Method for increasing addition amount of waste steel in refining process and application

Abstract

The invention belongs to the technical field of steel smelting, and particularly relates to a method for increasing the addition amount of waste steel in the refining process and application. The method comprises the following steps: carrying out foaming slag making, first reducing slag making treatment and second reducing slag making treatment in LF refining; in the foaming slag, first waste steel is added into molten steel at the temperature of 1610 DEG C or above; in the first reducing slag making treatment, second waste steel is added into molten steel with the temperature of 1600 DEG C or above. According to the method, the steel scrap can be rapidly melted and uniformly mixed by adjusting the steelmaking process conditions and adding the steel scrap for multiple times in a segmented manner, so that the addition amount of the steel scrap is increased, the unit consumption of molten iron is reduced, the carbon emission of the steel scrap is reduced, the desulfurization efficiency is high, the influence on the quality of molten steel is small, and the purposes of increasing the steel yield and the economic benefit are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel smelting, and particularly relates to a method and application for increasing the scrap addition amount in the refining process. Background Art

[0002] As a recyclable resource, scrap steel has high economic, environmental and social benefits. Increasing the scrap ratio and reducing the unit consumption of hot metal not only saves energy and reduces emissions, but also effectively solves the problems of insufficient iron resources and surplus scrap steel resources. In the past decade, the scrap ratio of converters in China has gradually increased from 6% to 22%. When the scrap ratio of the converter increases to a certain extent, the heat balance of the converter is broken, resulting in difficulties in melting scrap steel in the converter, increasing the overblow rate and reblow rate at the end point, enhancing the oxidability of the final slag, severely eroding the lining bricks of the furnace, and increasing the consumption of steel materials. Therefore, it is necessary to find additional ways to add scrap steel to reduce the unit consumption of hot metal.

[0003] Currently, scrap steel is generally added in the secondary refining process. However, although adding scrap steel in the refining process can effectively recover beneficial elements and improve the scrap steel yield, there are still the following problems: on the one hand, adding scrap steel to the molten steel will cause a huge temperature drop, which will affect the fluidity of the molten steel and the refining desulfurization, deoxidation and alloying; on the other hand, the larger the scrap steel addition amount, the longer the melting time, resulting in greater erosion of the ladle refractories and affecting the ladle life. Therefore, the amount of scrap steel added in the LF furnace refining is relatively low, so that the effect of reducing the unit consumption of hot metal is small. Summary of the Invention

[0004] The present invention provides a method and application for increasing the scrap addition amount in the refining process. The method solves the problems of serious imbalance in the temperature of the molten steel in the ladle, difficult slag formation, high desulfurization difficulty and difficult composition control.

[0005] The present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a method for increasing the scrap addition amount in the refining process, including the following steps:

[0007] In the LF refining, foam slag making, first reducing slag making treatment and second reducing slag making treatment are carried out;

[0008] In the foam slag making, first scrap steel is added to the molten steel at a temperature above 1610 °C;

[0009] In the first reducing slag making treatment, second scrap steel is added to the molten steel at a temperature above 1600 °C.

[0010] In some possible implementation manners, the temperature of the first scrap steel is above 500 °C.

[0011] In some possible implementation manners, the addition amount of the first scrap steel is 30 kg / t to 50 kg / t.

[0012] In some possible implementation manners, the temperature of the second scrap steel is above 500°C.

[0013] In some possible implementation manners, the addition amount of the second scrap steel is 20 kg / t to 50 kg / t.

[0014] In some possible implementation manners, in the treatment of the second slag-making reducing slag, third scrap steel is added to the molten steel at a temperature above 1600°C.

[0015] In some possible implementation manners, the temperature of the third scrap steel is above 500°C.

[0016] In some possible implementation manners, the addition rate of the first scrap steel is 500 kg / min to 2000 kg / min.

[0017] In some possible implementation manners, the addition rate of the second scrap steel is 500 kg / min to 2000 kg / min.

[0018] In some possible implementation manners, the addition rate of the third scrap steel is 500 kg / min to 2000 kg / min.

[0019] In some possible implementation manners, slag-making alloying treatment is also carried out in the LF refining;

[0020] In the slag-making alloying treatment, pure calcium wire is fed in the calcium treatment mode, and the soft blowing time of the molten steel with argon is not less than 6 min.

[0021] In a second aspect, the present invention provides an application of a method for increasing the addition amount of scrap steel in the refining process in the field of iron and steel smelting.

