KR101581592B1 - Method for manufacturing plate - Google Patents

Abstract

Disclosed is a method to manufacture a plate. According to an embodiment of the present invention, the method to manufacture the plate comprises: a step of setting a target crack index of a plate which is produced from a slab; a step of measuring content of phosphorous (P) of the slab; a step of setting a threshold thickness of the plate; a step of predicting an expected thickness of the plate for production using an established target crack index, the measured content of the phosphorous and a mathematical equation 1 below; and a step of judging whether to proceed a post process, by comparing an expected thickness with the threshold thickness. [Mathematical equation 1] Y = -30.0 + 0.614[T] + 582[P] (here, Y is a crack index of the plate, [T] is a thickness (mm) of the plate, and [P] is the content (%) of the phosphorous (P) included in the slab).

Description

[0001] METHOD FOR MANUFACTURING PLATE [0002]

The present invention relates to a method for producing a plate.

Plate is a steel-plate manufactured through a rolling process, and widely used for ships, offshore structures, and steel structures.

A general plate manufacturing process will be briefly described. First, after the slab is heated in a heating furnace by heating, scales (iron oxide generated on the surface) are removed, and the required hot rolling process (for example, rough rolling, Rolled). The rolled plate is subjected to a cooling process, and then the plate is completed by shearing and heat treatment.

A related art is disclosed in Korean Patent Laid-Open Publication No. 10-2002-0044880 (published on Dec. 12, 2000, entitled "Cold-rolled steel sheet with excellent moldability and its manufacturing method").

The embodiments of the present invention predict cracks at the central portion of the plate from the thickness and phosphorus content of the plates to be produced and estimate the defects of the plate to be produced using the plate crack index, To thereby improve the quality of the product.

According to an aspect of the present invention, there is provided a method of manufacturing a slab, comprising: setting a target crack index of a plate to be produced from a slab; Measuring a phosphorus (P) content of the slab; Setting a critical thickness of the plate; Predicting a predetermined thickness of the plate to be produced using the predetermined target crack index, the content of the measured phosphorus, and the following equation (1); And comparing the predetermined thickness with the critical thickness to determine the progress of the subsequent process of the plate.

[Equation 1]

Y = -30.0 + 0.614 [T] + 582 [P]

Where [Y] is the crack index of the plate, [T] is the thickness (mm) of the plate, and [P] is the content (%) of phosphorus (P) contained in the slab.

The plate manufacturing method may further include the step of rolling the plate to the predetermined thickness when the predetermined thickness is equal to or less than the critical thickness.

Wherein the plate manufacturing method includes: a changing step of changing the thickness of the plate to be produced to be less than the threshold thickness when the predetermined thickness exceeds the critical thickness; And

And a rolling step of rolling the plate with the changed plate thickness.

The target crack index may be 0.5.

According to another aspect of the present invention, a target crack index of a plate to be produced from a slab is determined and a phosphorus (P) content of the slab is measured to predict a predetermined thickness of the plate through the following equation (1) And comparing the predetermined critical thickness of the plate with the predetermined thickness of the plate to change the thickness of the plate that is scheduled to be produced to less than the critical thickness if the predetermined thickness exceeds the critical thickness.

[Equation 1]

Y = -30.0 + 0.614 [T] + 582 [P]

Where [Y] is the crack index of the plate, [T] is the thickness (mm) of the plate, and [P] is the content (%) of phosphorus (P) contained in the slab.

The plate manufacturing method may roll the plate to the predetermined thickness when the predetermined thickness is equal to or less than the critical thickness.

The target crack index may be 0.5.

According to the embodiments of the present invention, it is possible to predict cracks at the central portion of the plate from the thickness and phosphorus content of the plates to be produced, estimate defects of the plates to be produced using the plate crack indexes, It is possible to realize a plate manufacturing method capable of improving the quality of a product.

1 is a flowchart illustrating a method of manufacturing a plate according to an embodiment of the present invention.
2 is a graph showing the plate crack index according to the phosphorus (P) content of the slab.
3 is a graph showing the plate crack index according to the thickness of the plate.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method of manufacturing a plate according to the present invention will be described in detail with reference to the accompanying drawings. In the following description with reference to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, A description thereof will be omitted.

FIG. 1 is a flowchart showing a plate manufacturing method according to an embodiment of the present invention, and FIG. 2 is a graph showing a plate crack index according to phosphorus (P) content of a slab. 3 is a graph showing the plate crack index according to the thickness of the plate.

