WO2019221459A1

WO2019221459A1 - Radiant heating device for continuous heat treatment and support structure

Info

Publication number: WO2019221459A1
Application number: PCT/KR2019/005684
Authority: WO
Inventors: 김형수
Original assignee: (주)넥스이앤에스
Priority date: 2018-05-15
Filing date: 2019-05-12
Publication date: 2019-11-21
Also published as: KR20190130938A

Abstract

The present invention relates to a radiant heating device for indirectly heating, in a non-oxidizing atmosphere, a steel sheet that moves within a continuous annealing furnace and a support structure therefor. Particularly, the present invention relates to a radiant heating device and a support structure therefor, the radiant heating device increasing the rigidity to resist bending deformation caused by the self-weight of the radiant heating device so as to decrease deformation of the radiant heating device, and mitigating the stress concentration of a support unit so as to prevent the support unit from breakage.

Description

Radiation Heater and Support Structure for Continuous Heat Treatment Furnace

The present invention relates to a radiant heating apparatus and a support structure for indirectly heating a steel sheet moving in a continuous annealing furnace in an anoxic atmosphere, and in particular, to increase the rigidity resistant to bending deformation caused by the self-weight of the radiant heating apparatus. The present invention relates to a radiant heating device and a support structure thereof capable of reducing deformation of the device and relieving stress concentration of the support to prevent breakage of the support.

In general, the radiant heating device is used to indirectly heat the steel sheet in an oxidizing atmosphere during the production of cold rolled or surface treated steel sheets. Use parallel to the direction of travel. A burner is installed in the radiant tube to burn the fuel in the burner in the radiant tube so that the tube is heated by the heat of combustion, and the hot tube radiates radiant thermal energy to heat the low temperature steel sheet. The oxidation of the steel sheet can be prevented by maintaining the atmosphere in the heat treatment furnace in a reducing atmosphere such as hydrogen or nitrogen and heating the steel sheet using radiant heat of the radiation tube. Since the radiant tube is heated to a high temperature of about 1,000 ^o C, the radiant tube is made of heat-resistant steel containing a large amount of high Ni-Cr component to prevent oxidation and corrosion at high temperatures and maintain proper strength. .

However, when a certain amount of fuel is combusted in a narrow tube by a burner installed in a radiant tube, local overheating due to a flame collision is avoided at the end of the radiant tube where the hot flame generated in the limited space reverses the direction of travel. It becomes impossible. Most radiant tubes have a structure in which the support of the radiant tube is joined to the overheated end by welding, and is mounted on the fixing part installed on the furnace wall. At this time, the weld-bonded support of the radiation tube is concentrated due to the notch shape, so the highest tensile stress acts on the radiation tube, while the yield strength and tensile strength of the material decreases rapidly as the temperature increases, so that the support portion may be damaged. Will be higher. In addition, during thermal expansion and contraction of the radiation tube, frictional force that resists deformation occurs between the radiation tube support and the fixed portion of the furnace wall, which causes a large internal stress on the radiation tube support and the radiation base material, resulting in damage of the radiation tube. Done.

As a result, an increase in the internal stress of the support part due to stress concentration, a decrease in the allowable tensile strength of the material due to local overheating, and frictional resistance of the support part make the support part of the radiation tube easy to crack and break, More than half occur in the supports. In addition, radiation tubes with relatively large weights and long span lengths, such as duplex P-type or W-type radiating tubes, generate creep deformation with time of use, and these creep deformations increase the temperature of the radiating tubes. As it increases, the internal stress acting on the radiation tube increases. Accordingly, the center of the span direction of the first straight pipe portion of the radiation pipe where a burner is installed in the radiation pipe to form a high-temperature flame is deformed into a narrowing section in which the circular cross section is distorted, and a permanent deformation in which the center portion of the straight pipe sag in the direction of gravity appears and radiates. Frequent problems require replacing the tubes. In general, in the non-oxidation continuous annealing furnace, most of the replacement objects of the radiation tube are caused by the above-described support breakage and narrowing and deflection of the straight tube.

In order to solve the above problems, in CN 201778075 U, in the existing W-type radiant pipe, the support part is joined to the end of each bent part, and the first bent part support part is supported by the support means installed on the furnace wall, and the first bent part and The support method of the structure connecting the support part of a 3rd bend part and connecting the support part and a 1st straight part of a 2nd bend part was proposed to reduce the deformation of a radiation pipe.

In addition, EP 2825831 B1 devises a method of installing a roller on the fixing part of the furnace wall to prevent frictional resistance generated during thermal deformation between the radiating tube support and the fixing part of the furnace wall, and to prevent the deformation of the radiating tube and the geomagnetism. I've done it.