[0022] A method for increasing the addition amount of scrap steel in the refining process provided by the present invention, compared with the prior art, has at least the following beneficial technical effects:

[0023] (1) The method of the present invention, by adjusting the steel-making process conditions and adding scrap steel in multiple stages, ensures that the scrap steel can be quickly melted and mixed, thereby increasing the addition amount of scrap steel, reducing the unit consumption of hot metal, reducing the carbon emission of scrap steel, having a high desulfurization efficiency and little influence on the quality of molten steel on the premise of ensuring quality and stable production, and further achieving the purpose of increasing steel production and economic benefits.

[0024] (2) The method of the present invention enables the total addition amount of scrap steel in the LF refining to be as high as 100 kg / t to 130 kg / t; the recycled continuous casting residue in the refining can quickly form a foam slag with a lower oxidation degree, and the rapid slag formation can efficiently and deeply desulfurize, reducing the influence of adding scrap steel on the strong oxidation and large sulfur increase of the steel slag. Specific Embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be described and explained below in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided by the present invention without making creative efforts fall within the scope of protection of the present invention.

[0026] Obviously, the following description is only some examples or embodiments of the present invention. For those of ordinary skill in the art, the present invention can also be applied to other similar scenarios without making creative efforts. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed by the present invention, some design, manufacturing or production changes based on the technical content disclosed by the present invention are only conventional technical means and should not be understood that the content disclosed by the present invention is insufficient.

[0027] However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present invention and is not intended to limit the subject matter recited in the claims.

[0028] Without special instructions, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0029] In the current process of adding scrap steel in secondary refining, considering the large investment in secondary baking equipment and plant requirements, the method of adding scrap steel in secondary refining has the characteristics of small investment, limited demand space, high scrap steel recovery rate, energy conservation and environmental protection, and is a relatively mature and suitable choice. Increasing the use of scrap steel in the LF secondary refining process can not only reduce carbon emissions, but also be of great significance for reducing production costs and improving enterprise efficiency.

[0030] The term "baking and preheating device" refers to the electromagnetic direct injection heat exchange system provided by Henan Weimeng Vibrating Equipment Co., Ltd.

[0031] During refining, the temperature requirement for molten steel is strict. Large temperature fluctuations will seriously affect the fluidity of molten steel, refining desulfurization, deoxidation, alloying, etc. Reducing the addition of scrap steel is an effective method to reduce temperature fluctuations. However, for this reason, the utilization rate of scrap steel in iron and steel smelting cannot be improved. If the melting time is increased when adding scrap steel, it will lead to serious erosion of the ladle refractories and affect the ladle life.

[0032] In order to balance increasing the addition amount of scrap steel and reducing the melting time to maintain the ladle life, the embodiment of the present invention proposes a method for increasing the addition amount of scrap steel in the refining process. By adjusting the steelmaking process conditions, on the premise of not affecting the fluidity of molten steel, refining desulfurization, deoxidation, alloying, etc., the scrap steel is added in multiple segments, which increases the addition amount of scrap steel and reduces the unit consumption of hot metal. Moreover, due to the multiple additions of scrap steel, the melting time of scrap steel remains unchanged, maintaining the ladle life.

[0033] The following is a detailed description of a method for increasing the addition amount of scrap steel in the refining process according to an embodiment of the present invention.

[0034] The embodiment of the present invention provides a method for increasing the addition amount of scrap steel in the refining process, including the following steps:

[0035] S10. Conduct foamed slag making, first reducing slag making treatment, and second reducing slag making treatment during LF refining;

[0036] During foamed slag making, add the first scrap steel to the molten steel at a temperature above 1610°C;

[0037] In the first reducing slag making treatment, add the second scrap steel to the molten steel at a temperature above 1600°C.

[0038] For the method for increasing the addition amount of scrap steel in the refining process provided by the embodiment of the present invention, during foamed slag making and the first reducing slag making treatment, the temperature of the molten steel is adjusted before adding the scrap steel, reducing the temperature difference generated by adding the scrap steel and reducing the impact of adding the scrap steel on the fluidity of molten steel, refining desulfurization, deoxidation, alloying, etc. Adding the scrap steel in multiple segments increases the addition amount of scrap steel, reduces the unit consumption of hot metal on the premise of ensuring quality and stable production, and maintains the ladle life.

[0039] In some embodiments, in the above step S10, the foamed slag making includes the following steps:

[0040] S101. After adding hot continuous casting residue to the molten steel, heat it to above 1610°C, add the first scrap steel, and then add a deoxidizer.

