JPH046247A - Steel for waste incineration furnace boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steel for waste incinerator boilers that can be used at steam temperatures up to 400°C.

[Conventional technology]

In order to effectively utilize the exhaust heat generated by combustion as an energy source, municipal waste incinerators are increasingly equipped with exhaust heat boilers to generate electricity. It is obvious that the thermal efficiency of a power generation boiler improves as the steam conditions become higher temperature and higher pressure. Due to the combustion of vinyl chloride, etc., which is contained in large amounts in
If the temperature exceeds 300°C, corrosion will be significantly accelerated, and in order to avoid corrosion, the current situation is that steam conditions must be kept below 300°C to operate at low efficiency. However, from the perspective of effective energy use, increasing the temperature and pressure of waste power generation is strongly desired.

In hydrogen chloride gas and molten hydrochloride environments, Cr forms chlorides with high vapor pressure, so conventional corrosion-resistant alloys such as stainless steel cannot provide sufficient corrosion resistance.
Although Cr is relatively effective in this environment, it has the disadvantage of becoming expensive as the content increases, and currently waste incineration boilers do not use Cr.
-Mo based low alloy steel is used.

[Problem to be solved by the invention]

An object of the present invention is to provide a steel for a waste incinerator boiler that can be used up to the current steam temperature of 400° C. and is inexpensive.

[Means to solve the problem]

As a result of research conducted to solve the above problems, the present invention found that when the steam temperature is up to 400°C, the volatilization of Cr chloride limits the rate of corrosion, so the addition of Cr is harmful and needs to be kept below 10%. It was found that under these conditions, Si
It was completed based on the finding that high-temperature corrosion resistance by hydrogen chloride gas and molten hydrochloride is significantly improved by containing 0.5% or more and forming an austenite phase. , C in weight%
: 0.02-0.1%, St: 0.5-5%, Mn: 5
% or less, Cr: 5-10%, Ni: 5-30%, Mo:
(1) N: 0.05-0.4%, Cu: 0.2
-0.5% of one or more types, (2) Nb: 0.05-2%, Ti: 0.02-0
．． A steel for a waste incinerator boiler is characterized in that the steel contains 5% of one or more of the two or more items, and the balance is Fe and inevitable impurities.

[For production]

The reasons for limiting the ingredients will be explained below.

C is harmful to corrosion resistance due to hydrogen chloride and molten hydrochloride, and it is desirable to reduce it as much as possible, but since it is necessary to ensure strength at high temperatures and is also effective in stabilizing the austenite phase, each The upper limit was set to 0.1% and the lower limit was set to 0.02% as a range that does not impair the characteristics.

Si is an extremely effective element for ensuring corrosion resistance in hydrogen chloride and molten hydrochloride environments. However, if the content exceeds 5%, workability and weldability will deteriorate, and if it is less than 0.5%, a sufficient corrosion resistance effect cannot be obtained, so the upper limit was set at 5% and the lower limit was set at 0.5%.

Mn is an element that contributes to austenite phase formation,
Excessive addition causes problems in melting and hot processing, so the upper limit was set at 5%.

Cr is effective for general high-temperature oxidation and improving high-temperature corrosion properties, but at steam temperatures up to 400°C, hydrogen chloride,
In a molten hydrochloride environment, the volatilization of Cr chloride is rate-limiting for corrosion and is rather harmful, so it is desirable to keep it as low as possible, and it is set at 10% or less. However, in order to ensure resistance to hydrochloric acid dew point corrosion due to dew condensation when the boiler is stopped and resistance to steam oxidation on the inner surface of the boiler steel pipes, addition of 5% or more is essential. Therefore, the upper limit was set to 10% and the lower limit was set to 5%.

Ni is preferable for improving corrosion resistance in a hydrogen chloride or molten hydrochloride environment, and is also a necessary component for forming an austenite phase. Since the amount necessary for stabilizing the austenite phase is determined depending on the above-mentioned amounts of Cr and Si, it is necessary to add 5% or more. On the other hand, as the Ni content increases, the price of steel material also increases, but if it exceeds 30%, the properties cannot be improved enough to justify the price.

Therefore, the upper limit was set to 30% and the lower limit was set to 5%.

Although Mo has no effect on corrosion resistance at high temperatures, it is a necessary component to prevent hydrochloric acid dew point corrosion caused by dew condensation when the boiler is stopped, and for that purpose it is necessary to add 0.5% or more. be. However, in order to stabilize the austenite phase, the upper limit was set at 3%.

In the present invention, the following components may also be added.

