JPH0261434A - Heater for cooking - Google Patents

Abstract

PURPOSE:To enable efficient radiation of a sufficient quantity of far infrared rays by forming a downward-directed wall surface of a surface combustion burner from a far infrared radiating material comprising a stainless steel which contains specified metals, has a specified surface roughness and is provided on a surface thereof with alumina whiskers having a specified length, and using the surface provided with the alumina whiskers as a downward-directed surface of the burner. CONSTITUTION:The composition of a stainless steel is so controlled as to contain 20-35wt.% of Cr, 0.5-5wt.% of Mo, up to 3wt.% of Mn and up to 3wt.% of Si, and alumina whiskers are provided on a surface of the stainless steel in an amount of 0.2mg/cm<2> so that far infrared rays are radiated from the surface when the steel is heated. The alumina whiskers will not be released from the surface under external forces, and exfoliation of a high-temperature oxide film in use can be perfectly prevented. The stainless steel having the high-temperature oxide film thereon is used for forming a downward-directed wall surface of a surface combustion burner or a heat-radiating plate, for radiating far infrared rays downward onto a food, or inner wall surfaces of heat-radiating walls in manufacturing a heater for cooking, and the surface having the oxide film thereon is used as the downward-directed surface of the surface combustion burner or heat-radiating plate or as the inner surfaces of the heat-radiating walls. It is thereby possible to efficiently radiate far infrared rays sufficient for satisfactorily grilling fish and meat.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, table stove grills, ovens,
The present invention relates to a heating appliance for cooking, such as a roaster, which is equipped with a heating means that emits far infrared rays from above onto food.

More specifically, the present invention relates to improvements in a surface combustion burner as a heating means, a heat radiating plate, and a heat radiating wall serving as a heating means and a partition wall.

[Conventional technology]

Previously, all heating means were made of ordinary stainless steel.

[Problem to be solved by the invention]

However, ordinary stainless steel does not emit enough far-infrared rays, which is important for deliciously grilling fish and meat, and there is a technical issue in generating far-infrared rays sufficiently and efficiently to improve food heating performance. there were.

An object of the present invention is to provide a heating appliance for cooking that can efficiently radiate far-infrared rays sufficient to deliciously grill fish, meat, etc., and is excellent in practical terms.

[Means to solve the problem]

The characteristic structure of the first invention is that Fe, Cr is used in a surface combustion burner as a means for heating food from above, a heat radiation plate, or a heat radiation wall that partitions a heating chamber and a high-temperature gas flow path.
The surface combustion burner or A downward facing wall surface of the heat radiating plate or an inner wall surface of the heat radiating wall is formed, and the surface with the alumina whiskers becomes the downward facing surface of the surface combustion burner or the heat radiating plate, or the inner wall surface of the heat radiating wall. Its function is as follows.

[For production]

In other words, if the surface combustion burner, heat radiation plate, or heat radiation wall is made of any material, it will be possible to efficiently generate far-infrared rays sufficient to grill fish and meat deliciously, and there will be no hygiene problems. The following facts were discovered as a result of conducting various experiments to find out whether it could be put to practical use under these conditions.

The surface of stainless steel containing Fe and Cr5Af is formed to have alumina whiskers with a length of 2 μm or more in most parts and a roughness Ra of 0.5 μm or more, and far infrared rays are emitted from the surface by heating the stainless steel. When radiated, a much higher emissivity (about 0.7 to 0.9) was obtained than that of ordinary stainless steel (about 0.4 to 0.5).

In addition, since the alumina whiskers have grown sufficiently, they do not peel off due to external force. Moreover, since the surface roughness Ra is sufficiently large, the density of alumina whiskers becomes large, which also suppresses the peeling of alumina whiskers.
Overall, it was possible to completely prevent alumina whiskers from peeling off during use.

