A method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel

Abstract

The invention provides a method for controlling slag overflow in a ladle during aluminum alloying of 38CrMoAl steel, which specifically comprises the following steps: adjusting the composition of alloy elements other than Al element to within the range of process requirements in a refining furnace at a later stage, and adjusting the argon flow rate of the ladle to (100-150) NL / min after the adjustment; immediately increasing the argon flow rate to (300-350) NL / min after an aluminum block is added to the ladle, performing a melting reaction for 4.5-5.5 minutes, adding fluorite during the reaction, and then immediately adjusting the argon flow rate to (50-100) NL / min, continuing to melt for 4.5-5.5 minutes, and then increasing the argon flow rate to (200-300) NL / min until the melting reaction is completed; compared with the prior art, the invention does not affect the output of a single furnace, and effectively solves the problem of slag overflow in the ladle during aluminum alloying of 38CrMoAl steel.

Description

Technical Field

[0001] The invention belongs to the field of alloy production, and in particular relates to a method for controlling slag overflow from a ladle during aluminum alloying of 38CrMoAl steel. Background Art

[0002] Alloy structural steel 38CrMoAl has high surface hardness, wear resistance and fatigue strength. It is often used to manufacture parts with special requirements and is widely used in the production of screws and sleeves for injection molding machines.

[0003] Although 38CrMoAl steel has a wide range of applications and a large market demand, there are relatively few domestic companies producing 38CrMoAl steel. The main reason is that 38CrMoAl steel has a high Al content of 0.9%-1.0%. On the one hand, it is easy to have flocculent problems during the casting process, resulting in poor product quality and high production costs; on the other hand, aluminum alloying is difficult during the smelting process, and there are certain process safety risks. Specifically, during aluminum alloying, a 1-ton (or other weight) aluminum wire / aluminum ingot is usually hoisted directly into the ladle by a crane. In this process, the melting of aluminum releases a large amount of heat and aluminum vapor, causing the refined steel slag in the ladle to suddenly overflow, which can damage the ladle trolley and cause production interruption, or even cause fires and casualties. For this process safety problem, major domestic steel companies have no permanent solution.

[0004] Some steel companies reduce the output of 38CrMoAl steel per furnace and increase the free space of the ladle (generally the free space is ≥600mm) to reduce the risk of refined slag overflowing from the ladle during aluminum alloying. However, this method will not only result in low output per furnace and increased production costs, but is also not suitable for the process route of converter-refining furnace-RH furnace-continuous casting, because the increase in the free space of the ladle will make it impossible to evacuate the RH furnace.

[0005] At present, the existing technology has not solved the problem that the output of a single furnace is low due to increasing the free space of the ladle and is not suitable for the process route of converter-refining furnace-RH furnace-continuous casting. Summary of the invention

[0006] The purpose of the present invention is to provide a method for controlling slag overflow from a ladle during aluminum alloying of 38CrMoAl steel, thereby solving the problem of slag overflow from a ladle during aluminum alloying of 38CrMoAl steel, reducing process safety risks, ensuring safe production of high-quality 38CrMoAl steel, and overcoming the problem of low output caused by the prior art. The present invention can also be applied to different production process routes of 38CrMoAl steel, overcoming the disadvantage that the prior art is not applicable to a process route of a converter-refining furnace-RH furnace-continuous casting.

[0007] The specific technical solutions of the present invention are as follows:

[0008] A method for controlling slag overflow from a ladle during aluminum alloying of 38CrMoAl steel, specifically comprising: in a refining furnace process, before adding aluminum blocks to the ladle for aluminum alloying, adjusting the argon flow rate of the ladle to (100-150) NL / min; after the aluminum blocks are added to the ladle, increasing the argon flow rate, performing a melting reaction for 4.5-5.5 minutes, adding fluorite during the reaction, reducing the argon flow rate, continuing to melt for 4.5-5.5 minutes, and increasing the argon flow rate until the melting reaction is completed;

[0009] Furthermore, after the aluminum block is added into the ladle, the argon flow rate is increased to (300-350) NL / min;

[0010] Furthermore, after the melting reaction for 4.5-5.5 min, the argon flow rate was reduced to (50-100) NL / min;

[0011] Furthermore, after continuing melting for 4.5-5.5 minutes, the argon flow rate was increased by (200-300) NL / min.

