Electroslag remelting process for producing H13 round steel by using return slag

Abstract

The invention relates to an electroslag remelting process for producing H13 round steel by using return slag, which comprises the following steps of: pre-treating the return slag: carrying out magnetic separation on the return slag to remove metal particles mixed in the return slag, then crushing until the particle size is less than or equal to 10mm, and calculating by mass percent: the mixed slag comprises 60-65% of CaF2, 5-10% of CaO, 25-30% of Al2O3 and 1-3% of SiO2; before production, a consumable electrode of H13 steel is subjected to shot blasting treatment, the consumable electrode is used for direct arcing production, the slag adding time is controlled to be smaller than or equal to 40 min, the overall slag melting time is controlled to be smaller than or equal to 75 min, argon protection is adopted in the remelting stage, molten steel air suction and slag oxidation are prevented, voltage swing control and melting speed control dual-control power production is adopted in the remelting stage, the voltage swing control is smaller than or equal to 1, and the melting speed is controlled to be smaller than or equal to 2. The melting speed is controlled according to 0.7 time of the average diameter of the crystallizer, the electroslag production crystallizer is cooled by circulating water, the temperature of the crystallizer is controlled to be less than or equal to 40 DEG C, the water cooling strength is uniform, and the electroslag ingot is uniformly crystallized.

Description

Technical Field

[0001] The invention belongs to the technical field of electroslag metallurgy production, and in particular relates to an electroslag remelting process for producing H13 round steel by utilizing returned slag. Background Art

[0002] As a hot working die steel, H13 round steel has good toughness, thermal fatigue performance and wear resistance, and is widely used in die-casting molds, hot extrusion molds and other fields. In the traditional electroslag remelting process for producing H13 round steel, the slag material usually uses pre-melted slag in a configuration ratio, which is relatively expensive. At the same time, a large amount of return slag cake will be generated on the upper part of the electroslag ingot riser during the electroslag production process. If these return slags are directly discarded, it will not only waste resources, but also pollute the environment if discarded at will. How to effectively utilize the return slag for electroslag production, reduce production costs, and improve resource utilization has become an urgent problem to be solved in the electroslag industry. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide an electroslag remelting process for producing H13 round steel using returned slag by effectively treating returned slag and optimizing process parameters, thereby reducing production costs and ensuring high-quality production of H13 round steel.

[0004] The technical solution of the present invention is achieved as follows: an electroslag remelting process for producing H13 round steel using returned slag, the specific process steps are as follows:

[0005] Step 1), the returned slag needs to be pretreated first: collect the returned slag generated in the electroslag remelting production process. Because the electroslag process cannot remove the P content, the returned slag needs to be analyzed for S and P harmful elements using X-ray fluorescence spectroscopy before use to ensure that S≤0.03%, P≤0.025%, and ensure that the returned slag can be normally deployed and used; the returned slag cake contains CaF2, CaO, Al2O3, SiO2 and metal particles. The returned slag is magnetically separated to remove the metal particles mixed therein, and then crushed to a particle size of ≤10mm;

[0006] Step 2), the returned slag is prepared according to the slag ratio, the crushed returned slag is mixed and prepared with the newly added auxiliary materials in proportion, the composition of the mixed slag in mass percentage is CaF2: 60%-65%, CaO: 5%-10%, Al2O3: 25%-30%, SiO2: 1%-3%, and the rest are beneficial components remaining in the returned slag; the newly added auxiliary materials are high-purity fluorite powder, industrial alumina powder, lime or 244 pre-melted slag, SiO2 particles, and the specific proportion is 40%-50% of returned slag, 30%-35% of high-purity fluorite powder, 10%-15% of industrial alumina powder, 5%-10% of lime or 244 pre-melted slag, and 1%-3% of SiO2 particles;

[0007] Step 3), the electroslag remelting process of the returned slag electroslag to produce H13 round steel is as follows:

[0008] Step 3.1), electrode preparation stage: Shot blast the consumable electrode of H13 steel to remove the oxide scale, floating rust and floating dust on the surface to prevent the increase of H and O in the electroslag process;

