Dual-phase steel crack control method

Abstract

The invention provides a dual-phase steel crack control method. The dual-phase steel crack control method comprises the following steps that molten steel is cast; the casting process in the casting process comprises multi-section acceleration; the acceleration of each section in the multi-section acceleration process is independently 0.18 m / min < 2 > to 0.22 m / min < 2 >; the casting stopping process in the casting process comprises a deceleration process and an acceleration process; the acceleration in the deceleration process is 0.4 m / min < 2 >-0.6 m / min < 2 >; the acceleration of the acceleration process is 0.2 m / min < 2 > to 0.3 m / min < 2 >. According to the method, the accelerated speed of the casting process and the accelerated speed of the casting stopping process in the casting process are controlled, so that the time of the casting process is controlled, the low pulling speed time is shortened, and transverse cracks of the tail blank are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of steel smelting, and in particular to a method for controlling cracks in dual-phase steel. Background Art

[0002] Dual-phase steel is currently the most widely used high-strength automotive steel plate. It is an important material for the automotive industry to achieve lightweight body. It is widely used in automotive side beams, side members, cross beams, pillars, chassis reinforcements, fuel tank brackets and body structural parts, reinforcements and anti-collision parts. It has low yield strength ratio and high elongation characteristics.

[0003] However, when steel mills produce duplex steel, severe transverse cracks often appear on the wide surface of the head and tail ingots. The characteristics of the transverse cracks on the wide surface of the head and tail are:

[0004] 1) Location: It mainly appears under the wide surface of the inner arc, which is not easy to observe directly. It can be clearly seen after cleaning the surface of the casting:

[0005] 2) Crack size: about 20 mm in length, sometimes up to 50 mm to 150 mm.

[0006] 3) Crack depth: from 1mm to 10mm, the deepest at the corner can reach about 20mm.

[0007] The main reason for the cracks is that the low drawing speed stage is involved in the process of starting and stopping continuous casting. The surface cracks of the cast billet at this stage are serious and must be flame cleaned, but the crack defects cannot be completely removed and the billet can only be scrapped. The technical means used in related technologies are: tracking the billet head and tail according to the billet drawing length in the start-casting stage and the tail billet length in the tail billet stage, adjusting the secondary cooling water volume, achieving weak cooling of the head and tail billets of the slab, and reducing the probability of transverse cracks on the surface of the head and tail billets, but this technology only starts from reducing the secondary cooling intensity of the head and tail billets, and has limited control over the cracks in the head and tail billets.

[0008] Application Contents

[0009] The present application is made in view of the above-mentioned problems, and an object of the present application is to provide a dual-phase steel crack control method which can reduce the probability of crack generation.

[0010] Specifically, the present application provides a dual-phase steel crack control method, comprising the following steps:

[0011] Casting molten steel;

[0012] The pouring process in the casting process includes multiple stages of acceleration;

[0013] The acceleration of each section of the multi-stage acceleration process is independently 0.18m / min 2 ~0.22m / min2 ;

[0014] The stopping process in the casting process includes a deceleration process and an acceleration process;

[0015] The acceleration of the deceleration process is 0.4m / min 2 ~0.6m / min 2 ;

[0016] The acceleration of the acceleration process is 0.2m / min 2 ~0.3m / min 2 .

[0017] According to some technical solutions in the technical solution of this application, at least the following beneficial effects are achieved:

[0018] In the present application, the acceleration of the start-casting process and the stop-casting process in the casting process is controlled, thereby controlling the casting process time, reducing the low-speed drawing time, and thus reducing the transverse cracks in the tail billet.

[0019] According to some embodiments of the present application, the pouring process includes the following parameters:

[0020] The first stage constant speed: 0.2m / min~0.3m / min, time is 0.4min~0.6min;

[0021] The first stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the final acceleration speed is 0.6m / min~0.8m / min;

[0022] The second constant speed: time is 18s~22s;

[0023] The second stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0024] The third constant speed: time is 18s~22s;

[0025] The third stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0026] The fourth stage is constant speed: the time is 18s to 22s;

[0027] The fourth stage of acceleration: the acceleration is 0.18m / min2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0028] The fifth stage of constant speed: time is 18s~22s;

[0029] The fifth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0030] The sixth stage of constant speed: time is 18s~22s;

