A pin shooting method and a pin shooting device for measuring the shell thickness and solidification characteristics of a continuously cast strand

Abstract

The present application relates to a kind of measuring continuous casting shell thickness and solidification characteristic shot pin method and shot pin.The present application under the condition of stable pouring temperature interval, steel grade and section, excites the first shot pin of shot pin gun perpendicular to the surface of casting blank;Shot pin contains linear sulfide distributed along the length direction of shot pin and several tracer groups arranged along the length direction of shot pin;After the relative movement of shot pin device to casting blank along the direction of drawing blank is set distance, the second shot pin is carried out;After the continuous casting blank after shot pin is drawn, it is cooled, processing sample;According to the carbon, sulfur content of sample shot pin, the shell thickness of twice shot pin test is L1, L2;The distance between tracer and solidified shell L3, L4 is determined by the position of tracer of twice shot pin test;The shell solidification speed is the ratio of the difference of twice shot pin test shell thickness and shell solidification time, and the liquid steel diffusion speed is the ratio of the distance difference of twice shot pin test tracer and solidified shell and liquid steel diffusion time.

Description

Technical Field

[0001] This invention relates to the field of continuous casting billet shell thickness and solidification characteristics testing technology, and particularly to a method and a nail for measuring the shell thickness and solidification characteristics of continuously cast billets. Background Technology

[0002] Continuous casting, as a crucial process in steel production, has achieved relative technological maturity, but several issues still require further research, particularly regarding solidification control at the billet center and surface quality control. Rectangular billet continuous casting not only produces a wide variety of steel grades but also involves complex process conditions, with significant differences in solidification characteristics between different steel grades and specifications. The solidified shell thickness and liquidus cavity depth of continuously cast billets for different steel grades are critical parameters in continuous casting production. These parameters directly reflect the billet's cooling status and the appropriateness of the casting speed, providing direct reference for optimizing electromagnetic stirring and reduction parameters.

[0003] Currently, there are several methods for determining the thickness of the solidified shell and the depth of the liquid cavity in continuously cast billets:

[0004] (l) Piercing the billet shell method. After the billet exits the crystallizer, the solidified shell is pierced to allow the molten steel to flow out, and then the thickness of the solidified billet shell is measured.

[0005] (2) Isotope method. At a certain moment, a radioactive isotope (such as Au198) is added into the crystallizer along with the injection stream. The moving injection stream carries the isotope to a depth of 3-4 m in the liquid cavity. Because the steel containing Au198 is radioactive after solidification, while the steel that has already solidified when Au198 is added is not radioactive, the thickness of the solidified layer can be determined by taking samples of the cast billet at different locations and performing X-ray radiography. Patent CN105436452A adds lead tracer to the tundish at the end of the casting process. After the tail billet is pulled out, samples are taken at the same intervals. Each sample is sawn and planed, then scanned with an X-ray scanner, and the scanning results are recorded. Based on the scanning results, the samples are arranged in order of their numbers to find the sample where the liquid core at the end of solidification is located, and the length of the liquid core is determined by its corresponding number. Patent CN112207246A, based on this, establishes a mathematical model according to the actual production conditions of the casting machine on site to calculate the time for the tracer material lead liquid to flow to the penetration endpoint. After the billet solidification heat transfer model is used to perform multi-point correction calculation on the billet shell thickness at different positions, the billet solidification endpoint position is obtained.

[0006] (3) Nail-shot method. After the billet exits the crystallizer, a steel nail is shot into a certain position. The liquidus temperature of the steel nail is lower than that of the steel grade being measured. Therefore, the nail in the liquidus region is completely melted, the nail in the two-phase region is partially melted, and the nail in the solidus region is not melted. The thickness of the solidified billet shell can be directly measured by cutting off the billet with the nail.

[0007] (4) Determine the location of the liquid phase cavity by measuring the bulge of the slab. At a certain position close to the straightening point, appropriately increase the opening of the support rollers. If there is still liquid phase inside the slab, bulge will appear.

