KR20110137034A

KR20110137034A - Method and apparatus of hot press forming line

Info

Publication number: KR20110137034A
Application number: KR1020100057013A
Authority: KR
Inventors: 김병완; 정민수
Original assignee: 한화테크엠주식회사
Priority date: 2010-06-16
Filing date: 2010-06-16
Publication date: 2011-12-22
Also published as: KR101202121B1

Abstract

PURPOSE: Hot pressing method and device are provided to prevent the oxidizing of the surface of a steel plate and decarburization in hot pressing. CONSTITUTION: A hot pressing method comprises next steps. A plate-shaped material is put into a furnace(1). The material is heated at a temperature of over 700°C in the furnace. In a state nitrogen is filled in the heated material, HRX gas consisting of LNG and air is supplied to the heated material to prevent the generation of oxidized scales and decarburization. The heated material is discharged to the outside of the furnace. The discharged material is formed by press. Nitrogen and HDX gas are additionally supplied to the furnace. HRX gas consists of CO of 20~28%, H2 of 30~40%, CH of 0.1~1%, and N2 of 40~45%.

Description

Hot press forming method and apparatus {Method and apparatus of hot press forming line}

The present invention relates to a hot press molding method and apparatus, and more particularly, has one or more furnaces into which a material is input and heated to heat the material at 700 ° C. or higher in the furnace, and LNG and nitrogen together with the heated material. It is a hot press forming method and apparatus in which press molding is performed after supplying HRX gas mixed with air to prevent generation of an oxidized scale and discharging the material while preventing decarburization.

In recent years, with the increase in strength of exterior or structural steel sheets, the trend is to reduce the weight of automobiles. For this purpose, efforts are being made to reduce the thickness of steel sheets used in automobiles. However, there are a variety of problems to proceed with high strength while reducing the thickness of the steel sheet.

Firstly, the steel sheet is press-formed, especially deep drawing, and the strength of the steel sheet is increased after molding, and the contact pressure with the mold increases during molding, which causes the steel sheet to be worn or broken, that is, cracking. Will be produced. In order to solve this problem, intentionally lowering the blank holding force holding the edge of the steel sheet when drawing the steel sheet may increase the thickness of the product after the drawing or produce a product having a shape different from the desired shape.

In order to solve the problem of drawing, a method of applying a lubricant to a drawing mold is used in the field, but this method not only increases the production time, but is also a temporary measure and question the effect thereof.

In particular, compared to materials such as general steel sheet (SCP1), processing steel sheet (SCP2), and deep processing steel sheet (SCP3), high tensile steel sheets, that is, steel sheets such as SPFC 45, 60, and SPFC 35, 40, are inferior in elongation. Even cracks often occur.

Hot press forming or warm press forming has been proposed as a method of drawing and forming a high-strength steel sheet by press, but the biggest problem of conventional hot or warm press forming is that By molding the steel sheet, a problem occurs that the surface of the steel sheet is oxidized.

In order to solve this problem, a gas soft nitriding method has been developed and proposed, but the conventional gas soft nitriding method uses an ammonia (NH ₃ ) and carbon monoxide (CO) to oxynitrate the surface of a steel, and ammonia has many limitations due to its unique smell. And since carbon monoxide is also a very harmful substance to the human body, the equipment for using the gas soft nitriding method is very expensive equipment is required.

Accordingly, an object of the present invention is to provide a hot press forming method and apparatus capable of preventing the surface of a steel sheet from being oxidized and decarburization occurring, which is a problem occurring in the conventional hot press forming.

In addition, to form a furnace consisting of one or more zones for hot press molding, the material is heated and discharged in a state in which HRX gas mixed with LNG and air is introduced together in an atmosphere filled with nitrogen, and then drawn as a press. It is another object of the present invention to provide a hot press forming method and apparatus which suppresses generation of scale on the surface of a material and prevents decarburization.

Hot press forming method according to the present invention comprises the steps of injecting a plate-shaped material into the furnace; Heating the injected material to 700 ° C or higher; Supplying HRX gas in which LNG and air are mixed while nitrogen is charged to the heated material to prevent generation of an oxidative scale and to prevent decarburization; Discharging the heated material out of the furnace; Forming the discharged material by a press; constitutes.

