1. A smelting method for quickly raising the temperature of a refining furnace under the condition of low-alkalinity slag is characterized by comprising the following steps:

1) molten steel enters a station, a cover is uncovered, straight-through argon is opened to break slag, and temperature is measured;

2) adding 5.0-6.0 kg/t of lime, 1.0-1.5 kg/t of quartz sand and stirring for 0.5-1.0 min under the flow of large argon to ensure that slag materials are melted;

3) adjusting the argon flow to 60-120L/min, transmitting power, adjusting arc flow and arc voltage, supplying power by short arc in the whole process, and adding 1-1.5 kg/t of carbonaceous deoxidizer in the power transmission process;

4) judging the deoxidation condition according to the color of the smoke in the furnace, and selecting whether to add a deoxidizer or not;

5) the control target of the main components of the refining slag at the early stage of refining is as follows: CaO: 40 to 46% of SiO₂：15～20% ，Al₂O₃: 10-15%, MgO: 9-12%, FeO + MnO: not more than 2.0 percent, and controlling the alkalinity R value of the slag within the range of 2.2-2.8;

6) determining submerged arc power transmission time according to the temperature of molten steel before power transmission, theoretically calculating to raise the temperature to the refining outbound temperature, stopping power and measuring temperature, adding 3.0-4.0 kg/t of quartz sand to adjust alkalinity, and controlling the main component control target of refining slag in the middle and later refining stages: CaO: 36-42% of SiO₂：20～28% ，Al₂O₃：10～15%，MgO：9～12%，FeO+MnO：≤1.0%，R：1.5～2.0；

7) Continuously supplying power, stopping power after the slag is completely melted, further observing the cooled slag condition by adhering slag, wherein the weakly alkaline slag is gray black and has a small amount of hanging wires, and if the slag is gray white and can be naturally pulverized, adding an acid slag-making material for slag adjustment;

8) after the slag is well adjusted, normal component smelting and temperature adjustment of LF refining are carried out.

2. The smelting method for rapidly increasing the temperature of a refining furnace under the condition of low-alkalinity slag according to claim 1, wherein the carbonaceous deoxidizer is calcium carbide or a carburant.

3. The smelting method for rapidly increasing the temperature of the refining furnace under the condition of the low-alkalinity slag according to claim 1, wherein the flow rate of the large argon in the step 2) is controlled to be 700-800L/min.

Background

At present, with the development of the industry in China, the demand of various industries on high-performance materials, particularly special steel is greatly increased, and the development of automobile steel needs technical improvement, structure adjustment, variety optimization, quality improvement and product optimization. The non-quenched and tempered steel used for the automobile engine expansion-fracture connecting rod is an important material adopted by many automobile production enterprises in Europe, and the localization of steel supply is basically realized at present in China.

The sulfur element is considered as harmful impurities in general special steel, the lower the control is required to be, the better the control is, and in the non-quenched and tempered steel used for the expansion-fracture connecting rod, a certain content of sulfur is required to be combined with manganese in the steel, so that the sulfur in the steel forms MnS with a higher melting point, a FeS film on a grain boundary is avoided, the hot brittleness of the steel is eliminated, the hot workability is improved, and the non-quenched and tempered steel plays a very beneficial role. Because sulfur has chemical properties in steel, the sulfur is easy to enter slag from molten steel in a reducing atmosphere, so that the sulfur content in the slag is unstable and difficult to control, and therefore, low-alkalinity slag is generally required to be manufactured by a refining furnace when producing sulfur-containing non-quenched and tempered steel.

In the actual production process, when low-alkalinity slag is produced in an LF furnace, because the slag foaming effect is poor, electric arcs cannot be effectively buried in the power transmission process, the temperature rise in the refining process is difficult, the refining period is long, and multi-furnace continuous casting and large-scale production are difficult to realize.

Disclosure of Invention

The invention aims to provide a smelting method for quickly heating a refining furnace under the condition of low-alkalinity slag, which can quickly heat the refining furnace under the condition of low-alkalinity slag and ensure the stable content of sulfur in steel.