According to the embodiments of the present invention, the center crack index (Y) of the plate can be predicted from the thickness (T) and phosphorus (P) content (%) of the plate to be produced, It is possible to realize a plate manufacturing method capable of improving the quality of the final product by appropriately changing the thickness of the plate to be produced when a defect is expected.

Hereinafter, the plate manufacturing method according to the present embodiment will be described with reference to FIG. 2, FIG. 3, and Table 1.

Generally, a phenomenon that a specific component is biased to a part of a steel (slab in this case) (for example, a thickness center part) may occur due to a time deviation in solidification of molten steel in a center part of a slab produced through a performance process. In this way, the part where certain elemental elements are biased in a certain region of the steel is called a segregation.

When the plate is produced through rolling in the subsequent process in the state where the slab is segregated in the central portion of the thickness of the slab, cracks may be generated in the plate due to the accumulation of hydrogen, which may adversely affect the quality of the product.

Representative components of segregation include phosphorus (P) as shown in Table 1 below. Particularly, the distribution coefficient indicating the degree of distribution between constituent elements contained in the steel is in inverse proportion to segregation. That is, the smaller the distribution coefficient is, the greater the possibility of occurrence of segregation.

Solute Partition coefficient in steel Aluminum 0.92 Carbon 0.20 Chromium 0.95 Manganese 0.90 Nitrogen 0.25 Nickel 0.83 Phosphorus 0.13 Silicon 0.83 Sulfur 0.02 Titanium 0.40

Therefore, the higher the content of phosphorus (P) is, the more segregation is concentrated at the center of the thickness of the produced plate, and the possibility of occurrence of cracks increases. This can be confirmed by increasing the crack index of the plate according to the phosphorus (P) content of the slab, as shown in FIG.

Further, as the thickness of the plate to be produced becomes thicker, the release of hydrogen remaining in the slab becomes more difficult, and the possibility of cracking in the center of the thickness of the plate is increased. This can be confirmed by increasing the crack index of the plate according to the thickness of the plate, as shown in FIG.

In the present embodiment, the center crack index Y of the plate can be predicted from the thickness T and phosphorus (P) content of the plate to be produced, and the defect of the plate to be produced is predicted using the plate crack index And if the defect is expected, the quality of the final product can be improved by appropriately changing the thickness of the plate to be produced.

Referring to FIG. 1, a plate manufacturing method according to an embodiment of the present invention includes setting a target crack index of a plate to be produced from a slab (S10); Measuring a phosphorus (P) content of the slab (S20); Setting a critical thickness of the plate (S30); (S40) of predicting a predetermined thickness of the plate using the predetermined target crack index, the measured phosphorus content, and the following equation (1); And comparing the predetermined thickness with the critical thickness to determine the progress of the subsequent process of the plate.

[Equation 1]

Y = -30.0 + 0.614 [T] + 582 [P]

Where [Y] is the crack index of the plate, [T] is the thickness (mm) of the plate, and [P] is the content (%) of phosphorus (P) contained in the slab.

First, it is necessary to set the target crack index (Y) of the plate to be produced from the slab (S10).

Here, the plate crack index is an index indicating the probability of occurrence of cracks in the plate after the rolling process depending on the degree of segregation formed at the center of the thickness of the plate. As shown in FIGS. 2 and 3, The plate crack index (Y) can be calculated from the regression equation of Equation (1) from the content (T) and phosphorus (P) content (%

According to this embodiment, the target crack index of the plate may be, for example, 0.5. Referring to FIGS. 2 and 3, it can be seen that a relatively high-quality plate can be produced in a region where the crack index of the plate is 0.5 or less.

By appropriately changing the thickness of the plate to be produced in accordance with the phosphorus content (content) of the slab to be supplied in accordance with the situation on the basis of the target crack index of the plate thus set, deterioration of plate quality due to cracking can be reduced, Can be produced in large quantity.

For this purpose, it is necessary to measure the content of phosphorus (P) contained in the slab produced in the performance process, which is a preceding process (S20).

For example, in order to maintain the crack index of the plate to be produced at 0.5 or less, which is the target crack index, the thickness of the plate to be produced is set at A reference value for resetting (i.e., critical thickness) is required. Therefore, it is necessary to set in advance a critical thickness as a reference for changing the plate thickness to be produced (S30).

