JPS5911660B2 - Stainless steel for combustion equipment heat absorption radiator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Cr-A7 stainless steel for use in heat absorbing radiators of combustion equipment, which has excellent heat absorbing and radiating properties.

In combustion equipment such as oil stoves, gas stoves, or gas ranges, fuel is burned to produce a heat-absorbing radiator (
(hereinafter referred to as a heating body for convenience),
The heating element radiates its thermal energy to provide space or heat the object to be heated.In the case of an open stove, the main part or flame plate is the main part, and in the case of a forced ventilation stove, the main part is In the case of a gas range, a heat radiation plate serves as a heating element for each of these devices.

Currently, SUS430 is used as the material for the heating body of these combustion equipment.
(18% Cr type) or 12~20% Cr type stainless steel containing 2~5% Al (hereinafter simply referred to as Cr-Al type stainless steel). The latter is increasingly being used5.

The reason why SUS430 stainless steel was used for the heating element is because it has a certain degree of heat resistance and is economically affordable.The reason why it is being replaced by Cr-A7 stainless steel is because it is economically affordable. Although they are more expensive, they have better heat resistance, and materials have been selected with heat resistance as the main focus. However, when considering the function of the heating element, it goes without saying that it must be economical and have a certain degree of heat resistance, but the following two performances are more essential than these.

a0 The ability of the heating element to absorb and radiate combustion heat.

In other words, it is a matter of how much thermal energy a heating element absorbs and emits from a certain amount of combustion heat, and the better the material is, the better the material is for use as a heating element. b8 Degree of deterioration of the above abilities over time.

That is, it is an excellent material for use as a material heating element, with little deterioration in absorption and radiation ability after long-term combustion. However, materials have not been selected from this perspective so far. Various types of Cr-AI heat-resistant steels having excellent high-temperature oxidation resistance are known.

For example, in JP-A No. 48-89117, Cr: 13-2
8%, Al: 2-5%, C: 0.005-0.03
%, Si: 1% or less, Mn: 1% or less, Ti: 0.0
A Cr--Al heat-resistant steel for exhaust gas products is disclosed comprising 5% to 0.5%, the balance Fe and normal impurities. The inventors of the present application reexamined the composition of this type of steel from the above perspective, and investigated the heat absorption and heat radiation abilities of each component and their contribution to durability. Although Ti is harmful to sex, S1 is
It has been found that Cr-
Completed A7 series stainless steel.

According to the present invention, in weight %, Cr: 12.0 to 20%,
A7: 2.0-6.0% Si: 0.10-0.90%
, Ti: 0.01 to 0.40%, C: 0.03% or less,
Mn20. 38% or less, and the remainder consists of Fe and unavoidable impurities, and if the relationship between Ti content and Si content is 0.30% or less, the Si content can be changed to any content within the above range. and Ti exceeds 0.30% and 0.4
If it is 0% or less, increase the Si content to 0.50% or more and 0.90
% or less, there is provided a stainless steel for heat absorbing radiators of combustion equipment having excellent heat absorbing and radiating characteristics.

In the composition of the steel of the present invention, the content of Cr and Al is the same as the known Cr-A7 stainless steel (12-20% Cr, 2-6%
%A7,18Cr-3A1 system and 14Cr-5A1 system).

In the steel of the present invention, C is specified to be 0.03% or less from the viewpoint of improving the corrosion resistance, workability, and cleanliness of the steel. C
In r-Al stainless steel, Ti has the effect of fixing carbon in the alloy, refining crystal grains, increasing toughness, and suppressing abnormal oxidation at high temperatures. It is an element that is unfavorable for the sustainability of heat absorption and radiation ability, so in that sense it is desirable to have as little as possible, but as described later, its harmfulness can be alleviated by Si, so 0.40% It can be contained up to.

On the other hand, Ti is an essential component for preventing cracking during agglomeration and for preventing high-temperature abnormal oxidation, and for this purpose it must be contained at least 0.01%. Si is an essential component as a deoxidizing agent, and in the case of the steel of the present invention, it is important as an antagonistic component to Ti, but if it is too high, it increases the hardness of the steel, impairs workability, and reduces toughness, making it difficult to process in the normal manufacturing process. It becomes extremely difficult to manufacture such plates. Considering such a balance, 0.90% is set as the upper limit. The lower limit was set at 0.10% in consideration of deterioration in heat resistance in a general sense and deterioration in flowability of molten steel. Although Mn is an essential element as a deoxidizing agent, it is an element harmful to high temperature oxidation resistance.

In this type of steel, Mn is normally allowed to be about 1%, but in the case of the present invention, it is preferable to keep Mn as low as possible in order to improve high-temperature oxidation resistance, but from manufacturing considerations, the upper limit is 0. .38%. The correlation between Ti content and Si content will be made clear in the detailed description below.

The content of experiments to determine the composition range of Cr-I stainless steel as a heating element for various combustion equipment of the present invention will be described.

1 Among the components of the experimental sample material Cr-A7 stainless steel, Cr, A7,
Test materials were made of the components shown in Table 1, in which the Si and Ti components were varied.