Hot press forming method and apparatus according to the present invention is formed by forming at least one furnace for hot press molding and injecting the HRX gas mixed with LNG and air in the atmosphere filled with nitrogen to discharge the heated material after press By drawing in a furnace, it is possible to prevent the surface of the steel sheet, which is a problem occurring during conventional hot press forming, is oxidized and decarburization occurs.

1 is a configuration example of the present invention
FIG. 2 is a circuit diagram of FIG. 1.
3 and 4 are partial cross-sectional views of the present invention.
5 is a partial configuration example of the present invention

The present invention relates to a hot press molding method and apparatus, and more particularly, has one or more furnaces into which a material is input and heated to heat the material at 700 ° C. or higher in the furnace, and LNG and nitrogen together with the heated material. It is a hot press forming method and apparatus in which press molding is performed after supplying air mixed HRX gas to prevent generation of oxidation scale and at the same time discharging the material in a decarburization prevention state.

Hot press forming method according to the present invention comprises the steps of injecting a plate-shaped material into the furnace; Heating the injected material to 700 ° C or higher; Supplying HRX gas in which LNG and air are mixed while nitrogen is charged to the heated material to prevent generation of an oxidative scale and to prevent decarburization; Discharging the heated material out of the furnace; Forming the discharged material into a press.

Hereinafter, preferred embodiments of the present invention by referring to the accompanying drawings in detail as follows.

1 is a configuration example of the present invention, Figure 2 is a configuration circuit diagram of Figure 1, Figures 3 and 4 is a partial cross-sectional view of the present invention, Figure 5 is a partial configuration example of the present invention, according to the present invention The hot press forming apparatus includes an inlet 2 into which a plate-shaped material is introduced, a furnace 1 having one or more zones 1a to 1i for heating the injected material to 700 ° C or higher, and an outlet through which the heated material is discharged. It is configured to include (3), wherein the furnace (1) is configured to supply HRX gas mixed with LNG and air together with nitrogen in order to prevent the generation of oxidation scale in the heated material.

First, the input and discharge of the material is preferably to use the automated robot 4, in particular, the material discharged from the outlet 3 side is discharged in a state heated to 700 ℃ or more should be discharged by the robot.

The material is introduced into the furnace 1 through the inlet 2 and is heated step by step the material introduced into the furnace (1). In the illustrated embodiment, the number of zones formed in the furnace is nine in total, and the first and second zones 1a and 1b are heated to a temperature of 700 to 760 ° C, and the third and fourth zones 1c. , 1d) is heated to a temperature between 760 and 800 ° C, and is heated between 800 and 860 ° C in the 5th and 6th zones (1e and 1f), and 860 to 910 in the 7th and 9th (1g and 1i) th zones. Heat between ° C. After that, the heated material is discharged to the outlet 3 and immediately subjected to a drawing (forming) process in the press.

The furnace 1 may be used as a heat source of the heater 7 using various raw materials such as LNG and LPG.

In addition, a gas inlet 5 should be formed in at least one of the zones of the furnace, and the HRX gas in which LNG and air are mixed is supplied to the gas inlet 5.

In general, LNG (liquefied natural gas, liquefield natural gas) is liquefied by cooling a gas mainly composed of methane (CH ₄ ) obtained by refining natural gas. The advantage is that natural gas is desulfurized and dehumidified before liquefaction. It is known to be better, cleaner and harmless.

The present invention can use the LNG as a combustion fuel in the furnace, by supplying the HRX gas mixed with LNG and air in the furnace to prevent the generation of oxide scale on the heating material.

The mixing ratio of LNG and air to generate HRX gas may vary depending on the material to be treated and may vary depending on the concentration of oxygen (O ₂ ) in the furnace.

The reason why decarburization of steel occurs in the heat treatment furnace is that when the carbon concentration in the furnace is lowered, the carbon inside the steel moves to the surface by diffusion and combines with oxygen to go out as carbon monoxide (CO). Carburization is the diffusion of carbon atoms into the steel as a result of the adsorption of CO molecules on the surface of the steel and pyrolysis.