In the present embodiment, it can be seen that the critical plate thickness [T] is 49.4-947.9 [P] in order to achieve Y = 0.5, which is the target crack index, by using Equation (1). At this time, when the phosphorus content [P] of the slab provided through the playing process is, for example, 0.01%, the reference critical plate thickness for producing a good plate having a target crack index of 0.5 or less may be 39.9 mm.

Next, the predetermined thickness of the plate to be produced (that is, to be produced from the slab) can be predicted by using the predetermined target crack index (Y), the measured phosphorus content (P) and the above formula (1) S40), it is possible to determine the progress of the subsequent process of the plate to be produced by comparing the predetermined thickness and the critical thickness as shown in FIG.

For example, when the target crack index (Y) of the plate is 0.5 and the phosphorus content (P) of the slab provided in the performance process is 0.01%, the predetermined thickness T of the plate to be produced, Can be predicted to be 39.9 mm or less, which is a preset critical thickness, through Equation (1). Therefore, when a plate is produced from the slab to a thickness of 39.9 mm or less, it is possible to mass-produce a plate having a plate thickness center crack index of 0.5 or less.

That is, when the predetermined thickness of the plate to be produced is less than or equal to the critical thickness, the plate may be rolled to the predetermined thickness (S50).

On the contrary, when the predetermined thickness exceeds the critical thickness, when the plate is produced with the predetermined thickness, the center crack index of the plate produced by the final product exceeds the target crack index of 0.5, The probability of occurrence is very high. Therefore, in this case, it is necessary to adjust the thickness (i.e., the predetermined thickness) of the plate to be produced from the corresponding slab to a critical thickness of 39.9 mm or less.

To this end, the plate manufacturing method according to the present embodiment includes a changing step (S60) of changing the thickness of the plate to be produced to be less than or equal to the critical thickness when the predetermined thickness exceeds the critical thickness; And a rolling step (S70) of rolling the plate to be produced with the plate thickness thus changed.

As described above, according to the present embodiment, it is possible to predict the center crack index Y of the plate from the thickness T of the plate to be produced and the phosphorus content P of the slab, It is possible to realize a plate manufacturing method capable of significantly reducing the defect rate of the final product and improving the quality of the product by appropriately changing the thickness of the plate to be produced when the defect is expected.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention as set forth in the appended claims. The present invention can be variously modified and changed by those skilled in the art, and it is also within the scope of the present invention.

100: Reaction furnace
110: catalyst
120: Burner
200:
210: injection chamber
220: Nozzle
300: cooling section
310: first cooling chamber
320: second cooling chamber
400: Desulfurization unit
500: sulfur storage tank

Claims (7)

Setting a target crack index of the plate to be produced from the slab;
Measuring a phosphorus (P) content of the slab;
Setting a critical thickness of the plate;
Predicting a predetermined thickness of the plate to be produced using the predetermined target crack index, the content of the measured phosphorus, and the following equation (1);
Comparing the predetermined thickness with the critical thickness to determine the progress of the subsequent process of the plate; And
And rolling the plate to the predetermined thickness when the predetermined thickness is equal to or less than the critical thickness.
[Equation 1]
Y = -30.0 + 0.614 [T] + 582 [P]
Where [Y] is the crack index of the plate, [T] is the thickness (mm) of the plate, and [P] is the content (%) of phosphorus (P) contained in the slab.
delete The method according to claim 1,
A changing step of changing the thickness of the plate, which is to be produced, to be less than or equal to the critical thickness when the predetermined thickness exceeds the critical thickness; And
Further comprising the step of rolling the plate with the plate thickness changed.
The method according to claim 1,
Wherein the target crack index is 0.5.
Determining a target crack index of a plate to be produced from the slab and measuring a phosphorus content of the slab to predict a predetermined thickness of the plate through the following equation 1 and determining a predetermined critical thickness And when the predetermined thickness exceeds the critical thickness, the thickness of the plate to be produced is changed to be less than the critical thickness and rolled.
[Equation 1]
Y = -30.0 + 0.614 [T] + 582 [P]
Where [Y] is the crack index of the plate, [T] is the thickness (mm) of the plate, and [P] is the content (%) of phosphorus (P) contained in the slab.
6. The method of claim 5,
And rolling the plate to the predetermined thickness when the predetermined thickness is equal to or less than the critical thickness.
6. The method of claim 5,
Wherein the target crack index is 0.5.

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