KR100502854B1 - Chromuium-based stainless steel of good bonding ability to glass and acid resistance after high heat treatment - Google Patents

Abstract

The present invention relates to a method for producing a chromium stainless steel produced by adjusting the content of ferrite stainless steel to excellent glass sealing properties and acid resistance after high temperature heat treatment. In order to achieve the above object, the present invention is a carbon (C) 0.030% or less, silicon (Si) 0.3% or less, manganese (Mn) 0.5% or less, phosphorus (P) 0.040% or less, sulfur (S) 0.030% Chromium (Cr) 15% to 30%, nitrogen (N) 0.030% or less, aluminum (Al) 0.010% or less, titanium (Ti) 0.60% or less, the remaining iron (Fe) and other inevitable impurities Ferritic stainless steel, characterized in that Ti is 15 times or more of (C + N), Ti is 10 times or more of (C + N), and (Ti + Nb) is 20 times or more of (C + N). . Through the present invention, by improving the acid resistance of the surface oxide layer in the oxidation heat treatment process can not only prevent the rust generated on the surface of the sealing metal in the pickling process, it can also significantly reduce the sealing failure rate of the sealing alloy and glass.

Description

CHROMUIUM-BASED STAINLESS STEEL OF GOOD BONDING ABILITY TO GLASS AND ACID RESISTANCE AFTER HIGH HEAT TREATMENT}

The present invention relates to a method for producing chromium-based stainless steel having excellent glass sealing property and acid resistance after high temperature heat treatment, and more particularly, to a chromium system prepared by adjusting a component of ferritic stainless steel to have excellent glass sealing property and acid resistance after high temperature heat treatment. A method for producing stainless steel.

In the technical field of the present invention, stainless steel is a steel made of iron (Fe) in a substantial amount of chromium (usually 12% or more) to prevent rust, carbon (C), nickel (Ni), and silicon, if necessary. (Si), manganese (Mn), molybdenum (Mo) and the like are alloy steels containing a complex component containing a small amount. The stainless steel produced in this way has a very excellent characteristic in view of the characteristics of Fe which are the main components and are not possessed by ordinary steel, that is, the beauty of the surface, the rust, the resistance to heat, and the strong resistance to external impact. have. However, there are significant changes in mechanical properties, heat treatment properties, etc., depending on the content of chromium and other components, and there is also a big difference in the degree of rust. In recent years, various stainless steels with different components and performances are made to be suitable for various applications.

Stainless steel contains Cr as its main component, forming a very thin layer of chromium oxide (Cr ₂ O ₃ ) on the surface of the steel, which acts as a passive film that blocks oxygen from entering the metal matrix. Make sure that it has no corrosion resistance. In order to have corrosion resistance inherent in stainless steel, the stainless steel should contain at least about 12% Cr so that a very thin Cr ₂ O ₃ is formed by the Cr component.

Stainless steel is largely divided into iron-chromium stainless steel and iron-nickel-chromium stainless steel, where the iron-chromium stainless steel is ferritic stainless steel and martensitic stainless steel depending on its composition and structure. Divided.

Here, the ferritic stainless steel is a high chromium steel containing 11% to 18% Cr, 0.1% carbon (C) and the like and has a ferrite structure. Corrosion resistance is worse than austenitic stainless steel, but better than martensitic stainless steel, ferromagnetic and slightly weldable.

Stainless steel has been particularly used for general kitchens, building materials, and chemical plants due to its excellent corrosion resistance, but recently, the use of stainless steel has been expanded to materials for electric and electronic parts. When applied for electronic device parts, stainless steel often forms a unit part in a state of being sealed with glass. Stainless steel used as a sealing material for glass must not only have a similar coefficient of thermal expansion with glass, but also require acid resistance for sealing with glass.

