JPS5930782B2 - Stainless steel for combustion equipment heat absorption radiator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Cr--Al stainless steel containing Ca and/or a rare earth metal, which is used as a heat-absorbing radiator for combustion equipment and has excellent heat-absorbing and radiation properties.

Combustion appliances such as kerosene stoves, gas stoves, and gas ranges burn fuel to provide thermal energy to a heat-absorbing radiator (hereinafter referred to as a heating element for convenience), and radiate that thermal energy to heat or heat objects. Currently, the heating element is mainly made of SUS430 series (18% Cr) stainless steel or 12-20% Cr stainless steel (18% Cr) containing 2-6% A7. Both ferritic stainless steels (which are sometimes divided into -3AA series and 14Cr-5A7 series, hereinafter simply referred to as Cr-AA series stainless steels) are used. Both of these ferritic stainless steels are used because of their economical efficiency and heat resistance, and in the past they have been selected with emphasis on heat resistance. However, when considering the function as a heating body, it goes without saying that it must be economical and have a certain degree of heat resistance, but the following two performances are even more essential.

10 Ability to absorb and radiate combustion heat.

In other words, it is a matter of how much heat energy it absorbs and radiates from a certain amount of combustion heat, and the better it is, the better the material is. 28 Degree of deterioration of the above abilities over time.

In other words, in terms of the degree of deterioration of the above-mentioned absorption and radiation ability after long-term combustion, a material with less deterioration can be said to be a superior material.
Various C-AA heat-resistant steels having excellent high-temperature oxidation resistance are known.

For example, in Japanese Patent Application Laid-Open No. 48-89117, Cr■ 13~
28%, AA ■ 2-6 articles, C: 0.005-0003
%, Si: 1 thread or less, Mn: 1% or less, Ti: 0.0
A Cr-A7 heat-resistant steel for exhaust gas products is disclosed, consisting of 5% to 0.5%, the balance Fe and normal impurities. Furthermore, the idea of adding Ca and/or rare earth metals to this type of steel is already known. Japanese Patent Publication No. 51-14119
The numbers include C: 0.03 or less, Si: 1.0 or less, C
r: 12-25 sections, Al: 2-6 sections, Ti: 0.1-0
．． 5%, and 0.00i to 0.1% of one or more rare earth elements or alkaline earth elements. Fe-C
An r-Al-based heat-resistant alloy is disclosed. However, in this steel, rare earth elements or alkaline earth elements are added solely to prevent abnormal oxidation.
There is no intention or recognition of improvement in heat absorption and radiation properties in connection with Ti and Si.

Based on such conventional technology, the present inventors reexamined the composition of this type of steel from the above-mentioned viewpoint, and investigated the effects of each component on heat absorption and radiation and their durability. , Ti is harmful to the sustainability of the heat absorption and radiation ability of steel, but Si has an antagonistic effect on the harmful effects of Ti, and in the presence of trace amounts of Ca and/or rare earth metals, Ti By adding a suitable amount of Si, an amount of T close to that allowed for known Cr-A7 stainless steels can be achieved.
The present invention was completed based on the finding that the heat absorption and radiation characteristics do not deteriorate even if i is contained.

According to the present invention, Cr212.0 to 20.0% by weight,
A7: 2.0-6.0, Si: 0.1-0.90
Ti: 0.01-0.45%, Ca and one or more rare earth metals: 0.001-0.050
Contains C: 0.03% or less, Mn: 0.38% or less, and the remainder consists of iron and unavoidable impurities, and the relationship between Ti content and Si content is 0.35% or less. In the case of , the Si content is any content within the above range, and T
When i is more than 0.3s% and less than 0.45%, the Si content is 0.50% or more and 0.90% or less.A combustion equipment with excellent heat absorption and radiation characteristics. Body stainless steel is provided. In the composition of the steel of the present invention,
The contents of Cr and Al are known in Cr-AA stainless steel (
12-20% Cr, 2-6% Al, 13Cr-3A1
(Sometimes they are considered separately into 14Cr-5A1 series and 14Cr-5A1 series). 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.

In Cr-A# stainless steel, Ti has the effect of fixing carbon in the alloy, refining grains, increasing toughness, and suppressing abnormal oxidation at high temperatures. It is a component that is unfavorable for the sustainability of the heat absorption and radiation ability of steel, and it is desirable to reduce it as much as possible, but as described later, its toxicity is due to the presence of one or more metals selected from Si, Ca, and rare earth metals. can be contained up to 0.45%.

On the other hand, Ti is an essential component to prevent cracking during agglomeration and to prevent high-temperature abnormal oxidation.
% must be included. 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 too much Si increases the hardness of the steel and impairs workability.
This reduces toughness and makes it extremely difficult to manufacture plates using normal manufacturing processes.