[0012] Further, the amount of fluorite added is controlled to be 0.42-0.83 kg / ton of steel fluorite;

[0013] Preferably, the method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel provided by the present invention is specifically as follows:

[0014] In the refining furnace process, before adding the aluminum block to the ladle, adjust the argon flow rate of the ladle, and the flow rate value is controlled at (100-150) NL / min, and the aluminum block is added during this period; after the aluminum block is added to the ladle, immediately adjust the argon flow rate to (300-350) NL / min, and the melting reaction is carried out for 5 minutes. During the melting reaction, 0.42-0.83 kg / ton of fluorite is added. After the melting reaction is completed for 5 minutes, immediately adjust the argon flow rate to (50-100) NL / min. After continuing the melting reaction for 5 minutes (after the 10th minute of the melting reaction), immediately adjust the argon flow rate to (200-300) NL / min until the melting reaction is completed.

[0015] Preferably, the method for controlling slag overflow from the ladle during aluminum alloying of 38CrMoAl steel comprises the following steps:

[0016] 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making;

[0017] 2) Refining furnace process: In the later stage of 38CrMoAl steel refining furnace, the composition of other alloy elements except Al element is adjusted to the range of process requirements. After the adjustment is completed, the argon flow rate of the ladle is adjusted to (100-150) NL / min, and the aluminum block is added at this flow rate. After the aluminum block is added to the ladle, the argon flow rate is immediately increased to (300-350) NL / min, and the melting reaction is 4.5-5.5 minutes. During this period, fluorite is added, and then the argon is immediately adjusted to (50-100) NL / min. After continuing to melt for 4.5-5.5 minutes, the argon flow rate is increased to (200-300) NL / min until the melting reaction is completed;

[0018] 3) RH furnace process.

[0019] In step 1), the processes of converter blowing, alloying and pre-slag making of 38CrMoAl steel are performed according to the high-quality steel process; it can be performed according to the high-quality steel process known in the art;

[0020] In step 2), the smelting process of the 38CrMoAl steel refining furnace in the front and middle stages can be performed according to conventional high-quality steel processes; it can be performed according to high-quality steel processes known in the art;

[0021] Step 2) The middle and front of the refining furnace are referred to as the white slag front; the late stage of the refining furnace is referred to as the white slag post;

[0022] In step 3), the RH furnace process is evacuated according to the conventional high-quality steel process, the evacuation time is 15 minutes, the ultimate vacuum pressure is ≤67 Pa, and after the evacuation is completed, the ladle is opened to the argon blowing position for soft blowing, the soft blowing time is not less than 30 minutes, and the soft blowing flow rate is 50-80NL / min. Execution according to the conventional high-quality steel process means that it can be executed according to the high-quality steel process known in the art.

[0023] Design principle of the present invention:

[0024] At the beginning of adding aluminum blocks into the ladle, since its density is smaller than that of molten steel, it floats on the molten steel, so the argon flow rate should be appropriately increased to promote its melting. As the melting cycle is prolonged, on the one hand, the aluminum blocks not only react with oxides (SiO2, FeO, etc.) in the slag and oxygen in the air to release a large amount of heat, as shown in formula 1-3; and the aluminum blocks melt rapidly, forming a large amount of aluminum vapor, which causes the slag to overflow instantly due to thermal expansion; on the other hand, in order to ensure the purity of 38CrMoAl steel liquid, the refined slag is high-basicity slag before the aluminum blocks are added. The specific composition is shown in Table 1. The high-basicity slag has a high viscosity, which further aggravates the slag overflow of the ladle after aluminum feeding; add an appropriate amount of fluorite at a large flow rate to obtain thin slag; after adding fluorite, the argon flow rate needs to be reduced; as the melting cycle exceeds 9-11min, the aluminum blocks are basically completely melted. In order to ensure the uniformity of the aluminum element composition, the argon flow rate needs to be increased to promote the circulation of the molten steel.