[0008] (5) Calculate the solidified billet shell thickness based on the feedback results of the pressing down. Chinese Patent CN104493121A discloses a method for controlling the liquid core thickness by comparing the feedback data of the pressure and pressing down of the casting roll of the tension leveler with the thermal tracking model established by the nail shooting method. Chinese Patent CN115229149A uses the casting roll to apply a large mechanical pressing deformation to the thickness direction of the billet with liquid core, squeezing the unsolidified molten steel in the core of the billet to flow towards the crystallizer, thereby increasing the degree of liquid level fluctuation in the crystallizer, and calculating the billet shell / liquid core thickness and the solidification end position at the pressing position based on the change in the liquid level fluctuation value of the crystallizer.

[0009] (6) Ultrasonic testing. Chinese patents CN104439144A and CN111473752A employ an electromagnetic ultrasonic testing device installed on the continuous casting machine. The electromagnetic ultrasonic testing device located above the upper surface of the continuous casting billet is used to excite and receive electromagnetic ultrasonic transverse waves on the upper surface of the continuous casting billet; the electromagnetic ultrasonic testing device located below the lower surface of the continuous casting billet and coaxially perpendicular to the continuous casting billet is used to excite and receive electromagnetic ultrasonic longitudinal waves on the upper surface of the continuous casting billet.

[0010] Analysis of the above methods: Method (1) is a destructive test, and the on-site handling is extremely difficult; Method (2) will produce certain radioactive pollution, and the test is complex and has poor operability; Method (3) cannot detect solidification and diffusion characteristics; Methods (4), (5), and (6) are simple but have very poor measurement accuracy; In addition, Methods (1), (2), (4), and (5) will affect normal production and artificially generate some waste. Summary of the Invention

[0011] In order to solve the above-mentioned technical problems, or at least partially solve the above-mentioned technical problems, the present invention provides a method for measuring the thickness and solidification characteristics of a continuously cast billet shell and a nail.

[0012] In a first aspect, the present invention provides a method for measuring the thickness and solidification properties of a continuously cast billet shell using a nail gun, comprising:

[0013] Under stable casting temperature range, steel grade, and cross-sectional conditions, the nail gun is activated to perform the first nailing perpendicular to the surface of the billet; wherein, the nail contains linear sulfides distributed along the length direction of the nail and several tracer clusters spaced apart along the length direction of the nail;

[0014] After the nail gun moves a set distance relative to the billet along the billet pulling direction, it is activated to perform a second nailing perpendicular to the billet surface.

[0015] After the continuously cast billet is shot, it is pulled out, cooled, processed, and sampled.

[0016] The thicknesses of the billet shell for the two nail-shooting tests were determined as L1 and L2 based on the carbon and sulfur content at the nail-shooting point of the sample; the distances between the tracer and the solidified billet shell were determined as L3 and L4 based on the position of the tracer in the two nail-shooting tests.

[0017] The solidification rate of the billet shell is the ratio of the difference in billet shell thickness between the two nail-shooting tests to the solidification time of the billet shell, and the diffusion rate of molten steel is the ratio of the difference in distance between the tracer and the solidified billet shell between the two nail-shooting tests to the diffusion time of molten steel.

[0018] Furthermore, the sampling process includes: removing the surface of the sample layer by layer until the overall morphology of the nail can be observed; acid etching the sample with the surface removed; and polishing the acid-etched sample.

[0019] Furthermore, low-magnification morphology images after acid etching were recorded, and the preliminary location of the billet shell was determined using these images. Holes were drilled near the location of the billet shell to collect chips, and carbon and sulfur were detected using a carbon and sulfur analyzer. Based on the obtained carbon and sulfur content, the thickness of the billet shell in the two nail-shooting tests was precisely defined as L1 and L2.

[0020] Furthermore, the sample was scanned with an X-ray scanner to determine the position of the tracer in the two nail-shooting tests. Based on the position of the tracer and the thickness of the billet L1 and L2, the distances L3 and L4 between the tracer and the solidified billet were determined.

[0021] Furthermore, under a stable pulling speed v, the solidification time of the billet shell and the diffusion time of the molten steel during the two nail-shooting tests are obtained by dividing the set distance L by the pulling speed v.

[0022] Furthermore, before continuous casting begins, a nail gun is installed at the nail gun position. The casting temperature range and cross-sectional conditions at the nail gun position are stable. The nail gun includes a nail gun, an excitation controller, gunpowder, and a fixed bracket. The distance from the nozzle of the nail gun to the surface of the billet is 10–30 mm.