In this table and all of Tables 2.3.4 below, the trial numbers marked with a △ symbol are steels other than those of the present invention, that is, comparative steels. All test materials used were cold rolled steel plates with a thickness of 0.4 m that underwent the same manufacturing process as ordinary Cr-Ad stainless steel cold rolled steel plates, and the surfaces were JIS G43O5 (cold rolled stainless steel plates) 7. Finished to a 7g64 finish as specified in . 2. Performance test test method The various combustion devices mentioned above use fuels whose main components are hydrocarbons such as kerosene, city gas, or liquefied petroleum gas, and the composition of the combustion gas produced when they are combusted is , there is no big difference in either fuel, N2, CO? ,H2O
, O2 as the main components, and trace amounts of CO, CnHm, NOX, and SOX depending on the combustion conditions and fuel type, and the components are almost the same.

Therefore, in this experiment, we conducted a combustion experiment using a kerosene stove as a representative example of combustion equipment. The stove used in the experiment was an open radiant stove specified in JISS2Ol9 (kerosene stove), but in order to improve the accuracy of the experiment, the outer flame tube during combustion was approximately 750 mm.
One that shows a temperature of ℃ and one that shows a temperature of about 850 ℃.
For each type of stove, the same model of stove from the same manufacturer was used.

In addition, 1 stipulated in JISK22O3 (kerosene) was used in the experiment.
The stove uses JISS2Ol9.
7.9. Combustion was performed according to the combustion test conditions specified in 1(2).

In the case of an open-type radiant kerosene stove, the flame tube consisting of an outer flame tube and an inner flame tube, a heat dissipation net, and a coil play the role of the heating element. , by evaluating the performance of the outer flame strip.
The performance of the experimental material as a heating body was evaluated.

The materials of the components of the combustion tube of the stove used in the experiment are shown below for reference.

Outer tube: Heat-resistant glass outer flame tube, inner flame tube: Manufactured using the experimental materials shown in Table 1 Heat dissipation net, coil: Heating wire FCH-2
(Things specified by JIS.C.252O (heating wires and bands)) Cross pin...SUS43O (JIS.G.4
3O8 (stainless steel wire) standard] Evaluation of the performance of the outer flame tube The two performances mentioned above are essential for the performance of the outer flame tube, that is, as a heating element, but the evaluation method is an extremely important issue. Become.

In the present invention, evaluation was performed using the following two methods.
1) Measuring the temperature of the outer flame tube with a thermocouple How much heat of combustion of kerosene is absorbed by the outer flame tube is expressed in other words as how much the temperature of the outer flame tube rises due to the heat of combustion. That's what it means.

Therefore, a thermocouple is welded to a fixed position on the outer flame tube,
By measuring the temperature of the outer flame tube, the ability of the outer flame tube to absorb combustion heat was measured. 2) Measuring the temperature of the outer flame cylinder using an infrared thermometer One way to measure how much thermal energy an object emits is to measure the radiated infrared energy. As a device, we used an infrared thermometer that measures infrared energy by converting it into temperature.

In the case of this experiment, infrared energy had to be measured through heat-resistant glass due to the structure of the combustion tube of the kerosene stove used, so it was necessary to measure infrared energy through heat-resistant glass.
A two-color infrared thermometer was used that can measure at both μm and 2.3 μm wavelengths simultaneously and eliminates the effects of emissivity and gray attenuation. 3. Test results Initial performance of the sample materials The combustion of a kerosene stove is unstable if the combustion tube or wick is completely new, so the initial performance is the performance 10 hours after the start of combustion. The results of the measurement values are summarized in Table 2.

The following can be seen from Table 2. Combustion heat absorption capacity The temperature of the outer flame tube made of each sample material measured by thermocouple as a measure of combustion heat absorption capacity is 750-7 in the case of a 750℃ stove.
Variation was observed in the temperature range of 30°C, and in the case of an 850°C stove, variation was observed in the range of 850 to 830°C.

In the case of kerosene stoves, even if the same model from the same manufacturer is burned under the same conditions, the temperatures of the outer flame tubes are generally not the same. Therefore, using combustion tubes made of the same material, we investigated whether the above-mentioned variations were due to differences between individual stoves or differences in the material of the outer flame tube.
As a result, it was found that the above-mentioned variations were due to differences between individual stoves, and that there was no difference in combustion heat absorption ability depending on the material of the test material, and the initial combustion heat absorption ability was It became clear that there was no difference between all the experimental materials. Thermal radiation ability The temperature value of the outer flame tube measured by an infrared thermometer, which is a measure of thermal energy radiation ability, is 750.
In the case of a ℃ stove, the variation between 730 and 710℃ is 8
In the case of a 50°C stove, a variation of 830 to 810°C was observed.

Experiments similar to those for combustion heat absorption ability revealed that this variation was due to differences among individual stoves, and that there was no difference in the initial heat radiation ability of all the experimental materials. Long-term performance of the test material The combustion of the stove is performed with a cycle of 8 hours of combustion and 16 hours of cooling, and the performance after combustion for 320 hours (40 cycles) is defined as the long-term performance (sustainability of heat absorption radiation), and its measured value is are summarized in Table 3.

