Cutting method for mixed casting blanks of different steel types

Abstract

The invention relates to the technical field of hot-rolled wide and thick plate different-steel-grade continuous casting, in particular to a cutting method for a different-steel-grade mixed casting blank. The method comprises the steps that continuous casting is conducted on different steel grades in a constant pulling speed mode, and the starting point position and the final point position of a mixed casting blank are judged by calculating time; wherein the different steel types comprise the first steel type and the second steel type; the continuous casting sequence of the first steel grade and the second steel grade is adjusted according to the planned cutting length of the continuous casting billets of the first steel grade and the second steel grade; and according to the planned cutting length of the continuous casting billets of the first steel grade and the second steel grade, the cutting mode of the mixed casting billet is adjusted. The technical problem that the cutting effect of existing mixed casting blanks of different steel types is poor is solved.

Description

Technical Field

[0001] The present application relates to the technical field of continuous casting of hot-rolled wide and thick plates with different steel grades, and in particular to a method for cutting mixed billets with different steel grades. Background Art

[0002] With the development of modern continuous casting technology, continuous casting of different steel grades, known as heterogeneous steel grade continuous casting, is often used to improve production efficiency and yield rates. This process produces a large number of mixed billets. Since wide and thick slabs are produced in a wide variety of varieties with significant variations in alloy composition, and heterogeneous steel grade continuous casting is performed frequently, mixed billets are very likely to be produced during the continuous casting process. The presence of mixed billets has a significant impact on the yield rate of continuous casting slabs. Furthermore, during the continuous casting process, to meet orders and the needs of the next process, the billets must be cut into slabs of a certain length, a process known as continuous casting slab cutting. Because continuous casting is a continuous process, the mixed billets produced during the production process need to be rescheduled to ensure that those slabs that do not meet the composition requirements are removed after they are removed from the production line. This ensures that order requirements are met to the greatest extent possible while minimizing the production of mixed billets.

[0003] Currently, most steel mills use cutting rules based on continuous casting information, slab temperature information, slab weight, and a preset target slab weight and length to determine the slab weight deviation. However, this results in a certain weight loss and reduces the yield rate. Furthermore, this method increases the number of mixed slabs and the overall length of the mixed slab when used on mixed steel grades, which in turn reduces the yield rate. Therefore, a more accurate method for cutting continuous casting slabs during mixed casting of different steel grades is urgently needed. Summary of the Invention

[0004] The present application provides a method for cutting mixed billets of different steel grades, so as to solve the technical problem that the existing cutting effect of mixed billets of different steel grades is poor.

[0005] In a first aspect, the present application provides a method for cutting a mixed billet of different steel grades, the method comprising:

[0006] Continuously casting different steel grades using a constant casting speed method, and determining the starting position and the end position of the mixed casting blank by calculating the time; wherein the different steel grades include a first steel grade and a second steel grade;

[0007] Adjusting the continuous casting sequence of the first steel grade and the second steel grade by cutting the continuous casting slabs of the first steel grade and the second steel grade to a planned length;

[0008] The cutting mode of the mixed cast slab is adjusted according to the planned cutting lengths of the continuous cast slabs of the first steel grade and the second steel grade.

[0009] Optionally, the time corresponding to the starting position of the mixed casting blank satisfies the following relationship:

[0010] F(t)=H / V*60+T1

[0011] H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T1 represents the mixing time of the different steel grades of molten steel in the tundish corresponding to the starting position of the mixed casting, s.

[0012] Optionally, the time corresponding to the end position of the mixed casting blank satisfies the following relationship:

[0013] F(t)=H / V*60+T2

[0014] H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T2 represents the mixing time of different steel grade molten steel in the tundish corresponding to the end position of the mixed casting, s.

[0015] Optionally, the pulling speed is 0.65-0.95 m / min.

[0016] Optionally, adjusting the continuous casting sequence of the first steel grade and the second steel grade according to the planned cutting lengths of the continuous casting slabs of the first steel grade and the second steel grade includes:

[0017] When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab,

[0018] The second steel grade is then placed in the first heat during continuous casting;

[0019] The heat of the first steel grade is arranged in the next heat.

