JP3327050B2 - Half muffle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffle structure of a bright annealing furnace, and more particularly to a muffle structure of a bright annealing furnace for annealing a structure obtained by welding and / or cold working stainless steel in a non-oxidizing atmosphere. It relates to the improvement of the structure.

[0002]

2. Description of the Related Art A stainless steel flexible pipe (also referred to as a corrugated pipe) is formed by bending a strip-shaped stainless steel hoop material, welding both ends of the hoop material, and further processing the die in an axial direction. Is a tubular material having a corrugated shape and a corrugated shape or a spiral shape having a corrugated surface. As described above, the welded or cold-worked stainless steel generates residual stress due to the thermal effect of being quenched after the solution treatment after welding or working. In the case of ferritic or martensitic stainless steel, part or all of it is hardened microscopically, and in the case of austenitic stainless steel, C
The formation of a Cr-enriched phase such as r-carbide causes a micro Cr-poor phase in the vicinity thereof (referred to as sensitization), which deteriorates toughness and corrosion resistance. Further, when these stainless steels are cold-worked, they are work-hardened to increase the strength but to decrease the toughness. In particular, austenitic stainless steels are widely used due to their high corrosion resistance and toughness, although their alloy components are large and their prices are high, and their corrosion resistance and toughness are reduced by the above-mentioned processing steps (they become brittle). ) The material may be broken or corroded during the subsequent assembling process or during use. Therefore, the above properties are improved by solution heat treatment to restore the original properties of austenitic stainless steel and supply it to users. Is done.

A typical example of such a heat treatment is annealing.
In the case of austenitic stainless steel, this is a solution treatment for standardizing the structure, and is generally performed at 1100 to 1200 ° C.
After heating to a temperature in the range described above for a predetermined time and then cooling to remove residual stress, the microstructure is improved by diffusion to restore corrosion resistance and toughness. A typical example of a heating furnace used for the above heat treatment is a bright annealing furnace. Often made of steel into which neutral or inert gas flows. The configuration of a bright annealing furnace using a muffle and an example of annealing a flexible tube after processing will be described below with reference to FIGS. FIG. 2 is a sectional side view showing a main part of the bright annealing furnace 1 according to the related art, and FIG. 3 is a sectional view taken along the line AA of FIG. In this example, the bright annealing furnace 1 of FIG. 2 is covered with a refractory brick 2 having a rectangular cross section and entirely hollow tubular, as shown in FIG. Is also provided with a rectangular and hollow tubular muffle 3 made of stainless steel, a heating section 4 on the right side and a cooling section 5 on the left side, and a heat insulating wall 6 between the heating section 4 and the cooling section 5. Can be A heating element 7 is provided on the outer peripheral side of the muffle 3 of the heating section 4.
However, three cooling pipes 8 through which cooling water flows are provided at lower portions on the outer peripheral side of the muffle 3 of the cooling unit 4.

Further, a hydrogen supply pipe 9 for introducing a reducing gas or an inert gas, in this example, hydrogen gas, into the muffle 3 is communicated substantially at the center of the muffle 3 in FIG. Is set to a hydrogen atmosphere, and this hydrogen is discharged from both ends of the muffle 3 after taking predetermined safety measures. Reference numeral 10 denotes an endless belt made of stainless steel that is continuously circulated and moved counterclockwise by a driving roller 11 as shown by an arrow B in FIG.
Of the flexible tube 13 as the material to be treated
(Illustrated by omitting the waveform of the outer shape) is placed on the endless belt 10 moving in the muffle 3, and the inside of the muffle 3 of the bright annealing furnace 1 has a predetermined speed from the right side to the left side in FIG. To move in the heating unit 4 to 1100 to 1200
After being heated to ℃, it is cooled in the cooling unit 5 and is annealed so as to be cooled to a temperature at which there is no danger of oxidation even when it is discharged into the atmosphere, and a flexible tube having the original properties of austenitic stainless steel To be. The endless belt 10 is repeatedly circulated by the driving force of the driving roller 11 in the order of the high-temperature heating section in the bright annealing furnace 1, the intermediate-temperature cooling section, and the normal temperature outside the furnace. It is greatly consumed by being subjected to a large number of thermal cycles from room temperature to room temperature, and its life is short in spite of the high cost of using expensive materials such as high melting point metal materials. On the other hand, the muffle 3 is necessary for safety such that hydrogen is not diffused and released especially in a high temperature part, and in order to obtain structurally necessary strength,
In this temperature environment, a wall thickness of 5 mm or more is required, and expensive materials having a high melting point cannot be used. For these reasons, austenitic stainless steel has been mainly selected as the material.

[0005]

The endless belt slides and moves on the floor in the muffle, and the flexible pipes slide and move slightly on the endless belt. Abrasion powder is generated. Most of the generated powder stays in the muffle, and is exposed to high temperature for a long time, melts and solidifies, and forms projections in the muffle. Although the melting mechanism is not clear, the stainless steel powder generated by abrasion is fine, has high surface activity, and receives the load of the endless belt and the frictional force between the endless belt and the muffle, It is considered that the surface melts in spite of the temperature lower than the melting point at atmospheric pressure, and is fused to a stainless steel muffle of the same material. The formed protrusions cause the endless belt to wear further,
On the other hand, a worn endless belt has a rough surface and causes the muffle to wear more severely.
Wear is accelerated synergistically. In addition, the endless belt is caught by the protrusion in the muffle and is pulled by the force of the driving roller, so that the endless belt may be cut. Due to such factors, the life of the endless belt is as short as about 2 weeks, and the life of the muffle is as short as 3 to 4 months. Each time the muffle is replaced, the temperature of the bright annealing furnace is lowered, and the temperature is raised again after returning. There is a time loss due to the work. An object of the present invention is to provide a bright annealing furnace having a muffle structure that does not have the above-described problems.