[0031] The sixth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0032] The seventh stage of constant speed: time is 18s~22s;

[0033] The seventh stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0034] The seventh stage of constant speed: time is 18s~22s;

[0035] The seventh stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0036] The eighth stage of constant speed: time is 18s~22s;

[0037] The eighth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0038] The ninth stage of constant speed: time is 18s~22s;

[0039] The ninth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0040] The tenth stage of constant speed: time is 18s~22s;

[0041] The tenth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0042] Stage 11 constant speed: time is 18s~22s;

[0043] The eleventh stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0044] The twelfth stage of constant speed: time is 18s~22s;

[0045] The twelfth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0046] The thirteenth stage of constant speed: time is 18s~22s;

[0047] The thirteenth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0048] The fourteenth stage of constant speed: time is 18s~22s;

[0049] The fourteenth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min;

[0050] The fifteenth stage is constant speed: time is 18s to 22s;

[0051] The 15th stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min.

[0052] According to some embodiments of the present application, the edge cooling water is turned off after the pulling speed is stabilized.

[0053] According to some embodiments of the present application, the edge portion includes the first to eighth edge portions.

[0054] According to some embodiments of the present application, the pouring suspension process includes:

[0055] The first stage of constant speed: speed is 0.9m / min~1.1m / min, time is 0.05min~0.15min;

[0056] The first deceleration: acceleration is 0.4m / min 2 ~0.6m / min 2 , final speed 0.2m / min~0.4m / min;

[0057] The second stage of constant speed: time is 2.5min~3.5min;

[0058] The first stage of acceleration: acceleration is 0.2m / min 2 ~0.3m / min 2 , final speed 0.9m / min~1.1m / min.

[0059] According to some embodiments of the present application, the tail water flow rate is 0.2m / min to 0.4m / min.

[0060] According to some embodiments of the present application, the pouring slag in the pouring process includes the following components in percentage by mass:

[0061] SiO2 37%~42%, CaO 29%~35%, Al2O3 1.5%~3.5%, Na2O 7.0%~9.0%, F - 9.0%~12.0%, MgO 0.4%~0.6% and Fe2O3 12%~16%.

[0062] According to some embodiments of the present application, the melting point of the cast slag is 1000°C to 1050°C.

[0063] According to some embodiments of the present application, the protective slag in the casting process includes the following components in mass percentage:

[0064] SiO2 30%~32%, CaO 36%~40%, Al2O3 3%~7%, Na2O+K2O+Li2O4.0%~10.0%, F - 7%~8% and MgO 1%~4%.

[0065] According to some embodiments of the present application, the viscosity of the protective slag at 1300° C. is 0.2 Pa·s to 0.3 Pa·s.

[0066] According to some embodiments of the present application, the method for controlling the amount of secondary cooling water during the casting process includes:

[0067] When the pulling speed is 0m / min~0.4m / min, the water volume of L03 circuit is 90L / min~110L / min;

[0068] When the pulling speed is 0.6m / min, the water volume of L03 circuit is 140L / min~160L / min;

[0069] According to some embodiments of the present application, when the pulling speed is 0.8 m / min, the water volume of the L03 circuit is 280 L / min to 300 L / min.

[0070] According to some embodiments of the present application, when the pulling speed is 1.0 m / min, the water volume of the L03 circuit is 320 L / min to 340 L / min.

[0071] According to some embodiments of the present application, when the pulling speed is 1.2 m / min, the water volume of the L03 circuit is 400 L / min to 420 L / min.

[0072] According to some embodiments of the present application, when the pulling speed is 1.4 m / min, the water volume of the L03 circuit is 470 L / min to 490 L / min.

[0073] According to some embodiments of the present application, when the pulling speed is 1.6 m / min, the water volume of the L03 circuit is 540 L / min to 560 L / min.

[0074] According to some embodiments of the present application, when the pulling speed is 1.8 m / min, the water volume of the L03 circuit is 600 L / min to 620 L / min.

[0075] According to some embodiments of the present application, when the pulling speed is 2.0 m / min, the water volume of the L03 circuit is 630 L / min to 650 L / min.

