High-efficiency and high-recovery-rate RH online cold steel melting method

Abstract

The invention belongs to the technical field of ferrous metallurgy, and relates to a high-efficiency and high-recovery-rate RH online cold steel melting method, which comprises the following steps: using molten steel refined by an LF furnace, firstly hoisting to an RH cold steel melting station after converter tapping, carrying out normal vacuum treatment for 3-5 minutes, and after vacuum is finished, starting to melt cold steel in a manner of combining baking with blowing oxidation cold steel at a large coal-oxygen ratio, and the cold steel directly enters the steel ladle, and the steel ladle is hoisted to the LF for treatment after the cold steel melting is finished. And the time loss and the cost loss of transferring and crushing after the slag hopper is used for receiving the cold steel are reduced, the metal yield is improved, the usage amount of fluorite and a fluxing agent in the LF deoxidation slagging process is reduced, and the LF desulfurization rate and the desulfurization efficiency are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a method for efficiently and highly recovering RH online cold steel. Background Art

[0002] During the RH smelting process, a large amount of cold steel will accumulate in the vacuum tank. The conventional method is to use oxygen to melt the cold steel, then transport the cold steel to the slag treatment process, and return it to the scrap steel area to be added to the converter for digestion after crushing and magnetic separation. Such methods have problems such as difficulty in magnetizing the cold steel, low metal recovery rate, and blowing loss.

[0003] During the LF smelting process, in addition to the conventional lime slag materials, a slag melting agent needs to be added for slag melting and adjusting the slag system composition to achieve the metallurgical purposes of desulfurization and inclusion removal. The slag melting agent contains fluorite and a fluxing agent, and their market unit prices are relatively high. Moreover, using a large amount of fluorite for slag melting also has environmental pollution problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for efficiently and highly recovering RH online cold steel, reducing processes such as transfer and crushing after using the slag bucket to receive cold steel in RH, effectively reducing costs; reducing temperature loss and blowing loss caused by the cold steel entering the converter for digestion, and improving the metal recovery rate.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a method for efficiently and highly recovering RH online cold steel, including the following steps:

[0006] a. Select the molten steel that needs to be treated by the LF refining furnace, blow for 30 minutes in advance, and control the end point temperature at 1630 - 1650 °C;

[0007] b. When 1 / 3 of the steel is tapped from the converter, add top slag lime, fluorite, and fully pre-melted fluxing agent into the ladle;

[0008] c. According to the end point oxygen, add aluminum-manganese iron into the ladle, set the bottom blowing flow rate at 80 m 3 / h and stir for 2 - 3 minutes to melt the top slag well;

[0009] d. Lift the ladle to the RH station where cold steel needs to be melted, start vacuum pumping after lifting the ladle;

[0010] e. After 3 - 5 minutes of vacuum, break the vacuum and manually lower the ladle;

[0011] f. Select the combustion mode for the RH oxygen lance, bake the vacuum tank for 15 - 20 minutes, and the cold steel in the tank starts to melt and drip into the ladle;

[0012] g. After baking until there is no obvious dripping of cold steel from the immersion tube, switch to the oxygen blowing mode to completely melt the cold steel in the tank.

[0013] Further, in step b, 800 kg of top slag lime, 100 kg of fluorite, and 200 - 300 kg of fully pre - melted flux are charged; in step c, 400 - 600 kg of ferromanganese - aluminum is charged.

[0014] Further, during the vacuum process in step d, the lifting gas flow rate of the dipping tube is set to 180 - 200 m 3 / h, and the vacuum cycle time is 3 - 5 min.

[0015] Further, in step e, the ladle is manually lowered to a position where the distance between the ladle slag surface and the lower edge of the dipping tube of the vacuum tank is 100 - 150 mm.