Considering such a balance, 0.90% is set as the upper limit. The lower limit was set at 0.10% in consideration of deterioration of heat resistance and deterioration of flowability of molten steel in a general sense. Mn is a necessary component as a deoxidizer, and is a component harmful to high-temperature oxidation resistance, but in this type of steel,
Normally, up to 1 section is allowed.

In the steel of the present invention, Mn is preferably as low as possible from the viewpoint of improving high temperature oxidation resistance, but in consideration of manufacturability, the upper limit was set to 0.38%. In the steel of the present invention, Ca and rare earth metals are thought to enhance the antagonistic effect of Si against the harmful effects of Ti.

Even when Ti is contained in an amount of 0.35 to 0.45%, at least 0.001% is necessary to achieve this purpose.
The effect reaches saturation at approximately 0.01%, but the upper limit was set at 0.05% in consideration of certainty of the effect and economy. Below, Cr-A as a heating element for various combustion equipment of the present invention
This article describes the content of the experiment that determined the composition range of l-series stainless steel. 1. Among the components of the experimental sample material Cr-Al stainless steel, Cr, Al,
The first product with different compositions of Si, Ti, Ca, and rare earth metals
The test materials had the components shown in the table.

In this table and all of Tables 2, 3, and 4 below, the sample 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 mm that had gone through the same manufacturing process as ordinary Cr-AA stainless steel cold-rolled steel plates, and the surfaces were JIS G43O5 (cold-rolled stainless steel plates) 7. Finished with Arashi 4 finish specified by. 2
．． Performance test test method Gas stoves, kerosene stoves, and gas ranges use fuels whose main components are hydrocarbons such as kerosene, city gas, or liquefied petroleum gas. The gas components are almost the same for both fuels: N2, CO2, H2O, O? ,CO,NO
, SOx, CnHm, etc.

Therefore, in the present invention, an experiment was conducted using a kerosene stove as a representative example. The stove used in the experiment is an open radiant stove specified by JIS821O9 (oil stove), and the temperature of the outer flame cylinder during combustion is approximately 750.
There are two types of kerosene, one with a temperature of approximately 850°C and one with a temperature of approximately 850°C, and the kerosene is No. 1 kerosene specified in JIS K22O3 (kerosene).

Also, the combustion is based on JISS2Ol9, 7.9.1. It was burned in accordance with the combustion test specified in (2). In the case of an open radiant kerosene stove, a flame tube consisting of an outer flame tube and an inner flame tube, a heat dissipation net, and a coil serve as the heating body. The performance of the experimental material was evaluated by fabricating all of the flame tubes using the experimental material and evaluating the performance of the outer flame strip. Method for evaluating performance of outer flame tube Although it is extremely difficult to evaluate the above-mentioned two essential performances, in the present invention, the following two methods were used for evaluation.

a) Measuring the temperature of the outer flame tube using a thermocouple How much heat of combustion of kerosene is absorbed by the outer flame tube is, in other words, how much the temperature of the outer flame tube rises due to the heat of combustion. .

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. b) Measuring the temperature of the outer flame cylinder using an infrared thermometer One way to measure how much thermal energy a heated object is emitting is to measure the emitted infrared energy. Using this method, we used an infrared temperature measurement device that measures infrared energy by converting it into a temperature number.

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

The following can be seen from Table 2. Temperatures measured by thermocouples as a measure of the ability to absorb heat of combustion, and temperatures measured by infrared thermometers as a measure of the ability to radiate heat, have a variation of up to about 20°C, which is the same for both 750°C and 850°C stoves, respectively. It shows. This variation is
This is due to the characteristics of the individual stoves used in the experiment, and is not due to differences in the experimental materials; the initial performance is the same for all experimental materials. Long-term performance of the test material The stove was burned with a cycle of 8 hours of combustion and 16 hours of cooling, and the performance after 320 hours of burning time (40 cycles) was defined as long-term performance (durability), and the measured values are shown in Table 3. Shown all together.

However, since it is easy to understand that the measured value shows how much the performance after 40 cycles has deteriorated from the initial level, Table 3 shows the temperature decreased from the initial temperature (Δt'C). Figures 1 to 4 were created based on the measured values in Table 3. 1st~
In Figure 4, the vertical axis is the temperature difference (Δt
'C), the horizontal axis indicates the total amount of Ca, rare earth metal, or two or more thereof. Also, A in the figure,
b) The content of Ti and Si is displayed in each curve C, d, and e, and the a line is sample number 25 to 27, that is, Ti content 0.2
3 to 0.28 ratio (0.30 ratio or less) and Si content 0.2
0 to 0.37 ratio (less than 0.50 ratio); B line is trial number 15 to
24, that is, Ti content 0.31 to 0.34 (0.3
(over 0 coefficient and below 0.35 coefficient) and Si content 0.20 to 0
．． Section 59 (arbitrary amount); C line is trial number 9 to 14, that is, Ti
Content: 0.36 to 0.43 (over 0.35 and 0.4
5 or less) and the Si content is 0.53 to 0.70 (0.5
0 coefficient or higher); d-line is trial number 4 to 8, that is, Ti content is 0.
Si content is 0.23 to 0.36 (less than 0.50);
E-line is trial number 1 to 3, i.e. Ti content 0.48 to 0.51
(If it exceeds 0.45, the Si content is 0.50 to 0.
．． It represents Section 72 (more than 0.50%).

