KR20080028767A - Heating apparatus for billet - Google Patents

Abstract

A billet heating apparatus is provided to remove radiation heat transfer from a furnace wall by supporting a billet in a state that the billet is opened to the atmosphere, and accomplish heating capacity and thermal efficiency beyond an electromagnetic induction heating process by heating the billet only by convection heat transfer from a flame. A billet heating apparatus comprises: a body case(2) including a frame(3) of which inner and outer portions are in communication without installing a furnace wall; skid rails for supporting a billet(W) charged into the body case in a state that the billet is opened to the atmosphere; and a plurality of pure oxygen or oxygen enriched burners(4) for heating the billet by colliding a combustion flame with an outer surface of the billet along the entire length and periphery of the billet, wherein a ratio(D/L) of diameter of the nozzles to a distance L from the outer surface of the billet to nozzles of the burners is in a range of 0.02 to 0.04, and pitch P of the nozzles is 30 to 50 times of the diameter D of the nozzles.

Description

Billet Heating Device {HEATING APPARATUS FOR BILLET}

TECHNICAL FIELD This invention relates to the billet heating apparatus for extrusion molding, such as an aluminum alloy and a copper alloy.

An extrusion molding billet (hereinafter referred to as a billet) composed of round rods such as aluminum alloy or copper alloy billet produced by continuous casting is a billet heating apparatus in which an entire billet is heated to an extrusion molding temperature. Then, it is shape | molded to a predetermined shape by the extrusion molding machine in the downstream process.

Conventionally, as a heating method of a billet, there exist an electromagnetic induction heating system and the combustion heating system by a burner. The electromagnetic induction heating method has a drawback of high heating capability and high operating cost due to power consumption. Burner heating by burners has lower operating costs than electromagnetic induction heating, but since the heating capacity is low, it is necessary to increase the length of the furnace to ensure heating time, resulting in high equipment costs. There is this.

Patent Document 1 and Patent Document 2 disclose a method of charging a billet into a furnace and heating a burner toward the outer circumferential surface of the billet. This heat transfer form is radiation heat from the furnace wall and convection heat from the flame.

Since the billet made of aluminum alloy or copper alloy has low emissivity, the amount of heat radiated from the furnace wall is small, and in order to compensate for this, the flame is heated toward the outer peripheral surface of the billet. However, since the flame from the burner is a combustion method by air, the amount of convection heat is small and it cannot be heated in a short time like the electromagnetic induction heating method.

(Patent Document 1)

Microfilm of Japanese real element 57-2613 (real number 57-147256)

(Patent Document 2)

Japanese Patent No. 3085620

This invention is made | formed in view of the said conventional problem, and makes it a subject to provide the billet heating apparatus which can achieve the heating capability and thermal efficiency more than an electromagnetic induction heating system.

In order to solve the said subject, the billet heating apparatus which concerns on this invention,

Main body case which consists of frame which communicated inside and outside without installing furnace wall,

A skid rail for supporting the billet charged in the main body case in an air-open state;

A plurality of pure oxygen or oxygen enrichment burners attached to the main body case to heat the billet by impinging a combustion flame on an outer surface over the electric field and pole of the billet,

The ratio D / L of the diameter D of the nozzle to the distance L from the outer surface of the billet to the nozzle of the burner is set from 0.02 to 0.04, and the pitch P of the nozzle is 30 to 50 times the diameter D of the nozzle. will be.

It is preferable that the said pure oxygen or oxygen enrichment burner is a water-cooled structure.

The skid rail is hollow and a pipe having a plurality of injection holes is inserted in the longitudinal direction therein, and the water supplied to the pipe is injected toward the inner surface of the portion supporting the billet from the injection hole. It is desirable to.

The skid rail is preferably triangular in cross section.

It is preferable that the said billet is an aluminum alloy or a copper alloy.

According to the present invention, by supporting the billet in the open state of the air, the radiant heat transfer from the furnace wall is eliminated, and the flame which is burned with pure oxygen or enriched oxygen by the pure oxygen or oxygen enrichment burner impinges on the outer surface of the billet's electric field and pole By heating the billet only by the convective heat transfer from the flame, the heating ability and the thermal efficiency of the electromagnetic induction heating method or more can be achieved.