[0076] According to some embodiments of the present application, the method for controlling the amount of secondary cooling water during the casting process includes:

[0077] When the pulling speed is 0m / min~0.4m / min, the water volume of L04 circuit is 70L / min~90L / min;

[0078] When the pulling speed is 0.6m / min, the water volume of L04 circuit is 100L / min~130L / min.

[0079] According to some embodiments of the present application, when the pulling speed is 0.8 m / min, the water volume of the L04 circuit is 220 L / min to 240 L / min.

[0080] According to some embodiments of the present application, when the pulling speed is 1.0 m / min, the water volume of the L04 circuit is 260 L / min to 280 L / min.

[0081] According to some embodiments of the present application, when the pulling speed is 1.2 m / min, the water volume of the L04 circuit is 310 L / min to 330 L / min.

[0082] According to some embodiments of the present application, when the pulling speed is 1.4 m / min, the water volume of the L04 circuit is 370 L / min to 390 L / min.

[0083] According to some embodiments of the present application, when the pulling speed is 1.6 m / min, the water volume of the L04 circuit is 420 L / min to 440 L / min.

[0084] According to some embodiments of the present application, when the pulling speed is 1.8 m / min, the water volume of the L04 circuit is 470 L / min to 490 L / min.

[0085] According to some embodiments of the present application, when the pulling speed is 2.0 m / min, the water volume of the L04 circuit is 490 L / min to 510 L / min.

[0086] According to some embodiments of the present application, the method for controlling the amount of secondary cooling water during the casting process includes:

[0087] When the pulling speed is 0m / min~0.4m / min, the water volume of L05 circuit is 70L / min~90L / min;

[0088] When the pulling speed is 0.6m / min, the water volume of L05 circuit is 90L / min~110L / min.

[0089] According to some embodiments of the present application, when the pulling speed is 0.8 m / min, the water volume of the L05 circuit is 200 L / min to 220 L / min.

[0090] According to some embodiments of the present application, when the pulling speed is 1.0 m / min, the water volume of the L05 circuit is 240 L / min to 260 L / min.

[0091] According to some embodiments of the present application, when the pulling speed is 1.2 m / min, the water volume of the L05 circuit is 300 L / min to 320 L / min.

[0092] According to some embodiments of the present application, when the pulling speed is 1.4 m / min, the water volume of the L05 circuit is 350 L / min to 370 L / min.

[0093] According to some embodiments of the present application, when the pulling speed is 1.6 m / min, the water volume of the L05 circuit is 410 L / min to 430 L / min.

[0094] According to some embodiments of the present application, when the pulling speed is 1.8 m / min, the water volume of the L05 circuit is 460 L / min to 480 L / min.

[0095] According to some embodiments of the present application, when the pulling speed is 2.0 m / min, the water volume of the L05 circuit is 490 L / min to 510 L / min.

[0096] According to some embodiments of the present application, the pulling speed is reduced to 0.3 m / min during the casting process, and the secondary cooling 3-7 circuits are switched to manual control.

[0097] According to some embodiments of the present application, a cooling element is added during the casting process.

[0098] According to some embodiments of the present application, the casting machine is scored during the casting process.

[0099] According to some embodiments of the present application, the scoring items of the casting machine include:

[0100] Closed circuit water, roll gap, nozzle and arc alignment.

[0101] According to some embodiments of the present application, the requirements for closed-circuit water are as follows:

[0102] There shall be no closed-circuit water leakage in the inner and outer arcs before section 8.

[0103] According to some embodiments of the present application, the requirements for the roll gap are as follows:

[0104] Continuous casting machine roll gap: ≤ standard requirement + 1mm.

[0105] According to some embodiments of the present application, the requirements for the nozzle are as follows:

[0106] There is no blockage in sections 0 to 3; the total number of blockages in sections 4 to 8 is ≤5.

[0107] According to some embodiments of the present application, the requirements for arc centering are as follows:

[0108] Strict centering system. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0110] Figure 1 This is the appearance diagram of the cooling element in this application.