As soft glass sealing alloys, stainless steel containing 27% to 28% of chromium has been used for a long time. Recently, with the development of color TV CRT tubes using X-ray leak-proof glass, it was found that the thermal expansion coefficient of the glass and the coefficient of thermal expansion of 18Cr-Fe alloy were well matched. Therefore, 18Cr-Fe-based alloys are widely used as alloys for sealing glass. come.

The glass sealing alloy not only has to coincide well with the coefficient of thermal expansion with glass, but also forms an oxide film on the surface in order to ensure sealing with glass. The oxide film formed on the metal surface improves the bonding strength and airtightness by increasing the bonding strength with the glass, and also serves to alleviate the difference in thermal expansion between the glass and the metal.

Patent application 94-704731 describes a ferritic stainless steel having excellent high temperature oxidation resistance and scale adhesion. According to the description herein, carbon (C) 0.03% or less, silicon (Si) 0.08% to 120%, manganese (Mn) 0.60% to 1.50%, chromium (Cr) 11.0% to 15.5%, and niobium (Nb) ) 0.20% to 0.80%, titanium (Ti) 0.1% or less (with no additives), copper (Cu) 0.02% to less than 0.30%, nitrogen (N) 0.03% or less, aluminum (Al) 0.05% or less (with no additives), The remainder is iron (Fe) and unavoidable impurities, and the amount of Mn and Si is regulated so that the ratio of Mn / Si is 0.7-1.5 in the range of Mn and Si,

0.7 ≤Mn / Si ≤ 1.5

1.4 ≤Nb + 1.2Si ≤2.0

1221.6 (C + N) -55.1Si + 65.7Mn-8.7Cr-99.5Ti-40.4Nb + 1.1Cu + 54 ≤O

Cr + Mn + Si ≤14.7

The amount of each alloying element is adjusted to satisfy the following conditions, and the oxidation weight after continuous heating at 900 ° C. for 100 hours in an air atmosphere is 0.02 kg / m ² or less, the scale peeling amount is 0.01 kg / m ² or less, and 1000 ° C. and 100 hours of continuous oxidation weight after heating 0.4kg / m ² or less, and the amount of scale peeling 0.02kg / m ² or less in high-temperature oxidation resistance and scale adhesion is excellent ferritic stainless steel characterized in that a.

In order to control the structure of the oxide scale, such ferritic stainless steel, which was also used as a conventional sealing alloy, chose a method of controlling the Si content of the alloy to 0.3% or less. In this case, the adhesion between the glass and the encapsulating metal was improved by controlling the porosity of the oxide film and the metal interface, but it was difficult to secure the uniformity of the scale layer of the surface, and the encapsulation part was encapsulated before the encapsulation when the encapsulation part was pickled in a mixed solution of nitric acid and hydrofluoric acid. The disadvantage was that the oxide layer formed on the substrate was completely removed, causing voids at the interface between the glass and the metal. In other words, the pickling solution penetrates the interface and remains in a small amount even after washing, causing corrosion and lowering the bonding strength. This phenomenon causes a drop in the degree of vacuum when applied as a component in a vacuum atmosphere.

In order to solve the problems of the prior art, the present invention provides a method for producing stainless steel that can produce an oxide film layer having excellent acid resistance properties after sealing the glass and the metal, and then preventing the generation of voids between the metal and the glass interface during pickling. To provide.

In the present invention, to control the amount of Ti and Ti + Nb added in a small amount in order to improve the drawing processability of the glass sealing alloy to produce a dense oxide scale to provide a stainless steel excellent in sealing and acid resistance of the glass.

In addition, the present invention improves the acid resistance of the surface oxide layer in the oxidative heat treatment process, which is a pretreatment process for glass sealing by adding Ti, to prevent rust occurring on the surface of the sealing metal, and to lower the sealing failure rate of the sealing alloy and glass Let's do it.