[0016] Further, in step f, the RH oxygen lance selects the combustion mode, the gas flow rate of the gas is set to 500 - 650 m 3 / h, the coal - oxygen ratio is set to 1:1.6 - 1:1.8, and during the baking of the vacuum tank, the lifting gas flow rate of the dipping tube is set to 100 m 3 / h to avoid blocking the lifting gas pipeline;

[0017] Further, in step g, the oxygen flow rate in the oxygen - blowing mode is 1500 - 2000 m 3 / h, the lance position is 5000 mm - 7500 mm, and oxygen is blown in four cycles, and the oxygen blowing volume is 100 - 300 m 3 .

[0018] Further, after the cold steel melting in step g is completed, the following operating steps are carried out:

[0019] 1) Set the gas flow rate of the gas to 300 m 3 / h and the coal - oxygen ratio to 1:1.1 for baking and heat preservation;

[0020] 2) After the cold steel melting is completed, the ladle is lifted to LF, 800 - 1000 kg of lime is charged into the ladle, 100 - 150 kg of aluminum pellets are added, 300 - 400 m of aluminum wire is fed, and the bottom - blowing flow rate is set to 80 m 3 / h for strong stirring for 3 - 5 min to deeply remove the oxygen in the steel and in the slag;

[0021] 3) Select the third - gear heating, the first - stage temperature - rising target is > 1580 °C, and samples are taken, desulfurized, and the composition is adjusted;

[0022] 4) After the temperature and composition are appropriate, the bottom - blowing flow rate is set to 10 - 20 m 3 / h for soft blowing for 5 min;

[0023] 5) Subsequently, 200 - 400 m of calcium wire is fed into the ladle, and the bottom - blowing flow rate is set to 5 - 10 m 3 / h for soft blowing for 10 min.

[0024] The present invention has the following beneficial effects:

[0025] 1. The method for online melting of RH cold steel in the present invention reduces the time loss and cost loss in transportation and crushing after using the slag ladle to receive cold steel.

[0026] 2. The method for online melting of RH cold steel in the present invention reduces the temperature loss and blowing loss during the process of RH cold steel first solidifying in the slag basin and then entering the converter for digestion, and improves the metal yield.

[0027] 3. The method for online melting of RH cold steel in the present invention eliminates the problem that RH cold steel cannot be transported by a magnetic crane when added to the converter for blowing as scrap steel.

[0028] 4. The method for online melting of RH cold steel in the present invention reduces the usage amount of fluorite and flux during the LF deoxidation and slag-making process, improves the fluidity of the slag during the LF smelting process, forms slag quickly, reduces slag agglomeration, and improves the LF desulfurization rate and desulfurization efficiency.

[0029] 5. Compared with the other online cold steel recovery methods, the method for online melting of RH cold steel in the present invention can effectively reduce the influence of strongly oxidizing cold steel on the cleanliness of molten steel, and improve the quality and cleanliness of the molten steel for online cold steel connection. Detailed implementation mode

[0030] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the protection scope of the present invention is not limited to these embodiments. Any change or equivalent substitution that does not deviate from the concept of the present invention is included in the protection scope of the present invention.

[0031] A method for online melting of high-efficiency and high-recovery RH cold steel includes the following steps:

[0032] Select the molten steel to be treated by the LF refining furnace, blow for 30 minutes in advance, and control the end point temperature at 1630-1650 °C.

[0033] When 1 / 3 of the converter is tapped, 800 kg of top slag lime, 100 kg of fluorite, and 200-300 kg of fully pre-melted flux are put into the ladle.

[0034] According to the end point oxygen, 400-600 kg of aluminum-manganese iron is put into the ladle, and the bottom blowing flow rate is set at 80 m 3 / h and stirred for 2-3 minutes to melt the top slag well.

[0035] Lift the ladle to the working position of the RH cold steel to be melted, start vacuum pumping after lifting the ladle; during the vacuum process, the lifting gas flow rate of the immersion tube is set at 180-200 m 3 / h, and the vacuum circulation time is 3-5 minutes.