[0023] Secondly, this application provides a nail for measuring the thickness and solidification characteristics of a continuously cast billet shell, comprising: a nail body, a tail plate at the tail of the nail body for limiting the depth of the nail's entry, a long groove in the elongation direction of the nail body, a sulfide disposed in the long groove, and a plurality of tracer clusters disposed at intervals in the nail body, wherein the tracer has the characteristics of being miscible with the main fluid of the continuously cast body, not undergoing a chemical reaction and not undergoing phase transfer.

[0024] Furthermore, the liquidus temperature of the nail body is lower than the liquidus temperature of the continuously cast billet steel grade being measured.

[0025] The technical solutions provided in the embodiments of the present invention have the following advantages compared with the prior art:

[0026] This invention, under stable casting temperature range, steel grade, and cross-sectional conditions, involves activating a nail gun perpendicular to the surface of the cast billet for the first nailing operation. The nail contains linear sulfides distributed along its length and several tracer clusters spaced apart along the same length. After the nailing device moves a set distance relative to the cast billet along the casting direction, a second nailing operation is performed. The continuously cast billet after nailing is pulled out, cooled, processed, and sampled. The billet shell thicknesses L1 and L2 are determined based on the carbon and sulfur content at the nailing point of the sample, resulting in more accurate measurements. The distances L3 and L4 between the tracer and the solidified billet shell are determined by the positions of the tracer in the two nailing tests. The billet shell solidification rate is the ratio of the difference in billet shell thickness between the two nailing tests to the billet shell solidification time, and the molten steel diffusion rate is the ratio of the difference in distance between the tracer and the solidified billet shell between the two nailing tests to the molten steel diffusion time. This application achieves both the measurement of billet shell thickness and the calculation of billet shell solidification rate, as well as the calculation of molten steel diffusion rate, by using two nail-shooting tests and utilizing the combination of sulfide and tracer groups in the nails used in the two nail-shooting tests. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart of a nail-shooting method for measuring the thickness and solidification properties of a continuously cast billet shell, provided in an embodiment of the present invention;

[0030] Figure 2 An example diagram of the nailing position for a nailing method for measuring the thickness and solidification properties of a continuously cast billet shell, provided in an embodiment of the present invention;

[0031] Figure 3 Low-magnification topographic image of the nail position at 1 / 4 of section 8 to section 9 of the 250mm×1800mm slab continuous casting machine;

[0032] Figure 4 Low-magnification topographic image of the nail position at 1 / 4 of section 10 to section 11 of the 250mm×1800mm slab continuous casting machine;

[0033] Figure 5Low-magnification topographic images of the nail positions in sections 11 to 12 of the Φ600mm round billet continuous casting machine.

[0034] Figure 6 Low-magnification topographic images of the nail positions in sections 11 to 12 of a 180×220mm rectangular billet continuous casting machine.

[0035] Figure 7 This is a schematic diagram of a nail used to measure the thickness and solidification properties of a continuously cast billet shell, as provided in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] See Figure 1 As shown, the present invention provides a method for measuring the thickness and solidification properties of a continuously cast billet shell using a nail gun, comprising:

[0039] Before continuous casting begins, a nail-shooting device is installed at the nail-shooting position. The casting temperature range and cross-sectional conditions at the nail-shooting position are stable. The nail-shooting device includes a nail gun, an excitation controller, gunpowder, and a fixing bracket. The distance from the nozzle of the nail gun to the surface of the cast billet is 10–30 mm. The nail gun supports the complete penetration of the test nail into the cast billet.

[0040] Under stable casting temperature range, steel grade, and cross-sectional conditions, the nail gun is activated perpendicularly to the surface of the cast billet for the first nailing operation; (See also...) Figure 2 The nail shown contains linear sulfides distributed along the length of the nail and several tracer clusters spaced apart along the length of the nail.

[0041] After the nail-shooting device moves a set distance relative to the billet along the casting direction, the nail gun is activated to perform a second nail-shooting action perpendicular to the billet surface. The specifications of the nails used in both shots are identical. The positional relationship between the billet and the nails after the two shots is as follows: Figure 2 As shown.