Therefore, the above-mentioned stainless steel with alumina whiskers is used to form the surface combustion burner, the downward wall surface of the heat radiation plate, and the inner wall surface of the heat radiation wall for radiating far infrared rays from above the food of the cooking heating appliance, and the alumina whiskers are By using the surface with the heat radiation as the downward facing surface of a surface combustion burner, a heat radiating plate, or the inner surface of a heat radiating wall, it is possible to efficiently radiate far-infrared rays sufficient to grill fish and meat deliciously.

By the way, if a known far-infrared radiation paint is attached to the downward facing surface of a surface combustion burner, a heat radiation plate, or the inside surface of a radiation wall, the paint will peel off early, reducing the far-infrared radiation performance and causing damage to fish, meat, etc. Although it is impossible or extremely difficult to commercialize the product due to the risk of contamination with peeling paint, the above-mentioned stainless steel with alumina whiskers can be used as a heating appliance for heating and cooking without any problems caused by peeling. can.

[Means to solve the problem]

The characteristic configuration of the second invention is that 20 to 35% by weight of Cr is used in a surface combustion burner, a heat radiation plate, or a heat radiation wall that partitions a heating chamber and a high-temperature gas flow path as means for heating food from above. , Fe-Cr-M containing 0.5-5 wt% Mo, 3 wt% or less Mn and 3 wt% or less Si
o The downward wall surface of the surface combustion burner or heat radiation plate, or the inner wall surface of the heat radiation wall is The surface with the high-temperature oxide film is the downward surface of the surface combustion burner or heat radiating plate, or the inner surface of the heat radiating wall, and its function is as follows.

[For production]

In other words, if the surface combustion burner, heat radiation plate, or heat radiation wall is made of any material, it will be possible to efficiently generate far-infrared rays sufficient to grill fish and meat deliciously, and there will be no hygiene problems. As a result of further investigation through various experiments, the following facts were discovered.

The composition of stainless steel is 20 to 35% by weight of Cr.

0.5-5% by weight of Mo, 3% by weight or less of Mn and 3
If the stainless steel is adjusted to contain less than % by weight of Si, the surface of the stainless steel is provided with a high-temperature oxide film of 0.2 mg/cm2 or more, and far infrared rays are emitted from the surface by heating the stainless steel, ordinary The emissivity was much higher than that of stainless steel.

Further, the high temperature oxide film with a concentration of 0.2 mg/cTli or more did not peel off due to external force, and peeling of the high temperature oxide film during use was completely prevented.

Therefore, the above-mentioned stainless steel with a high-temperature oxide film is used to form the surface combustion burner, the downward wall surface of the heat radiation plate, and the inner wall surface of the heat radiation wall for radiating far-infrared rays from above the food of the cooking heating appliance. By making the surface with the oxide film the downward facing surface of a surface combustion burner, a heat radiation plate, or the inner surface of a heat radiation wall, it is possible to efficiently radiate far-infrared rays sufficient to grill fish and meat deliciously, as in the first invention, and It can be used as a heating device for cooking without any problems due to peeling.

〔Effect of the invention〕

As a result, it has become possible to provide a much higher-performance cooking heating appliance that allows foods such as fish and meat to be deliciously grilled using a sufficient amount of far infrared rays and to be cooked in a hygienic condition free from foreign matter contamination.

(Example〕 Next, examples will be shown.

(Example A) As shown in Fig. 1, a surface combustion burner (3) is provided above the inside of the grill (2) provided on the table stove (1),
The structure is such that the food (4) is heated by radiant heat from above.

To form the surface combustion burner (3), as shown in Figure 2, a flat box-shaped burner body (6) is connected to the fuel supply pipe (5) that supplies a mixed gas of gas fuel and combustion air. A large number of small flame ports (7) are formed on the downward wall surface (6a) of the burner body (6), and the flame formed by the small flame ports (7) and the radiant heat from the downward wall surface (6a) are transferred to the food ( 4).

(Example B) As shown in Fig. 3, a burner (8) and a heat reflector (9) are installed inside and above the grill (2) provided on the table stove (1).
, and is configured to heat the food (4) with radiant heat from above.