[0036] After vacuuming for 3 - 5 minutes, break the vacuum, lower the ladle manually until it reaches a position where the distance between the ladle slag surface and the lower edge of the immersion tube of the vacuum tank is 100 - 150 mm.

[0037] Select the combustion mode for the RH oxygen lance, set the gas flow rate of the gas to 500 - 650 m 3 / h, set the coal - oxygen ratio to 1:1.6 - 1:1.8, bake the vacuum tank for 15 - 20 minutes. The cold steel in the tank starts to melt and drip into the ladle; during the baking of the vacuum tank, set the lifting gas flow rate of the immersion tube to 100 m 3 / h to avoid blocking the lifting gas pipeline.

[0038] After baking until there is no obvious dripping of cold steel from the immersion tube, switch to the oxygen - blowing mode, with the oxygen flow rate of 1500 - 2000 m 3 / h, blow oxygen in four cycles at a lance position of 5000 mm - 7500 mm, and the oxygen - blowing volume is 100 - 300 m 3 , completely remove the cold steel in the tank.

[0039] After the cold - steel melting is completed, set the gas flow rate of the gas to 300 m 3 / h and the coal - oxygen ratio to 1:1.1, bake for heat preservation.

[0040] After the cold - steel melting is completed, lift the ladle to LF. Put 800 - 1000 kg of lime into the ladle, add 100 - 150 kg of aluminum pellets, feed 300 - 400 m of aluminum wire, and set the bottom - blowing flow rate to 80 m 3 / h for strong stirring for 3 - 5 minutes to deeply remove oxygen in the steel and in the slag.

[0041] Select heating gear 3, the first temperature - rising target is > 1580 °C, take samples, desulfurize, and adjust the composition.

[0042] After the temperature and composition are appropriate, set the bottom - blowing flow rate to 10 - 20 m 3 / h for soft blowing for 5 minutes.

[0043] Subsequently, feed 200 - 400 m of calcium wire into the ladle, and set the bottom - blowing flow rate to 5 - 10 m 3 / h for soft blowing for 10 minutes.

[0044] Application Example 1

[0045] For heat - treatment lot 1, after the RH vacuum tank has been normally smelted for 10 heats, execute the cold - steel recovery process. After tapping from the converter, the free space in the ladle is 300 mm. The RH online cold - steel melting method of the present invention is used for cold - steel recovery. After completion, the free space in the ladle is 280 mm, and it is estimated that about 1 t of cold steel is recovered. During the LF refining process, 112 kg of aluminum pellets, 316 m of aluminum wire, and 320 m of calcium wire are added. During the continuous casting process, the stopper stroke is stable and the castability is good.

[0046] The molten steel refined by the LF furnace is used in the present invention. After tapping from the converter, it is first lifted to the RH station where cold steel needs to be melted. It is subjected to normal vacuum treatment for 3 - 5 minutes. After the vacuum treatment ends, the method of combining baking with a large coal - oxygen ratio and blowing to melt the cold steel is adopted to start melting the cold steel. The cold steel directly enters the ladle. After the cold steel melting is completed, the ladle is then lifted to the LF for treatment.

[0047] The RH cold steel directly enters the ladle, reducing the processes such as transferring and crushing the cold steel after using the slag bucket to receive it, effectively reducing costs. At the same time, the hot cold steel slag directly enters the ladle, reducing the temperature loss and blowing loss caused by the cold steel entering the converter for digestion, and improving the metal recovery rate. In addition, the Al2O3 contained in the RH cold steel enters the ladle, which can play a role in adjusting the slag system composition, reducing the overall melting point of the slag system, and quickly forming slag. At the same time, the RH cold steel contains about 60% of metal elements, which are reduced and enter the molten steel during the slag making and deoxidation process in the LF and can be directly recycled.

[0048] The present invention is not limited to the above - mentioned embodiments. Anyone should know that the structural changes made under the inspiration of the present invention, as long as they have the same or similar technical solutions as the present invention, fall within the protection scope of the present invention.