[0025] 2Al+3O=Al2O3 ΔG=-1632KJ / mol Formula 1

[0026] 4Al+3SiO2=2Al2O3+3Si ΔG=-668.58KJ / mol Formula 2

[0027] 2Al+3FeO=Al2O3+3Fe ΔG=-788.39KJ / mol Formula 3

[0028] Table 1 Refined steel slag components before aluminum addition / %

[0029] Substance name CaO Al2O3 SiO2 MgO FeO Binary Alkalinity(R) Other substances content / % 50-55 23-25 1-2 7-8 ≤1 25-55 9-18

[0030] Note: The basicity calculation formula is the ratio of CaO to SiO2.

[0031] Compared with the prior art, the present invention does not need to add additional process flow; moreover, the method of the present invention has a wide range of applications, does not affect the output of a single furnace, and effectively reduces production costs; the present invention effectively solves the problem of ladle slag overflow during aluminum alloying of 38CrMoAl steel, and eliminates production safety risks. The present invention effectively increases the output of a single furnace and reduces production costs; the standard furnace capacity output is 120-125 tons, the increase in the free space of the ladle is controlled at 600-800mm, the corresponding furnace capacity is 110-115 tons, and the furnace capacity output corresponding to the method of the present invention is 120-125 tons. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a picture of the ladle slag overflow site in comparative example 1;

[0033] Figure 2 This is a picture of the ladle slag overflow site in Scheme 1 of Comparative Example 2;

[0034] Figure 3 This is a picture of the ladle slag overflow site in Scheme 2 of Comparative Example 2;

[0035] Figure 4 This is a scene picture of the invention without slag overflow. DETAILED DESCRIPTION

[0036] Through the description of the embodiments, the specific implementation methods of the present invention are further explained in detail to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0037] The elements and mass percentages of the 38CrMoAl steel produced by the present invention are shown in Table 2. The remainder not shown in Table 2 is Fe and unavoidable impurities.

[0038] Table 2 Element content of 38CrMoAl steel (wt%)

[0039] C Si Mn P S Cr Mo Al 0.35-0.42 0.20-0.45 0.3-0.6 ≤0.02 ≤0.01 0.80-1.1 0.15-0.25 0.7-1.1

[0040] Example 1

[0041] A method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel, for 38CrMoAl steel produced on April 30, 2022, with one experimental heat, comprising the following steps:

[0042] 1) Converter process: The converter blowing, alloying and pre-slag making process of 38CrMoAl steel shall be carried out in accordance with the conventional high-quality special steel process; the following details shall be noted in the setting of the process plan: 1) Before tapping the converter of a single batch, a certain amount of recarburizer shall be added to the ladle, and the carbon deoxidation process may be used to reduce the free oxygen content in the molten steel; 2) For the types of alloys required for alloying after the converter, only high-carbon ferromanganese alloy, high-carbon ferrochromium alloy and ferromolybdenum alloy can be used for this type of steel; 3) The deoxidizer used in the converter tapping process is only aluminum iron (or aluminum block). After tapping is completed, a certain amount of aluminum wire may be added at the argon blowing position to ensure that the Al content in the molten steel is between 0.06% and 0.08% before entering the refining furnace.

[0043] 2) Refining furnace process: The smelting process of 38CrMoAl steel refining furnace before and during the middle stage (generally referred to as before white slag) can be executed according to the conventional high-quality steel process; but it is necessary to pay attention to the setting of the process plan: ① Before white slag, there is no need to add aluminum wire; ② The types of deoxidizers required for smelting before white slag are 90 carbon powder and aluminum particles, and no Si-containing materials are allowed to be added; ③ Before white slag, it is necessary to ensure that the content of alloy elements other than Al and Si elements meets the process requirements.