As shown in FIG. 4, a fuel supply pipe (1) that supplies a mixed gas of gas fuel and combustion air forms a burner (8).
0), connect the U-shaped burner body (11),
A flame opening (12) is formed along the inner edge of the burner body (11). Then, a heat reflector (9) is arranged to cover the upper part of the burner body (11), and the flame formed by the flame port (12) and the radiant heat from the heat reflector (9) are applied to the food (4). It is configured to do so.

(Example C) As shown in FIGS. 5 and 6, a cylindrical heat reflecting wall (14) is provided inside the case (13), and a heating chamber (1
5) and a partition wall that partitions the surrounding high-temperature gas flow path (16), and a heat radiation wall (14) that serves as a heating means for applying radiant heat to the food (4) from above and below and from both sides.

A fan (17) is installed between the case (13) and the heat radiation wall (14).
) and a gas burner (18), and a gas inlet (19) from the high temperature gas flow path (16) to the heating chamber (15) is formed in the heat radiation wall (14), and the high temperature generated by the gas burner (18) is provided. The gas is passed through the high-temperature gas flow path (
16), the material is swirled around the heat radiation wall (14) and then sent to the heating chamber (15).

The surface combustion burner (3), the downward wall surface of the heat radiation plate (9), and the heat radiation wall (14) in the above-mentioned Examples A to C are formed of a far-infrared radiation material, and the far-infrared radiation material is explained below. do.

(Example D) The far-infrared radiating material is a stainless steel containing Fe, Cr and A2 with alumina whiskers on the surface, and the surface is suitable for use in surface combustion burners (3) and heat radiation plates (9).
) is the inner surface of the heat radiation wall (14).

The content of Cr is 12% by weight or more from the viewpoint of rust prevention, and
From the viewpoint of preventing embrittlement, the content is preferably 28% by weight or less.

The content of AP is 2% by weight from the alumina whisker forming surface.
The content is preferably 6% by weight or less from the viewpoint of preventing embrittlement.

If stainless steel contains C, Si, and Mn, the C content should be 0.03% by weight or less to prevent cracking, the Si content should be 1% by weight or less to maintain ductility, and the Mn content should be reduced to 1% by weight or less to maintain ductility. From the viewpoint of preventing deterioration of toughness and maintaining high-temperature oxidation resistance, it is desirable that the content be 1% by weight or less.

In order to improve toughness and oxidation resistance, stainless steel may contain 0.5% by weight or less of Ti, Nb, or Zr, or
0.3% by weight or less of YSCe to improve peeling resistance,
Stainless steel may contain rare earth elements such as La and Nd.

Most of the alumina whiskers have a length of 2 μm or more,
As a result, the structure is designed to improve far-infrared radiation efficiency and prevent alumina whiskers from peeling off due to external force.

To form alumina whiskers of 2 μm or more, stainless steel is heated at 850 to 1000”C at 411 rpm in an oxidizing atmosphere.
It is necessary to perform a high-temperature oxidation treatment, preferably 9
High temperature oxidation treatment is performed at 20 to 930°C for about 16 hours.

In order to form alumina whiskers in a high-density state to more effectively improve far-infrared radiation efficiency and prevent alumina whiskers from peeling off due to external force, the roughness Ra of the stainless steel surface is set to 0.5 μm or more. It's Nishide. still,
Roughness Ra is measured using a stylus type surface roughness measuring device (JIS BO65
Center line average roughness measured in 1) (JIS 80601)
It is.

In order to make the surface roughness Ra 0.5 μm or more, a blast treatment is performed before the high temperature oxidation treatment.

Plast treatment is performed using, for example, alumina or silicon carbide abrasive grains with a roughness of 100 to 400, or a diameter of 0.05 to 1.0 m.
This is done by projecting iron balls, iron grids, etc.

If the L content is less than 3% by weight, or if the processing strain on the stainless steel surface due to the blast treatment is insufficient, pre-oxidation is performed before the high-temperature oxidation treatment to ensure sufficient length and density of the alumina whiskers. It is desirable to carry out treatment.