Since the burner has a water-cooled structure, the burner can be protected from thermal shock during heating.

Since the skid rail has a water-cooled structure, durability against heat shock is excellent, and there is no fear of spalling in the case of refractory material or melting loss in the case of metal.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described according to an accompanying drawing.

1 and 2 show a heating apparatus for billet W according to the present invention.

This heating apparatus has a main body case 2 provided on the mount 1. The main body case 2 has the steel frame 3 of inverted U shape on the charging side and the extraction side of the billet W. As shown in FIG. Inside these frames 3, a plurality of water-cooled structures (6 in the embodiment) of oxygen or oxygen enriched burner units 4 (hereinafter simply referred to as burner units) are supported and attached. The burner unit 4 is arrange | positioned at equal intervals in the circumferential direction, and is extended toward the extraction side from the longitudinal direction of the main body case 2, ie, charging side. The main body case 2 does not have a furnace wall and is in a state where the inside and the outside communicate with each other, and the burner unit 4 is attached in the air-open state. On both sides of the burner unit 4 at the lowest position, a pair of skid rails 5 supporting the billet W are extended from the charging side toward the extraction side.

At the charging side of the main body case 2, a charging door 6 and a pusher 7 are provided. The charging door 6 is capable of lifting up and down by the lifting up and down cylinder 8. The pusher 7 charges the billet W into the main body case 2 via the skid rail 5, and can convey it toward the extruder which is not shown in the extraction side. On the extraction side of the main body case 2, the extraction door 9 is provided by the lifting cylinder 10 so that the lifting / lowering is possible. In the extraction door 9, an exhaust port 11 communicating with the inside of the main body case 2 is formed.

In the burner unit 4, as shown in FIG. 3A, a plurality of flame spray nozzles 12 are formed in a predetermined arrangement and pitch. Although the arrangement of the nozzle 12 is an equilateral triangle, it is not limited to this. Each nozzle unit 4 is divided into a plurality of heating regions (four regions of A to D in the embodiment) in the longitudinal direction, and the combustion capacity can be adjusted independently for each heating region.

The convection average heat transfer rate Hcm due to the combustion flame from the plurality of burner units 4 is P (m) and nozzle diameter D (m) when the discharge flow velocity of the nozzle 12 is constant. When the distance from the outer circumferential surface of the billet to the nozzle 12 of the burner unit 4 is L (m) and the constant is k, it is represented by Formula 1.

(Equation 1)

Hcm = k × 1 / P ^{0 .375} × D / L

The inventors carried out experiments in order to determine the optimum nozzle pitch P, nozzle diameter D, and the distance L from the outer circumferential surface of the billet to the nozzle 12 based on Equation 1. As a result, the ratio D / L of the nozzle diameter D to the distance L from the outer surface of the billet W to the nozzle 12 is set from 0.02 to 0.04. If D / L is 0.02 or less, heating will become inadequate and the heating capacity equivalent to electromagnetic induction heating cannot be obtained. Moreover, when D / L is 0.04 or more, the part which the flame of billet W hits directly is melted. On the other hand, the nozzle pitch P is made into 30-50 times the nozzle diameter D. This was decided in order to satisfy both heating time and thermal efficiency which correspond to an electromagnetic induction heating system, and 40 times is most preferable. For example, when the nozzle diameter D is 1 mm, the nozzle pitch P is 40 mm, and when the nozzle diameter D is 0.5 mm, the nozzle pitch P is 20 mm. The nozzle diameter D is in the range of 1.0 mm to 0.5 mm. If it is 1.0 mm or more, thermal efficiency will be 37.1% or less, and thermal efficiency equivalent to an electromagnetic induction heating system will not be ensured, and it will become difficult to process a hole at 0.5 mm or less. The faster the flow velocity of the flame from the nozzle 12 is, the faster the convection heat transfer rate can be, but it is 200 m / s or less. It is because when it sets to 200 m / s or more, combustion noise will be high and a trouble will arise in a working environment.

