A method for controlling a process for producing a rare earth steel

Abstract

The application discloses a process control method for producing rare earth steel, which comprises the following steps: 1) using rare earth functional refractory material to solve the problems of rare earth burning loss, rare earth yield fluctuation and continuous casting flow control failure caused by the corrosion of rare earth elements in the steel to functional refractory materials such as continuous casting nozzle and stopper during the rare earth steel pouring process; 2) using the non-uniform pulse electric field technology in the continuous casting process to improve the castability of the rare earth molten steel; and using the crystallizer wire feeding method to add rare earth alloy, so as to improve the sulfide form, distribution and size in the casting blank, and improve the low-temperature impact toughness, transverse toughness and high-temperature plasticity of the steel. The application aims to provide a process control method for producing rare earth steel, based on the effective identification of the existing research results of the rare earth steel, the stable control of the rare earth steel production process parameters is realized through the systematic rare earth steel process control technology, and the stable and controllable performance difference of the rare earth steel product is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steelmaking, and particularly relates to a process control method for producing rare earth steel. BACKGROUND

[0002] In recent years, the theoretical research and application technology of rare earth steel have developed rapidly. A large number of steel enterprises and research institutions have realized the optimization and upgrading of the performance of steel through rare earth treatment. Rare earth steel has become one of the main ways of innovation in the steel industry. At the same time, the development of rare earth steel has been limited by many problems such as continuous casting "flocculation flow", rare earth oxidation loss, and rare earth yield fluctuation, which has hindered the mature promotion of the industrial application of rare earth steel. Therefore, it is urgent to establish a rare earth steel production process control technology to effectively support the industrialization transformation of the research and development achievements of rare earth steel. Chinese patent "Rare earth heavy rail steel rare earth adding method and rare earth heavy rail steel (CN 109593913A)" specifies the control conditions before adding rare earth, provides a rare earth adding method and its key control parameters, and is mainly applied to the production of heavy rail steel. The literature "Research status of rare earth steel continuous casting process nozzle clogging" analyzes the principle of rare earth steel flocculation flow from the principle, and puts forward the technical methods to control the flocculation flow, including: controlling the composition of the protective slag, improving the purity of the molten steel, passing in argon protection, improving the geometry and material of the nozzle, and passing in the current. It is clear that the prevention and control effect of improving the nozzle and passing in the current is more significant; it is particularly necessary to improve the nozzle material and develop special refractory material for rare earth steel, and the nozzle material is recommended to be selected with magnesium-carbon material. The literature "Production practice of rare earth beam steel BT700L" details the process control technology, including: control of molten steel oxygen and sulfur, control of FeO% of the slag, and continuous casting machine protection pouring, etc., which significantly improves the low-temperature impact toughness of the product. SUMMARY

[0003] The purpose of the present application is to provide a process control method for producing rare earth steel, which realizes the stable control of the process parameters of rare earth steel and the stable and controllable performance of rare earth steel products by adopting a systematic rare earth steel process control technology on the basis of effectively identifying the existing research achievements of rare earth steel.

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] The present application provides a process control method for producing rare earth steel, which comprises the following steps:

[0006] 1) Adopting rare earth functional refractory material to solve the problems of rare earth loss and rare earth yield fluctuation and continuous casting flow loss caused by the erosion of functional refractory material such as continuous casting nozzle and stopper by rare earth elements in the rare earth steel pouring process;

[0007] 2) Adopting non-uniform pulse electric field technology in the continuous casting process to improve the castability of rare earth molten steel

[0008] The process parameters include: pulse power input voltage is 380V AC, output waveform is positive, negative and proportional pulse rectangular wave, duty cycle range is 35-65%, pulse width range is 200-800ms, pulse period range is 200-800ms, maximum output current is 1000A, maximum average current is 500A, and maximum output voltage is 36V;

[0009] 4) Rare earth alloy is added by using a crystallizer wire feeding method to improve the sulfide morphology, distribution and size in the casting blank, and to improve the low temperature impact toughness, transverse toughness and high temperature plasticity of the steel

[0010] The rare earth content is Re%≥99%, wherein the rare earth content is Ce%:La%=2:1, other elements are Fe≤0.5%, Si≤0.07%, P≤0.01%, and S≤0.02%, the diameter of the rare earth cored wire is 2.5±0.2mm, the thickness of the iron sheet is 0.3mm, the wire feeding speed is ≥5m / min, and the rare earth addition amount is controlled according to RE%(addition amount):S%(content in the molten steel) = 1.5-3.5.