In the preliminary oxidation treatment, in order to improve the formation of alumina whiskers, the Ot concentration in the atmosphere was set to 0.1% or less, the heating temperature was set to 700°C or more, and the treatment time was set to 10 seconds or more. heating temperature to 1000°C
Do the following.

(Example E) The far-infrared radiating material has a high-temperature oxide film of 0.2 mg/aa or more on the surface of stainless steel containing Fe, Cr, and Mo, and the surface is used as a surface combustion burner (3).
, the downward facing surface of the heat radiation plate (9), and the inner surface of the heat radiation wall (14).

The content of Cr needs to be 20% by weight or more in order to improve corrosion resistance, and 35% by weight or less in order to prevent embrittlement and ease of workability.

The content of Mo needs to be 0.5% by weight or more to improve corrosion resistance, and 35% by weight or less to prevent embrittlement and ease of workability.

If Mn is included, it needs to be 3% by weight or less in order to prevent deterioration of toughness and oxidation resistance at high temperatures.

When Si is included, oxidation resistance at high temperatures is improved and high-temperature oxidation treatment becomes easier, but in order to prevent ductility deterioration, 3% by weight is added.
The following are desirable.

When one or more selected from the group consisting of Ti, Nb, and Zr is contained, it is desirable that the content be 0.5% by weight or less to improve toughness and oxidation resistance.

When one or more selected from the group consisting of La, Ce, Nd, and Y is included, it is desirable that the content is 0.3% by weight or less to improve the peeling resistance of the high-temperature oxide film.

To form a high-temperature oxide film, it is desirable to heat stainless steel at 900 to 1200°C in an oxidizing atmosphere.

In other words, when the heating temperature is less than 900°C, the diffusion of Cr in stainless steel is slow, so the amount of Cr that diffuses from the inside to the surface becomes smaller than the amount of Cr that escapes as oxides at the surface. Cr over a thickness of several tens of μm on the surface side
A layer with a low content is formed and the corrosion resistance is significantly deteriorated, but when heated at 900'C or higher, the diffusion rate of Cr inside becomes sufficiently high and sufficient corrosion resistance is obtained. Also, if the heating temperature exceeds 1200°C, the high temperature deformation of stainless steel will become severe and it cannot be put to practical use.
Heating at temperatures below C can sufficiently suppress deformation.

The heating program to form a high-temperature oxide film at 0.2 μ/d or higher can be selected appropriately, but - for boat fishing, 900°
C or more and less than 1100'C, the temperature is T ("C) and the time is t (win), and the heating time is set so that t≧142.5-0.125T. At temperatures below 1200°C, heat at least 5ml.
The heating temperature may be changed appropriately during heating.

The oxidizing atmosphere can be provided by air, oxygen-enriched gas, water vapor-enriched gas, combustion gas, or any other suitable gas.

The optimal high-temperature oxide film is 0.5 to 2 cm/cnl, and in order to make it difficult to peel off, it is desirable to keep it to 10 mg/cnl or less.

It is desirable to increase the surface roughness of stainless steel to increase the radiation area of far infrared rays, and in this case, processing distortion is applied to the surface by blasting or dull skin pass rolling before heating.

[Experiment example]

Next, an experimental example will be shown.

<Experimental Example 1> A steel plate having the composition shown in Table 1 above and made of stainless steel that was processed in the order of rolling, annealing, and pickling was prepared.

The steel plates are 10 cm square and 1 mm thick, A-1 to A-3 have compositions corresponding to the stainless steel of the present invention, and B-1 and B-2 have compositions corresponding to conventional products. ,
The units in Table 1 are weight %.

Samples A-1 to A-3 in Table 1 were subjected to some or all of the blasting treatment, preliminary oxidation treatment, and high-temperature oxidation treatment, and the treatment conditions were changed and the roughness Ra, alumina whisker length, radiation The ratio was measured and the results shown in Table 2 below were obtained.