N is an element effective in improving high-temperature strength and forming an austenite phase, and is added as necessary depending on the amount of Cr and Si.
It is necessary to add more than %. However, the addition of 0.4% sardine generates bubbles in the steel, and the formation of nitrides becomes significant, leading to deterioration of toughness, so the upper limit was set to 0.4% and the lower limit was set to 0.05%.

Nb and Ti are added when high-temperature strength is required, and in order to obtain this effect, Nb is added to 0.
．． 0.05% or more, and Ti is required to be 0.02% or more.

However, when Nb and Ti exceed 2% and 0.5%, respectively, the amount of carbides and nitrides produced becomes excessive.
On the contrary, it causes a decrease in strength. Therefore, the amount of Nb added is 0.0
The amount of Ti added was 0.02 to 0.5%.

Cu is an element effective in forming an austenite phase.

It also has the effect of improving acid resistance, especially when corrosion resistance at low temperatures such as hydrochloric acid dew point corrosion is required.
Add 5%. The reason why the lower limit was set to 0.2% is that sufficient effects cannot be obtained with less than this, and the upper limit was set to 0.2%.
．． The reason why it is set at 5% is that if it is added in excess of 0.5%, hot workability will be significantly impaired.

The present invention is a steel developed and invented as a superheating device for waste incineration boilers that can be used under steam conditions up to 400°C.

〔Example〕

20 kg of each steel having a composition according to any one of Claims 1 to 4 shown in Table 1 Nα1 to Nα1 to Nα32 was melted using a vacuum induction heating furnace. This was hot rolled into a plate with a thickness of 10 mm, heated at 1150°C for 601n, then rapidly cooled,
A test piece measuring 25 x 41 was prepared. Conventional materials include
JIS standard 5TBA24゜5U of chemical components shown in Table 1
S304 was used. The corrosion test is as shown in Figure 1.
The test piece was immersed in synthetic ash mixed with equal moles of KCj and NaCl, and 0.2% Hα + 30% H20 + 5% O2
+ba! , 500℃×24h in a mixed gas flow of H2
This was done by heating. 500℃ is steam temperature 40
In the case of 0°C, this is the temperature considered as the outer surface of the tube. The corrosion test results were evaluated based on the corrosion weight loss after descaling. The corrosion test results are also shown in Table 1. While the amount of corrosion of the conventional material is 25+sg/d or more, the amount of corrosion of the steel of the present invention is less than 20s+g/cr1, showing much higher corrosion resistance. In this way, the steel of the present invention can contain hydrogen chloride gas,
It has been revealed that it exhibits extremely high corrosion resistance in a molten hydrochloride environment.

Furthermore, for the steels of the present invention shown in Table 1, sufficient values were obtained for high temperature strength, toughness after aging, workability, and weldability as steels for boilers.

〔Effect of the invention〕

According to the present invention, hydrogen chloride gas,
It has become possible to provide a material with excellent corrosion resistance due to molten hydrochloride, which will greatly contribute to the development of industry.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the corrosion test method. Code 1 is the test piece, code 2 is the synthesis method, code 3 is the quartz dish, code 4
5 indicates a heating furnace, and 5 indicates a corrosive gas.

Claims (4)

[Claims] (1) In weight% C: 0.02-0.1% Si: 0.5-5% Mn: 5% or less Cr: 5-10% Ni: 5-30% Mo: 0.5-3% A steel for a waste incinerator boiler, characterized in that the remainder consists of Fe and unavoidable impurities. (2) In weight% C: 0.02-0.1% Si: 0.5-5% Mn: 5% or less Cr: 5-10% Ni: 5-30% Mo: 0.5-3% Garbage characterized by further containing one or two of Cu: 0.2-0.5% N: 0.05-0.4%, with the remainder consisting of Fe and inevitable impurities. Steel for incinerator boilers. (3) In weight% C: 0.02-0.1% Si: 0.5-5% Mn: 5% or less Cr: 5-10% Ni: 5-30% Mo: 0.5-3% In addition to Nb: 0.05-2% Ti: 0.02-0.5% A garbage incinerator characterized in that it further contains one or two of the following, with the remainder consisting of Fe and inevitable impurities. Steel for boilers. (4) In weight% C: 0.02-0.1% Si: 0.5-5% Mn: 5% or less Cr: 5-10% Ni: 5-30% Mo: 0.5-3% In addition, one or two of Cu: 0.2-0.5% N: 0.05-0.4% and Nb: 0.05-2% Ti: 0.02-0.5% A steel for a waste incinerator boiler, characterized in that it contains one or two of the following, with the remainder consisting of Fe and inevitable impurities.