[0006]

According to the present invention, in a stainless steel muffle having a rectangular cross section and a hollow tubular shape as a whole, the muffle having the same length as the muffle and having a U-shaped cross section opens upward, A melting point higher than steel, and made of a metal or alloy that is not soft, particularly preferably a half muffle made of molybdenum is arranged, and the above problem is solved by sliding an endless belt on the upper surface of a concave portion of the half muffle. Settled.

[0007]

According to the present invention, the endless belt made of stainless steel slides, for example, on a concave portion of a molybdenum half-muffle to remove abrasion powder of stainless steel and abrasion powder of molybdenum. Although molybdenum has a high melting point even if the surface of the stainless steel abrasion powder is melted, they do not fuse, and molybdenum abrasion powder has a partial melting point much higher than the furnace temperature of 1100 to 1200 ° C. , And the formation of protrusions was suppressed.

[0008]

1 is a cross-sectional front view of a muffle 3 of a bright annealing furnace in which a half muffle 14 according to the present invention is arranged, which is cut at a right angle to the longitudinal direction of the muffle 3. FIG. The configuration outside the muffle 3 of the bright annealing furnace is the same as that according to the prior art, and the description is omitted. 3 in FIG.
Is a muffle, 10 is an endless belt, 13 is a flexible tube, 14 is a half-muffle having a U-shaped cross section arranged with its opening upward in the muffle 3, and the endless belt 10 moves in the concave portion 14a. I do. The muffle 3 and the endless belt 10 are both made of stainless steel as in the prior art, but the half muffle 14 is made of a metal or alloy having a higher melting point than stainless steel. Materials for the half muffle 14 include molybdenum (melting point: 2622 ± 10 ° C., according to the third edition of the Physical and Chemical Dictionary, the same applies hereinafter), tungsten (melting point: 3382
° C), tantalum (2850 ° C) and alloys thereof, but soft materials having a high melting point, especially expensive ones are not suitable. In addition, half muffle 14
Since it is disposed in the muffle 3, it is used in a reducing or inert gas such as hydrogen, so that it is possible to use a material which is easily oxidized at high temperature, and molybdenum is most suitable particularly in terms of availability and price. .

In order to dispose and move the endless belt 10 in the concave portion 14a of the half muffle 14, it is necessary to provide a fixing means (not shown) for preventing the position of the half muffle 14 from being shifted in the longitudinal direction with respect to the muffle 3. Of course. Thus, in the present invention, since the half muffle 14 is arranged in the muffle 3 and the endless belt 10 slides on the concave portion 14a of the half muffle 14,
Even if the abrasion powder of the endless belt 10 is generated on the half muffle 14 and the surface of the fine abrasion powder is melted, the abrasion powder does not fuse with the half muffle 14 because the half muffle 14 itself has a high melting point and does not melt. Is discharged outside the furnace without forming protrusions. Also, half muffle 14
Even if it was worn, it did not fuse due to its high melting point. As a result, the service life of the endless belt is extended to about 4 weeks, the service life of the muffle and half muffle is extended to one year or more, respectively, and the non-operating time (idle time) of the bright annealing furnace for updating these members is greatly increased. Was reduced to

[0010]

According to the present invention, a half-muffle made of a metal having a melting point higher than that of stainless steel or a metal alloy thereof, for example, a molybdenum-made half-muffle having a U-shaped cross section having the same length as the muffle and having a U-shape cross section. In the muffle,
The configuration in which the endless belt is slid on the upper surface of the concave portion of the half muffle suppresses the formation of protrusions even when abrasion powder of stainless steel or molybdenum is generated, and the life of the endless belt is doubled to about four weeks. The life of muffles and half-muffles is quadrupled to more than one year, the downtime of bright annealing furnaces is significantly reduced, and the cost of manufacturing stainless steel welding and / or cold-worked structures such as flexible tubes is greatly reduced. Has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional front view of the inside of a muffle of a bright annealing furnace in which a half muffle according to the present invention is arranged, which is cut at a right angle to a longitudinal direction of the muffle.

FIG. 2 is a sectional side view showing a main part of a bright annealing furnace according to the prior art.

FIG. 3 is a sectional view taken on line AA of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bright annealing furnace 3 Muffle 10 Endless belt 14 Half muffle 14a Recess

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) C21D 1/00 112 C21D 1/00 113 C21D 9/08 F27B 5/00-5/18

Claims (2)

(57) [Claims] 1. A muffle furnace for bright annealing of a work-hardened material to be heat-treated , a furnace wall made of a refractory material, a stainless steel muffle having a hollow tubular section housed in the furnace wall and a muffle made of stainless steel. And a stainless steel endless belt that slides and moves on the floor surface of the material. The material to be heat-treated mounted on the endless belt has a reducing property such as hydrogen or nitrogen introduced into the muffle. in bright annealing furnace for annealing in an inert gas atmosphere, the bright annealing furnace, further the melting point than the stainless steel on the bottom of the muffle rather high, and manufactured in soft no gold <br/> genus or alloy The cross section is a U-shape, having a half muffle fixedly arranged with the U-shaped opening facing upward, and sliding the endless belt on the upper surface of the concave portion of the half muffle. A half muffle of a muffle furnace for bright annealing characterized by the fact that: 2. A half muffle for a bright annealing muffle furnace according to claim 1, wherein said half muffle is made of molybdenum.