[0041] In the above foamed slag making, heating the molten steel to above 1610°C can promote the rapid slag formation of the slag, shorten the melting time of the scrap steel, and reduce the too low temperature after adding the scrap steel.

[0042] The continuous casting residue, including molten steel and refining slag remaining in the ladle after the molten steel treated by a refining furnace (including LF and RH furnaces) is sent to the continuous casting process for casting, is a mixture of molten steel and refining slag. Such refining slag is characterized by high alkalinity, low oxidability, and high sulfur capacity, and contains a large amount of active calcium oxide and alumina and other components, with a low melting temperature and great value for cyclic recycling.

[0043] In some embodiments, in the above step S101, the addition amount of the continuous casting residue is 10 kg / t to 17 kg / t. In this case, the continuous casting residue can preliminarily deoxidize and desulfurize the molten steel, improving the purity of the steel.

[0044] In some embodiments, in the above step S101, the molten steel is heated to above 1610 °C by means of power transmission for temperature increase.

[0045] In some embodiments, in the above step S101, the temperature of the first scrap steel is above 500 °C. In this case, the addition of scrap steel with a temperature above 500 °C can further reduce the temperature drop fluctuation of the molten steel, reduce the influence brought by the temperature drop fluctuation, promote the rapid melting of the scrap steel, and at the same time reduce the risk of hydrogen and oxygen increase in the molten steel caused by the decomposition of crystal water in the scrap steel at high temperature.

[0046] In some embodiments, in the above step S101, the temperature of the first scrap steel is 500 °C to 1000 °C.

[0047] In some embodiments, the preparation of the first scrap steel includes:

[0048] Selecting scrap steel with a size length ≤ 600 mm and thickness ≤ 200 mm;

[0049] Using a baking and preheating device to heat and bake the scrap steel to above 500 °C, preferably 500 °C to 1000 °C.

[0050] In some embodiments, the sources of the first scrap steel include threaded steel pellets, hot-rolled trimmed materials, cold-rolled trimmed wires, externally purchased recycled profiles, loose scrap, etc.

[0051] In some embodiments, in the above step S101, the addition amount of the first scrap steel is 30 kg / t to 50 kg / t. In this case, the added first scrap steel reaches the maximum addition amount under a lower temperature fluctuation.

[0052] In some embodiments, in the above step S101, the addition rate of the first scrap steel is 500 kg / min to 2000 kg / min.

[0053] In some embodiments, in the above step S101, the deoxidizer includes at least one of calcium-silicon-aluminum alloy, ferrosilicon alloy, ferrotitanium alloy, calcium-silicon alloy, and ferromanganese alloy.

[0054] In some embodiments, in the above step S101, the addition amount of the deoxidizer is 1.0 kg / t to 2.0 kg / t. In this case, the oxidizability of the refining slag can be reduced, a low-oxidizability foamed slag can be formed, and a certain amount of acid-soluble aluminum can be maintained, reducing the nitrogen and oxygen increase in the molten steel and improving the cleanliness of the molten steel.

[0055] In some embodiments, in the above step S101, bottom blowing argon is carried out when adding the first scrap steel, that is, bottom blowing argon while adding the first scrap steel.

[0056] In some embodiments, when adding the first scrap steel, the flow rate of the bottom blowing argon is 400 NL / min to 1000 NL / min.

[0057] In some embodiments, in the slag obtained by deoxidation, the total iron content of the slag is ≤ 3%.

[0058] In some embodiments, in the above step S10, the first reduction slag making treatment includes the following steps:

[0059] S102. Heat the molten steel to ≥ 1600 °C, add the second scrap steel, and then add the first slag-making agent to make slag.

[0060] In the above first reduction slag making treatment, it is necessary to heat the temperature to 1600 °C, reduce the single power-on time, timely adjust the subsequent operations, reduce the ladle erosion, and save time.

[0061] In some embodiments, in the above step S102, the molten steel is heated to above 1600 °C by means of power-on heating.

[0062] In some embodiments, in the above step S102, the temperature of the second scrap steel is above 500 °C. In this case, the addition of the scrap steel with a temperature above 500 °C can further reduce the temperature drop fluctuation of the molten steel, reduce the influence caused by the temperature drop fluctuation, promote the rapid melting of the scrap steel, and at the same time reduce the risk of hydrogen and oxygen increase in the molten steel caused by the decomposition of the crystal water in the scrap steel at high temperature.

