KR102389502B1 - Self-assembled carbon coated steel and method of manufacturing the same - Google Patents

Abstract

The present invention provides a self-assembled carbon-coated steel material having oxidation resistance, sour resistance and hydrogen-induced cracking resistance, which can be formed by utilizing the existing heat treatment process of the steel material. According to an embodiment of the present invention, the self-assembly type carbon-coated steel, a steel base; an iron-silicide layer located on the steel matrix; and a carbon layer positioned on the iron-silicide layer.

Description

Self-assembled carbon coated steel and method of manufacturing the same

The technical idea of the present invention relates to a steel material, and more particularly, to a self-assembled carbon-coated steel material and a manufacturing method thereof.

Recently, steel materials for pressure vessels are being used in extreme environments such as high temperature, high pressure, cryogenic temperature and sour environment due to the enlargement of facilities. Therefore, in addition to basic physical properties, the required functions and qualities such as hydrogen induced cracking (HIC) resistance, high temperature physical properties, and low temperature toughness are becoming stricter. In order to simultaneously secure such complex properties related to high functionality and durability, new steel manufacturing processes such as alloy composition adjustment, reduction of impurity elements, and NACT (Normalizing and Accelerated Cooling and Tempering) are being introduced. In particular, in order to improve corrosion resistance, a post-treatment process such as forming a protective coating such as ceramic coating, polymer coating, nano material deposition, and self-assembly type nano coating is performed.

Recently, various types of two-dimensional nanomaterials for protective films have been in the spotlight due to their excellent mechanical and chemical properties. Materials for protective films currently used mainly include graphite, WSe, MoS ₂ , hexagonal boron nitride (hBN), etc., and are generally formed to a thickness of several hundred nanometers on the surface of the base material using chemical vapor deposition. . Since it is very difficult to secure uniformity and coverage for such a nano-sized protective film, optimization of related processes must be accompanied.

Korean Patent Application No. 10-2012-0150130

In the case of manufacturing a thick plate, it can be manufactured by performing post-heat treatment such as normalizing or tempering, like steel for pressure vessels. Since this heat treatment has process conditions similar to the conditions for forming various types of coating layers using an interfacial reaction, the coating layer can be formed on the surface of the steel material using the existing heat treatment process.

The technical problem to be achieved by the technical idea of the present invention is to provide a self-assembled carbon-coated steel material having oxidation resistance, sour resistance, and hydrogen-induced cracking resistance, which can be manufactured by utilizing the existing heat treatment process of steel, and a method for manufacturing the same will do

However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.

According to one aspect of the present invention, there is provided a self-assembled carbon-coated steel material having oxidation resistance, sour resistance and hydrogen-induced cracking resistance, and a method for manufacturing the same.

According to an embodiment of the present invention, the self-assembled carbon-coated steel material may include a steel, an iron-silicide layer positioned on the steel, and a carbon-coated layer positioned on the iron-silicide layer.

According to an embodiment of the present invention, it may further include a silicon oxide layer located on the carbon coating layer.

According to an embodiment of the present invention, the silicon oxide layer may further include silicon carbide.

According to one aspect of the present invention, there is provided a method for manufacturing a self-assembled carbon-coated steel material having oxidation resistance and hydrogen-induced cracking resistance.

According to an embodiment of the present invention, the method for manufacturing the self-assembled carbon-coated steel material includes: forming a silicon carbide layer on the surface of the steel material; and heat-treating the steel to form a carbon coating layer from the silicon carbide layer; may include

According to an embodiment of the present invention, the heat treatment may be performed simultaneously with the normalizing treatment of the steel, or may be performed simultaneously with the tempering treatment of the steel.

According to an embodiment of the present invention, in the heat treatment step, iron atoms diffused from the steel and silicon atoms diffused from the silicon carbide layer are chemically combined to form an iron-silicide layer, and the carbon from the silicon carbide layer A coating layer can be formed.

According to an embodiment of the present invention, before performing the step of forming a silicon carbide layer on the surface of the steel, hot rolling the steel; and primary cooling of the hot-rolled steel material.

According to an embodiment of the present invention, after performing the step of heat-treating the steel material, the step of secondary cooling the heat-treated steel material; may further include.