[0044] In the later stage of 38CrMoAl steel refining furnace, the alloying elements except Al element are adjusted to the range of process requirements. After the adjustment, the argon flow rate of the ladle is adjusted to 120NL / min; after the aluminum block is added to the ladle, the argon flow rate is immediately increased to 330NL / min, and the melting reaction is 5min. During this period, 60 kg of fluorite is added, and the argon is immediately adjusted to 50NL / min. At the same time, after the melting reaction for 5min (the 10th minute of the whole melting), the argon is immediately adjusted to 250NL / min until the melting reaction is completed. From the tracking situation, there is no slag overflow from the ladle during the aluminum alloying process.

[0045] 3) RH furnace process: The RH furnace vacuum process is carried out according to the conventional high-quality steel process. The vacuum time is 15 minutes and the ultimate vacuum pressure is ≤67 Pa. After the vacuum is completed, the ladle is opened to the argon blowing position for soft blowing. The soft blowing time is not less than 30 minutes and the soft blowing flow rate is 50-80NL / min.

[0046] Example 2

[0047] A method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel, which is 38CrMoAl steel produced on May 23, 2022, with 3 experimental heats, comprising the following steps:

[0048] 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making process are performed according to conventional high-quality special steel process; same as step 1 of Example 1;

[0049] 2) Refining furnace process: The smelting process of the front and middle stages of the 38CrMoAl steel refining furnace can be performed according to the conventional high-quality special steel process; the same as step 2 of Example 1;

[0050] In the later stage of 38CrMoAl steel refining furnace, the alloying elements except Al element are adjusted to the range of process requirements. After the adjustment, the flow value is controlled at 140NL / min. After the aluminum block is added to the ladle, the argon flow rate is immediately adjusted to 350NL / min, and the argon is immediately adjusted to 70NL / min after 5 minutes of melting reaction. At the same time, 80 kg of fluorite is added, and the argon is immediately adjusted to 260NL / min after 5 minutes of melting reaction (the 10th minute of the whole melting) until the melting reaction is completed. From the tracking situation, there is no slag overflow from the ladle during the aluminum alloying process.

[0051] 3) RH furnace process: The RH furnace vacuuming process is performed according to the conventional high-quality steel process. After the vacuuming is completed, the ladle is opened to the argon blowing position for soft blowing, and the soft blowing time is not less than 30 minutes; the same as step 3 of Example 1).

[0052] The above 3 furnaces are controlled in the same way.

[0053] Example 3

[0054] A method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel, for 38CrMoAl steel produced on June 4, 2022, with 10 experimental heats (full pouring times), comprising the following steps:

[0055] 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making process are performed according to conventional high-quality special steel process; same as step 1 of Example 1;

[0056] 2) Refining furnace process: The smelting process of the front and middle stages of the 38CrMoAl steel refining furnace can be performed according to the conventional high-quality special steel process; the same as step 2 of Example 1;

[0057] In the later stage of the 38CrMoAl steel refining furnace, the composition of other alloy elements except Al element is adjusted to the range of process requirements. After the adjustment is completed, the argon flow rate of the ladle is adjusted, and the flow value is controlled at (100-150) NL / min; after the aluminum block is added to the ladle, the argon flow rate is immediately adjusted to (300-350) NL / min, and the melting reaction is 5 minutes. During the melting reaction, 0.42-0.83 kg / ton of steel fluorite is added, and then the argon is immediately adjusted to (50-100) NL / min. After the melting reaction is 5 minutes (the 10th minute of the entire melting), the argon is immediately adjusted to (200-300) NL / min until the melting reaction is completed. Step 2) The specific adjustment parameters of each furnace are shown in Table 3 below.

[0058] 3) RH furnace process: The RH furnace vacuum process is performed according to the conventional high-quality steel process. After the vacuum is completed, the ladle is opened to the argon blowing position for soft blowing, and the soft blowing time is not less than 30 minutes. Same as step 3 of Example 1;

[0059] Table 3 Specific parameters of step 2) of each heat of Example 3

[0060]

[0061]

[0062] From the tracking situation, no slag overflow from the ladle occurred during the aluminum alloying process of the above 10 furnaces.