[0009] Step 3.2), arcing and slag-melting stage: use consumable electrodes to directly start arcing, slag adding time is controlled to be ≤40min, and the overall slag-melting time is controlled to be ≤75min; the current of the slag-melting stage is controlled to be 5000-13000A, and the voltage is controlled to be 42-48V;

[0010] Step 3.2), remelting stage: use argon protection, the flow rate is set to 40-100NL / min to prevent molten steel from inhaling air and slag oxidation; the remelting stage adopts voltage swing control and melting speed control dual control power production, the voltage swing control is ≤1, and the melting speed is controlled at 0.7 times the average diameter of the crystallizer;

[0011] Step 3.3), crystallization control: The electroslag production crystallizer adopts circulating water cooling, and the crystallizer temperature is controlled to be ≤40 degrees to ensure uniform water cooling intensity and uniform crystallization of electroslag ingots.

[0012] The present invention has the following positive effects:

[0013] 1. The returned slag is pretreated: the returned slag generated in the electroslag remelting production process needs to be collected first, and the S and P harmful elements are analyzed by X-ray fluorescence spectroscopy to ensure that S≤0.03% and P≤0.025%, so as to ensure that the returned slag can be normally prepared and used. The components of the returned slag cake include CaF2, CaO, Al2O3, and SiO2. Metal particles are easily wrapped or deposited in the returned slag. The metal particles are tiny metal particles remaining due to insufficient local melting or uneven distribution of the slag pool during the electroslag process. The returned slag is subjected to magnetic separation to remove the entrained metal particles therein, and then crushed to a particle size of ≤10 mm. Therefore, the present invention ensures the effective treatment of the returned slag, plays a purification treatment at the initial stage of the entire process, and ensures the safe and reliable operation of the process.

[0014] 2. The returned slag needs to be proportioned, and the crushed returned slag is mixed with newly added auxiliary materials in a certain proportion. Calculated by mass percentage, the composition of the mixed slag material is CaF2: 60%-65%, CaO: 5%-10%, Al2O3: 25%-30%, SiO2: 1%-3%, and the rest are the beneficial components remaining in the returned slag. The newly added auxiliary materials are high-purity fluorite powder, industrial alumina powder, lime or 244 premelted slag is used instead, and SiO2 particles. The specific proportion is 40%-50% of the returned slag + 30%-35% of the high-purity fluorite powder + 10%-15% of the industrial alumina powder + 5%-10% of the 244 premelted slag + 1%-3% of the SiO2 particles. The above ratio is the best technical solution obtained by the inventor through a large number of experimental comparisons, and it is also the substantial difference between the present invention and the prior art. The change in the ratio will lead to the change of the whole process. For example, a high proportion of the returned slag material will lead to a decrease in the inclusion removal ability of the overall slag system, and a high proportion of the newly added auxiliary materials will lead to a change in the calorific value of the slag system, which is likely to cause problems with the surface quality of the electroslag ingot.

[0015] 3. When the returned slag is used for electroslag production of H13 round steel, the electroslag remelting process is as follows:

[0016] 1). Electrode preparation stage: The consumable electrode of H13 steel is shot blasted to remove the scale, floating rust, floating ash, etc. on the surface to prevent the increase of H and O during the electroslag process.

[0017] 2). Arc starting and slag melting stage: Direct arc starting production is used with the consumable electrode. The slag addition time is controlled ≤ 40 min, and the overall slag melting time is controlled ≤ 75 min. During the slag melting stage, the current is controlled at 5000 - 13000 A, and the voltage is controlled at 42 - 48 V.

[0018] 3). Remelting stage: Argon protection is adopted, and the flow rate is set at 40 - 100 NL / min to prevent the molten steel from inhaling gas and the slag material from oxidizing. During the remelting stage, double control power production is adopted with voltage swing control and melting speed control. The voltage swing control is ≤ 1, and the melting speed is controlled according to 0.7 times the average diameter of the mold.

[0019] 4). Crystallization control: The mold for electroslag production is cooled by circulating water, and the mold temperature is controlled ≤ 40 degrees. Ensure that the water cooling intensity is uniform to make the electroslag ingot crystallize uniformly.