According to the technical idea of the present invention, it is possible to manufacture a carbon-coated steel material in which a self-assembled carbon coating layer or a carbon/silicon oxide composite layer is formed on the surface of the steel material by using an existing heat treatment process. The self-assembled carbon coating layer formed of the steel material may have excellent oxidation resistance, sour resistance, and hydrogen-induced cracking resistance.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a flowchart illustrating a method of manufacturing a self-assembled carbon-coated steel material according to an embodiment of the present invention.
2 and 3 are cross-sectional views illustrating a method of manufacturing a self-assembled carbon-coated steel material according to an embodiment of the present invention.
4 is a cross-sectional view showing a self-assembled carbon-coated steel material according to an embodiment of the present invention.
5 is a cross-sectional view showing a self-assembled carbon-coated steel material according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the technical spirit of the present invention to those skilled in the art. In this specification, the same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

In general, in order to secure the corrosion resistance and hydrogen induced cracking (HIC) resistance of steel materials, a method of securing cleanliness of steel materials or a method of controlling microstructure or precipitates has been applied. This method requires strict management of all processes, such as optimization of alloy design, steelmaking/casting/rolling/heat treatment, etc., so the production volume is lower than that of general materials and the production cost can be increased. As another method, there is a limitation in that a separate post-processing production process must be added in a method through painting and formation of a protective film.

The technical idea of the present invention relates to a self-assembled carbon-coated steel material having corrosion resistance and sour resistance and a method for manufacturing the same, and to form a self-assembled carbon-coated steel material based on heat treatment. Specifically, by inducing an interfacial reaction rate control and selective interfacial reaction based on Gibbs free energy through a heat treatment process between pre-formed silicon carbide and steel, a carbon layer or a carbon/silicon oxide composite layer is formed on the surface of the steel material. It is possible to manufacture a steel material having oxidation resistance, sour resistance, and hydrogen-induced cracking resistance.

1 is a flowchart illustrating a method of manufacturing a self-assembled carbon-coated steel material according to an embodiment of the present invention.

Referring to Figure 1, the method of manufacturing the self-assembled carbon-coated steel material, the step of hot rolling the steel (S110); First cooling the hot-rolled steel material (S120); forming a silicon carbide layer on the surface of the steel (S130); heat-treating the steel material so that a carbon coating layer is formed from the silicon carbide layer (S140); and secondary cooling of the heat-treated steel material (S150).

The steel material may include various steel materials, and may have various shapes such as a steel plate, a round bar, and a section steel.

The step (S110) of hot rolling the steel is a step of rolling a cast steel material such as a slab formed in a continuous casting process at a high temperature, for example, wide rolling, rough rolling, and finishing rolling may be configured.

The step (S120) of the primary cooling of the hot-rolled steel material is a step of cooling from the rolling end temperature to room temperature (about 25° C.), and may be made in various ways, such as air cooling, compressed air cooling, water cooling, and the like.

Forming a silicon carbide (SiC) layer on the surface of the steel (S130) may be performed in various ways. For example, DC magnetron sputtering, RF sputtering, chemical vapor deposition, or a deposition method such as plasma enhanced chemical vapor deposition is performed, or is performed using a coating method such as paste application or spray spraying, or silicon carbide film , a silicone film, or a carbon film may be appropriately attached. The thickness of the silicon carbide layer may vary depending on a desired purpose, for example, may be in the range of 1 nm to 1 mm.

To form a carbon coating layer from the silicon carbide layer, the step of heat-treating the steel (S140) may be performed at various temperatures. Specifically, the silicon constituting the silicon carbide layer may be carried out in a temperature range at which diffusion into the steel is possible. For example, the step of heat-treating the steel (S140) may be performed simultaneously with the normalizing treatment of the steel, for example, at an Ac3 temperature or higher, for example, 700 ℃ ~ 1,000 ℃, for example 850 ℃ It can be carried out at a temperature of ~ 950 °C. Alternatively, the step (S140) of heat-treating the steel material may be performed simultaneously with the tempering treatment of the steel material, for example, below the Ac3 temperature, for example, at a temperature of 400°C to 700°C, for example, 550°C. It can be carried out at a temperature of ~ 700 °C.

The secondary cooling of the heat-treated steel material (S150) is a step of cooling from the heat treatment temperature to room temperature (about 25° C.), and may be made in various ways, such as air cooling, compressed air cooling, water cooling, and the like.

However, the manufacturing method of the self-assembled carbon-coated steel material of FIG. 1 is exemplary, and the technical spirit of the present invention is not limited thereto. For example, the heat treatment may be performed separately from the normalizing treatment or tempering treatment of the steel material.

2 and 3 are cross-sectional views illustrating a method of manufacturing a self-assembled carbon-coated steel material according to an embodiment of the present invention.

Referring to FIG. 2 , a silicon carbide layer 120 is formed on the surface of the steel material 110 .

Referring to FIG. 3 , the steel material 110 and the silicon carbide layer 120 are heat-treated. The heat treatment may be performed at a temperature of 500 ℃ ~ 1,000 ℃. By the heat treatment, iron (Fe) atoms are diffused from the steel material 110 in the direction of the silicon carbide layer 120 , and silicon (Si) atoms are diffused from the silicon carbide layer 120 in the direction of the steel material 110 . Carbon (C) atoms diffuse to the upper side of the silicon carbide layer 120 .