[0111] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0112] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0113] Obviously, the following descriptions are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in the field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0114] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0115] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0116] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0117] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0118] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0119] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0120] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0121] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0122] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0123] Example 1

[0124] This embodiment is a dual-phase steel crack control method, comprising the following steps:

[0125] In this embodiment, the casting steel type is dual-phase steel (DP450), and the specifications of the continuous casting billet are: 240mm×1320mm;

[0126] Casting molten steel;

[0127] The pouring curve of the casting in this embodiment is as follows:

[0128] Casting curve:

[0129] Initial pulling speed (constant speed in the first stage): 0.25m / min, holding time is 0.5min;

[0130] The first stage of acceleration: from 0.25m / min to 0.7m / min, the acceleration is 0.2m / min 2 , the acceleration time is 1.75min;

[0131] The second stage constant speed: 0.7m / min, maintained for 20s;

[0132] The second stage of acceleration: from 0.7m / min to 0.75m / min, the acceleration is 0.2m / min 2 ;

[0133] The third stage constant speed: 0.75m / min, maintenance time is 20s;

[0134] The third stage of acceleration: from 0.75m / min to 0.8m / min, the acceleration is 0.2m / min 2 ;

[0135] The fourth stage is constant speed: 0.75m / min, and the maintenance time is 20s;

[0136] The fourth stage of acceleration: from 0.75m / min to 0.8m / min, the acceleration is 0.2m / min 2 ;

[0137] The fifth stage is constant speed: 0.8m / min, and the maintenance time is 20s;

[0138] The fifth stage of acceleration: from 0.8m / min to 0.85m / min, the acceleration is 0.2m / min 2 ;

[0139] The fifth stage is constant speed: 0.85m / min, and the maintenance time is 20s;

[0140] The fifth stage of acceleration: from 0.85m / min to 0.9m / min, the acceleration is 0.2m / min 2 ;

[0141] The sixth stage is constant speed: 0.9m / min, and the maintenance time is 20s;

[0142] The sixth stage of acceleration: from 0.9m / min to 0.95m / min, the acceleration is 0.2m / min 2 ;

[0143] The seventh stage constant speed: 0.95m / min, the maintenance time is 20s;

[0144] The seventh stage of acceleration: from 0.95m / min to 1.0m / min, the acceleration is 0.2m / min 2 ;

[0145] The eighth stage is constant speed: 1.0m / min, and the maintenance time is 20s;

[0146] The eighth stage of acceleration: from 1.0m / min to 1.05m / min, with an acceleration of 0.2m / min 2 ;

[0147] The ninth stage constant speed: 1.05m / min, maintaining time is 20s;

[0148] The ninth stage of acceleration: from 1.05m / min to 1.1m / min, with an acceleration of 0.2m / min 2 ;

[0149] The tenth stage constant speed: 1.1m / min, the maintenance time is 20s;

[0150] The tenth stage of acceleration: from 1.1m / min to 1.15m / min, with an acceleration of 0.2m / min 2 ;

[0151] Stage 11: Constant speed: 1.15m / min, maintained for 20s;

[0152] The eleventh stage of acceleration: from 1.15m / min to 1.2m / min, the acceleration is 0.2m / min 2 ;

[0153] The twelfth stage constant speed: 1.2m / min, maintaining time is 20s;

[0154] The twelfth stage of acceleration: from 1.2m / min to 1.25m / min, the acceleration is 0.2m / min 2 ;

[0155] The 13th stage constant speed: 1.25m / min, maintaining time is 20s;

[0156] The thirteenth stage of acceleration: from 1.25m / min to 1.3m / min, the acceleration is 0.2m / min 2 ;

[0157] The fourteenth stage constant speed: 1.3m / min, maintaining time is 20s;

[0158] The fourteenth stage of acceleration: from 1.3m / min to 1.35m / min, the acceleration is 0.2m / min 2 ;

[0159] The fifteenth stage constant speed: 1.35m / min, maintaining time is 20s;

[0160] The fifteenth stage of acceleration: from 1.35m / min to 1.4m / min, the acceleration is 0.2m / min 2 ;

[0161] The target pulling speed is 1.4m / min. After the pulling speed stabilizes, manually close the edge cooling water of sections 1-8.

[0162] Stop pouring curve:

[0163] The first stage constant speed: 1.4m / min, maintaining time is 0.1min;

[0164] Deceleration: from 1.4m / min to 0.3m / min (close the stopper after deceleration), acceleration is 0.5m / min 2 ;

[0165] The second stage constant speed: 0.3m / min, maintained for 3min (time required for capping);

[0166] Acceleration: from 0.3m / min to 1.1m / min (tail exit speed), acceleration is 0.25m / min 2 .

