High-phosphorus steel electroslag remelting slag system and smelting method

Abstract

The invention discloses a high-phosphorus steel electroslag remelting slag system and a smelting method, and belongs to the technical field of electroslag special metallurgy. The slag system comprises the following components in percentage by weight: 47 to 57 percent of CaF2, 32 to 40 percent of Al2O3, 4 to 6 percent of SiO2, 3 to 6 percent of 3CaO. P2O5, 1 to 2 percent of MgO and impurities. The smelting method comprises the working procedures of crushing before electroslag remelting, arc striking agent preparation, arc striking slag melting, remelting and the like. By adding 3 CaO. P2O5 into a slag system, phosphorus oxidation burning loss in the process of electroslag remelting of the high-phosphorus steel can be inhibited, the yield is stably controlled to be 95% or above, it can be guaranteed that electroslag ingots are uniform in component and structure, the subsequent machinability of materials is guaranteed, and the quality of the high-phosphorus steel is improved. The problems that in the prior art, the stability of electroslag system components is poor, the air permeability of the slag system is large, and the yield of alloy ingot elements is low are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electroslag special metallurgy, and in particular relates to a high-phosphorus steel electroslag remelting slag system and a smelting method. Background Art

[0002] Electroslag remelting is a process for re-refining steel produced by general smelting methods. Its working principle is that electric current passes through the slag pool to generate high temperature to heat the consumable electrode. The top of the consumable electrode gradually melts to form molten metal droplets, which fall off and pass through the slag pool. After being cooled by a water-cooled crystallizer, they solidify in the molten metal pool to form ingots. Its main purpose is to desulfurize and dephosphorize and obtain clean, uniform and dense steel ingots.

[0003] At present, my country has an increasing demand for various wear-resistant and rust-resistant steels for mechanical equipment. P is a harmful element for most steels, but it has good rust resistance. Therefore, P usually appears in some agricultural machinery steels with a high content due to its low price. During steelmaking, phosphorus easily reacts with oxygen to form P 2 O 5 However, this oxide cannot exist stably and usually forms Ca with calcium in the slag. 3 P 2 , Ca 3 (PO 4 ) 2 And other compounds, so as to achieve the purpose of dephosphorization.

[0004] The loss mechanism of P in the electroslag smelting process is that during the high-temperature molten slag melting of the consumable electrode, the P element is oxidized and combines with the calcium oxide in the slag to form a stable salt (tricalcium phosphate). In the early stage of remelting, the slag surface is relatively low, and under the protection of inert gas, the oxidation of the P element is mainly caused by the oxygen supply of the initial surface oxide scale. The oxidation loss of P in the middle and late stages of remelting is mainly due to the increase in slag permeability and the unreasonable slag system ratio, which causes the loss of phosphorus. In severe cases, the loss of phosphorus can reach about 20%.

[0005] When using the existing slag system for smelting, the yield is low and difficult to control, and the P content in various parts of the electroslag ingot often fails to meet the standard and is unevenly distributed. In addition, there are few reports on electroslag remelting of high-phosphorus steel. Therefore, achieving accurate control of the P content in the electroslag smelting process of high-phosphorus steel is of great significance for the development of wear-resistant and rust-resistant mechanical equipment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a high-phosphorus steel electroslag remelting slag system and a smelting method. The method of the present invention can achieve accurate and uniform control of the P content, and improve the problems in the prior art of poor stability of the electroslag slag system components, high slag permeability, and low alloy ingot element recovery rate.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a high phosphorus steel electroslag remelting slag system, the weight percentage of each component of the slag system is: CaF 2 :47~57%,Al 2 O 3 :32~40%,SiO 2 :4~6%,3CaO·P 2 O 5 : 3~6%, MgO: 1~2% and impurities.

[0008] In the slag system of the present invention, 3CaO·P 2 O 5 The amount of addition m is based on the formula To calculate, where P% is the phosphorus content in the alloy ingot before electroslag remelting, where P% is the phosphorus content in the alloy ingot before electroslag remelting.

[0009] The phosphorus content of the electroslag ingot before electroslag remelting of the high-phosphorus steel of the present invention is between 0.1% and 0.3%.