[0020] Optionally, the adjusting the cutting mode of the mixed-cast slab according to the planned cutting lengths of the continuous-cast slabs of the first steel grade and the second steel grade includes:

[0021] When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab,

[0022] Setting the starting point of the mixed casting billet at the head of the continuous casting billet;

[0023] The end point of the mixed casting billet is set at the tail position of the continuous casting billet for cutting.

[0024] Optionally, the starting position and the ending position of the mixed casting blank cutting satisfy the following relationship:

[0025]

[0026] Where S 混 is the total length of the mixed casting, m; S 混1is the length of the first mixed casting, m; S 混2 is the length of the second mixed casting, m; S 混n is the length of the last mixed casting, m; S 坯头 is the position of the head of the continuous casting billet where the mixed casting billet starts, m; S 坯尾 is the tail position of the continuous casting billet where the mixed casting billet starts, m; S 混开始 is the starting position of the mixed casting, m; S 混结束 is the end position of the mixed casting, m.

[0027] Optionally, during the continuous casting process, the weight of the molten steel in the tundish is 20-100t.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The cutting method of the mixed billets of different steel grades provided in the embodiment of the present application adopts time as the criterion to optimize the cutting rules and casting sequence in the continuous casting process of different steel grades, thereby achieving accurate cutting of the mixed billets produced in the production process of wide and thick plate continuous casting slabs of different steel grades, reducing the number of mixed billet blocks and the overall length of the mixed billets, and achieving the shortest overall length of the mixed billets, thereby maximizing the yield rate of the continuous casting slabs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 A schematic flow chart of a method for cutting a mixed billet of different steel grades provided in an embodiment of the present application;

[0033] Figure 2 A schematic diagram of the position of the starting point for cutting a mixed casting blank provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0036] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0038] In the first aspect, the present application provides a method for cutting mixed billets of different steel grades, see Figure 1 , the method comprising:

[0039] S1. Continuously casting different steel grades using a constant casting speed, and determining a starting position and an end position of a mixed casting blank by calculating time; wherein the different steel grades include a first steel grade and a second steel grade;

[0040] In some embodiments, the time corresponding to the starting position of the mixed casting blank satisfies the following relationship:

[0041] F(t)=H / V*60+T1

[0042] H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T1 represents the mixing time of different steel grade molten steel in the tundish corresponding to the starting position of the mixed casting, s.

[0043] H / V*60 represents the time it takes for the molten steel to travel from the mold to the cutting point of the continuous casting billet. The time corresponding to the starting position of the mixed billet satisfies the positive effect of the above relationship: the starting position of the mixed billet can be accurately determined.

[0044] In some embodiments, the time corresponding to the end position of the mixed casting blank satisfies the following relationship:

[0045] F(t)=H / V*60+T2

[0046] H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T2 represents the mixing time of different steel grade molten steel in the tundish corresponding to the end position of the mixed casting, s.

[0047] The positive effect of the time corresponding to the end position of the mixed casting blank satisfying the above relationship is that the starting position of the mixed casting blank can be accurately determined.

[0048] In some embodiments, the pulling speed is 0.65-0.95 m / min.

[0049] The positive effect of using constant casting speed to continuously cast different steel grades is to avoid the influence of variable casting speed and liquid level changes on the mixing casting process.

[0050] The positive effect of controlling the casting speed to 0.65-0.95 m / min is that it can accurately cover the casting speed range of medium and thick plate continuous casting. Specifically, the casting speed can be 0.65 m / min, 0.85 m / min, 0.95 m / min, etc.

[0051] S2. Adjusting the continuous casting sequence of the first steel grade and the second steel grade according to the planned cutting lengths of the continuous casting slabs of the first steel grade and the second steel grade;

[0052] In some embodiments, adjusting the continuous casting sequence of the first and second steel grades according to the planned cutting lengths of the continuous casting slabs of the first and second steel grades includes:

[0053] When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab,

[0054] The second steel grade is then placed in the first heat during continuous casting;

[0055] The heat of the first steel grade is arranged in the next heat.

