CN103429958A

CN103429958A - Radiant tube

Info

Publication number: CN103429958A
Application number: CN2012800135173A
Authority: CN
Inventors: 日根野实; 坂本伸之; 冈野宏昭; 中村茂树
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2011-03-31
Filing date: 2012-03-28
Publication date: 2013-12-04
Also published as: CA2831302A1; KR20140045350A; US20140053826A1; WO2012133539A1; JPWO2012133539A1

Abstract

A radiant tube made of refractory metal is provided with at least one bent tube (3A, 3C) which connect straight tubes (2A, 2B, 2C, 2D). Combustion air from a burner (5) is fed through one of the straight tubes (2A, 2B, 2C, 2D), and the radiant tube is characterized by using a cast product with an external diameter of 150-210 mm and a thickness of 3-8 mm at least as the bent tube (3A, 3C) closest to the burner (5).

Description

Radiant tube

Technical field

The present invention relates to a kind of radiant tube, its metal tube by casting forms, and has at least one bend pipe and a pair of straight tube be connected with the two ends of this bend pipe, is blown into the burning gases of burner from a side of a pair of straight tube.

Background technology

As the prior art documentation & info relevant with this radiant tube, the patent documentation 1 shown in following is arranged.The radiant tube that a kind of two open ends at bend pipe are provided with the neck extended with the Len req linearity is disclosed in this patent documentation 1, in this structure, be recited as: because the compression stress equalization of the compression stress of bend pipe side and straight tube side acts on the weld part of bend pipe and straight tube, therefore, the stress that the thermal expansion that weld part produces brings is by equalization, and weld part is difficult to produce be full of cracks.

The prior art document

Patent documentation

Patent documentation 1: Japanese patent laid-open 10-227420 communique (0007 paragraph, the 0015-16 paragraph, Fig. 1)

Invent problem to be solved

But, in the radiant tube of putting down in writing at patent documentation 1, there is such structure: bend pipe be split into bend pipe circular-arc central shaft outer circumferential side large diameter portion and in the path part of the inner circumferential side of this central shaft, these large diameter portions and path part are welded under state relative to each other.Therefore, except the problem of the weld part of bend pipe and straight tube, the possibility that produces be full of cracks because of thermal expansion etc. is arranged in two welding positions that extend along the bend pipe axle center.

Summary of the invention

Therefore, the object of the invention is to, the problem in view of above illustrative conventional art is brought radiant tube, provide a kind of radiant tube, and its extremely hot condition durability for the burning gases that come free burner to be blown into is high, can use more over a long time.

For solving the means of problem

Radiant tube of the present invention, for heating resisting metal system, there is at least one bend pipe will connected between straight tube, be blown into the burning gases of burner from a side of described straight tube, at least as close to the bend pipe of described burner, the use external diameter is the cast body that 150～210mm, wall thickness are 3～8mm.

In the radiant tube of said structure characteristics, owing to using the cast body that wall thickness is 3～8mm, as extremely the hottest condition close to the bend pipe of burner, therefore, with utilizing, plate stamping processing is resulting compares the bend pipe that is welded between the body end face etc., the wall thickness of pipe is more even, and in addition, that stress concentration portion position of the weld part extended to the bend pipe length direction also disappears.Therefore, be difficult to produce the thermal crack(ing that dramatic temperature rises or dramatic temperature descends and causes that the burning gases by burner cause, result, can obtain that heat resistance is high, the radiant tube of anti-long-term use.

In addition, because the wall thickness of cast body is the thin-walled property of 3～8mm, therefore, the increase of the compactness of metal structure cooling velocity during based on casting and being enhanced.Therefore, be enhanced close to heat resistance and the resistance to sudden heating of the bend pipe of the burner of extremely hot condition, can obtain more anti-in the radiant tube of long-term use.

In addition, by the part of the bend pipe of extremely hot condition, make thin-walled property, the distortion that stress brings just easily produces.Its result, easily absorb thermal stress, even the temperature sharply that the burning gases of burner bring rises, also is difficult to produce thermal crack(ing.

In addition, by making thin-walled property close to the bend pipe of burner, the rate of rise in temperature of the bend pipe that the burning gases of burner bring just uprises, and the temperature of wall thickness direction descends and to diminish, and therefore than conventional art, also can suppress the consumption of fuel.