[0010] Another object of the present invention is to provide a smelting method for a high-phosphorus steel electroslag remelting slag system, the smelting method comprising the following steps: S1: proportioning according to the percentage of slag system materials, and keeping warm at 1550°C for 1.5 hours after proportioning. After cooling, crush it to 0.1-0.15mm and dry it, and take it out for use before electroslag remelting; S2: prepare an arc starter of the same composition before electroslag remelting, and add aluminum particles to the arc starter; S3: prepare relevant smelting equipment and lower the electrode to perform arc striking operation, adjust the voltage to 25-42V and the current to 2.0-4.0KA, then add slag material to slag after arc striking, and carry out slagging; S4: after entering the remelting period, control the voltage to 43-51V and the current to 3.5-4.5KA, and control the melting rate to 2.2-2.5Kg / min during the remelting stage.

[0011] The smelting method of the present invention also includes, S5: during the compensation period, the voltage and current are gradually reduced from 43-51V and 3.5-4.5KA to 30-35V and 2-2.5KA, and after the smelting is completed, demoulding is waited for.

[0012] In the smelting method of the present invention, the surface of the ingot is polished and ground before electroslag treatment until the metallic luster is exposed.

[0013] According to the smelting method of the present invention, the recovery rate of phosphorus in steel can reach more than 95%.

[0014] In the smelting method of the present invention, the segregation coefficient of each part in the ingot is between 0.98 and 1.02

[0015] The design principle of the present invention is as follows: In the initial stage: grinding the surface can effectively inhibit the oxidation of phosphorus in the ingot by the surface oxide scale in the early stage of electroslag remelting, thereby avoiding the loss of phosphorus; in the remelting stage: using the slag system can reduce the permeability of the slag system, thereby inhibiting the entry of air and reducing the oxidation loss of phosphorus in the steel. By controlling the melting rate, the depth of the molten pool can be controlled to reduce the solidification time and reduce component segregation.

[0016] The beneficial effect of adopting the above technical scheme is that: the present invention can not only inhibit the phosphorus oxidation and burning during the electroslag remelting of high-phosphorus steel and stably control the yield rate at more than 95% by adjusting the slag composition and optimizing the process parameters, but also ensure that the ingot composition and structure are uniform, and the segregation coefficient of each part in the ingot is between 0.98 and 1.02, thereby improving the subsequent processability of the material and effectively ensuring the metallurgical quality of the material after electroslag remelting and the product processing yield. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with specific embodiments.

[0018] The electroslag remelting slag of the present invention adopts the following mass ratio components: CaF 2 :47~57%,Al 2 O 3 :32~40%,SiO 2 :4~6%,3CaO·P 2 O 5 :3~6%,MgO:1~2% and impurities. The surface of the ingot is polished and bright before electroslag remelting, and an arc starter with the same composition is used and a small amount of aluminum particles are added. Compared with the ordinary slag system, the slag system of the present invention adds a certain amount of MgO, SiO 2 、3CaO·P 2 O 5 , which can reduce the permeability of slag, improve the surface quality of electroslag ingot (i.e. ingot) and inhibit the loss of phosphorus in the ingot.

[0019] The electroslag remelting process is carried out in the following order:

[0020] S1: Proportioning is carried out according to the percentage of slag-based materials. After the proportioning is completed, the mixture is kept at 1550°C for 1.5 hours, and after cooling, it is crushed into 0.1-0.15mm and dried, and then taken out for use before electroslag remelting;

[0021] S2: Prepare an arc starter with the same composition before electroslag remelting, and add a certain amount of aluminum particles into the arc starter;

[0022] S3: Prepare relevant smelting equipment and lower the electrode to start the arc operation. Adjust the voltage to 25-42V and the current to 2.0-4.0KA, then add slag to start the arc and perform slag melting.

[0023] S4: After entering the remelting period, the voltage is controlled at 43-51V, the current is controlled at 3.5-4.5KA, and the melting speed is controlled at 2.2-2.5Kg / min during the remelting stage;

[0024] S5: During the shrinkage compensation period, the voltage and current gradually decrease from 43-51V and 3.5-4.5KA to 30-35V and 2-2.5KA. After the smelting is completed, wait for demoulding.

[0025] Examples 1-6

[0026] A high phosphorus steel electroslag remelting slag system, the weight percentage of each component of the slag system is: CaF 2 :47~57%,Al 2 O 3 :32~40%,SiO 2 :4~6%,3CaO·P 2 O 5 : 3~6%, MgO: 1~2% and the remainder are inevitable impurities. 2 O 5 The amount of addition m is based on the formula The slag composition of each embodiment is shown in Table 1.

[0027] Table 1 Slag composition and particle size (wt%) of each example

[0028]

[0029]

[0030] The phosphorus content of the high-phosphorus steel of the present invention is between 0.1% and 0.3%, and the surface of the ingot is polished and ground before electroslag treatment until the metallic luster is exposed.