[0056] The positive effect of setting the above continuous casting sequence is that the length of the cut mixed billet is minimized.

[0057] S3. Adjusting a cutting mode of the mixed cast slab according to the planned cutting lengths of the continuous cast slabs of the first steel grade and the second steel grade.

[0058] In some embodiments, adjusting the cutting mode of the mixed-cast slab according to the planned cutting lengths of the continuous-cast slabs of the first and second steel grades includes:

[0059] When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab,

[0060] Setting the starting point of the mixed casting billet at the head of the continuous casting billet;

[0061] The end point of the mixed casting billet is set at the tail position of the continuous casting billet for cutting.

[0062] The positive effect of setting the above cutting mode is to minimize the length of the cut mixed billet.

[0063] In some embodiments, the starting position and the ending position of the mixed casting blank cutting satisfy the following relationship:

[0064]

[0065] Where S 混 is the total length of the mixed casting, m; S 混1 is the length of the first mixed casting, m; S 混2 is the length of the second mixed casting, m; S 混n is the length of the last mixed casting, m; S 坯头 is the position of the head of the continuous casting billet where the mixed casting billet starts, m; S 坯尾 is the tail position of the continuous casting billet where the mixed casting billet starts, m; S 混开始 is the starting position of the mixed casting, m; S 混结束 is the end position of the mixed casting, m.

[0066] The exact position of the starting point and the end point after the mixed casting solidifies is used as the basis for the length of the continuous casting billet where the starting point and the end point are located. That is, the starting point after the mixed casting solidifies needs to be closer to the head position of the continuous casting billet where the starting point and the end point of the mixed casting solidify need to be closer to the tail position of the continuous casting billet where the end point is located after the mixed casting solidifies, so as to ensure the shortest length of the mixed casting billet. Figure 2 The schematic diagram of the position of the starting point for cutting the mixed billet is shown. The position of the starting point for cutting the mixed billet must satisfy the above relationship.

[0067] In some embodiments, during the continuous casting process, the weight of the molten steel in the tundish is 20-100t.

[0068] The positive effect of controlling the weight of the molten steel in the tundish to 20-100 tons is that it covers the vast majority of tundish volumes, and the determination is most accurate within this volume range. Specifically, the weight of the molten steel in the tundish can be 20 tons, 60 tons, 100 tons, etc.

[0069] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0070] Example 1

[0071] An industrial experiment of continuous casting of different steel grades was carried out on a slab continuous casting machine in a certain steel plant. The initial weight of the molten steel in the tundish was 20 tons, the production process was converter + RH refining + continuous casting, the continuous casting steel grades were Q345 and D36, the slab thickness was 300mm, the width was 2000mm, the pulling speed was 0.95m / min, and the metallurgical length was 31m. The numerical simulation method was used to calculate the mixing time of the molten steel of different steel grades in the tundish corresponding to the starting position and the end position of the mixed billet: T1 was 450s and T2 was 840s. The length of the Q345 continuous casting billet before cutting was 2.8m in three pieces, 3.2m in 7 pieces, and a total of 10 pieces. The length of the D36 continuous casting billet after cutting was 4.5m in all, and a total of 7 pieces. The mixed billet cutting method was determined as follows:

[0072] (1) In the process of continuous casting of different steel grades, the time t is used to accurately determine the starting point and end point of the solidification of the mixed casting billet of different steel grades for medium and thick plates, where t needs to meet the following requirements: F(t) = H / V*60+T1

[0073] According to the above formula, the starting time of the solidification of the mixed casting in the process of continuous casting of different steel grades is

[0074] F(tstart) = 31 / 0.95*60+450 = 2407.9s, i.e., 2407.9s after the second heat of molten steel enters the tundish is the starting point of the solidification of the mixed billet;

[0075] The time to the end point after the mixed billet solidifies during the continuous casting of different steel grades is F(t)=H / V*60+T2