In addition, due to, close to the thin-walled property of the bend pipe of burner, and make the whole lightweight of radiant tube, therefore, also reduced and changed the required labour's burden of operation.

Another design feature of the present invention is, described bend pipe with being connected of described straight tube near the wall thickness of section become thinner than other position of described bend pipe.

With the junction of straight tube, become the easy especially position that in use produces undercapacity during because of the textural undercapacity close to end surfaces or for the welding that connects because being heated the material fragilityization caused etc. in bend pipe.But, adopt this structure, because other position of the wall ratio bend pipe that connects near section is thin, therefore, the cooling velocity of the compactness of metal structure based on when casting increases and special the raising, can guarantee the durability generally partly be complementary with bend pipe except near section connecting for the extremely hot condition from burning gases.

Another design feature of the present invention is, has a plurality of described bend pipes, for these a plurality of described bend pipes, all uses the cast body that wall thickness is 3～8mm.

Also can be only to close to the bend pipe of burner, using the cast body of wall thickness 3～8mm, adopt this structure, because a plurality of bend pipes are all used the cast body of wall thickness 3～8mm, therefore, can obtain stable on heating reliability further improve, anti-in the radiant tube of long-term use.

In addition, because the lightweight of radiant tube integral body further improves, therefore, also further reduced and changed the required labour's burden of operation.

Another design feature of the present invention is that the wall thickness of described straight tube becomes below 7mm.

As this structure, by straight tube also being made to the thin-walled mated with bend pipe, with the structure of only straight tube being made to the heavy wall state, compare, can guarantee than highland the intensity of the connecting portion of bend pipe and straight tube.

Another design feature of the present invention is, described straight tube with being connected of described bend pipe near the wall thickness of section become thinner than other position of described straight tube.

In straight tube, with the junction of bend pipe, material fragilityization of being heated caused during because of the textural undercapacity close to end surfaces or for the welding that connects etc. becomes the easy especially position that in use produces undercapacity.But, adopt this structure, because other position of the wall ratio straight tube that connects near section is thin, therefore, the cooling velocity of the compactness of metal structure based on when casting increases and special the raising, can guarantee the durability generally partly be complementary with straight tube except near section connecting for the extremely hot condition from burning gases.

Another design feature of the present invention is, as described straight tube, to use wall thickness to surpass the cast body of the wall thickness of described bend pipe.

Adopt this structure, than use, there is the structure with the straight tube of the equal wall thickness of described bend pipe wall thickness, more easily obtain that heat resistance further improves and anti-in the radiant tube of long-term use.

The accompanying drawing explanation

Fig. 1 is the side elevation in partial section of modal representation radiant tube of the present invention.

Symbol description

2 straight tubes (2A, 2B, 2C, 2D)

3 bend pipes (3A, 3C)

5 burners

The specific embodiment

Below, with reference to accompanying drawing, one embodiment of the present invention is described.But scope of the present invention is not subject to these explanation constraints, except following illustration, can suitably change enforcement without departing from the spirit and scope of the present invention.

Radiant tube 1 shown in Fig. 1, have four horizontal

straight tube

2A, 2B, 2C, 2D that substantially uniformly-spaced are arranged side by side up and down, utilize to amount to three

bend pipe

3A, 3B, 3C between two neighbouring straight tubes 2 and connect, and wholely substantially is horizontal W word shape.

Radiant tube 1, utilize the straight tube 2A of the superiors and undermost straight tube 2D and be bearing in drying oven or other the furnace wall 10 of heat-treatment furnace of sintering furnace on, the end of these

straight tubes

2A, 2D and burner 5 with between sandwich the heat storage 4 that the heat recovery efficiency that consists of ceramic honeycomb etc. is high state be connected.

These burners 5, carry out exhaust from undermost straight tube 2D and heat extraction is recovered in the heat storage 4 of below when the water heater 5 that makes for example to be connected with the straight tube 2A of the superiors burns, when burning being switched to the burner 5 be connected with undermost straight tube 2D, utilization by the combustion air preheating, becomes the backheating type that can reduce the required fuel use amount of burner combustion by the heat extraction of below heat storage 4 recovery thus.