However, the measured value is based on the initial performance (at the time of 10 hours of combustion).
Since it is easy to understand how much the performance has deteriorated (temperature drop) after 0 cycles, it is expressed as a temperature difference (Δt° C.) lowered from the initial temperature. The following can be seen from Table 3. I) Among the alloy components, Cr and All components, which are considered to have the greatest effect on heat resistance, fall within the component range of the present invention, i.e.
In the case of 18Cr-3A1 stainless steel, Crl7~
20%, Al2. In the range of 0 to 4.0%: 14
In Cr-5A1 stainless steel, Crl2~16%,
In the range of Al from 3.5% to 6.0%, long-term performance is hardly affected. 2) Ti and Si, which are thought to have a slight effect on heat resistance, have a particularly large effect on long-term performance.

Therefore, in order to further clarify the influence of Ti and Si, based on the measured values in Table 3, the long-term performance and Ti,S
The relationship with the i content is shown in Figures 1 to 4.

In Figures 1 to 4, the vertical axis represents the temperature difference (Δt'c) indicating performance deterioration, and the horizontal axis represents the Si content.
The content is indicated by lines A, b, c, and d in the figure, where the a line indicates Ti content of 0.20% or less, and the b line indicates Ti content of 0.20% or less.
% and 0.30% or less, C line exceeds 0.30% and 0.
40-% or less, and the d-line is in the 0.4% range exceeding 0.40%. From these figures, the results shown in the following items can be summarized. In the case of a 750°C stove 1) Combustion heat absorption capacity after long-term combustion as shown in Figure 1.

The following can be understood from the figure.

a) As the Ti content increases, the performance deteriorates.

b) Si influences the correlation with Ti. That is, the higher the Ti content, the greater the influence of Si. Therefore, when the Ti content is high, the decrease in long-term heat absorption capacity becomes smaller as the Si content increases.

However, when the amount of Ti is less than 0.20%, Si
The amount of heat absorption has almost no effect on the deterioration of long-term heat absorption capacity.

Based on the above results and the idea that a material whose deterioration temperature difference in long-term combustion heat absorption capacity is up to about 55°C in Figure 1 is an extremely good material, Ti and When determining the allowable content range of Si,
If the Ti content is 0.30% or less, the arbitrary amount of Si and T
If the i content is more than 0.30% and less than 0.40%, S
The purpose is achieved when the i content is 0.50% or more.

As mentioned above, in the steel of the present invention, Si is at least 0.
1% is required, and 0.90% due to consideration of processability etc.
limited to. Also, if Ti exceeds 0.40%, Si
There is no point in adding more than 0.90%. Therefore, the composition of the steel of the present invention is limited as set forth in the claims. 2)
Heat radiation capacity after long-term combustion This is shown in Figure 3.

The following can be understood from the figure.

a) Long-term heat radiation ability deteriorates as the Ti content increases.

b) Si influences in correlation with Ti; the higher the Ti content, the greater the influence of Si, and the deterioration of the ability is smaller in proportion to the Si content.

However, when the Ti content is low, 0.20% or less, the amount of Si has almost no effect on the deterioration of the breaking force.

As described above, the same results as in the case of the combustion heat absorption ability described above are obtained, and with the composition described above, that is, the composition of the present invention, the deterioration temperature difference is kept at about 60'C. In contrast, that of the comparative steel reaches 90'C. In the case of an 850°C stove, the relationship with combustion heat absorption capacity is shown in Figure 2, and the relationship with heat radiation capacity is shown in Figure 4.

These figures are exactly the same as in the case of a 750°C stove, and therefore the results are exactly the same as the results for a 750°C stove. For the composition of the steel of the present invention, the deterioration temperature difference is approximately 90°C for the combustion heat absorption capacity, Approximately 100℃ for heat radiation ability
can be suppressed to On the other hand, in comparison steel, the deterioration temperature difference is 120°C for heat absorption and 140°C for heat radiation.
As described above, the present invention utilizes Cr-Al with excellent heat resistance.
ferrite steel with limited Mn content and Ti and Si
The purpose of the present invention is to provide a useful steel with excellent durability in heat absorption and radiation performance by adjusting the content of .

[Brief explanation of drawings]

The attached drawings all show the durability of Cr-radiation collecting ability.
Shows significant correlation.

Claims (1)

[Claims] 1% by weight, Cr: 12.0-20%, Al: 2.0
~6.0%, Si: 0.10~0.90%, Ti: 0.
01-0.40%, C: 0.03% or less, Mn: 0.3
8% or less, with the remainder consisting of Fe and unavoidable impurities, and the relationship between the Ti content and the Si content is such that Ti is 0.
If Ti is 30% or less, set the Si content to any content within the above range, and if Ti is more than 0.30% and 0.40% or less, set the Si content to 0.50% or more and 0.90% or less. Stainless steel for heat absorbing radiators of combustion equipment with excellent heat absorbing and radiating properties.