[0011] Further, an artificial synthetic material composed of rare earth elements, aluminum elements and carbon elements is used as a coating raw material to coat the working interface of the submerged entry nozzle and the stopper in the tundish.

[0012] Further, the coating material can be directly purchased or artificially synthesized; the artificial synthesis method is as follows: 200-mesh rare earth oxide fine powder and Al2O3 fine powder are mixed according to a mass ratio of 75%:25%, and then are fired at a furnace temperature of ≥1500°C in a shuttle kiln for ≥5 hours to prepare rare earth aluminate;

[0013] The rare earth aluminate is ground into 200-mesh fine powder and mixed with 80-mesh graphite carbon powder, phenolic resin is used as a binder to prepare a coating, and the coating is coated on the working surface of the functional refractory material and the matrix material and is isostatic pressed.

[0014] Further, the coating thickness is 4.5-5.5mm.

[0015] Further, the mass addition amounts of the phenolic resin and the graphite carbon powder are 4.5% and 12% respectively.

[0016] Compared with the prior art, the present application has the following beneficial technical effects:

[0017] The castability of the rare earth steel is significantly improved, and under the condition that the rare earth addition amount is ≥50PPm, the continuous casting furnace number is ≥10; the effective inclusion level in the rare earth steel is significantly improved, and the main rare earth oxysulfide in the steel is ≤3μm. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present application will be further described below in combination with the description of the drawings.

[0019] Figure 1 Structure diagram of rare earth functional refractory material used in the examples;

[0020] Figure 2 Operation situation of the crystallizer feeding rare earth line used in the examples;

[0021] Figure 3 Rare earth oxysulfide for modifying the inclusions in steel into fine and dispersed distribution. DETAILED DESCRIPTION

[0022] A process control method for producing rare earth steel, the specific content is:

[0023] 1. Using rare earth functional refractory material, solving the problem of rare earth burnout and rare earth yield fluctuation and continuous casting flow control failure caused by the erosion of rare earth elements in steel to continuous casting nozzle and stopper and other functional refractory materials during rare earth steel pouring process.

[0024] The preferred process is: using artificial synthetic material of rare earth elements, aluminum elements and carbon elements as coating raw material, coating the coating on the working interface of the tundish immersion nozzle and stopper.

[0025] The coating material mentioned above can be directly purchased or artificially synthesized. The artificial synthesis method is: selecting 200 mesh rare earth oxide fine powder and Al2O3 fine powder, mixing according to the mass ratio of 75%:25%, and firing in a shuttle kiln at a temperature of ≥1500℃ for ≥5 hours to produce rare earth aluminate.

[0026] Further, the artificially synthesized rare earth aluminate is ground into 200 mesh fine powder and mixed with 80 mesh graphite carbon powder, and phenolic resin is used as a binder to make a coating, which is coated on the working surface of the functional refractory material and the matrix material is isostatic pressing. The addition amount of phenolic resin and graphite carbon powder is. The preferred coating thickness is 4.5-5.5mm.

[0027] 2. The non-uniform pulse electric field technology is used in the continuous casting process to improve the castability of rare earth molten steel. The hardware and process design are provided by Beijing University of Science and Technology. The preferred process parameters include: the input voltage of the pulse power supply is 380V AC, the output waveform is positive, negative and proportional pulse rectangular wave, the duty cycle range is 35-65%, the pulse width range is 200-800ms, the pulse period range is 200-800ms, the maximum output current is 1000A, the maximum average current is 500A, and the maximum output voltage is 36V.

[0028] 3. The method of adding rare earth alloy by crystallizer feeding wire is used to improve the sulfide shape, distribution, size in the casting blank, and to improve the low temperature impact toughness, transverse toughness, high temperature plasticity of the steel. The preferred process uses Re% ≥ 99%, wherein the rare earth content Ce%: La% = 2: 1, other elements Fe ≤ 0.5%, Si ≤ 0.07%, P ≤ 0.01%, S ≤ 0.02%, the rare earth cored wire diameter is 2.5 ± 0.2mm, the iron sheet thickness is 0.3mm, the feeding speed is ≥ 5m / min, and the rare earth addition amount is controlled according to RE% (addition amount): S% (content in the molten steel) = 1.5-3.5.