[0076] F(tstart) = 31 / 0.95*60+840 = 2797.9s, i.e. the end point of the mixed billet after solidification is 2797.9s after the second heat of molten steel starts to enter the tundish;

[0077] (2) Optimization of casting sequence: Since the planned lengths of the continuous casting slabs after cutting are different before and after the mixed casting of different steel grades, the heat Q345 with the shorter continuous casting slab length after cutting is arranged in the first heat during continuous casting, and the next heat of different steel grades is the heat D36 with the longer continuous casting slab length after cutting;

[0078] (3) Optimization of cutting mode: The exact positions of the starting point and the end point after the solidification of the mixed billet are used as the basis for the length of the continuous casting billet where the starting point and the end point are located. That is, the starting point after the solidification of the mixed billet needs to be closer to the head position of the continuous casting billet where the starting point and the end point of the mixed billet are located after the solidification of the mixed billet need to be closer to the tail position of the continuous casting billet where the end point is located after the solidification of the mixed billet. To ensure that the length of the mixed billet is the shortest, the starting point position of the mixed billet cutting must meet the following conditions:

[0079]

[0080] The numerical simulation results show that the length of the first mixed casting blank at the beginning of mixing is Smix1 = 2.8m; Smix2 = 2.8m; Smixend is the end position of the mixed casting blank, that is, the length of the last mixed casting blank is Smixn = 4.5m; from this, it can be seen that the total length of the mixed casting blank is Smix = 10.1m.

[0081] Example 2

[0082] An industrial experiment of continuous casting of different steel grades was carried out on a single-strand slab continuous casting machine in a steel plant. The initial weight of the tundish steel liquid was 100 tons, the production process was converter + RH refining + continuous casting, the continuous casting steel grades were X65 and E36, the slab thickness was 400mm, the width was 2000mm, the pulling speed was 0.65m / min, and the metallurgical length was 33.2m. The numerical simulation method was used to calculate the mixing time of the tundish steel liquid of different steel grades corresponding to the starting position and the end position of the mixed casting billet: T1 was 670s and T2 was 1730s. The length of the X65 continuous casting billet before cutting was 3.2m, totaling 10 pieces. The length of the E36 continuous casting billet after cutting was 3.8m for 2 pieces and 4.5m for 6 pieces, totaling 8 pieces. The mixed casting billet cutting method was determined as follows:

[0083] (1) In the process of continuous casting of different steel grades, the time t is used to accurately determine the starting point and end point of the solidification of the mixed casting billet of different steel grades for medium and thick plates, where t needs to meet the following requirements: F(t) = H / V*60+T1

[0084] The starting time of the solidification of the mixed billet during the continuous casting of different steel grades is

[0085] F(tstart) = 33.2 / 0.65*60+670 = 3734.6s, i.e., 3734.6s after the second heat of molten steel enters the tundish is the starting point of the solidification of the mixed billet;

[0086] The time to the end point after the mixed billet solidifies during the continuous casting of different steel grades is F(t)=H / V*60+T2

[0087] F(tstart) = 33.2 / 0.65*60+1730 = 4794.6s, i.e. the end point of the mixed billet after solidification is 4794.6s after the second heat of molten steel starts to enter the tundish;

[0088] (2) Optimization of casting sequence: Since the planned lengths of the continuous casting slabs after cutting are different before and after the mixed casting of different steel grades, the heat X65 with a shorter continuous casting slab length after cutting is arranged as the first heat during continuous casting, and the next heat of different steel grades is the heat E36 with a longer continuous casting slab length after cutting;

[0089] (3) Optimization of cutting mode: The exact positions of the starting point and the end point after the solidification of the mixed billet are used as the basis for the length of the continuous casting billet where the starting point and the end point are located. That is, the starting point after the solidification of the mixed billet needs to be closer to the head position of the continuous casting billet where the starting point and the end point of the mixed billet are located after the solidification of the mixed billet need to be closer to the tail position of the continuous casting billet where the end point is located after the solidification of the mixed billet. To ensure that the length of the mixed billet is the shortest, the starting point position of the mixed billet cutting must meet the following conditions:

[0090]

[0091] The numerical simulation results show that the length of the first mixed casting blank at the beginning of mixing is Smix1 = 3.2m; Smix2 = 3.2m; Smix3 = 3.2m; Smixend is the end position of the mixed casting blank, that is, the length of the last mixed casting blank is Smixn = 3.8m; from this, it can be seen that the total length of the mixed casting blank is Smix = 13.4m.