[0167] In this embodiment, the slag for opening is selected from the slag for opening B;

[0168] The composition of the pouring slag B includes:

[0169] SiO2 39.5%, CaO 32%, Al2O3 2.5%, Na2O 8.0%, F - 10.5%, MgO 0.5% and Fe2O3 14.5%.

[0170] The melting point is 1021℃±20℃.

[0171] The mold slag used in this embodiment is mold slag A:

[0172] The mold slag A includes the following components in mass percentage:

[0173] SiO2 31.02%, CaO 38.34%, Al2O3 6.83%, Na2O+K2O+Li2O 4.55%, F - 7.0% and MgO1.02%;

[0174] The viscosity of mold slag A at 1300°C is 0.275 Pa·s, R is 1.23, the melting point is 1210°C, and the water content is 0.3%.

[0175] The configuration of the secondary cooling water in this embodiment is shown in Table 1.

[0176] Table 1

[0177]

[0178] In this embodiment, after the continuous casting tundish stops pouring and the tail is discharged, a cooling member is added into the crystallizer.

[0179] Example 2

[0180] This embodiment is a dual-phase steel crack control method, which differs from Embodiment 1 in that:

[0181] The steel grade is DP600.

[0182] Example 3

[0183] This embodiment is a dual-phase steel crack control method, which differs from Embodiment 1 in that:

[0184] The steel grade is DP780.

[0185] Example 4

[0186] This embodiment is a dual-phase steel crack control method, which differs from Embodiment 1 in that:

[0187] The steel grade is DP980.

[0188] Example 5

[0189] This embodiment is a dual-phase steel crack control method, which differs from Embodiment 1 in that:

[0190] The steel grade is DP1180.

[0191] Comparative Example 1

[0192] This comparative example is a dual-phase steel casting method, which differs from Example 1 in that:

[0193] In this comparative example, the slag B is replaced by the slag A.

[0194] The composition of the slag A includes:

[0195] SiO2 37.2%, CaO 30.36%, Al2O3 3.55%, Na2O 8.73%, K2O 0.16%, F - 11.61%, MnO2 0.12%, MgO 0.56% and Fe2O3 18.19%.

[0196] Slag A also includes 0.24% water.

[0197] The density of slag A is 1.03 g / mL and the melting point is 1077°C.

[0198] Comparative Example 2

[0199] This comparative example is a dual-phase steel casting method, which differs from Example 1 in that:

[0200] In this comparative example, mold slag A is replaced by mold slag B.

[0201] The mold slag B includes the following components in mass percentage:

[0202] SiO2 30.75%, CaO 36.83%, Al2O3 3.42%, Na2O+K2O+Li2O 9.67%, F - 7.54% and MgO 3.57%;

[0203] The viscosity of mold slag A at 1300°C is 0.127 Pa·s, R is 1.2, melting point is 1089°C, and water content is 0.06%.

[0204] Comparative Example 3

[0205] This comparative example is a dual-phase steel casting method, which differs from Example 1 in that:

[0206] The adjustment method of the secondary cooling water volume in this comparative example is shown in Table 2.

[0207] Table 2

[0208]

[0209] Comparative Example 4

[0210] This comparative example is a dual-phase steel casting method, which differs from Example 1 in that:

[0211] No cooling element was used in this comparative example.

[0212] The crack conditions in the examples of this application are shown in Table 3.

[0213] Table 3

[0214]

[0215]

[0216] The criteria for judging slight cracks are as follows: there are cracks on the surface, 1mm to 3mm in length (not including 3mm), and 0.5mm to 1.5mm in depth (not including 1.5mm).

[0217] The criteria for judging light cracks are as follows: small cracks exist on the surface, with a length of 3mm to 7mm (excluding 7mm) and a depth of 1.5mm to 2.5mm (excluding 2.5mm).

[0218] The criteria for judging medium cracks are as follows: small cracks exist on the surface, with a length of more than 7mm and a depth of more than 2.5mm.

[0219] In the present application, the secondary cooling water volume at low pulling speed is adjusted to reduce by 20% to ensure that the head and tail billets are not overcooled. When the casting is stopped and the tail is discharged, when the pulling speed drops to 0.3m / min, the secondary cooling 3-7 circuit is switched to manual control, which is equivalent to the water volume locked at 0.3m / min. This greatly reduces the incidence of transverse cracks in the tail billet.