As shown in FIG. 4, the said skid rail 5 is a triangular hollow cross section, and the pipe 13 is inserted in the inside. A plurality of injection holes 14 are formed in the pipe 13 in the longitudinal direction, and the right angle portion having the largest thermal load in which water supplied to the pipe supports the billet W from the injection holes 14 is formed. It can be sprayed toward the inner surface of the back. Water injected from the pipe 13 is discharged from the discharge port 15 provided in the end surface of the extraction side of the skid rail 5. In addition, although the cross section of the skid rail 5 is not limited to a triangle, circular, spherical, semi-circular, and elliptical may be sufficient, but the injection hole 14 supports the billet W in either shape. Spray toward the inner surface of the part.

Next, operation | movement of the heating apparatus which consists of the said structure is demonstrated.

The charging door 6 is opened by the lifting cylinder 8, the billet W is charged into the main body case 2 by the pusher 7 through the skid rail 5, and then the charging door 6 is closed. Then, the plurality of burner units 4 are ignited by ignition means (not shown), and the combustion capacity of the charging end side combustion basin of the burner unit 4 is extracted at the end side (the extruder side of the next step). ) Inclined heating is performed such that the temperature of the charged end side combustion region of the billet W is controlled to be lower than the combustion capacity of the combustion region, for example, 400 ° C and the temperature of the extraction end side combustion region, for example, 500 ° C. do.

Here, since the billet W is supported on the skid rail 5 in the open air | atmosphere state without a furnace wall, there is no radiation heat transfer from a furnace wall. However, the billet W is heated only by convective heat transfer from the flame by impinging a flame burned with pure oxygen or enriched oxygen by the burner unit 4 instead of combustion by air, on the outer surface of the billet W. Therefore, the heating capability and thermal efficiency more than an electromagnetic induction heating system can be achieved.

Since the burner unit 4 is a water-cooled structure, it is protected from thermal shock during heating. In addition, since the skid rail 5 also has a water-cooled structure for supplying water from the internal pipe 13 to the inner surface of the right angle part supporting the billet W, it has excellent durability against thermal shock and spalling in the case of refractory materials. In the case of metals and metals, there is no fear of loss.

When heating of the said billet W is complete | finished, each said burner unit 4 is extinguished, the extraction door 9 is opened to the lifting cylinder 10, and the heated billet W is pushed by the pusher 7 It conveys to the extruder arrange | positioned downstream. Thereafter, the foregoing processing is executed intermittently.

Next, the experiment example concerning the heating apparatus of the billet W of this invention is demonstrated.

The six burner units 4 (4a-4f) divided into four heating zones A-D of the longitudinal direction were spaced apart 45 mm from the outer peripheral surface of the billet W of (phi) 156 * 400L, and were arrange | positioned in the circumferential direction. .

The specification of the said burner unit 4 and the combustion capacity for every heating area are as Table 1 and Table 2 showing.

Table 1

Pure Oxygen or Oxygen Enriched Burner Unit Specifications

  Burner length    490 mm   Number of nozzles    28 holes   Burner count    6   fuel    LPG   Low calorific value 91 MJ / m ³ [nor] (21800 kcal / m ³ [nor])   Theoretical oxygen 5.0m ³ / m ³ [nor]   Oxidant    Pure oxygen (supply from bomb)   Oxygen rain    1.0 or 1.1   Coolant flow rate 5m ³ / h [nor] at 0.2MPa

Table 2

Combustion capacity per heating area of the burner unit

Zone      A      B      C      D     Sum Number of nozzles 4 holes x 6 units 8 holes x 6 units 8 holes x 6 units 8 holes x 6 units 28 holes x 6 units Combustion capacity MJ / h     209     418     418     418     1463

Experimental example (1) of Table 3 is an experimental example which heats the billet W of normal temperature (30 degreeC) to 500 degreeC, and confirms the heating capability and thermal efficiency at that time. High thermal efficiency (imported calories / injection) of 37.1% because it is a method of impinge heating (collision heating) the high-temperature combustion flame injected from the burner unit 4 to the outer surface of the billet W electric field and pole. Calorie) can heat billet W to 500 ° C. in 79 seconds.