Incidentally, in the blasting process, SiC is a case where No. 180 SiC shot is used, and Fe is a case where a 0.1 mm iron ball shot is used. Also, the emissivity is 400°
Far-infrared radiation intensity at wavelengths of 5 to 15 μm at C is shown as an average ratio to blackbody radiation.

Table 2 From the results in Table 2, when the surface has alumina whiskers with a length of 2 μm or more and the roughness Ra of the surface is 0.5 μm or more, a high emissivity of 0.7 or more is obtained. It turns out that it can be obtained.

Next, samples No. 1 to 5 (products of the present invention) in Table 2 above,
Samples B-1 and B-2 in Table 1 above coated with commercially available alumina/silica far-infrared paint (conventional product)
The heating/cooling cyclic tests described in items (A) and (El) below were conducted.

(b) After heating to 700°C, let it cool in the air for 20 minutes, and repeat the heating and cooling process.

(El) After heating to 700°C, cool with water mist for 20 minutes, and repeat the heating and cooling.

As a result, all of the products of the present invention showed no change at all after 20 repeated heating and cooling cycles, and remained in good properties that did not peel off due to external force. However, the conventional product B-1 is
In the test in (A) above, the paint cracked after 17 heating and cooling cycles, and in the test in (TI) above, the paint of conventional product 8-2 turned brown after 5 heating and cooling cycles. In both cases, the paint became susceptible to peeling off due to external force.

In other words, since the product of the present invention does not peel off due to external force even when used at high temperatures, it has been found that it can be put to practical use by placing alumina whiskers on the bottom side of the heating means that radiates far-infrared rays from above onto food in heating appliances for cooking.

<Experiment example 2> A stainless steel plate having the composition shown in Table 3 below was prepared.

The steel plate has a thickness of 1 + n + n per 10 cm square. C
-1 to C-6 are commercially available stainless steels that have been annealed and pickled, and D-1 and D-2 are stainless steels that have been experimentally melted and treated in the order of rolling, annealing, and pickling. be. The units in Table 3 are weight %.

The samples in Table 3 were surface-treated or subjected to high-temperature oxidation treatment without surface treatment, the treatment conditions were changed, the roughness Ra, the amount of high-temperature oxide film, and the emissivity were measured, and the corrosion resistance was examined. The results shown in Table 4 above were obtained.

In addition, in the surface treatment, SiC was blasted using No. 180 SiC shot, Fe was blasted using 0.1 iron ball shot, and rolling was done by rolling with a roll with a rough surface. This is a dull skin pass rolling process.

The zero amount of high-temperature oxide film is determined by measuring the weight of the stainless steel plate before and after high-temperature oxidation treatment, determining the weight increase per unit surface area, and multiplying the weight increase by 3.3. In other words, according to X-ray analysis, the high-temperature oxide film consists mostly of CrzO+, and the molar weight ratio of CrzO= and 02 (Crz(hl
ox) is 3.3, the amount of high-temperature oxide film was determined as described above.

The emissivity was determined in the same manner as in Experimental Example 1.

Corrosion resistance was determined by salt spray test (JIS z2371) 4
Time went.

From the results in Table 4, re -Cr -Mo stainless steel contains 20 to 35 wt% Cr, 0.5 to 5 wt% Mo,
Contains 3% by weight or less of Mn and 3% by weight or less of Si, and has a high temperature oxide film of 0.2 / d or more on the surface, that is, in Nos. 1 to 5, a high temperature of 0.7 or more It was found that it not only provides good emissivity but also has excellent corrosion resistance and does not peel off due to external force.

Therefore, in a heating device for cooking, it is possible to put the high-temperature oxide film on the lower side of the heating means that radiates far-infrared rays from above onto food.

[Another example]

Next, another embodiment will be described.

The present invention can be applied to various devices such as ovens, ranges, toasters, and roasters, which are collectively referred to as cooking heating devices.

Surface combustion burner (3), heat radiation plate (9), heat radiation wall (1)
The specific structure of 4) can be appropriately selected from known structures.