[0063] Comparative Example 1

[0064] Before the scheme of the present invention is proposed, 38CrMoAl steel is produced during January-February 2022, with 35 production heats, including the following steps:

[0065] 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making process are performed according to conventional high-quality special steel process; same as step 1 of Example 1;

[0066] 2) Refining furnace process: The smelting process of the front and middle stages of the 38CrMoAl steel refining furnace can be performed according to the conventional high-quality special steel process; the same as step 2 of Example 1;

[0067] In the later stage of 38CrMoAl steel refining furnace, the alloying elements except Al are adjusted to the process requirements, and then the aluminum block is added to the ladle to adjust the Al content. From the addition of the aluminum block to the complete melting of the aluminum block, there is no special requirement for the argon flow control of the ladle. Generally, the argon flow value is controlled at (300-500) NL / min, and fluorite is not added during the addition of the aluminum block. The specific adjustment parameters are shown in Table 4

[0068] 3) RH furnace process: The RH furnace vacuuming process is performed according to the conventional high-quality steel process. After the vacuuming is completed, the ladle is opened to the argon blowing position for soft blowing, and the soft blowing time is not less than 30 minutes; the same as step 3 of Example 1).

[0069] Comparative Example 1 has serious slag overflow.

[0070] Table 4 Comparative Example 1 Step 2) Process Parameters

[0071]

[0072]

[0073]

[0074] Comparative Example 2

[0075] After the technical route shown in the present invention was proposed, during the production of 38CrMoAl steel on March 7 and March 15, 2022, experiments were conducted on the flow rate of argon gas and the amount of fluorite added at different times. The main schemes are divided into two schemes. From the experimental results, according to scheme one, the ladle slag overflow was serious after the aluminum block was added, and the effect was not obvious; according to scheme two, the ladle slag overflow was alleviated after the aluminum block was added, but the slag overflow phenomenon still existed. The specific situation is as follows:

[0076] Scheme 1: The argon flow rate at different times is implemented according to the original scheme, and the amount of fluorite added is 0.42-0.83 kg / ton of steel;

[0077] Specific process steps of scheme 1:

[0078] 1) Converter process: The converter blowing, alloying and pre-slag making process of 38CrMoAl steel is performed according to the conventional high-quality special steel process; the same as step 1 of Example 1;

[0079] 2) Refining furnace process: The smelting process of the front and middle stages of the 38CrMoAl steel refining furnace can be performed according to the conventional high-quality special steel process; the same as step 2 of Example 1;

[0080] In the later stage of 38CrMoAl steel refining furnace, the alloying elements other than Al are adjusted to the process requirements, and then the aluminum block is added to the ladle to adjust the Al content. From the addition of the aluminum block to the complete melting of the aluminum block, there is no special requirement for the argon flow control of the ladle. Generally, the argon flow value is controlled at (300-500) NL / min, and fluorite is added during the addition of the aluminum block. The specific adjustment parameters are shown in Table 5.

[0081] 3) RH furnace process: The RH furnace vacuuming process is performed according to the conventional high-quality steel process. After the vacuuming is completed, the ladle is opened to the argon blowing position for soft blowing, and the soft blowing time is not less than 30 minutes; the same as step 3 of Example 1;

[0082] Table 5 Parameter control of step 2) in scheme 1 of comparative example 2

[0083]

[0084] According to the implementation situation at the site, in Plan 1, the ladle had serious slag overflow after the aluminum block was added.