Table 3

Heating ability test 1

       Combustion capacity (MJ / h) Heating time Input calories Temperature rise Imported calories Thermal efficiency  A  B  C  D Sum  second  MJ   ℃  MJ   % Experimental Example (1) 209 418 418 418 1463  79 32.1   470 11.9   37.1

Input calories = combustion capacity x heating time

Imported calories = heating rate × average specific heat × billet weight

Experimental example (2) shown in Table 4 shows an experimental example in which gradient heating is performed on billet W heated to 250 ° C in advance. This is an experiment assuming, for example, oblique heating of the billet W conveyed by the continuous casting machine. Of the four heating regions A to D of the burner unit 4, B to D are ignited and only A is not ignited. As a result of heating without heating, the temperature difference ΔT = 73 ° C./400 mm between the billet W front end and the rear end became 43 ° C. in the heating time 43 seconds. It has become oblique heating of (degreeC / 1000 mm) or more.

Table 4

Inclined Heating Test 2

       Combustion capacity (MJ / h) Heating time Initial temperature Trailing end temperature Shear temperature Temperature difference  A  B  C  D Sum  second  ℃   ℃   ℃   ℃ Experimental Example (2)  0 418 418 418 1254  43  255   419   492    73 Experimental Example (3)  0 418 418 418 1254  76   30   343   449   106

Experimental example (3) of Table 4 shows the experimental example which performs gradient heating to the billet W of normal temperature. Combustion conditions were the same as the above Experimental Example (2). As a result, the billet W at room temperature was 76 seconds, and the temperature difference ΔT = 106 ° C./400 mm between the front end and the rear end was converted into a billet W of 1000 mm. In this experiment, in this experiment as well, the inclined heating of the ideal temperature gradient (100 ° C./1000 mm) or more is obtained.

Thus, according to the heating apparatus of the present invention, since a high-temperature combustion flame using pure oxygen or oxygen-enriched air is heated by colliding with the outer surface over the electric field and pole of the billet W supported in the open air state, It has also been found from (iii) that the billet can be heated to the extrusion molding temperature in a short time, and the inclined heating can be easily performed only by controlling the combustion capacity of the burner unit in the longitudinal direction of the billet W.

1 is a cross-sectional view of a billet heating apparatus according to the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1. FIG.

3 is a front view (a) showing the nozzle arrangement of the burner unit, and a cross sectional view showing the arrangement of the burner unit and the skid rail;

4 is a cross sectional view (a) and a longitudinal sectional view (b) of a skid rail;

* Explanation of symbols for the main parts of the drawings

2: body case

3: frame

4: burner unit

5: skid rail

12: nozzle

13: pipe

14: nozzle

W: Billet

Claims (5)

Main body case which consists of frame which communicated inside and outside without installing furnace wall, A skid rail for supporting a billet charged in the main body case in an open air state; A plurality of pure oxygen or oxygen enrichment burners which are attached to the main body case and heat the billets by impinging a combustion flame on an outer surface covering the entire length and the entire length of the billet. Done, The ratio D / L of the diameter D of the nozzle to the distance L from the outer surface of the billet to the nozzle of the burner is set from 0.02 to 0.04, and the pitch P of the nozzle is the diameter D of the nozzle. Billet heating apparatus characterized in that 30 to 50 times. The billet heating apparatus according to claim 1, wherein the pure oxygen or oxygen enrichment burner has a water cooling structure. The said skid rail is hollow, The pipe which has a some injection hole along the longitudinal direction is inserted, and the said skid rail supports the said billet from the said injection hole for the water supplied to the said pipe. The billet heating apparatus characterized by spraying toward the inner surface of a part. 4. The billet heating apparatus according to claim 3, wherein the skid rail is triangular in cross section. The billet heating device according to any one of claims 1 to 4, wherein the billet is an aluminum alloy or a copper alloy.

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