According to the present invention, carbon (C) 0.030% or less, silicon (Si) 0.3% or less, manganese (Mn) 0.5% or less, phosphorus (P) 0.040% or less, sulfur (S) 0.030% or less, chromium (Cr) 15% to 30%, nitrogen (N) 0.030% or less, aluminum (Al) 0.010% or less, titanium (Ti) 0.60% or less, the rest is composed of iron (Fe) and other inevitable impurities, and Ti ( It is characterized by a ferritic stainless steel that is at least 15 times C + N).

In addition, the present invention is a carbon (C) 0.030% or less, silicon (Si) 0.3% or less, manganese (Mn) 0.5% or less, phosphorus (P) 0.040% or less, sulfur (S) 0.030% or less, chromium (Cr) ) 15% to 30%, nitrogen (N) 0.030% or less, aluminum (Al) 0.010% or less, titanium (Ti) 0.60% or less, niobium (Nb) 0.020% or less, the remainder is Fe and other unavoidable impurities It is characterized in that the ferritic stainless steel, Ti is at least 10 times (C + N), (Ti + Nb) is at least 20 times (C + N).

Moreover, in this invention, such a ferritic stainless steel can also be used for glass sealing.

In this invention, it adds especially for each purpose and limits the quantity with respect to each alloy element contained in stainless steel. Each of these components is explained below.

First, in the case of carbon (C), it is necessary to contain a certain amount because it is an austenitic stabilizing element and serves to increase the strength of the steel, but in order to reduce the corrosion resistance of the steel, the present invention is limited to 0.030% or less. Silicon (Si) is limited to 0.05% or less in the present invention because silicon excessively increases the strength of the steel and causes peeling between the oxide film and the alloy. Manganese is an austenitic stabilizing element, and induces the formation of MnS and lowers the corrosion resistance, so it is limited to 0.50% or less in the present invention. Sulfur is limited to 0.30% or less since it segregates at grain boundaries or in the center like phosphorous and inhibits corrosion resistance of steel. Chromium not only stabilizes ferrite and improves the corrosion resistance of the steel, but is also closely related to the coefficient of thermal expansion, so it is limited to 15% to 30%. Titanium is used in the range of 15% ~ 30% because it makes carbon or nitrogen and metal compound to stabilize ferrite phase of steel and improve the oxidation resistance of steel and is closely related to coefficient of thermal expansion. Titanium (Ti) is limited to 0.60% or less because it not only stabilizes the ferritic phase of the steel by forming a carbon or nitrogen and intermetallic compound, but also improves the oxidation resistance of the steel or generates impurities in the steel by molten steel reoxidation when a large amount is added. Nitrogen (N), like carbon, is an austenitic stabilizing element, and not only increases the strength of the steel but also lowers the corrosion resistance of the steel, so it is limited to 0.030% or less in the present invention. Aluminum (Al) is not limited to 0.01% or less because it stabilizes the ferrite phase to enable continuous annealing as well as to improve the oxidation resistance of the steel or to cause an appearance defect by increasing the reoxidation of the steel when a large amount is added. Ti / (C + N) is limited to 15% or more because it is thought that carbon and nitrogen in the steel are made of TiC or TiN type compounds to improve the ferrite stabilization and corrosion resistance of the steel, and to form a dense oxidation scale. do.

In the case of another stainless steel of the present invention, the reason for adding the aforementioned alloying elements is the same. In addition to the alloying elements described above, in another stainless steel of the present invention, (Ti + Nb) / (C + N) is characterized in that the ferrite phase stabilization effect and the improvement of corrosion resistance of the steel, the formation of a dense oxide scale layer while increasing the Ti input amount In order to minimize the reoxidation in the steel by the limit to 20 or more.

In the present invention, the steel of such a composition is first heated at 1250 ° C. for 2 hours and then hot rolled to 3.0 t at a finishing temperature of 800 ° C. to 820 ° C. Next, after annealing at 960 ° C. for 2 minutes, the annealed specimens are pickled in a mixed solution of nitric acid and hydrofluoric acid. The pickled specimen was cold rolled to 0.8t, then annealed at 960 ° C. for 1 minute, and then pickled again in the same manner as the hot rolled steel sheet. The steel of the present invention manufactured by this method was compared with the steel produced by the method used in the conventional experiment was carried out to confirm the characteristics.