[0020] The advantages of the above steps are as follows: Shot blasting the consumable electrode to prevent the increase of H and O caused by the scale, floating rust, and floating ash on the electrode surface. Controlling the slag addition time, melting current, voltage, etc., to make the slag material melt completely during the slag melting stage and ensure the quality of the bottom of the electroslag ingot. Argon protection during the production process to prevent the increase of gas during the remelting process. Adopting double control of voltage swing control and melting speed control to effectively avoid serious segregation caused by fluctuations in melting speed and voltage. Controlling the water cooling intensity to make the ingot solidify sufficiently and prevent general porosity problems. DETAILED DESCRIPTION

[0021] The present invention provides a process for producing H13 round steel with electroslag remelting by using returned slag, and the specific process steps are as follows:

[0022] The return slag needs to be pre-treated first: collect the return slag generated in the electroslag remelting process, use X-ray fluorescence spectrometry to analyze the harmful elements S and P, ensure S≤0.03%, P≤0.025%, and ensure that the return slag can be normally deployed and used; the return slag cake contains CaF2, CaO, Al2O3, SiO2, and the return slag is easy to wrap or deposit metal particles. The metal particles are electrode materials that are not completely melted during the electroslag process, that is, the consumable electrode due to insufficient local melting or uneven distribution of the slag pool, and the residual tiny metal particles Cr and Ni. The return slag is magnetically separated to remove the mixed metal particles, and then crushed to a particle size of ≤10mm.

[0023] The return slag needs to be adjusted to a slag ratio, and the crushed return slag is mixed with the newly added auxiliary materials in a certain proportion. Calculated by mass percentage, the mixed slag composition is CaF2: 60%-65%, CaO: 5%-10%, Al2O3: 25%-30%, SiO2: 1%-3%, and the rest are beneficial components remaining in the return slag. The newly added auxiliary materials are high-purity fluorite powder, industrial alumina powder, lime or 244 pre-melted slag instead, SiO2 particles, and the specific ratio is 40%-50% return slag + 30%-35% high-purity fluorite powder + 10%-15% industrial alumina powder + 5%-10% 244 pre-melted slag + 1%-3% SiO2 particles.

[0024] The electroslag remelting process when the return slag electroslag is used to produce H13 round steel is as follows:

[0025] Electrode preparation stage: Shot blast the H13 steel consumable electrode to remove the oxide scale, floating rust, floating dust, etc. on the surface to prevent the increase of H and O in the electroslag process.

[0026] Arcing and slag-forming stage: Use consumable electrodes to directly start arcing, control the slag-adding time to ≤40min, and the overall slag-forming time to ≤75min. The current in the slag-forming stage is controlled at 5000-13000A, and the voltage is controlled at 42-48V.

[0027] Remelting stage: argon protection is used, and the flow rate is set at 40-100NL / min to prevent molten steel from inhaling air and slag oxidation. The remelting stage adopts dual control power production of voltage swing control and melting speed control, the voltage swing control is ≤1, and the melting speed is controlled at 0.7 times the average diameter of the crystallizer.

[0028] Crystallization control: The crystallizer in electroslag production is cooled by circulating water, and the temperature of the crystallizer is controlled ≤ 40 °C. Ensure uniform water cooling intensity to make the electroslag ingot crystallize uniformly.

[0029] Example 1:

[0030] Step 1), Formulate production details:

[0031] Electroslag ingot furnace number of H13 round steel Specification Ingot weight 15H25001 Φ970 / Φ1040 13.3t

[0032] Step 2), Return slag pretreatment: Collect 1000 kg of return slag, remove 20 kg of metal particles by magnetic separation, and then crush it to a particle size ≤ 10 mm.

[0033] Step 3), Slag material preparation: Take 200 kg of the pretreated return slag, add 175 kg of fluorite, 70 kg of industrial alumina powder, 35 kg of 244 pre-melted slag, and 9 kg of SiO2, and mix evenly to obtain the slag material, with a total slag volume of 489 kg.