[0220] This application uses cooling parts when stopping casting. When the tail of the continuous casting tundish stops pouring, cooling parts are added to the crystallizer to quickly cool the tail billet, and then the speed is quickly increased.

[0221] The present application reduces the crack incidence rate of the head and tail billets of duplex steel by optimizing the start-casting growth rate curve and the tail-out curve, optimizing the start-casting slag, optimizing the protective slag, optimizing the secondary cooling water, and using cooling parts when casting is stopped. The crack incidence rate of the head and tail billets of duplex steel is reduced from the initial 100% to about 3% after improvement.

[0222] The improvement of the surface quality of the head and tail billets of duplex steel effectively reduces the loss rate of flame cleaning, shortens the product delivery cycle, and greatly improves the quality of the head and tail billets of duplex steel.

[0223] Quality of Comparative Example 1: The head blank has very serious transverse cracks, the crack size is: length 40mm, depth 3mm, the head blank can only be judged as scrap;

[0224] The tail blank has serious cracks, the size is: length 10mm, depth 2mm, and it needs to be flame cleaned and ground before the quality is qualified.

[0225] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A dual-phase steel crack control method, characterized in that: The following steps are involved: Casting molten steel; The pouring process in the casting process includes multiple stages of acceleration; The acceleration of each section of the multi-stage acceleration process is independently 0.18m / min 2 ~0.22m / min 2 ; The stopping process in the casting process includes a deceleration process and an acceleration process; The acceleration of the deceleration process is 0.4m / min 2 ~0.6m / min 2 ; The acceleration of the acceleration process is 0.2m / min 2 ~0.3m / min 2 .

2. The dual-phase steel crack control method according to claim 1, characterized in that: The pouring process includes the following parameters: The first stage constant speed: 0.2m / min~0.3m / min, time is 0.4min~0.6min; The first stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the final acceleration speed is 0.6m / min~0.8m / min; The second constant speed: time is 18s~22s; The second stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The third constant speed: time is 18s~22s; The third stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The fourth stage is constant speed: the time is 18s to 22s; The fourth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The fifth stage of constant speed: time is 18s~22s; The fifth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The sixth stage of constant speed: time is 18s~22s; The sixth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The seventh stage of constant speed: time is 18s~22s; The seventh stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The eighth stage of constant speed: time is 18s~22s; The eighth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The ninth stage of constant speed: time is 18s~22s; The ninth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The tenth stage of constant speed: time is 18s~22s; The tenth stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; Stage 11 constant speed: time is 18s~22s; The eleventh stage of acceleration: the acceleration is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The twelfth stage of constant speed: time is 18s~22s; The twelfth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The thirteenth stage of constant speed: time is 18s~22s; The thirteenth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The fourteenth stage of constant speed: time is 18s~22s; The fourteenth stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; The fifteenth stage is constant speed: time is 18s to 22s; The 15th stage of acceleration: the acceleration rate is 0.18m / min 2 ~0.22m / min 2 , the speed increment is 0.04m / min~0.06m / min; And / or, the edge cooling water is turned off after the pulling speed is stabilized; And / or, the edge portion includes the first to eighth edge portions.

3. The dual-phase steel crack control method according to claim 1, characterized in that: The stop pouring process includes: The first stage of constant speed: speed is 0.9m / min~1.4m / min, time is 0.05min~0.15min; The first deceleration: acceleration is 0.4m / min 2 ~0.6m / min 2 , final speed 0.2m / min~0.4m / min; The second stage of constant speed: time is 2.5min~3.5min; The first stage of acceleration: acceleration is 0.2m / min 2 ~0.3m / min 2 , final speed 0.9m / min~1.1m / min; And / or, the water velocity of the tail outlet is 0.2m / min to 0.4m / min.

4. The dual-phase steel crack control method according to claim 1, characterized in that: The pouring slag in the pouring process includes the following components in percentage by mass: SiO2 37% to 42%, CaO 29% to 35%, Al2O3 1.5% to 3.5%, Na2O 7.0% to 9.0%, F - 9.0% to 12.0%, MgO 0.4% to 0.6% and Fe2O3 12% to 16%. And / or, the melting point of the cast slag is 1000°C to 1050°C.