[0042] This application requires measuring the time between the first and second nail-shooting processes as the billet solidification time and molten steel diffusion time between the first and second nail-shooting processes. In one embodiment, the billet drawing speed is controlled to be stable. Under stable drawing speed v, the billet solidification time and molten steel diffusion time during the two nail-shooting tests are obtained by dividing a set distance L by the drawing speed v.

[0043] After the continuously cast billet is pulled out after nailing, it is cooled, processed, and sampled.

[0044] In the specific implementation process, the sampling procedure includes: making cuts of 50-100 mm above and below the nail hole location to ensure sample integrity. After cutting out the sample containing the nail, the surface of the sample is planed layer by layer until the overall morphology of the nail can be observed. The planed sample is then acid-etched, and low-magnification images of the morphology are recorded. These low-magnification images are used to determine the preliminary location of the blank. Finally, the acid-etched sample is polished.

[0045] The billet shell thicknesses for the two nail-shooting tests were determined as L1 and L2 based on the carbon and sulfur content at the nail point of the sample. The distances between the tracer and the solidified billet shell, L3 and L4, were determined by the position of the tracer in the two nail-shooting tests. In the specific implementation process, low-magnification morphology images after acid etching were recorded. These images were used to determine the preliminary billet shell position. Chips were collected near the billet shell position, and carbon and sulfur content were measured using a carbon-sulfur analyzer. Based on the obtained carbon and sulfur content, the billet shell thicknesses for the two nail-shooting tests were precisely determined as L1 and L2. Because the temperature at the billet shell position is low, while the temperature of the internal molten steel portion is high, the nails within the molten steel area melt after entering the billet. The sulfides within the nails diffuse within the molten steel, resulting in a significant difference in sulfur content distribution at the boundary between the billet shell and the molten steel. Therefore, the billet shell thickness can be accurately determined by the distribution of carbon and sulfur content. In the specific implementation process, the sample is scanned with an X-ray scanner to determine the position of the tracer in the two nail shooting tests. The distances L3 and L4 between the tracer and the solidified shell are determined according to the position of the tracer and the thickness L1 and L2 of the shell.

[0046] The solidification rate of the billet shell is the ratio of the difference in billet shell thickness between the two nail-shooting tests to the solidification time of the billet shell. The diffusion rate of molten steel is the ratio of the difference in distance between the tracer and the solidified billet shell between the two nail-shooting tests to the diffusion time of the molten steel.

[0047] V 凝 =|L1-L2| / t;

[0048] V 扩 =|L3-L4| / t; where, V 凝 V represents the solidification rate of the billet shell. 扩 The velocity of molten steel diffusion is represented by t = L / v, where v represents the drawing speed of the billet.

[0049] See Figure 3 and Figure 4 As shown, the present invention was applied to a 250mm×1800mm slab continuous casting machine in a steel plant, and a nail-shooting test was conducted at a casting speed of 1.2m / min, steel grade Q235B, and positions 8 to 9 and 10 to 11.

[0050] Under stable casting speed, pouring temperature range, steel grade, and cross-section conditions, the nail gun is activated to drive the nails. Subsequently, the nail-driving device moves a set distance L = 4.76m relative to the billet and drives the nails again.

[0051] After the nail-shooting test, the continuously cast billet was pulled out, cooled, processed, and sampled, and numbered according to the nail-shooting position. Carbon and sulfur were measured using a carbon-sulfur analyzer, and based on the obtained carbon and sulfur content, the billet shell thicknesses for the two nail-shooting tests were determined to be L1 = 108 mm and L2 = 113.5 mm.

[0052] The sample was scanned using an X-ray scanner to determine the location of the tracer and the distance between the solidified shell and the solidified shell in the two nail-shooting tests, respectively: L3 = 2.5 mm and L4 = 7 mm.

[0053] The solidification rate of the billet shell and the diffusion rate of the molten steel were calculated, namely:

[0054] t=L / v=4.76 / 1.2=3.967min,

[0055] V 凝 =|L1-L2| / t=|113.5-108| / 3.967=1.386mm / min,

[0056] V 扩 =|L3-L4| / t=|7-2.5| / 3.967=1.134mm / min.