4 is a cross-sectional view showing a self-assembled carbon-coated steel material 100 according to an embodiment of the present invention.

Referring to FIG. 4 , the carbon-coated steel material 100 is a steel material 110 , an iron-silicide layer 130 located on the steel material 110 , and an iron-carbon-coated steel layer 140 located on the iron-silicide layer 130 ). includes

As a result of the heat treatment shown in FIG. 3 , the carbon coating layer 140 may be formed from the silicon carbide layer 120 by diffusion of the silicon (Si) atoms. In addition, an iron-silicide (Fe-Si) layer 130 may be formed between the steel material 110 and the carbon coating layer 140 . The iron-silicide layer 130 may be formed by chemical bonding between iron (Fe) atoms diffused from the steel material 110 and silicon (Si) atoms diffused from the silicon carbide layer 120 .

The iron-silicide layer 130 may be formed through the following reaction.

Fe + SiC -> Fe ₃ Si + Fe ₂ Si + C

Fe ₃ C+Fe(Si) -> Fe ₃ Si + Fe ₂ Si + C

In addition, the silicon carbide layer 120, silicon is removed by diffusion, carbon remains and self-assembled (self-assembled), the carbon coating layer 140 can be formed. The carbon coating layer 140 may include various types of carbon, for example, graphite.

5 is a cross-sectional view showing a self-assembled carbon-coated steel material 100a according to another embodiment of the present invention.

5, the carbon-coated steel material 100a is, the steel 110, the iron-silicide layer 130 located on the steel 110, the iron-carbon-coated steel layer 140 located on the silicide layer 130, and a silicon oxide (SiO ₂ ) layer 150 positioned on the carbon coating layer 140 . That is, it may include a composite layer including the carbon coating layer 140 and the silicon oxide layer 150 . In addition, the silicon oxide layer 150 may further include silicon carbide therein.

The silicon oxide layer 150 may be formed by combining silicon diffused in the iron-silicide layer 130 with oxygen in the air. In addition, the silicon carbide interposed in the silicon oxide layer 150 may be a material remaining from the silicon carbide layer 120 .

According to the technical idea of the present invention, using a heat treatment process such as normalizing treatment or tempering treatment, a carbon coating layer or a composite layer of a carbon layer/silicon oxide layer of a steel material using a selective interfacial diffusion reaction of silicon in a silicon carbide layer It can be formed on the surface. The carbon coating layer has a thin film shape, and the steel material on which the carbon coating layer is formed may provide excellent oxidation resistance, sour resistance, and hydrogen-induced cracking resistance. This manufacturing method can minimize the change in the physical properties of the steel. The steel material is not limited to a specific steel material, and may include all steel types to which normalizing treatment or tempering treatment is applied.

The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.

100a, 100: carbon coated steel,
110: steel, 120: silicon carbide layer
130: iron-silicide layer, 140: carbon coating layer
150: silicon oxide layer

Claims (8)

delete delete delete hot rolling the steel;
first cooling the hot-rolled steel;
forming a silicon carbide layer on the surface of the steel;
heat-treating the steel to form a carbon coating layer from the silicon carbide layer; and
A method of manufacturing a self-assembled carbon-coated steel material comprising a; secondary cooling of the heat-treated steel material,
The heat treatment is performed at the same time as the normalizing treatment of the steel at a temperature of 700 ℃ ~ 950 ℃,
In the heat treatment step, iron atoms diffused from the steel and silicon atoms diffused from the silicon carbide layer are chemically bonded to form an iron-silicide layer, and the carbon coating layer is formed from the silicon carbide layer,
The self-assembled carbon-coated steel material,
steel;
an iron-silicide layer located on the steel; and
Including; a carbon coating layer located on the iron-silicide layer;
A method for manufacturing a self-assembled carbon-coated steel material. hot rolling the steel;
first cooling the hot-rolled steel;
forming a silicon carbide layer on the surface of the steel;
heat-treating the steel material to form a carbon coating layer from the silicon carbide layer; and
A method of manufacturing a self-assembled carbon-coated steel material comprising a; secondary cooling of the heat-treated steel material,
The heat treatment is performed at the same time as the tempering treatment of the steel at a temperature of 400 ℃ ~ 700 ℃,
In the heat treatment step, iron atoms diffused from the steel and silicon atoms diffused from the silicon carbide layer are chemically bonded to form an iron-silicide layer, and the carbon coating layer is formed from the silicon carbide layer,
The self-assembled carbon-coated steel material,
steel;
an iron-silicide layer located on the steel; and
Including; a carbon coating layer located on the iron-silicide layer;
A method for manufacturing a self-assembled carbon-coated steel material. delete delete delete

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