[0063] In some embodiments, in the above step S102, the temperature of the second scrap steel is 500 °C to 1000 °C.

[0064] In some embodiments, the preparation of the second scrap steel includes:

[0065] Select scrap steel with a size length ≤ 600 mm and a thickness ≤ 200 mm;

[0066] Use a baking and preheating device to heat and bake the scrap steel to above 500 °C, preferably 500 °C to 1000 °C.

[0067] In some embodiments, the sources of the second scrap steel include deformed steel bar pellets, hot-rolled trimmed materials, cold-rolled trimmed wires, externally purchased recycled profiles, loose scrap, etc.

[0068] In some embodiments, in the above step S102, the addition amount of the second scrap steel is 20 kg / t to 50 kg / t. In this case, the addition amount of the scrap steel is adjusted according to the ladle free space, the production rhythm of the front and back processes, and the composition control state, leaving sufficient time for the subsequent processes, and reducing the impact on subsequent processes such as molten steel desulfurization and calcium treatment.

[0069] In some embodiments, in the above step S102, the addition rate of the second scrap steel is 500 kg / min to 2000 kg / min.

[0070] In some embodiments, in the above step S102, the first slag-forming agent includes aluminum blocks and calcium silicoaluminate. In this case, the oxygen brought in by the scrap steel can be quickly removed, and the oxygen in the molten steel and the top slag can be removed simultaneously, promoting the floating of inclusions and improving the cleanliness of the molten steel.

[0071] In some embodiments, the addition amount of the aluminum blocks is 0.25 kg / t to 0.5 kg / t. In this case, the oxygen brought in by the scrap steel in the molten steel is quickly removed.

[0072] In some embodiments, the addition amount of the calcium silicoaluminate is 0.5 kg / t to 1.5 kg / t. In this case, the oxygen brought in by the scrap steel in the slag is quickly removed.

[0073] In some embodiments, the mass ratio of the aluminum blocks to the calcium silicoaluminate is 1:2. In this case, the oxygen in the molten steel and the top slag can be removed simultaneously, promoting the floating of inclusions and improving the cleanliness of the molten steel.

[0074] In some embodiments, in the above step S102, bottom blowing argon is carried out when adding the second scrap steel, that is, the second scrap steel is added while bottom blowing argon.

[0075] In some embodiments, in the above step S102, when adding the second scrap steel, the flow rate of the bottom blowing argon is 400 NL / min to 1000 NL / min.

[0076] In some embodiments, in the above step S10, the treatment of the second reducing slag includes the following steps:

[0077] S103. Heat the molten steel to ≥1600 °C, add the third scrap steel, and then add the second slag-forming agent to make slag.

[0078] In the above treatment of the second reducing slag, the temperature needs to be heated to 1600 °C, reducing the single power-on time, timely adjusting the subsequent operations, reducing the ladle erosion, and saving time.

[0079] In some embodiments, in the above step S103, the molten steel is heated to above 1600 °C by means of power transmission and temperature increase.

[0080] In some embodiments, in the above step S103, the temperature of the third scrap steel is above 500 °C. In this case, the addition of scrap steel with a temperature above 500 °C can further reduce the temperature drop fluctuation of the molten steel, reduce the influence caused by the temperature drop fluctuation, promote the rapid melting of the scrap steel, and at the same time reduce the risk of hydrogen and oxygen increase in the molten steel caused by the decomposition of crystal water in the scrap steel at high temperatures.

[0081] In some embodiments, in the above step S103, the temperature of the third scrap steel is 500 °C to 1000 °C.

[0082] In some embodiments, the preparation of the third scrap steel includes:

[0083] Select scrap steel with a size length ≤ 600 mm and a thickness ≤ 200 mm;

[0084] Use a baking and preheating device to heat and bake the scrap steel to above 500 °C, preferably 500 °C to 1000 °C.

[0085] In some embodiments, the sources of the third scrap steel include threaded steel pellets, hot-rolled cut edges, cold-rolled cut edge wires, externally purchased recycled profiles, loose scrap, etc.