[0057] See Figure 5 As shown, the present invention was applied to a φ600mm round billet continuous casting machine in a steel plant, and a nail-shooting test was conducted at a casting speed of 0.25m / min, steel grade 42CrMo, and position 11-12.

[0058] Under stable casting speed, pouring temperature range, steel grade, and cross-section conditions, the nail gun was activated to fire nails. Subsequently, the nail-firing device was moved a set distance L = 1.7m relative to the billet, and the nail-firing experiment was conducted again.

[0059] After the nail-shooting test is completed, the continuously cast billet after nailing is pulled out, cooled, processed, and sampled, and numbered according to the nail-shooting position.

[0060] Carbon and sulfur were tested using a carbon-sulfur meter. Based on the obtained carbon and sulfur content, the blank thicknesses for the two nail shooting tests were determined to be L1 = 151 mm and L2 = 155 mm.

[0061] The sample was scanned with an X-ray scanner to determine the location of the tracer and the distance between the solidified shell in the two nail-shooting tests, L3 = 0.8 mm and L4 = 2.9 mm respectively.

[0062] The solidification rate of the billet shell and the diffusion rate of the molten steel were calculated, namely:

[0063] t=L / v=1.7 / 0.25=6.8min,

[0064] V 凝 =|L1-L2| / t=|151-155| / 6.8=0.588mm / min,

[0065] V 扩 =|L3-L4| / t=|0.8-2.9| / 6.8=0.309mm / min.

[0066] See Figure 6 As shown, the present invention was applied to a 180×220mm rectangular billet continuous casting machine in a steel plant, and a nail-shooting test was conducted at a casting speed of 1.2m / min, steel grade GCr15, and positions 11-12.

[0067] Under stable casting speed, pouring temperature range, steel grade, and cross-section conditions, the nail gun is activated to drive the nails. Subsequently, the nail-driving device moves a set distance L = 1.6m relative to the billet and drives the nails again.

[0068] After the nail-shooting test, the continuously cast billet was pulled out, cooled, processed, and sampled, and numbered according to the nail-shooting position. Carbon and sulfur content was measured using a carbon-sulfur analyzer, and the billet shell thicknesses for the two nail-shooting tests were determined to be L1 = 73 mm and L2 = 76 mm based on the obtained carbon and sulfur content.

[0069] The sample was scanned using an X-ray scanner to determine the location of the tracer and the distance between the solidified shell and the solidified shell in the two nail-shooting tests, respectively: L3 = 1 mm and L4 = 3.5 mm.

[0070] The solidification rate of the billet shell and the diffusion rate of the molten steel were calculated, namely:

[0071] t=L / v=1.6 / 1.2=1.333min,

[0072] V 凝=|L1-L2| / t=|73-76| / 1.333=2.251mm / min,

[0073] V 扩 =|L3-L4| / t=|1-3.5| / 1.333=1.875mm / min.

[0074] Example 2

[0075] See Figure 7 As shown, this invention provides a nail for measuring the thickness and solidification characteristics of continuously cast billet shells. The method for measuring the thickness and solidification characteristics of continuously cast billet shells using this nail includes: a nail body 1; a tail plate at the tail of the nail body 1 to limit the depth of nail insertion; a long groove along the elongation direction within the nail body 1; a sulfide 2 disposed within the long groove; and several tracer clusters 3 spaced apart within the nail body 1. The tracer has the characteristics of being miscible with the main fluid of the continuously cast body, not undergoing a chemical reaction, and not undergoing phase transfer. An exemplary example uses a lead tracer.

[0076] Furthermore, the liquidus temperature of the nail body is lower than the liquidus temperature of the continuously cast billet steel grade measured. An exemplary nail body 1 is made of carbon steel.

[0077] Example 3

[0078] This invention provides a nail-shooting device, which includes a nail gun, an activation controller, gunpowder, a nail changer / gunpowder changer, and a fixed bracket. The nail gun is fixed on the fixed bracket, and the nail changer and the gunpowder changer are disposed on the nail gun. The gunpowder changer replaces the activation gunpowder in the nail gun, and the gunpowder in the nail gun is activated by the activation controller.