[0085] Solution 2: The argon flow rate at different times is implemented according to the solution described in the present invention, and fluorite is not added during the process

[0086] 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making process are performed according to conventional high-quality special steel process; same as step 1 of Example 1;

[0087] 2) Refining furnace process: The smelting process of the front and middle stages of the 38CrMoAl steel refining furnace can be performed according to the conventional high-quality special steel process; the same as step 2 of Example 1;

[0088] In the later stage of 38CrMoAl steel refining furnace, the alloying elements except Al element are adjusted to the range of process requirements. After the adjustment, the argon flow rate of the ladle is adjusted, and the flow value is controlled at (100-150) NL / min; after the aluminum block is added to the ladle, the argon flow rate is immediately adjusted to (300-350) NL / min, and the melting reaction is 5 minutes, and then the argon is immediately adjusted to (50-100) NL / min, and the melting reaction is 5 minutes (the 10th minute of the whole melting), and then the argon is immediately adjusted to (200-300) NL / min until the melting reaction is completed. Fluorite is not added during the melting reaction. The specific adjustment parameters of each furnace are shown in Table 6 below.

[0089] 3) RH furnace process: The RH furnace vacuuming process is performed according to the conventional high-quality steel process. After the vacuuming is completed, the ladle is opened to the argon blowing position for soft blowing, and the soft blowing time is not less than 30 minutes; the same as step 3 of Example 1;

[0090] Table 6 Parameter control of step 2) in scheme 2 of comparative example 2

[0091]

[0092] On-site implementation of Plan 2 showed that slag overflow from the ladle was alleviated after the addition of aluminum blocks, but slag overflow still existed.

[0093] The present invention is described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for controlling ladle slag overflow during aluminum alloying of 38CrMoAl steel, characterized in that: The method is specifically as follows: in a refining furnace process, before adding aluminum blocks to a ladle for aluminum alloying, adjusting the argon flow rate of the ladle to (100-150) NL / min; after adding the aluminum blocks to the ladle, increasing the argon flow rate to (300-350) NL / min, and performing a melting reaction for 4.5-5.5 minutes, during which fluorite is added, and the amount of fluorite added is controlled to be 0.42-0.83 kg / ton of steel of fluorite, then reducing the argon flow rate to (50-100) NL / min, continuing to melt for 4.5-5.5 minutes, and then increasing the argon flow rate to (200-300) NL / min until the melting reaction is completed.

2. The method according to claim 1, characterized in that In the refining furnace process, before adding the aluminum block to the ladle, adjust the argon flow rate of the ladle, and the flow rate value is controlled at (100-150) NL / min, and add the aluminum block during the process; after the aluminum block is added to the ladle, immediately adjust the argon flow rate to (300-350) NL / min, and the melting reaction is carried out for 5 minutes. During the melting reaction, 0.42-0.83 kg / ton of steel fluorite is added. After the melting reaction is completed for 5 minutes, immediately adjust the argon to (50-100) NL / min. After continuing the melting reaction for 5 minutes, immediately adjust the argon to (200-300) NL / min until the melting reaction is completed.

3. The method according to claim 1, characterized in that The method for controlling slag overflow from a ladle during aluminum alloying of 38CrMoAl steel comprises the following steps: 1) Converter process: 38CrMoAl steel converter blowing, alloying and pre-slag making; 2) Refining furnace process: In the later stage of 38CrMoAl steel refining furnace, the composition of other alloy elements except Al element is adjusted to the range of process requirements. After the adjustment is completed, the argon flow rate of the ladle is adjusted to (100-150) NL / min, and the aluminum block is added at this flow rate. After the aluminum block is added to the ladle, the argon flow rate is immediately increased to (300-350) NL / min, and the melting reaction is 4.5-5.5 minutes. During this period, fluorite is added, and then the argon is immediately adjusted to (50-100) NL / min. After continuing to melt for 4.5-5.5 minutes, the argon flow rate is increased to (200-300) NL / min until the melting reaction is completed; 3) RH furnace process.

4. The method according to claim 1, characterized in that: In step 3), the RH furnace process is evacuated, the evacuation time is 15 minutes, and the ultimate vacuum pressure is ≤67 Pa.

5. The method according to claim 4, characterized in that In step 3), after the vacuuming is completed, the ladle is opened to the argon blowing position for soft blowing, the soft blowing time is not less than 30 minutes, and the flow rate of the soft blowing is (50-80) NL / min.

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