5. The dual-phase steel crack control method according to claim 1, characterized in that: The mold slag in the casting process includes the following components in percentage by mass: SiO2 30% to 32%, CaO 36% to 40%, Al2O3 3% to 7%, Na2O+K2O+Li2O4.0% to 10.0%, F - 7% to 8% Japanese MgO 1% to 4%; And / or, the viscosity of the protective slag at 1300° C. is 0.2 Pa·s to 0.3 Pa·s.

6. The dual-phase steel crack control method according to claim 1, characterized in that: The control method of the secondary cooling water amount during the casting process includes: When the pulling speed is 0m / min~0.4m / min, the water volume of L03 circuit is 90L / min~110L / min; When the pulling speed is 0.6m / min, the water volume of L03 circuit is 140L / min~160L / min; And / or, when the pulling speed is 0.8m / min, the water volume of L03 circuit is 280L / min~300L / min; And / or, when the pulling speed is 1.0m / min, the water volume of L03 circuit is 320L / min~340L / min; and / or, when the pulling speed is 1.2 m / min, the water volume of L03 circuit is 400 L / min to 420 L / min; and / or, when the pulling speed is 1.4 m / min, the water volume of L03 circuit is 470 L / min to 490 L / min; and / or, when the pulling speed is 1.6 m / min, the water volume of the L03 circuit is 540 L / min to 560 L / min; and / or, when the pulling speed is 1.8 m / min, the water volume of L03 circuit is 600 L / min to 620 L / min; And / or, when the pulling speed is 2.0m / min, the water volume of the L03 circuit is 630L / min~650L / min.

7. The dual-phase steel crack control method according to claim 1, characterized in that: The control method of the secondary cooling water amount during the casting process includes: When the pulling speed is 0m / min~0.4m / min, the water volume of L04 circuit is 70L / min~90L / min; When the pulling speed is 0.6m / min, the water volume of L04 circuit is 100L / min~130L / min; and / or, when the pulling speed is 0.8 m / min, the water volume of L04 circuit is 220 L / min to 240 L / min; And / or, when the pulling speed is 1.0m / min, the water volume of L04 circuit is 260L / min~280L / min; And / or, when the pulling speed is 1.2m / min, the water volume of L04 circuit is 310L / min~330L / min; and / or, when the pulling speed is 1.4 m / min, the water volume of L04 circuit is 370 L / min to 390 L / min; and / or, when the pulling speed is 1.6 m / min, the water volume of L04 circuit is 420 L / min to 440 L / min; and / or, when the pulling speed is 1.8 m / min, the water volume of L04 circuit is 470 L / min to 490 L / min; And / or, when the pulling speed is 2.0m / min, the water volume of the L04 circuit is 490L / min~510L / min.

8. The dual-phase steel crack control method according to claim 1, characterized in that: The control method of the secondary cooling water amount during the casting process includes: When the pulling speed is 0m / min~0.4m / min, the water volume of L05 circuit is 70L / min~90L / min; When the pulling speed is 0.6m / min, the water volume of L05 circuit is 90L / min~110L / min; And / or, when the pulling speed is 0.8m / min, the water volume of L05 circuit is 200L / min~220L / min; And / or, when the pulling speed is 1.0m / min, the water volume of L05 circuit is 240L / min~260L / min; And / or, when the pulling speed is 1.2m / min, the water volume of L05 circuit is 300L / min~320L / min; And / or, when the pulling speed is 1.4m / min, the water volume of L05 circuit is 350L / min~370L / min; and / or, when the pulling speed is 1.6 m / min, the water volume of L05 circuit is 410 L / min to 430 L / min; And / or, when the pulling speed is 1.8m / min, the water volume of L05 circuit is 460L / min~480L / min; And / or, when the pulling speed is 2.0m / min, the water volume of the L05 circuit is 490L / min~510L / min.

9. The dual-phase steel crack control method according to claim 1, characterized in that: During the casting process, the pulling speed is reduced to 0.3 m / min, and the secondary cooling 3-7 circuit is switched to manual control.

10. The dual-phase steel crack control method according to claim 1, characterized in that: A cooling element is added during the casting process.

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