[0086] In some embodiments, in the above step S103, the addition amount of the third scrap steel is 0 kg / t to 30 kg / t, but not 0 kg / t. In this case, adjust the addition amount of the scrap steel according to the ladle free space, the production rhythm of the front and back processes, and the composition control state, leave sufficient time for the subsequent processes, and reduce the influence on subsequent processes such as molten steel desulfurization and calcium treatment. When adding scrap steel, not only the ladle free space height and the ladle refractory condition need to be considered, but also the on-site actual situations such as scrap steel preheating, melting of scrap steel and slag materials, ladle bottom blowing permeability, molten steel composition of the front and back processes, and subsequent connection rhythm need to be checked in real time. If situations such as low ladle free space, thin ladle refractory thickness, poor ladle bottom blowing permeability, caking of scrap steel, molten steel composition close to the upper limit of the standard, and tight production rhythm occur, the addition amount of scrap steel should be reduced or no scrap steel should be added to avoid affecting normal and stable production and the quality of molten steel.

[0087] In some embodiments, in the above step S103, the addition rate of the third scrap steel is 500 kg / min to 2000 kg / min.

[0088] In some embodiments, in the above step S103, the second slag former includes aluminum blocks. In this case, the second slag former is used to produce a reducing slag, thereby improving the purity of the molten steel, optimizing the smelting process, and improving the quality of the molten steel.

[0089] In some embodiments, the addition amount of the aluminum block is 0.2 kg / t to 0.4 kg / t. In this case, the oxygen brought in by the scrap steel can be quickly removed, and at the same time, the oxygen in the molten steel can be removed, promoting the floating of inclusions and improving the cleanliness of the molten steel.

[0090] In some embodiments, in the above step S103, when adding the third scrap steel, bottom blowing argon is also carried out, that is, the second scrap steel is added while bottom blowing argon.

[0091] In some embodiments, when adding the third scrap steel, the flow rate of bottom blowing argon is 400 NL / min to 1000 NL / min.

[0092] In some embodiments, in the above step S10, slag-making alloying treatment is also carried out during LF refining. In the slag-making alloying treatment, pure calcium wire is fed in the calcium treatment mode, and the soft blowing time of the molten steel with argon is not less than 6 min.

[0093] In some embodiments, in the above step S10, the addition amount of the pure calcium wire is 1.5 m / t to 3.0 m / t.

[0094] In some specific embodiments, a method for increasing the addition amount of scrap steel in the refining process is provided, and the steps are as follows:

[0095] S11. Select scrap steel and heat it using a baking and preheating device.

[0096] S21. During LF refining, after adding hot continuous casting residue to the molten steel, the molten steel is heated to above 1610 °C by means of power-on heating. After adding the first scrap steel while bottom blowing argon, a deoxidizer is added.

[0097] S31. During LF refining, the molten steel is heated to above 1600 °C by means of power-on heating. After adding the second scrap steel while bottom blowing argon, the first slag-making agent is added to make slag.

[0098] S41. During LF refining, the molten steel is heated to above 1600 °C by means of power-on heating. After adding the third scrap steel while bottom blowing argon, the second slag-making agent is added to make slag.

[0099] S51. During LF refining, slag-making alloying treatment is carried out. In the slag-making alloying treatment, pure calcium wire is fed in the calcium treatment mode, and the soft blowing time of the molten steel with argon is not less than 6 min.

[0100] The following further illustrates the method for increasing the addition amount of scrap steel in the refining process provided by the embodiments of the present invention in conjunction with specific embodiments.

[0101] The sources of the scrap steel involved in the following examples and comparative examples are all threaded steel particles, hot-rolled cut edges, cold-rolled cut wires, externally purchased recycled profiles, loose scrap, etc.

[0102] The source of the hot continuous casting residue involved in the following examples and comparative examples is the ladle residue of the Q355B steel grade that has been cast on the continuous casting platform.

[0103] Example 1

[0104] In Example 1, molten steel with a ladle free space of 1000 mm after tapping from a converter for smelting Q355B in a 210t ladle refining furnace was selected to provide a method for increasing the scrap addition amount in the refining process. The steps are as follows:

[0105] S1-1. Select scrap with a length ≤ 600 mm and a thickness ≤ 200 mm, and use a baking and preheating device to heat the scrap to 800 °C.

[0106] S1-2. In LF refining, the mass of molten steel from the converter is 195t, 2t of hot continuous casting residue is poured in, the molten steel is heated to 1620 °C by power transmission for temperature rise, 9750 kg of baked scrap is added through the baking device while bottom-blowing argon, and then 390 kg of silicon-aluminum-calcium is added; the slag color turns into light yellow or light white, and the total iron content of the slag is 2.3%;

[0107] Among them, the temperature of the baked scrap entering the molten steel is 620 °C, the addition rate of the scrap is 1000 kg / min; the flow rate of bottom-blowing argon is 600 NL / min.