The specific scheme of the invention is as follows: a smelting method for quickly raising the temperature of a refining furnace under the condition of low-alkalinity slag is characterized by comprising the following steps:

1) molten steel enters a station, a cover is uncovered, straight-through argon is opened to break slag, and temperature is measured;

2) adding 5.0-6.0 kg/t of lime, 1.0-1.5 kg/t of quartz sand and stirring for 0.5-1.0 min under the flow of large argon to ensure that slag materials are melted;

3) adjusting the argon flow to 60-120L/min, transmitting power, adjusting arc flow and arc voltage, supplying power by short arc in the whole process, and adding 1-1.5 kg/t of carbonaceous deoxidizer in the power transmission process;

4) judging the deoxidation condition according to the color of the smoke in the furnace, and selecting whether to add a deoxidizer or not;

5) the control target of the main components of the refining slag at the early stage of refining is as follows: CaO: 40-46%, SiO 2: 15-20%, Al2O 3: 10-15%, MgO: 9-12%, FeO + MnO: the alkalinity R value of the slag is controlled to be within the range of 2.2-2.8, the situation that the desulfurization activity of the slag is larger due to too high alkalinity and the situation that the slag cannot form foam slag due to too low alkalinity, submerged arc power transmission is not facilitated, and the power transmission and temperature raising efficiency is influenced is prevented;

6) determining submerged arc power transmission time according to the temperature of molten steel before power transmission, theoretically calculating to raise the temperature to the refining outbound temperature, stopping power and measuring temperature, adding 3.0-4.0 kg/t of quartz sand to adjust alkalinity, and controlling the main component control target of refining slag in the middle and later refining stages: CaO: 36-42%, SiO 2: 20-28%, Al2O 3: 10-15%, MgO: 9-12%, FeO + MnO: less than or equal to 1.0 percent, R: 1.5 to 2.0;

7) continuously supplying power, stopping power after the slag is completely melted, further observing the cooled slag condition by adhering slag, wherein the weakly alkaline slag is gray black and has a small amount of hanging wires, and if the slag is gray white and can be naturally pulverized, adding an acid slag-making material for slag adjustment;

8) after the slag is well adjusted, normal component smelting and temperature adjustment of LF refining are carried out.

Further, the carbonaceous deoxidizer is calcium carbide or a carburant.

Further, the flow of the large argon in the step 2) is controlled to be 700-800L/min.

The invention can achieve the following beneficial effects:

1) the temperature rise in the early stage of refining is fast, the requirement of the temperature of the refining outlet can be quickly met, and the temperature rise pressure under the condition of low-alkalinity slag in the middle and later stages of refining is reduced.

2) The S content in the steel is stable in the refining process.

3) The process has strong operability, effectively reduces the refining period and ensures multi-furnace continuous casting.

4) By adopting the smelting method, the temperature rise rate of the refining furnace is greatly increased by 30-40%, and the refining period is shortened by 10-15 minutes.

Detailed Description

The invention relates to a smelting method for quickly raising the temperature of a refining furnace under the condition of low-alkalinity slag, which is characterized by comprising the following steps of:

1) molten steel enters a station, a cover is uncovered, straight-through argon is opened to break slag, and temperature is measured;

2) adding 5.0-6.0 kg/t of lime, 1.0-1.5 kg/t of quartz sand and stirring for 0.5-1.0 min under the flow of large argon to ensure that slag materials are melted;

3) adjusting the argon flow to 60-120L/min, transmitting power, adjusting arc flow and arc voltage, supplying power by short arc in the whole process, and adding 1-1.5 kg/t of carbonaceous deoxidizer in the power transmission process;

4) judging the deoxidation condition according to the color of the smoke in the furnace, and selecting whether to add a deoxidizer or not;

5) the control target of the main components of the refining slag at the early stage of refining is as follows: CaO: 40-46%, SiO 2: 15-20%, Al2O 3: 10-15%, MgO: 9-12%, FeO + MnO: the alkalinity R value of the slag is controlled to be within the range of 2.2-2.8, the situation that the desulfurization activity of the slag is larger due to too high alkalinity and the situation that the slag cannot form foam slag due to too low alkalinity, submerged arc power transmission is not facilitated, and the power transmission and temperature raising efficiency is influenced is prevented;

6) determining submerged arc power transmission time according to the temperature of molten steel before power transmission, theoretically calculating to raise the temperature to the refining outbound temperature, stopping power and measuring temperature, adding 3.0-4.0 kg/t of quartz sand to adjust alkalinity, and controlling the main component control target of refining slag in the middle and later refining stages: CaO: 36-42%, SiO 2: 20-28%, Al2O 3: 10-15%, MgO: 9-12%, FeO + MnO: less than or equal to 1.0 percent, R: 1.5 to 2.0;

7) continuously supplying power, stopping power after the slag is completely melted, further observing the cooled slag condition by adhering slag, wherein the weakly alkaline slag is gray black and has a small amount of hanging wires, and if the slag is gray white and can be naturally pulverized, adding an acid slag-making material for slag adjustment;

8) after the slag is well adjusted, normal component smelting and temperature adjustment of LF refining are carried out.