[0049] The technologies, shapes, and structures not described in detail in the present invention are all well - known technologies.

Claims

1. An efficient and high-recovery method for online cold steel in RH, characterized in that, It includes the following steps: a. Select the molten steel to be treated in the LF refining furnace, blow the oxygen 30 minutes in advance, and control the end temperature at 1630-1650 °C; b. When 1 / 3 of the molten steel is tapped from the converter, put top slag lime, fluorite, and fully pre-melted flux into the ladle; c. Input aluminum ferromanganese into the ladle according to the end-point oxygen, and set the bottom blowing flow rate to 80 m 3 / h and stir for 2 - 3 min to melt the top slag well; d. Hoist the ladle to the RH station where cold steel needs to be melted, start to evacuate the vacuum after lifting the ladle; e. After 3-5 minutes of vacuum, break the vacuum and lower the ladle manually; f. Select the combustion mode for the RH oxygen lance, bake the vacuum tank for 15-20 minutes, and the cold steel in the tank starts to melt and drip into the ladle; g. After baking until there is no obvious dripping of cold steel from the immersion tube, switch to the oxygen blowing mode to completely melt the cold steel in the tank.

2. The method for efficient and high-recovery-rate RH on-line cold steel as described in claim 1, characterized in that, In step b, 800 kg of top slag lime, 100 kg of fluorite, and 200-300 kg of fully pre-melted flux are put in; in step c, 400-600 kg of ferromanganese-aluminum is put in.

3. The method for efficient and high-recovery RH on-line cold steel as claimed in claim 1, characterized in that, During the vacuum process of step d, the lifting gas flow rate of the impregnation tube is set to 180 - 200 m 3 / h, and the vacuum cycle time is 3 - 5 min.

4. The method for online cold steel of RH with high efficiency and high recovery rate as claimed in claim 1, wherein, In step e, the ladle is lowered manually to a position where the distance between the ladle slag surface and the lower edge of the immersion tube of the vacuum tank is 100-150 mm.

5. The method for efficient and high-recovery-rate RH on-line cold steel as claimed in claim 1, characterized in that, In step f, the RH oxygen lance selects the combustion mode, the gas flow rate is set to 500 - 650 m 3 / h, the coal-oxygen ratio is set to 1:1.6 - 1:1.8, and the lifting gas flow rate of the dipping tube is set to 100 m 3 / h during the baking of the vacuum tank to avoid blocking the lifting gas pipeline.

6. The method for efficient and high-recovery RH on-line cold steel as claimed in claim 1, characterized in that, In step g, the oxygen flow rate in the oxygen blowing mode is 1500 - 2000 m 3 / h, the lance position is 5000 mm - 7500 mm, and oxygen is blown in four cycles once, with the oxygen blowing volume being 100 - 300 m 3 .

7. The method for online cold steel of high efficiency and high recovery rate RH as described in claim 1, characterized in that After the cold steel melting in step g is completed, the following operation steps are carried out: 1) Set the gas flow rate to 300 m 3 / h, set the coal-oxygen ratio to 1:1.1, bake and keep warm; 2) After the cold steel is melted, the ladle is hoisted to the LF. 800 - 1000 kg of lime is put into the ladle, 100 - 150 kg of aluminum pellets are added, 300 - 400 m of aluminum wire is fed, and the bottom blowing flow rate is set to 80 m 3 / h for strong stirring for 3 - 5 minutes to deeply remove oxygen in the steel and in the slag; 3) Select heating gear 3, the first temperature increase target > 1580 °C, take samples, desulfurize, and match the composition; 4) After the temperature and composition are appropriate, the bottom blowing flow rate is set to 10 - 20 m 3 / h for soft blowing for 5 min; 5) Subsequently, 200 - 400 m of calcium wire is fed into the ladle, and the bottom blowing flow rate is set to 5 - 10 m 3 / h for soft blowing for 10 min.