[0108] S1-3. In LF refining, the molten steel is heated to 1605 °C by power transmission for temperature rise, 9750 kg of baked scrap is added while bottom-blowing argon, and then 97.5 kg of aluminum blocks and 195 kg of silicon-aluminum-calcium are added to make a reducing slag;

[0109] Among them, the temperature of the baked scrap entering the molten steel is 800 °C, the addition rate of the scrap is 1500 kg / min; the flow rate of bottom-blowing argon is 600 NL / min.

[0110] S1-4. In LF refining, the molten steel is heated to 1600 °C by power transmission for temperature rise, 2925 kg of baked scrap is added while bottom-blowing argon, and 78 kg of aluminum blocks are added to make a reducing slag;

[0111] Among them, the temperature of the baked scrap entering the molten steel is 632 °C, the addition rate of the scrap is 1500 kg / min; the flow rate of bottom-blowing argon is 600 NL / min.

[0112] S1-5. In LF refining, for slag making and alloying treatment: Feed 351 m of pure calcium wire in the calcium treatment mode, the argon soft blowing time of the molten steel is 6 min, and the soft blowing flow rate is 100 NL / min.

[0113] Example 2

[0114] Example 2: Molten steel with a ladle free space of 1000 mm after tapping from a converter for smelting Q355B in a 210t ladle refining furnace was selected, and a method for increasing the scrap addition amount in the refining process was provided. The steps were basically the same as those in Example 1, except that:

[0115] Step S1-4 was not carried out.

[0116] Example 3

[0117] A method for increasing the scrap addition amount in the refining process provided in Example 3 had steps basically the same as those in Example 1, except that:

[0118] In step S1-1, a baking preheating device was used to heat the scrap to 600 °C.

[0119] In step S1-2, the scrap addition amount was 5850 kg, the temperature of the baked scrap entering the molten steel was 600 °C, the addition amount of calcium silicoaluminate was 195 kg, and the total iron content in the slag was 3.6%.

[0120] In step S1-3, the scrap addition amount was 3900 kg, and the temperature of the baked scrap entering the molten steel was 600 °C.

[0121] In step S1-4, the scrap addition amount was 3000 kg, and the temperature of the baked scrap entering the molten steel was 550 °C.

[0122] Example 4

[0123] A method for increasing the scrap addition amount in the refining process provided in Example 4 had steps basically the same as those in Example 1, except that:

[0124] In step S1-1, a baking preheating device was used to heat the scrap to 900 °C.

[0125] In step S1-2, the scrap addition amount was 8000 kg, the temperature of the baked scrap entering the molten steel was 800 °C, the addition amount of calcium silicoaluminate was 200 kg, and the total iron content in the slag was 2.5%.

[0126] In step S1-3, the scrap addition amount was 7590 kg, and the temperature of the baked scrap entering the molten steel was 800 °C.

[0127] In step S1-4, the scrap addition amount was 2470 kg, and the temperature of the baked scrap entering the molten steel was 750 °C.

[0128] Example 5

[0129] A method for increasing the scrap addition amount in the refining process provided in Example 5 had steps basically the same as those in Example 1, except that:

[0130] In step S1-1, a baking preheating device is used to heat the scrap steel to 1000°C.

[0131] In step S1-2, the addition amount of scrap steel is 9000 kg, the temperature of the baked scrap steel entering the molten steel is 900°C, the addition amount of calcium silicoaluminate is 300 kg, and the total iron content of the slag is 2.1%.

[0132] In step S1-3, the addition amount of scrap steel is 8000 kg, and the temperature of the baked scrap steel entering the molten steel is 900°C.

[0133] In step S1-4, the addition amount of scrap steel is 5850 kg, and the temperature of the baked scrap steel entering the molten steel is 800°C.

[0134] Example 6

[0135] In Example 6, the molten steel with a ladle clearance of 1200 mm after tapping from a converter for smelting Q235B is selected in a 100 t ladle refining furnace, and a method for increasing the addition amount of scrap steel in the refining process is provided. The steps are as follows:

[0136] S2-1. In LF refining, select scrap steel with a length ≤ 600 mm and a thickness ≤ 200 mm, and heat it to 900°C using a baking preheating device.