[0031] A smelting method for a high-phosphorus steel electroslag remelting slag system, wherein the slag system materials are proportioned according to the proportions, and after the proportions are completed, the slag is kept at 1550°C for 1.5 hours, and after cooling, the pre-melted slag is crushed to 0.1-0.15 mm and dried, and taken out for use before electroslag remelting. During the electroslag remelting process, the melting rate is controlled at 2.2-2.5 kg / min in the remelting stage. The specific process control is as follows:

[0032] S1: Proportioning is carried out according to the percentage of slag-based materials. After the proportioning is completed, the mixture is kept at 1550°C for 1.5 hours, and after cooling, it is crushed into 0.1-0.15mm and dried, and then taken out for use before electroslag remelting;

[0033] S2: Prepare an arc starter with the same composition before electroslag remelting, and add a certain amount of aluminum particles into the arc starter;

[0034] S3: Prepare relevant smelting equipment and lower the electrode to start the arc operation. Adjust the voltage to 25-42V and the current to 2.0-4.0KA, then add slag to start the arc and perform slag melting.

[0035] S4: After entering the remelting period, the voltage is controlled at 43-51V, the current is controlled at 3.5-4.5KA, and the melting speed is controlled at 2.2-2.5Kg / min during the remelting stage;

[0036] S5: During the shrinkage compensation period, the voltage and current gradually decrease from 43-51V and 3.5-4.5KA to 30-35V and 2-2.5KA. After the smelting is completed, wait for demoulding.

[0037] The smelting process control parameters of each embodiment are shown in Table 2, and the ingot composition, P element yield and segregation data are shown in Table 3.

[0038] Table 2 Smelting process control parameters of each embodiment

[0039]

[0040] Table 3 Ingot composition, P element yield and segregation of each example

[0041]

Claims

1. A high phosphorus steel electroslag remelting slag system, characterized in that: The weight percentages of the constituent substances of the slag system are: CaF2: 47-57%, Al2O3: 32-40%, SiO2: 4-6%, 3CaO·P2O5: 3-6%, MgO: 1-2% and impurities.

2. The high-phosphorus steel electroslag remelting slag system according to claim 1, characterized in that: In the slag system, the amount of 3CaO·P2O5 added m is calculated according to the formula To calculate, where P% is the phosphorus content in the electroslag ingot before electroslag remelting.

3. A high-phosphorus steel electroslag remelting slag system according to claim 1 or 2, characterized in that: The phosphorus content in the electroslag ingot of the high-phosphorus steel before electroslag remelting is between 0.1% and 0.3%.

4. A smelting method of a high-phosphorus steel electroslag remelting slag system according to claim 1, characterized in that: The smelting method comprises the following steps: S1: proportioning according to the percentage of slag-based materials, and keeping the mixture at 1550°C for 1.5 hours after proportioning, crushing the mixture to 0.1-0.15 mm after cooling, drying the mixture, and taking it out for use before electroslag remelting; S2: preparing an arc starter of the same composition before electroslag remelting, and adding aluminum particles to the arc starter; S3: preparing relevant smelting equipment and lowering the electrode for arc striking operation, adjusting the voltage to 25-42V and the current to 2.0-4.0KA, and then adding slag to slag after arc striking; S4: after entering the remelting period, controlling the voltage to 43-51V and the current to 3.5-4.5KA, and controlling the melting rate to 2.2-2.5Kg / min during the remelting stage.

5. The smelting method of a high-phosphorus steel electroslag remelting slag system according to claim 1, characterized in that: The smelting method also includes, S5: during the compensation period, the voltage and current are gradually reduced from 43-51V and 3.5-4.5KA to 30-35V and 2-2.5KA, and after the smelting is completed, demoulding is waited for.

6. A smelting method of a high-phosphorus steel electroslag remelting slag system according to claim 4 or 5, characterized in that: In the smelting method, the surface of the ingot is polished and ground before electroslag until the metallic luster is exposed.

7. The smelting method of a high-phosphorus steel electroslag remelting slag system according to claim 4 or 5, characterized in that: With the smelting method, the recovery rate of phosphorus in steel can reach more than 95%.

8. The smelting method of a high-phosphorus steel electroslag remelting slag system according to claim 4 or 5, characterized in that: According to the smelting method, the segregation coefficient of each part in the ingot is between 0.98 and 1.02.

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