This experiment will be described in detail through the following examples of the present invention.

For the specimens used for the experiments of the present invention, the content of the components for the six types of stainless steel and the six types of stainless steel of the present invention, which are conventionally used, is shown in Table 1 below. The comparative example in Table 1 refers to the stainless steel used in the prior art, the example refers to the stainless steel used in the present invention.

As shown in Table 1, in the first to third examples, the conditions in which Ti is 15 times or more of (C + N) by weight% are satisfied so as to be compared with the experimental results of the first to third comparative examples. Experiment using the stainless steel of the present invention.

Further, in Examples 4 to 6, in order to be compared with the experimental results of the fourth to sixth comparative examples, by weight%, (Ti + Nb) satisfies the condition that 20 times or more of (C + N). Experiments were made using the stainless steel of the invention.

For stainless steel specimens of the type shown in Table 1 below and of the size as shown in FIG. 1, as described above, they were cast into 50 kg ingots, heated at 1250 ° C. for 2 hours, and then at 800 ° C. to 820 ° C. After hot rolling at a finishing temperature of 3.0 t, annealing was performed at 960 ° C. for 2 minutes, and the annealed specimens were pickled in a mixed solution of nitric acid and hydrofluoric acid. The pickled specimens were cold rolled to 0.8 t, then annealed at 960 ° C. for 1 minute, and then pickled in the same manner as for hot rolled steel sheets. The cold rolled steel sheet produced in this manner is processed into a round plate having a diameter of 20 mm, and then pressed into the form as shown in FIG. 1.

1 shows a method of processing a specimen used in the embodiment of the present invention. As shown in Figure 1, in the embodiment of the present invention by compressing the upper portion of the cylindrical raw material to prepare a specimen for use in experiments. As shown in Fig. 1, the diameter (first diameter) of the upper cylinder is 4.5 mm, and the diameter (second diameter) of the lower cylinder is 9.8 mm in the prepared specimen. In addition, the height of the lower cylinder is 5.5mm. These specimens were oxidized at high temperature in a vertical tubular furnace under an atmosphere temperature of 1050 ° C., a holding time of 35 minutes to 40 minutes, a dew point of 18.5 ° C., and an atmosphere gas of 75% nitrogen and 25% hydrogen.

The following measurement was performed using the specimen which passed the above-mentioned processing process.

First, in order to investigate the characteristics of the oxidized oxide film, the specimen prepared by the above-described method was cut and polished to 0.05 µm, and observed with a scanning electron microscope (SEM).

The left side of FIG. 2 is a case of the first comparative example of the prior art, and the right side of FIG. 2 is a case of the first embodiment of the present invention. FIG. 2 compares the first comparative example and the first example and shows the shape of the surface oxide obtained by observing the specimen by SEM. Hereinafter, the form of the intermitted oxide as shown in the left side of FIG. 2 is called an A-type oxide layer, and the oxide continuously formed uniformly on the surface as in the right side of FIG. 2 is called a B-type oxide layer. As shown in FIG. 2, it can be seen that in the case of the B type oxide layer, the oxide layer is uniformly distributed on the surface as compared with the A type oxide layer.

Oxidation resistance evaluation of the above specimen was observed at 20 ° C. in a mixed solution of nitric acid and hydrofluoric acid with a composition of 5% hydrofluoric acid + 5% nitric acid at 20 ° C. for 2 hours, followed by observation of the surface state by visual observation and weight loss. It was carried out by the method of measuring. That is, the oxidation resistance was evaluated by precipitating the specimen in the acid mixture solution and measuring the degree of oxidation of the surface.