Utilization is installed in the combustion air fan 7 of supply combustion air and the transfer valve 6 between each burner 5, can use the burner 5 be connected with the straight tube 2A of the superiors to make the combustion air burning and its heat extraction is being recovered in to the state (meaning with solid line) in the heat storage 4 be connected with orlop straight tube 2D and use the burner 5 be connected with orlop straight tube 2D to make the combustion air burning and its heat extraction is recovered between the state (dotting) in the heat storage 4 be connected with the straight tube 2A of the superiors to be switched.

By the waste gas of heat storage 4, can be released in extraneous air by transfer valve 6 and emission-control equipment (not shown) etc.

Four straight tube 2A, the 2B, 2C, 2D and three

bend pipe

3A, 3B, the 3C external diameters that form radiant tube 1 are 180mm, and are formed by the cast steel (example of the cast body of heating resisting metal system) of the nickel of the chromium that contains 20～35 % by weight and 30～50 % by weight.

Straight tube 2 is connected with bend pipe 3, utilizes the welding of carrying out from outer circumferential side under the state docked between the end face by each pipe to carry out.

In three

bend pipe

3A, 3B, 3C, as, close to the 1st bend pipe 3A and the 3rd bend pipe 3C of burner 5, use the casting thin-wall body that wall thickness is 3～8mm.

As leaving burner 5 the 2nd bend pipe 3B far away and four

straight tube

2A, 2B, 2C, 2D, use the cast body that wall thickness is 5mm or 10mm.

In addition, used leaving and approaching vocabulary here, refer to by burner 5 produce and on the path of the inner mobile flame of radiant tube 1 or burning gases and between burner 5 apart from length.

So, be used as the bend pipe 3 close to burner 5 by the casting thin-wall body that is 3～8mm by wall thickness, thereby can obtain high, the more anti-radiant tube in long-term use 1 of heat resistance.

Its reason is considered to, in the formed integrally formed bend pipe of casting, to process bend pipe of being welded between the body end face of resulting left and right etc. by plate stamping with axle core along pipe compares, wall thickness is more even, in addition, the such stress concentration portion position of weld part of extending along the bend pipe length direction also disappears, and therefore, is difficult to produce dramatic temperature due to the burning gases of burner rises or dramatic temperature descends to be caused thermal crack(ing etc.

In addition, be considered to, because the wall thickness of cast body is made into the thin-walled property of 3～8mm, therefore the increase of the cooling velocity of the compactness of metal structure after based on casting and improving, heat resistance and resistance to sudden heating are improved.

In addition, be considered to, owing to being made into thin-walled property, easily because stress produces distortion, therefore easily absorb thermal stress, even the dramatic temperature that the burning gases of burner bring rises, also be difficult to produce thermal crack(ing.

In addition, by making thin-walled property close to the bend pipe 3 of burner 5, thereby the return bend temperature rate of climb that the burning gases of burner bring improves, and the temperature of wall thickness direction descends and diminish, therefore also suppressed Fuel Consumption than conventional art.

In addition,, therefore also reduced and changed the required labour's burden of operation by lightweight due to radiant tube integral body.

Four

straight tube

2A, 2B, 2C, 2D forming radiant tube 1 are manufactured by centre spinning.

On the other hand, because three

bend pipe

3A, 3B, 3C are used the attraction casting that gives negative pressure in the chamber utilized after vavuum pump etc. will inject motlten metal, therefore, when realizing thin-walled property, the general shrinkage cavity easily produced when motlten metal solidifies or shrinkage porosite disappear, and obtain also good bend pipe of surperficial cortex.

In addition, with purposes such as lightweights more, also can in straight tube, use to attract casting and obtain thin-walled property.

In addition, the external diameter that forms four horizontal

straight tube

2A, 2B, 2C, 2D of radiant tube 1 and three

bend pipe

3A, 3B, 3C is not limited to 180mm, also the scope of 150～210mm, as long as in this scope, just easily obtain the wall thickness of

bend pipe

3A, 3B, 3C made to the effect that 3～8mm brings.

Embodiment 1

Following table 1, mean when the radiant tube 1 shown in actual use Fig. 1, utilize simulated experiment and result that each characteristic of thermal stress that the 3rd bend pipe 3C is subject to is analyzed.

In this simulated experiment, the use of simulation backheating type, from each burner 5 alternative supply burning gases, make its burning over a period to come.

