Method for producing manganese-containing steel and manganese-containing steel

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