[0092] Example 3

[0093] An industrial experiment of continuous casting of different steel grades was conducted on a single-strand slab continuous caster in a steel plant. The initial weight of the molten steel in the tundish was 70 tons.

[0094] The production process route is converter + RH refining + continuous casting, the continuous casting steel grades are X65 and E36, the slab thickness is 400mm, the width is 2000mm, the drawing speed is 0.65m / min, the metallurgical length is 33.2m, and after the mixed casting starts, it is determined that the first two pieces are mixed castings of 3.2m in length and 6.4m in length, and the last two pieces are mixed castings of 9m in length. The total length of the mixed castings is 15.4m.

[0095] Through the method of the embodiment of the present application, the length of the mixed casting is minimized. At the same time, since time is used as the criterion, the deviation caused by factors such as weight and length is reduced, thereby improving the yield rate.

[0096] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for cutting a mixed cast billet of different steel grades, characterized in that: The method comprises: The different steel grades are continuously casted by a constant casting speed, and the starting position and the end position of the mixed casting are determined by calculating the time; wherein the different steel grades include a first steel grade and a second steel grade; According to the planned cutting length of the continuous casting slabs of the first steel grade and the second steel grade, the continuous casting sequence of the first steel grade and the second steel grade is adjusted; The cutting mode of the mixed casting billet is adjusted according to the planned cutting lengths of the continuous casting billets of the first steel grade and the second steel grade.

2. The method according to claim 1, characterized in that The time corresponding to the starting position of the mixed casting blank satisfies the following relationship: F(t)=H / V*60+T1 H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T1 represents the mixing time of the molten steel of different steel grades in the tundish corresponding to the starting position of the mixed casting, s.

3. The method according to claim 1, characterized in that The time corresponding to the end position of the mixed casting blank satisfies the following relationship: F(t)=H / V*60+T2 H represents the metallurgical length of the slab continuous casting machine, m; V represents the casting speed, m / min; T2 represents the mixing time of the molten steel of different steel grades in the tundish corresponding to the end position of the mixed casting, s.

4. The method according to claim 1, characterized in that The pulling speed is 0.65-0.95 m / min.

5. The method according to claim 1, characterized in that According to the planned cutting length of the continuous casting slabs of the first steel grade and the second steel grade, the continuous casting sequence of the first steel grade and the second steel grade is adjusted, including: When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab, The second steel grade is placed in the first furnace during continuous casting; The heat of the first steel grade is arranged in the next heat.

6. The method according to claim 1, characterized in that The planned cutting lengths of the continuous casting billets of the first steel grade and the second steel grade are adjusted according to the cutting mode of the mixed casting billet, including: When the planned cutting length of the first steel grade continuous casting slab is greater than the planned cutting length of the second steel grade continuous casting slab, The starting point of the mixed casting billet is set at the head of the continuous casting billet; The end point position of the mixed casting billet is set at the tail position of the continuous casting billet for cutting.

7. The method according to claim 6, characterized in that The starting point and end point of the mixed casting blank cutting satisfy the following relationship: In the formula, S 混 is the total length of the mixed casting, m; S 混1 is the length of the first mixed casting, m; S 混2 is the length of the second mixed casting, m; S 混n is the length of the last mixed casting, m; S 坯头 is the position of the head of the continuous casting billet where the mixed casting billet starts, m; S 坯尾 is the tail position of the continuous casting billet where the mixed casting billet starts, m; S 混开始 is the starting position of the mixed casting, m; S 混结束 is the final position of the mixed casting, m.

8. The method according to claim 1, characterized in that During the continuous casting process, the weight of the molten steel in the tundish is 20-100t.

Images