As shown in table 1, carry out various changes by the wall thickness by each bend pipe 3 and each straight tube 2, thereby obtain these wall thickness and be subject to the relation between each characteristic of thermal stress about the 3rd bend pipe 3C over a period to come from each burner 5 alternative supply burning gases.

The numerical value of the bend pipe wall thickness of putting down in writing in table is applicable to whole three

bend pipe

3A, 3B, 3C, and same, the numerical value of straight tube wall thickness is applicable to whole four

straight tube

2A, 2B, 2C, 2D.

Material as casting use, used KHR-48N.KHR-48N is the austenite superalloy in 1200 ℃ of lower acid resistances and shear strength excellence, the nickel of the chromium that contains 27 % by weight, 47 % by weight and the tungsten of 5 % by weight.

[table 1]

Think following situation from the measurement result of 0.2% endurance (MPa) of the bend pipe material of 1000 ℃ shown in table 1.

Make below 8mm by the wall thickness by bend pipe 3, and can guarantee in addition, below 8mm, to be preferably the numerical value over 100MPa below 7mm, more preferably, below 6mm, thinner this numerical value of wall thickness of bend pipe 3 is arranged with regard to higher tendency.

In addition, for the measurement result of maximum stress, make below 8mm by the wall thickness by bend pipe 3 equally, thereby the tendency that can guarantee the low numerical value below 55MPa is arranged.

In addition, above-mentioned each tendency, basically comprehensively see and be understood to not be subject to so straight tube 2 influences of wall thickness in any situation of the situation that is 5mm at the wall thickness at straight tube 2 positions and the situation of 10mm.

But, in the straight tube wall thickness is made to the example of 5mm, as long as see the measured value of bend pipe 0.2% endurance, just find that the straight tube wall thickness shows the tendency of high value over the radiant tube 1 of bend pipe wall thickness.

Embodiment 2

In embodiment 2, as the material beyond KHR-48N, use alloy 230 and KHR-35H, with embodiment 1 in the same manner, in the situation that reality is used the radiant tube 1 shown in Fig. 1, utilize simulated experiment to analyze each characteristic of the thermal stress that is subject to about the 3rd bend pipe 3C.

Here, also by the wall thickness of change each bend pipe 3 and each straight tube 2, and obtain these wall thickness and be subject to the relation between each characteristic of thermal stress about the 3rd bend pipe 3C over a period to come from each burner 5 alternative supply burning gases.

Table 2 means the result for alloy 230 (tungsten of the molybdenum of the nickel of the chromium that contains 22 % by weight, 57 % by weight, 2 % by weight and 14 % by weight), and table 3 means the result for KHR-35H (nickel of the chromium that contains 25 % by weight, 35 % by weight).

[table 2]

[table 3]

From the measurement result of 0.2% endurance (MPa) of the bend pipe material of 1000 ℃ shown in table 2 and table 3, even the steel beyond KHR-48N, the side that the wall thickness of bend pipe 3 is little also can obtain high numerical value.

For the measurement result of maximum stress, the little side of wall thickness that also can obtain bend pipe 3 obtains the same tendency of low numerical value.

In addition, in above-mentioned each table, mean evaluation result and " * " of use, refer to and especially using centered by bend pipe and produce infringement as crackle or distortion under the radiant tube functional class of heater.

(about analytical method)

In the analysis of each characteristic of the thermal stress that the 3rd bend pipe 3C that embodiment 1,2 carries out is subject to, use SolidWorks company software processed: SolidWorks Simulation, as types of models, applied burner has been advanced to two positions of hot side end (the straight tube 2A in Fig. 1,2D right-hand end) Complete Bind linear, isotropic elastic model under state after the face of furnace wall.

Size condition as the radiant tube 1 of analytic target, making width (length of the top ends from the cardinal extremity of the straight tube 2A, the 2D that are constrained in wall to bend

pipe

3A, 3C bending) is 1087mm for 2276mm * highly (length from the upper surface of the straight tube 2A of the superiors to the lower surface of orlop straight tube 2D), for

straight tube

2A, 2B, 2C, 2D and three

bend pipe

3A, 3B, the whole pipe external diameters of 3C, makes 187mm.

Following table 4 means to analyze each physical characteristic of each steel used.