In the case of USP 6047929 A, a method of protruding the radiator support outside the furnace is proposed to reduce the free expansion deformation of the radiator support and the temperature effect due to the high temperature.

However, the above known techniques have a function of dispersing or partially alleviating stress and deformation acting on the radiating tube support part or the straight tube part, but the rigidity of the radiating tube and the supporting part is not improved, and thus it is not a fundamental countermeasure method. The effect is limited.

The present invention has been devised to solve the above problems of the conventional radiant tubular indirect heating device, to reduce the stress concentration of the radiant heating device support to prevent breakage of the support and the base material of the radiant heating device, which is dependent on the shape of the radiant heating device. An object of the present invention is to provide a radiant heating device for indirect heating by increasing the rigidity and preventing high temperature creep deformation.

In order to achieve the above object, the radiant heating device and the supporting structure for indirectly heating the steel sheet in the non-oxidizing atmosphere in the continuous annealing furnace according to the present invention has a rectangular cross section on a plane facing the steel sheet, the burner is installed A radiant heating device in the form of a cuboid box having open sides; A rectangular flange that can fix the radiant heating device to an outer wall of the furnace; One side is joined and fixed to the lower flange of the radiant heating device by means of welding or the like, the support member for supporting the self-weight of the radiant heating device while the other side of the radiant heater is in contact with the radiant heating device; The free end opposite the fixed end of the support member is characterized in that it is supported by a fixing unit provided on the inner wall of the furnace

The radiant heating device of the rectangular cross section according to the present invention is relaxed by stress support by the support structure in contact with the radiant heating device installed in the lower portion, the permanent creep deformation is reduced due to the increased rigidity by more than 90 times, radiant heating There is an effect of increasing the life of the device. In addition, the support portion installed in the lower portion of the radiant heating device has an effect of improving the ease of maintenance by repairing or replacing only the support part without replacing the expensive radiant heating device in case of damage due to wear due to long-term use.

1 is a conventional double P-type radiation tube and support structure

Figure 2 is a conventional W-type radiation tube and support structure

3 is a schematic view of a radiant heat transfer apparatus according to the present invention;

Figure 4 is another embodiment of the radiant heat transfer apparatus according to the present invention

5 is an embodiment in which the burner is installed in the radiant heat transfer apparatus according to the present invention;

Figure 6 is a cross-sectional view taken along the 10-10 'cross-section of the radiant heat transfer apparatus according to the present invention

7 is an embodiment in which the support member of the radiating heat transfer apparatus according to the present invention is bonded to the flange

The present invention is a rectangular box-type radiant heating device having a rectangular cross section on a plane facing a steel plate moving in a continuous annealing furnace, and separated from the radiant heating device at the bottom of the radiant heating device. Provided is a radiant heating device having a support.

In the conventional radiation tube support structure shown in Figs. 1 and 2, the resistance or restraint against thermal deformation between the supports 23 and 40 and the fixing part is maintained through the supports 23 and 40 as they are. And increase the internal stress of the radiation tube and the support, resulting in breakage of the radiation tube substrate and weld. However, in the radiant heating apparatus according to the present invention shown in FIG. 3, since the support part 2 bears resistance to such deformation and the base material 1 has no restraint against thermal deformation, internal stress does not occur, and thus the risk of breakage is remarkably increased. Lowers.

The permanent creep deformation of the radiation tube depends on the cross-sectional shape, internal stress, temperature, and the like. In the conventional radiation tube, since the temperature of the first

straight pipes

21 and 30 where the burners are installed is the highest, the bending stress due to its own weight is the highest. 1 The largest creep deformation occurs at the center of the straight pipe. In order to reduce such creep deformation, the bending stress acting on the radiation tube should be reduced, and the bending stress decreases as the bending stiffness depending on the cross-sectional shape of the radiation tube increases. When the elastic modulus of the material is E, the outer diameter is d1, and the inner diameter is d2 in the conventional radiation tube shown in FIGS. 1 and 2, the bending rigidity of the straight pipe portion can be expressed by the following equation.

In the radiant heating apparatus according to the present invention, when the outer width in the z direction shown in FIG. 3 is d1, the inner width is d2, the outer height in the y direction is h1, and the inner height is h2, the flexural rigidity can be expressed by the following formula. have.

In the conventional radiation tube, the total height in the traveling direction of the steel sheet is about 5 times d1, and the height h1 of the rectangular cross section according to the present invention is 5 times d1, and the thickness h1-h2 is equal to d1-d2. The flexural stiffness of rectangular cross section is 90 times larger than that of cylindrical cross section. This means that the radiant heating apparatus of the rectangular cross section according to the present invention having a width of the same dimension as the conventional radiant tube diameter is about 90 times smaller in creep deformation than the conventional radiant tube.