[0029] The content of the present application is described in detail below through specific examples, and the examples are intended to help understand the present application, rather than limit the content of the present application.

[0030] Example 1: Production and application of rare earth heavy rail steel in Inner Mongolia Baogang Steel Joint Stock Co., Ltd.

[0031] Specifically includes the following steps:

[0032] 1) Application in the production of U76CrRe rare earth heavy rail steel in the 5# caster of the steelmaking plant, the casting blank section is 280x380mm, and a total of 18 heats are produced. The production process route is: KR hot metal pretreatment-converter-LF / VD refining-280x380mm bloom caster, and the steel composition is as follows:

[0033] Table 1 Heavy rail steel composition (%)

[0034]

[0035] 2) In this example, the nozzle and stopper with rare earth coated working surface are used, the structure and physical map are shown in the attached Figure 1 , and the use effect is good, and the process control flow is stable.

[0036] 3) The main process parameter control of this example is shown in the following table, and the rare earth addition method includes: adding 30% of rare earth cerium iron alloy 50ppm before each furnace VD process, and feeding rare earth wire at the second flow of the caster during the casting process of the caster, and the rare earth addition amount is controlled according to RE% (addition amount): S% (content in the molten steel) = 2.5, and the implementation process is shown in the attached Figure 2 .

[0037] Table 2 Main process parameters

[0038]

[0039]

[0040] 4) The pulse electric field process parameters in this embodiment are as follows: the input voltage of the pulse power supply is 380V AC, the output waveform is positive, negative and proportional pulse rectangular wave, the duty cycle range is 65%, the pulse width range is 300ms, the pulse period range is 300ms, the output current is 500A, and the output voltage is 36V.

[0041] Through the implementation of the present technology, the inclusions in the steel are substantially modified into fine and dispersed rare earth oxysulfides, as shown below Figure 3 , 18 heats are continuously cast, and the inclusions number density in the billet is less than 5 / mm 2 .

[0042] The above-described embodiments only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A process control method for producing a rare earth steel, characterized by: Comprise: 1) using rare earth functional refractory, solve the rare earth steel casting process, the rare earth elements in the steel erosion continuous casting nozzle and stopper function refractory caused by rare earth burn loss and rare earth yield fluctuation and continuous casting flow control failure problem; 2) continuous casting process using the application of non-uniform pulse electric field technology, improve the rare earth steel castability Process parameters include: pulse power input voltage of 380V AC, output waveform is positive, negative and proportional pulse rectangular wave, duty cycle range 35-65%, pulse width range 200-800ms, pulse period range 200-800ms, the maximum output current is 1000A, the maximum average current is 500A, the maximum output voltage is 36V; 3) using the method of crystallizer wire feeding of rare earth alloy, improve the sulfide morphology, distribution, size in the billet, improve the steel low temperature impact toughness, transverse toughness, high temperature plasticity Using Re% ≥ 99%, among which the rare earth content Ce%: La% = 2:1, other elements Fe ≤ 0.5%, Si ≤ 0.07%, P ≤ 0.01%, S ≤ 0.02%, rare earth cored wire diameter 2.5 ± 0.2mm, iron skin thickness 0.3mm, wire feeding speed ≥ 5m / min, the amount of rare earth added according to RE% added amount: S% steel liquid content = 1.5-3.5 control; Using artificial synthesis material made of rare earth elements, aluminum elements and carbon elements as coating raw material, coating on the working interface of submerged entry nozzle and stopper in tundish; The coating material is artificially synthesized; the method of artificial synthesis is: selecting 200 mesh rare earth oxide powder and Al2O3 powder, mixing according to the mass ratio of 75%:25%, and then sintering at ≥1500℃ for ≥5 hours in shuttle kiln to prepare rare earth aluminate; Mixing 200 mesh rare earth aluminate powder and 80 mesh graphite carbon powder, using phenolic resin as binder to prepare coating, and coating on the working surface of functional refractory and matrix material together isostatic pressing forming; The mass addition amount of phenolic resin and graphite carbon powder is 4.5% and 12% respectively.

2. The process control method for producing a rare earth steel according to claim 1, characterized in that: The thickness of the coating is 4.5-5.5mm.

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