[0079] When performing the nailing method for measuring the thickness and solidification properties of continuously cast billet shells, the nailing device, under stable casting temperature range, steel grade and cross-section conditions, activates the nail gun to perform the first nailing perpendicular to the billet surface; after the nailing device moves a set distance relative to the billet along the casting direction, it activates the nail gun to perform the second nailing perpendicular to the billet surface.

[0080] In the embodiments provided by this invention, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, structures, or units, and may be electrical, mechanical, or other forms.

[0081] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0082] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0083] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. 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 invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for measuring the thickness and solidification properties of a continuously cast billet shell using a nail gun, characterized in that, include: Under stable casting temperature range, steel grade, and cross-sectional conditions, the nail gun is activated to perform the first nailing perpendicular to the surface of the billet; wherein, the nail contains linear sulfides distributed along the length direction of the nail and several tracer clusters spaced apart along the length direction of the nail, the tracer having the characteristics of being miscible with the main fluid of the continuous casting, not undergoing chemical reaction, and not undergoing phase transfer; After the nail gun moves a set distance relative to the billet along the billet pulling direction, it is activated to perform a second nailing perpendicular to the billet surface. After the continuously cast billet is shot, it is pulled out, cooled, processed, and sampled. The thicknesses of the billet shell for the two nail-shooting tests were determined as L1 and L2 based on the carbon and sulfur content at the nail-shooting point of the sample; the distances between the tracer and the solidified billet shell were determined as L3 and L4 based on the position of the tracer in the two nail-shooting tests. The solidification rate of the billet shell is the ratio of the difference in billet shell thickness between the two nail-shooting tests to the solidification time of the billet shell, and the diffusion rate of molten steel is the ratio of the difference in distance between the tracer and the solidified billet shell between the two nail-shooting tests to the diffusion time of molten steel.

2. The method for measuring the thickness and solidification properties of continuously cast billet shells according to claim 1, characterized in that, The sampling process includes: removing the surface of the sample layer by layer until the overall morphology of the nail can be observed; acid etching the sample after surface removal; and polishing the acid-etched sample.

3. The method for measuring the thickness and solidification characteristics of a continuously cast billet shell according to claim 2, characterized in that, Record the low-magnification morphology image after acid etching, use the low-magnification morphology image to determine the preliminary position of the billet shell, drill holes near the position of the billet shell to collect chips, use a carbon-sulfur analyzer to detect carbon and sulfur, and based on the obtained carbon and sulfur content, accurately define the thickness of the billet shell in the two nail shooting tests as L1 and L2.

4. The method for measuring the thickness and solidification characteristics of a continuously cast billet shell according to claim 1, characterized in that, The sample was scanned with an X-ray scanner to determine the position of the tracer in the two nail-shooting tests. The distances L3 and L4 between the tracer and the solidified shell were determined based on the position of the tracer and the thicknesses L1 and L2 of the shell.

5. The method for measuring the thickness and solidification properties of a continuously cast billet shell according to claim 1, characterized in that, Under a stable pulling speed v, the solidification time of the billet shell and the diffusion time of the molten steel during the two nail shooting tests are obtained by dividing the set distance L by the pulling speed v.

6. The method for measuring the thickness and solidification properties of a continuously cast billet shell according to claim 1, characterized in that, Before continuous casting begins, a nail gun is installed at the nail gun position. The casting temperature range and cross-sectional conditions at the nail gun position are stable. The nail gun includes a nail gun, an excitation controller, gunpowder, and a fixed bracket. The distance from the nozzle of the nail gun to the surface of the billet is 10~30mm.

7. A nail gun for measuring the thickness and solidification properties of a continuously cast billet shell, implementing the nail gun method for measuring the thickness and solidification properties of a continuously cast billet shell as described in any one of claims 1-6, characterized in that, include: The nail body (1) has a tail plate at its tail end that limits the depth of the nail's entry. The nail body (1) has a long groove in the elongation direction. Sulfide (2) is placed in the long groove. Several tracer clusters (3) are arranged at intervals in the nail body (1). The tracer has the characteristics of being miscible with the main fluid of the continuous casting, not undergoing chemical reaction and not undergoing phase transfer.

8. The nail gun for measuring the thickness and solidification properties of continuously cast billet shells according to claim 7, characterized in that, The liquidus temperature of the nail body is lower than the liquidus temperature of the continuously cast billet steel grade being measured.

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