Figure 3 is a schematic diagram of a radiant heating device in the form of a rectangular parallelepiped box in which the stress concentration of the support and the radiant heating device in contact with the support is alleviated and the bending rigidity due to its own weight is increased. Figure 4 shows a modified embodiment according to the present invention, at the same time the support portion is installed in the lower portion of the radiant heating device at the same time the radiant heating device is installed on the plane facing the furnace wall and is supported by the fixing part of the furnace wall Thereby dispersing the stress acting on the lower portion of the radiant heater.

The radiant heating device in the form of a rectangular parallelepiped according to the present invention has all the surfaces installed in the furnace and the side where the burner is installed are all sealed by a heat insulating material except for the opening by the burner and the radiant heating device. The combustion gas inside is used to discharge to the burner's recuperator.

The radiant heating device 1 is fixed to the outer wall of the heat treatment furnace through the flange 6, and the lower part of the radiant heating device 1 is in contact with the member 2 supporting the radiant heating device 5, and the support member ( 2) is welded to the side of the flange 6 to be joined 8. The fixed part 4 of the furnace wall supports the load by the self-weight of the radiant heating device 1 and the support part 2. Accordingly, the self-weight of the radiant heating device is transferred to the support part 2 and supported by the fixing part 4, and the concentrated load due to the support reaction force acting between the fixing part 4 and the support part 2 is lowered in the radiant heating device. It acts as a distributed load on the contact surface 5 between the support and the support to relieve stress concentration in the radiant heating device.

Since the radiator heater base member 1 and the support member 2 are in contact with each other except a part commonly joined to the flange 6, the radiant heater base 1 and the support member 2 can be freely deformed at the contact surface without restraining each other even in a thermal deformation state. .

The radiant heating apparatus and the supporting member according to the present invention use heat-resistant steel containing 20% or more by weight of Ni-Cr component, and are manufactured by welding a part after bending the casting or plate according to the use temperature. In case of using heat-resistant steel with Ni content of 30-35%, the radiant heating device is manufactured with a thickness of 8-9mm through centrifugal casting or high pressure casting.Inconel material with Ni content of 50-60% has high temperature strength, It can be produced by bending a sheet thickness of mm and welding it. The supporting member should be made at least thicker than the thickness of the base material to support the load of the base material and to minimize deformation at high temperatures.

1: radiant heating device

2: support member of the radiant heating device

3, 3 ': furnace wall

4: fixing part of furnace wall

5: Contact portion of the radiant heating device and the support member

6: flange of radiant heater

7: flange fixing part of furnace wall

8: welded part of radiator support member

9: Bolt hole connecting flange of radiant heater and fixing part of furnace wall

10, 10 ': Cutting surface including the radiator support member and the fixing part of the high wall

11: refractory material in the radiant heater

12: burner

13: combustion gas discharge passage

14: Cover for finishing radiator

15: additional support member of the radiant heating device

16: additional fixing part of furnace wall

20, 20 ': second straight pipe portion of the conventional double P-type radiation tube

21, 21 ': first straight pipe portion of the conventional double P-type radiation tube

22, 22 ': curved portion of a conventional double P-type radiation tube

23: support member of the conventional double P-type radiation tube

30: first straight pipe portion of the conventional W-type radiation tube

31: second straight pipe portion of the conventional W-type radiation tube

32: second straight pipe portion of the conventional W-type radiation tube

33: fourth straight pipe portion of the conventional W-type radiation tube

34: curved portion of conventional W-type radiation tube

35: support member of the conventional W-type radiation tube

Claims

In the radiant heating device which is installed facing the steel plate moving in the continuous annealing furnace to heat-treat the steel sheet in an oxidizing atmosphere,

Radiation heating device in the form of a rectangular parallelepiped box having a rectangular cross section and open at one side thereof, and a support member separated from the radiant heating device at a lower portion of the radiant heating device. .
The method of claim 1,

The support member is a radiant heating device for a continuous heat treatment steel sheet, characterized in that the one end is joined to a flange for fixing the radiant heating device to the furnace wall, and the rest takes the form of an unconstrained cantilever beam.
The method of claim 1,

The support member is a radiant heating apparatus of a steel sheet for continuous heat treatment, characterized in that to use a thickness larger than the base material of the radiant heating apparatus.
The method of claim 1,

The radiant heating device of the steel sheet for continuous heat treatment, characterized in that the load by the self-weight of the radiant heating device is transmitted as a distributed load to the lower supporting member and the supporting member is supported by the fixing part of the furnace wall.