[0137] S2-2. In LF refining, the mass of the molten steel from the converter is 88 t, 1.5 t of hot continuous casting residue is poured in, the molten steel is heated to 1630°C by means of power supply for temperature rise, 4400 kg of baked scrap steel is added through a baking device while bottom-blowing argon, and then 132 kg of calcium silicoaluminate is added; the color of the slag turns into light white, and the total iron content of the slag is 2.8%;

[0138] Among them, the temperature of the baked scrap steel entering the molten steel is 900°C, the addition rate of the scrap steel is 1000 kg / min; the flow rate of bottom-blowing argon is 800 NL / min.

[0139] S2-3. In LF refining, the molten steel is heated to 1610°C by means of power supply for temperature rise, 4400 kg of baked scrap steel is added while bottom-blowing argon, and then 35.2 kg of aluminum blocks and 44 kg of calcium silicoaluminate are added to make a reducing slag;

[0140] Among them, the temperature of the baked scrap steel entering the molten steel is 660°C, the addition rate of the scrap steel is 1000 kg / min; the flow rate of bottom-blowing argon is 800 NL / min.

[0141] S2-4. In LF refining, the molten steel is heated to 1600°C by means of power supply for temperature rise, 1760 kg of baked scrap steel is added while bottom-blowing argon, and 35.2 kg of aluminum blocks are added to make a reducing slag;

[0142] Among them, the temperature of the baked scrap steel entering the molten steel is 532 °C, the addition rate of the scrap steel is 1000 kg / min; the flow rate of the bottom-blown argon gas is 800 NL / min.

[0143] S2-5. In LF refining, for slag-making alloying treatment: Feed pure calcium wire for 176 m in the calcium treatment mode, the soft blowing time of the molten steel with argon gas is 8 min, and the soft blowing flow rate is 150 NL / min.

[0144] Comparative Example 1

[0145] In Comparative Example 1, molten steel with a ladle free space of 1000 mm after tapping from a converter for smelting Q355B in a 210t ladle refining furnace was selected, and a method for LF refining was provided. The steps are as follows:

[0146] D1-1. Select scrap steel with a size length ≤ 600 mm and thickness ≤ 200 mm.

[0147] D1-2. In LF refining, the mass of the molten steel from the converter is 195t, pour 2t of hot continuous casting residue, heat the molten steel to 1580 °C by power supply heating, add 9750 kg of scrap steel while bottom-blowing argon gas, and then add 390 kg of calcium silicoaluminate; the color of the slag turns into light yellow or light white, and the total iron content of the slag is 2.3%.

[0148] Among them, the temperature of the scrap steel entering the molten steel is normal temperature (about 25 °C), the addition rate of the scrap steel is 1000 kg / min; the flow rate of the bottom-blown argon gas is 600 NL / min.

[0149] D1-3. In LF refining, heat the molten steel to 1590 °C by power supply heating, add 9750 kg of scrap steel while bottom-blowing argon gas, and then add 97.5 kg of aluminum blocks and 195 kg of calcium silicoaluminate to make a reducing slag.

[0150] Among them, the temperature of the scrap steel entering the molten steel is normal temperature (about 25 °C), the addition rate of the scrap steel is 1500 kg / min; the flow rate of the bottom-blown argon gas is 800 NL / min.

[0151] D1-4. In LF refining, heat the molten steel to 1590 °C by power supply heating, add 2925 kg of scrap steel while bottom-blowing argon gas, and add 78 kg of aluminum blocks to make a reducing slag.

[0152] Among them, the temperature of the scrap steel entering the molten steel is normal temperature (about 25 °C), the addition rate of the scrap steel is 1500 kg / min; the flow rate of the bottom-blown argon gas is 800 NL / min.

[0153] D1-5. In LF refining, for slag-making alloying treatment: Feed pure calcium wire for 351 m in the calcium treatment mode, with the soft blowing time of molten steel with argon being 6 min and the soft blowing flow rate being 100 NL / min.

[0154] Comparative Example 2

[0155] For Comparative Example 2, select the molten steel with a ladle free space of 1000 mm after tapping from the converter for smelting Q355B in a 210 t ladle refining furnace, and provide a method for LF refining, the steps are as follows:

[0156] D2-1. Select scrap steel with a size length ≤ 600 mm and a thickness ≤ 200 mm.

[0157] D2-2. In LF refining, the mass of the molten steel coming from the converter is 195 t, pour 2 t of hot continuous casting residue, heat the molten steel to 1610 °C by power supply for temperature rise, add 22.425 t (22425 kg) of scrap steel while bottom-blowing argon, and then add 390 kg of calcium silicoaluminate; the color of the slag turns into light yellow or light white, and the total iron content of the slag is 2.3%;

[0158] Among them, the temperature of the scrap steel entering the molten steel is normal temperature (about 25 °C), the addition rate of the scrap steel is 1000 kg / min; the flow rate of bottom-blowing argon is 600 NL / min.