Further, the carbonaceous deoxidizer is calcium carbide or a carburant.

Further, the flow of the large argon in the step 2) is controlled to be 700-800L/min.

The following describes the embodiments of the present invention in further detail with reference to specific parameters.

Example 1:

producing non-quenched and tempered steel C with S content ranging from 0.060 to 0.070 percent₇0S₆。

1) Molten steel enters the station, and the temperature is 1524 ℃.

2) Adding 800kg of lime, 150kg of quartz sand and 750L/min of large argon flow, stirring for 1 minute, and well melting slag materials.

3) Adjusting the argon flow to 90L/min, transmitting power, adjusting to 5, 42000A of arc flow and 200V of arc voltage; 120kg of calcium carbide and 40kg of carburant are added in the power transmission process.

4) The electric arc is stable in the power transmission process, the smoke in the furnace is milk white, and no deoxidizing agent is added.

5) Powering off after 20 minutes of power transmission, taking a slag sample (1), and measuring temperature: 1606 ℃, slag sample (1) main components: CaO: 43.16% of SiO₂：18.25%，Al₂O₃：13.96%，MgO：9.06%，FeO+MnO：1.49%，R：2.36。

6) Adding 500kg of quartz sand, continuing to supply power, cutting off power after 3 minutes, observing that the slag is gray black and has a small amount of hanging wires after being stained with slag, and measuring the temperature: and (3) taking a component sample and a slag sample (2) at 1610 ℃. The slag sample (2) comprises the following main components: CaO: 38.56% of SiO₂：23.85%，Al₂O₃：14.06%，MgO：11.84%，FeO+MnO：0.78%，R：1.62。

7) And (3) carrying out normal component and temperature adjustment on the component sample, stabilizing the content of S in the process, and carrying out refining and leaving S: 0.068%, temperature: 1614 ℃ refining period 52 minutes.

Example 2:

producing non-quenched and tempered steel 36MnVS with the S content of 0.035-0.045%₄。

1) Molten steel enters the station, and the temperature is measured at 1531 ℃.

2) 850kg of lime and 160kg of quartz sand are added, and the mixture is stirred for 1 minute under the condition of large argon flow, so that slag materials are well melted.

3) Adjusting the argon flow to 90L/min, transmitting power, adjusting to a gear 5, arc flow 42000A, arc voltage 200V, and adding 150kg calcium carbide in the power transmission process.

4) The electric arc is stable in the power transmission process, the smoke in the furnace is yellow-white, and 30kg of the electric stones are added.

5) And (3) power supply is carried out for 19 minutes, power failure is carried out, a slag sample (1) is taken, and temperature measurement is carried out: 1604 ℃. The slag sample (1) comprises the following main components: CaO: 42.58% of SiO₂：16.35%，Al₂O₃：12.57%，MgO：9.86%，FeO+MnO：1.64%，R：2.60。

6) Adding 480kg of quartz sand, continuously supplying power, cutting off power after 3 minutes, observing that the slag is gray black and has a small amount of hanging wires after being stained with slag, and measuring the temperature: and (4) taking component samples and slag samples (2) at the temperature of 1606 ℃. The slag sample (2) comprises the following main components: CaO: 39.26% of SiO₂：22.72%，Al₂O₃：14.32%，MgO：10.06%，FeO+MnO：0.68%，R：1.73。

7) And (3) carrying out normal component and temperature adjustment on the component sample, stabilizing the content of S in the process, and carrying out refining and leaving S: 0.042%, temperature: 1616 ℃ refining period 54 minutes.

The embodiment shows that the smelting method greatly improves the temperature rise rate of the refining furnace by 30-40 percent and shortens the refining period by 10-15 minutes.

The invention can achieve the following beneficial effects:

1) the temperature rise in the early stage of refining is fast, the requirement of the temperature of the refining outlet can be quickly met, and the temperature rise pressure under the condition of low-alkalinity slag in the middle and later stages of refining is reduced.

2) The S content in the steel is stable in the refining process.

3) The process has strong operability, effectively reduces the refining period and ensures multi-furnace continuous casting.