[0034] Step 4), Electrode preparation: Shot blast the consumable electrode made of H13 steel to remove the scale, floating rust, and floating ash on the surface.

[0035] Step 5), Arc starting and slag melting and gas protection:

[0036] Use a consumable electrode to start the arc cold, and use argon for protection during the production process. The argon flow rate is 40 - 100 NL / min, the slag addition time is controlled within 40 min, and the slag melting time is controlled within 75 min.

[0037] Step 6), Melting rate: The internal control target for the average melting rate is 700 kg / h.

[0038] Step 7), Power supply system:

[0039]

[0040] Step 8), Deoxidation system:

[0041] Add calcium silicate powder for deoxidation. At the beginning of increasing the current, add calcium silicate powder at 100 - 110 g / 5 minutes, and add 50 - 55 g / 5 minutes during the feeding stage.

[0042] Step 9), Quality of electroslag ingot:

[0043] After lifting the mold, observe the surface of the electroslag ingot, and the surface of the electroslag ingot is in good condition.

[0044] Step 10), Post-forging inspection:

[0045] Cut a 20-mm-thick test piece from the cross-section of the ingot tail and riser end of the forging to detect the chemical composition, gas content, and non-metallic inclusions. The test results are as follows:

[0046] 1) Chemical composition:

[0047]

[0048] 2) Gas detection:

[0049]

[0050] 3) Inclusion detection:

[0051]

[0052]

[0053] It can be seen from the test results that the H13 round steel produced by using this invention patent has uniform composition, dense structure, normal control of inclusion content, is consistent with the product standard level produced by traditional processes, and meets the requirements of high-end die manufacturing.

Claims

1. An electroslag remelting process for producing H13 round steel using returned slag, characterized in that: The specific process steps are as follows: Step 1), the returned slag needs to be pretreated first: collect the returned slag generated in the electroslag remelting production process. Because the electroslag process cannot remove the P content, the returned slag needs to be analyzed for S and P harmful elements using X-ray fluorescence spectroscopy before use to ensure that S≤0.03% and P≤0.025%, ensuring that the returned slag can be normally deployed and used; the returned slag cake contains CaF2, CaO, Al2O3, SiO2 and metal particles. The returned slag is magnetically separated to remove the metal particles mixed therein, and then crushed to a particle size of ≤10mm; Step 2), the returned slag is prepared according to the slag ratio, the crushed returned slag is mixed with the newly added auxiliary materials in proportion, and the composition of the mixed slag in mass percentage is CaF2: 60%-65%, CaO: 5%-10%, Al2O3: 25%-30%, SiO2: 1%-3%, and the rest are beneficial components remaining in the returned slag; the newly added auxiliary materials are high-purity fluorite powder, industrial alumina powder, lime or 244 pre-melted slag, SiO2 particles, and the specific proportions are 40%-50% of returned slag, 30%-35% of high-purity fluorite powder, 10%-15% of industrial alumina powder, 5%-10% of lime or 244 pre-melted slag, and 1%-3% of SiO2 particles; Step 3), the electroslag remelting process of the returned slag electroslag to produce H13 round steel is as follows: Step 3.1), electrode preparation stage: Shot blast the consumable electrode of H13 steel to remove the oxide scale, floating rust and floating dust on the surface to prevent the increase of H and O in the electroslag process; Step 3.2), arcing and slag-melting stage: use consumable electrodes to directly start arcing, slag adding time is controlled to ≤40min, and the overall slag-melting time is controlled to ≤75min; the current of the slag-melting stage is controlled to 5000-13000A, and the voltage is controlled to 42-48V; Step 3.2), remelting stage: use argon protection, the flow rate is set at 40-100NL / min to prevent molten steel from inhaling air and slag oxidation; the remelting stage adopts voltage swing control and melting speed control dual control power production, the voltage swing control is ≤1, and the melting speed is controlled at 0.7 times the average diameter of the crystallizer; Step 3.3), crystallization control: The electroslag production crystallizer adopts circulating water cooling, and the crystallizer temperature is controlled to be ≤40 degrees to ensure uniform water cooling intensity and uniform crystallization of electroslag ingots.

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