In order to prevent such decarburization, the present invention uses HRX gas containing almost no carbon dioxide (CO ₂ ) and water (H ₂ O) and whose main components are CO, H ₂ , and N ₂ together with nitrogen as an atmosphere gas in a furnace. As the HRX gas that can be used in the present invention, the concentration of CO is preferably 20 to 28%, H ₂ 30 to 40%, CH ₄ 0.1 to 1%, and N ₂ 40 to 45%. .

The HRX gas can be used for carburizing, carburizing and nitrification by having a strong carburizing property and a strong reducing property for iron, including a large amount of CO and H ₂ gas, as can be seen from the above component ratio.

The furnace may additionally supply HDX gas in addition to HRX gas.

The HDX gas can also be produced by mixing LNG and air, the HDX gas that can be used in the present invention is a concentration of CO ₂ 6 ~ 15%, CO 1 ~ 11%, H ₂ 0.5 ~ 10%, CH ₄ 0 ~ 1%, is preferably used in that the N ₂ 70 ~ 85%.

When the content of CO in the HDX gas is high, it can be used for bright annealing and heat treatment heat treatment of low carbon steel with weak reduction property against iron. A small amount of H ₂ can be used for the annealing of special steels and for the explosive, low oxidizing steels during air and combustion.

At least one of the inlet 2 and the outlet 3 is blown with nitrogen to prevent outside air from entering the furnace 1 and to prevent high heat from being transferred to the outside. It is more preferable to form.

In the furnace, a ceramic roller 8 is formed as shown in FIGS. 3 to 5 in order to handle the transfer of materials. The ceramic roller 8 is driven by a shaft 12 and a driving sprocket 9 formed outside the furnace. Received.

At this time, the ceramic roller 8 is more preferably formed of a ceramic material that is resistant to heat, and a coil spring 11 is formed between the ceramic roller 8 and the shaft 12 to prevent thermal deformation of the ceramic roller 8. It can be configured so that absorption is made.

The coil spring 11 has an effect of correcting the error in the rotational direction with absorption of the axial deformation of the ceramic roller (8).

Furnace 1a-1i. Zone
2. Inlet 3. Outlet
4.robot 5.gas inlet
6. Case 7. Heater
8. Ceramic Roller 9. Driving Sprocket
10. Insulation 11. Coil Spring
12. Shaft

Claims

Injecting the plate-shaped material into the furnace;
Heating the injected material to 700 ° C or higher;
Supplying HRX gas in which LNG and air are mixed while nitrogen is charged to the heated material to prevent generation of an oxidative scale and to prevent decarburization;
Discharging the heated material out of the furnace;
Molding the discharged material into a press;
Hot press molding method characterized by consisting of

The method of claim 1,
The furnace is hot press molding method characterized in that additionally supply HDX gas with nitrogen in addition to HRX gas

The method of claim 1,
The HRX gas is hot press molding method characterized in that the concentration of CO 20 ~ 28%, H ₂ 30 ~ 40%, CH ₄ 0.1 ~ 1%, N ₂ 40 ~ 45% of the total volume

The method of claim 2,
The HDX gas is hot press molding characterized in that the concentration of CO ₂ is 6 ~ 15%, CO 1 ~ 11%, H ₂ 0.5 ~ 10%, CH ₄ 0 ~ 1%, N ₂ 70 ~ 85% of the total volume Way

An inlet 2 into which the plate-shaped material is introduced, a furnace 1 having one or more zones 1a to 1i for heating the injected material to 700 ° C or more, and an outlet 3 through which the heated material is discharged. The furnace 1 is a hot press forming apparatus characterized in that configured to supply HRX gas mixed with LNG and air together with nitrogen in order to prevent the oxidation scale is generated in the heated material (1)

The method of claim 5,
Hot press forming apparatus characterized in that the furnace (1) in addition to the HDX gas in addition to the HRX gas

The method of claim 5,
At least one of the inlet (2) and the outlet (3) hot presser molding apparatus characterized in that the air curtain is formed by blowing nitrogen to prevent entering into the outside air furnace (1)

The method of claim 5,
The roller which is responsible for conveying the material in the furnace 1 is formed of a ceramic roller 8 mainly composed of ceramic, and a shaft 12 for transmitting rotational power is formed on one side of the ceramic roller 8. The hot press forming apparatus is characterized in that the coil spring 11 is formed between the ceramic roller 8 and the shaft 12 to absorb the heat deformation of the ceramic roller 8.