Note that although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structures and methods shown in the accompanying drawings.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a partially cutaway front view of a table stove, and FIG. 2 is a perspective view of the main part. 3 and 4 show another embodiment of the present invention, with FIG. 3 being a partially cutaway front view of the table stove, and FIG. 4 being an exploded perspective view of the main parts. 5 and 6 show further embodiments of the present invention,
FIG. 5 is a sectional view, and FIG. 6 is a view taken along the line VI-Vl in FIG. (3)...Surface combustion burner, (9)...
・Heat radiation plate, (14)...Heat radiation wall, (15)
... Heating chamber, (16) ... High temperature gas flow path.

Claims (1)

[Scope of Claims] 1. A heating appliance for cooking equipped with a heating means for emitting far infrared rays from above onto food, which has a surface made of stainless steel containing Fe, Cr and Al, with most of its length It has alumina whiskers of 2 μm or more, and the surface roughness R
A heating appliance for cooking, wherein the downward wall surface of the surface combustion burner (3) serving as the heating means is formed of a far-infrared radiation material in which a is 0.5 μm or more, and the surface with the alumina whiskers is the downward surface. 2. A heating appliance for cooking equipped with a heating means that radiates far infrared rays from above onto food, which is made of stainless steel containing Fe, Cr, and Al, and has alumina whiskers with a length of 2 μm or more on the surface. and the surface roughness R
A heating appliance for cooking, wherein the downward wall surface of the heat radiation plate (9) serving as the heating means is formed of a far-infrared radiation material in which a is 0.5 μm or more, and the surface with the alumina whiskers is the downward surface. 3. A heating appliance for cooking equipped with a heating means that radiates far infrared rays from above onto food, which is made of stainless steel containing Fe, Cr, and Al, and has alumina whiskers with a length of 2 μm or more on the surface of the stainless steel. and the surface roughness R
A heat radiation wall (14) made of a far-infrared radiation material with a of 0.5 μm or more, which also serves as the heating means and a partition wall that partitions the heating chamber (15) and the surrounding high-temperature gas flow path (16). ), and the surface with the alumina whiskers is the inner surface. 4. A heating appliance for cooking equipped with a heating means for emitting far infrared rays from above onto food, comprising 20 to 35% by weight of Cr;
A high-temperature oxide film of 0.2 mg/cm^2 or more is formed on the surface of Fe-Cr-Mo stainless steel containing 0.5 to 5 wt% Mo, 3 wt% or less Mn, and 3 wt% or less Si. A heating appliance for cooking, wherein a downward wall surface of a surface combustion burner (3) serving as the heating means is formed by a far-infrared radiating material, and the surface with the high temperature oxide film is a downward surface. 5. A heating appliance for cooking equipped with a heating means for emitting far infrared rays from above onto food, comprising 20 to 35% by weight of Cr;
A high-temperature oxide film of 0.2 mg/cm^2 or more is formed on the surface of Fe-Cr-Mo stainless steel containing 0.5 to 5 wt% Mo, 3 wt% or less Mn, and 3 wt% or less Si. A heating appliance for cooking, wherein a downward wall surface of the heat radiation plate (9) serving as the heating means is formed by a far-infrared radiation material provided, and the surface with the high-temperature oxide film is a downward surface. 6. A heating appliance for cooking equipped with a heating means for emitting far infrared rays from above onto food, comprising 20 to 35% by weight of Cr;
A high-temperature oxide film of 0.2 mg/cm^2 or more is formed on the surface of Fe-Cr-Mo stainless steel containing 0.5 to 5 wt% Mo, 3 wt% or less Mn, and 3 wt% or less Si. The provided far-infrared radiating material allows the heating means, the heating chamber (15), and the surrounding high-temperature gas flow path (1
6) A heating appliance for cooking in which an inner wall surface of a heat radiation wall (14) which also serves as a partition wall is formed, and the surface with the high-temperature oxide film is the inner surface.