[table 4]

The steel class	KHR-48N	Alloy 230	KHR-35H
				Destroy benchmark	Maximum equivalent	Maximum equivalent	Maximum equivalent
Coefficient of elasticity	105000MPa	72200MPa	93000MPa
				Poisson's ratio	0.3	0.3	0.3
Mass density	8200kg/m ³	8970kg/m ³	8050kg/m ³
				The temperature expansion rate	1.6e-005/℃	1.61e-0005/℃	1.8e-0005/℃

In addition, from the mutual part to be welded (scope of each end face 10～30mm of docking while leaving welding) of bend pipe and straight tube, the material fragilityization of being heated caused during because of the textural undercapacity close to end surfaces or welding etc. becomes the position that especially easily in use produces undercapacity.Therefore, for these parts to be welded, form thinlyyer, specifically, form than the thin 1～2mm in other position, to guarantee the purpose for the durability of the extremely hot condition from burning gases.

In addition, in the situation that practical application radiant tube 1, as the member that bears the physical property load, more by the situation that other brace makes between adjacent bend pipe or bend pipe is a part of and a straight tube part supports mutually, in this occasion, the position that is supported of in bend pipe and straight tube, brace being welded to use forms to obtain thick especially (about 10mm etc.) in part.As the object lesson that is supported position, the base end part lower surface of lower side of the position relative at above-below direction, bend pipe 3B and the upper surface position of nearest straight tube 2D etc. are arranged in the bend pipe 3A shown in Fig. 1,3C base end part mutually.

The bend pipe of describing in the defineds such as claim of the present invention, specification and the wall thickness value of straight tube, be applied to except these parts to be welded and be supported the general place position.

Bend pipe of the present invention, as long as for the adjustment of the bearing of trend of pipe, difference from a pipe to a plurality of pipes or a plurality of pipes are concentrated on to a first-class purpose of pipe and for connecting between a plurality of pipe section, thering is bend or the bend pipe of the section that buckles, be not limited to the U font pipe shown in Fig. 1, the junction block that comprises arbitrary shape.

(other embodiments)

<1>also can comprise and leave burner 5 the 2nd bend pipe 3B far away, the casting thin-wall body that all

bend pipe

3A, 3B, 3C are made to 3～8mm.

<2>, in the situation that need not be used as the burner 5 of backheating type the non-backheating type of for example supplying with all the time burning gases from the burner 5 be connected with the straight tube 2A of the superiors, also can be only the 1st bend pipe 3A close to this burner 5 commonly used be made to 3～8mm casting thin-wall body.But, also all

bend pipe

3A, 3B, 3C can be made to 3～8mm casting thin-wall body.

<3>to be not limited to aforesaid W word shape can be also the Y type to the shape of radiant tube 1.

<4>form the bend pipe of radiant tube 1 and the quantity of straight tube and be not limited to aforesaid example, as long as there is at least one bend pipe on a part forms, also can make and only use such as the pair of straight pipe and connect the radiant tube of the U font etc. of a bend pipe formation between a pair of straight tube.

Practicality on industry

The present invention can be used as the technology of heating resisting metal radiant tube processed that has at least one bend pipe of connecting between a pair of straight tube, is blown into the burning gases of burner from a side of these a pair of straight tubes.

Claims

1. a radiant tube, be heating resisting metal system, has at least one bend pipe will connected between straight tube, is blown into the burning gases of burner from a side of described straight tube, and this radiant tube is characterised in that,

At least as close to the bend pipe of described burner, the use external diameter is the cast body that 150～210mm, wall thickness are 3～8mm.

2. radiant tube as claimed in claim 1, is characterized in that, described bend pipe with being connected of described straight tube near the wall thickness of section become thinner than other position of described bend pipe.

As claim 1 or 2 described radiant tubes, it is characterized in that thering are a plurality of described bend pipes, all use for these a plurality of described bend pipes the cast body that wall thickness is 3～8mm.

4. radiant tube as claimed any one in claims 1 to 3, is characterized in that, the wall thickness of described straight tube becomes below 7mm.

5. radiant tube as described as any one in claim 1 to 4, is characterized in that, described straight tube with being connected of described bend pipe near the wall thickness of section become thinner than other position of described straight tube.

6. radiant tube as described as any one in claim 1 to 5, is characterized in that, as described straight tube, uses wall thickness to surpass the cast body of the wall thickness of described bend pipe.