The following conclusions can be drawn from these figures. In the case of a 750°C stove, the relationship between the durability of combustion heat absorption ability and composition is shown in Figure 1, and the relationship between durability of heat radiation ability and composition is shown in Figure 3.

From these figures, the influences of Ca and rare earth metals, Ti, and Si on the durability of both performances show exactly the same tendency, and can be summarized as follows.

a) The improvement effect due to the addition of Ca or rare earth metal is proportional to the amount added in a small amount, but as the amount increases, it approaches saturation.

The amount added alone or in total of two or more types is constant at about 0.010.

b) The greater the amount of Ti added, the greater the effect of adding Ca or rare earth metal becomes.

c) Si affects performance in relation to the Ti content, and the improvement effect of Si becomes greater when the Ti content is large.

Now, in Figure 1, based on the idea that a material with a performance deterioration temperature difference of up to about 55°C is an extremely good material, when determining the composition conditions to obtain a good material, the a curve is unconditionally It shows that it is a good material, and the b curve (Ti:0
．． 35% or less), the total amount of Ca and/or rare earth metal added is about 0.0005%, and in the C curve, it is a good material at 0.001%, but in the d and e curves, even if 0.05% is added. Good materials are not available.

To summarize from this, if Ca and/or rare earth metals are added in a total of 0.001% or more, Ti will be 0.
．． Even if it exceeds 35%, a good material can be obtained in the coexistence of Si with a coefficient of 0.5 or higher.

However, if Ti exceeds 0.45%, a good material cannot be obtained even in the coexistence of Si, Ca, and/or rare earth metals. Thus, the relationships described in the claims are derived. Considering this relationship in FIG. 3, the deterioration (temperature drop) in heat radiation ability is suppressed to about 65°C in the steel of the present invention, while it reaches 90°C in the comparative steel.

For 850 and C stove 850℃ stove has the ability to absorb combustion heat. The relationship between durability and composition is shown in Figure 2.

The same trend as in the case of the 750°C stove can be seen here as well, with the deterioration of heat absorption capacity (temperature drop) in the inventive steel being kept at about 90°C, while in the comparative steel it reaches 130°C. .

Durability of heat radiation ability of 850℃ stove The relationship between and the composition is shown in FIG.

Exactly the same tendency is seen here as well, with the deterioration of heat radiation ability (temperature drop) in the steel of the present invention being kept at about 100°C, while in the comparative steel it reaches 140°C.

As described above, the present invention is a Cr-Al stainless steel with excellent heat resistance, which contains Mn, Ti, Si, Ca, and/or at least one rare earth element, and has a heat absorbing material with adjusted amounts of Ti and Si. This provides steel with excellent durability in radiation performance.

[Brief explanation of the drawing]

The attached drawings all show the correlation of Ti, Si, Ca and/or rare earth metals on the durability of heat absorption and radiation ability of Cr-A7 stainless steel. Figure 1: Relationship between heat absorption capacity and durability in a kerosene stove with a combustion temperature of 750°C. Figure 2: Combustion temperature 850
Relationship between heat absorption capacity and durability in a kerosene stove at °C. Figure 3: Relationship between heat radiation ability and durability in a kerosene stove with a combustion temperature of 750°C. Figure 4: Relationship between heat radiation capacity and durability in a kerosene stove with a combustion temperature of 850°C. In these figures, A, b, c,
Each curve d and e represents the division of Ti and Si content,
a-line: TiO. 3O section and below, SiO. Less than 5O; b line: TiO. More than 3O ratio and less than 0.35 ratio, arbitrary amount of Si;
C line: TiO. more than 35 and less than 0.45%, SiO. 5
O section or higher; d line: TiO. More than 35 ratio and less than 0.45 ratio, SiO. less than 50%; e-line: TiO. Over 45%,
SiO. More than 50%.

Claims (1)

[Claims] 1 Cr: 12.0-20.0%, Al: 2.0 by weight
~6.0%, Si: 0.1~0.90%, Ti: 0.0
1 to 0.45%, one or two of Ca and rare earth metals
Species or higher: 0.001 to 0.050%, C: 0.03% or less, Mn: 0.38% or less, the remainder consists of iron and inevitable impurities, and the Ti content and Si content are The relationship is that when Ti is 0.35% or less, the Si content is set to an arbitrary content within the above range, and when Ti exceeds 0.35%, the Si content is set to an arbitrary content within the above range.
If the Si content is 45% or less, increase the Si content to 0.50% or more.
A stainless steel for use in heat absorbing radiators of combustion equipment, which has excellent heat absorbing and radiating properties of 90% or less.