3 and 4 show the photographs of the specimens of the first comparative example, the above-described prior art, and the photographs of the specimens after the oxidation resistance test were performed on the specimens of the first embodiment of the present invention, respectively. 3 and 4 show front and plan views, respectively, of such specimens. 3 and 4, the left side shows the specimen of the first comparative example of the prior art, and the right side shows the specimen of the first embodiment of the present invention.

3 and 4, the scale of the surface is almost removed in the case of the specimen of the first comparative example, but the scale of the specimen of the first embodiment remains almost without damage. Hereinafter, a state in which the scale of the surface is almost removed as shown in the left photograph of FIGS. 3 and 4 will be referred to as a pickling exterior C, and the form in which the scale is not removed will remain uniform on the surface as shown in the photographs on the right of FIGS. 3 and 4. It is called pickling appearance D.

Table 2 below shows the results of the cross-sectional investigation of the oxide layer and the appearance and surface loss after pickling of the conventional stainless steel and the stainless steel of the present invention after high temperature oxidation.

As shown in Table 2, in the embodiment of the present invention, the oxide layer of the specimen is not only type B but also the pickling appearance is also shown in the form of D as the weight loss after pickling is greatly reduced to 10 mg or less. Accordingly, it can be seen that the first to sixth embodiments of the present invention have more excellent effects than the first to sixth comparative examples of the prior art.

Through the embodiment of the present invention, by adding 15 times or more of Ti (C + N) to the existing glass alloy sealing alloy by weight percent, it was possible to obtain a glass sealing ferritic stainless steel excellent in acid resistance of the oxide layer. In addition, C and N of the present invention are stabilized by the combined addition of Ti and Nb, such that by weight% Ti is 10 times or more of (C + N) and (Ti + Nb) is 20 times of (C + N) In this case, the ferritic stainless steel for glass sealing excellent in the acid resistance of the oxide layer was obtained.

In the present invention, by adding an appropriate amount of Ti to the conventional glass sealing alloy to improve the acid resistance of the surface oxide layer in the oxidative heat treatment process, a pretreatment process for glass sealing occurs on the surface of the sealing metal in the pickling process, a subsequent process of sealing the glass sealing parts. Not only can prevent rust, but also significantly reduce the sealing failure rate between the sealing alloy and the glass.

1 is a view showing the specifications of the specimen used in the experiment of the present invention.

Figure 2 is a photograph comparing the cross section of the surface oxide layer of the steel in the comparative example of the prior art and the embodiment of the present invention.

Figure 3 is a front view of a specimen photograph shown in comparison with each other after the precipitation of the steel in the comparative example of the prior art and the embodiment of the present invention to the acid.

Figure 4 is a plan view of a specimen photograph shown in comparison with each other after precipitation of the steel in the comparative example of the prior art and the embodiment of the present invention in an acid.

Claims (3)

By weight%, carbon (C) 0.030% or less, silicon (Si) 0.3% or less, manganese (Mn) 0.5% or less, phosphorus (P) 0.040% or less, sulfur (S) 0.030% or less, chromium (Cr) 15% to 30%, nitrogen (N) 0.030% or less, aluminum (Al) 0.010% or less, titanium (Ti) 0.60% or less, the remainder is made of iron (Fe) and other inevitable impurities, A ferritic stainless steel for sealing glass, wherein Ti is 15 times or more of (C + N). By weight%, carbon (C) 0.030% or less, silicon (Si) 0.3% or less, manganese (Mn) 0.5% or less, phosphorus (P) 0.040% or less, sulfur (S) 0.030% or less, chromium (Cr) 15% to 30%, nitrogen (N) 0.030% or less, aluminum (Al) 0.010% or less, titanium (Ti) 0.60% or less, the remainder is made of iron (Fe) and other inevitable impurities, The ferritic stainless steel for glass sealing in which Ti is 10 times or more of (C + N), and (Ti + Nb) is 20 times or more of (C + N). delete