[0159] D2-3. In LF refining, heat the molten steel to 1600 °C by power supply for temperature rise, and add 97.5 kg of aluminum block and 195 kg of calcium silicoaluminate to make a reducing slag.

[0160] D2-4. In LF refining, heat the molten steel to 1600 °C by power supply for temperature rise, and add 78 kg of aluminum block to make a reducing slag.

[0161] D2-5. In LF refining, for slag-making alloying treatment: Feed pure calcium wire for 351 m in the calcium treatment mode, with the soft blowing time of molten steel with argon being 6 min and the soft blowing flow rate being 200 NL / min.

[0162] In order to verify the progressiveness of the method for increasing the addition amount of scrap steel in the refining process provided by the embodiments of the present invention, calculate the single consumption of hot metal and the total amount of added scrap steel for the methods provided by the embodiments and comparative examples, and respectively detect the temperature change of the molten steel after adding scrap steel for deoxidation treatment, the first reducing slag-making treatment and the second reducing slag-making treatment; the results are shown in Table 1 below.

[0163] Table 1

[0164]

[0165]

[0166] Note: In Table 1, the temperature difference in deoxidation treatment = the molten steel temperature heated by power supply during the deoxidation step - the molten steel temperature after adding scrap steel; the temperature difference in the first reduction slag treatment = the molten steel temperature heated by power supply during the first reduction slag treatment - the molten steel temperature after adding scrap steel; the temperature difference in the second reduction slag treatment = the molten steel temperature heated by power supply during the second reduction slag treatment - the molten steel temperature after adding scrap steel.

[0167] At least the following conclusions can be drawn from Table 1 above:

[0168] The method for increasing the scrap steel addition amount in the refining process provided by the embodiment of the present invention adds scrap steel in multiple segments, which not only increases the scrap steel addition amount, reduces the unit consumption of hot metal, but also reduces the temperature difference generated by adding scrap steel, reduces the influence of adding scrap steel on the fluidity of molten steel, refining desulfurization, deoxidation, alloying, etc., and the surface quality of the prepared molten steel is good.

[0169] It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the technical solution scope of the present invention are included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A method for increasing the amount of scrap steel added in a refining process, characterized in that: The steps include: LF refining includes foaming slag, first reducing slag treatment and second reducing slag treatment; In making the foamed slag, first scrap steel is added to molten steel at a temperature above 1610°C; In the first reducing slag treatment, the second scrap steel is added to the molten steel at a temperature above 1600°C.

2. The method for increasing the amount of scrap steel added in the refining process according to claim 1, characterized in that: The temperature of the first scrap steel is above 500°C.

3. The method for increasing the amount of scrap steel added in the refining process according to claim 1 or 2, characterized in that: The amount of the first scrap steel added is 30kg / t to 50kg / t.

4. The method for increasing the amount of scrap steel added in the refining process according to any one of claims 1 to 3, characterized in that: The temperature of the second scrap steel is 500° C. or higher.

5. The method for increasing the amount of scrap steel added in the refining process according to any one of claims 1 to 4, characterized in that: The amount of the second scrap steel added is 20kg / t to 50kg / t.

6. The method for increasing the amount of scrap steel added in the refining process according to any one of claims 1 to 5, characterized in that: In the second reducing slag treatment, the third scrap steel is added to the molten steel at a temperature above 1600°C.

7. The method for increasing the amount of scrap steel added in the refining process according to claim 6, characterized in that: The temperature of the third scrap steel is above 500°C.

8. The method for increasing the amount of scrap steel added in the refining process according to any one of claims 1 to 7, characterized in that: The first scrap steel is added at a rate of 500 kg / min to 2000 kg / min; and / or, the adding rate of the second scrap steel is 500kg / min to 2000kg / min; And / or, the adding rate of the third scrap steel is 500kg / min to 2000kg / min.

9. The method for increasing the amount of scrap steel added in the refining process according to any one of claims 1 to 8, characterized in that: The LF refining also includes slag alloying treatment; In the slag alloying treatment, the pure calcium wire is fed in calcium treatment mode, and the argon soft blowing time of the molten steel is not less than 6 minutes.

10. Use of the method for increasing the amount of scrap steel added in the refining process as claimed in any one of claims 1 to 9 in the field of steel smelting.

Images