KR20150086087A - Method for manufacturing ceramic backing materials - Google Patents

Abstract

The present invention relates to a method for manufacturing a ceramic welding support. The method includes the steps of: mixing the raw ceramic oxide powder ingredients including kaolin, talc, feldspar, and calcium carbonate; filling the raw ceramic oxide powder ingredients in a mold die at the packing density of 50-80% and molding a molded article having the molding density of 1.5-2.0 g/cm^2; and firing the molded article at 1200-1350°C to form the ceramic welding support having the firing density of 2.0-2.4 g/cm^2 and the absorption rate less than 3.0%.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing ceramic ceramic backing materials,

The present invention relates to a method for manufacturing a ceramic welded support, and more particularly, to a method for manufacturing a ceramic welded support, which can prevent overexposure of a backside bead and occurrence of defects, reduce a manufacturing cost, prevent excessive moisture absorption, To a method for manufacturing a ceramic welded support.

Ceramic welding supports generally used in shipbuilding, offshore, plant, and other steel structures are welded to relatively small structures, and the assembling department, which mainly welds the parts to be welded in parallel, In addition to this, it is widely used in the part where the block and the block manufactured by the assembly department are welded.

In recent years, it is required to increase the strength of the steel used in the shipbuilding industry and to improve the quality of the welding, because of the large capacity of shipbuilding such as container ships, working in a cryogenic region, and extending the life of order ships of ships and offshore structures. Therefore, the impact strength of the weld should be at least 60 Joules.

Welding materials that absorb moisture in the welding process are the most important causes of welding defects such as blow holes and the like. Moisture is a main cause of diffusible hydrogen generation. When diffusible hydrogen is incorporated into the welding part, This is a major cause of welding defects. Currently, Korea is changing to a sub-tropical climate due to global warming, and because humidity is rising, protection and prevention are required to prevent moisture absorption of welded materials.

     In order to control the hydrogen content of the welding base material to 4ml / 100g or less in accordance with this reality, researches have been conducted on many welding methods, and requirements for moisture and hydrogen control are increasing for the welding material manufacturers.

In addition, excessive backside beads are generated due to the use of high current and inappropriate quality of ceramic welded area, and welding defects such as high temperature cracks are generated, so that the height of the backside beads of the welds is controlled to be less than 2 mm. Such high temperature cracks can not be detected by visual inspection of welds. Therefore, UT (Ultrasonic Testing), which can detect the size of internal welding defects, and RT (Radiographic Testing), which detects internal welding defects, must be inspected. Failure to find such defects may also lead to vessel cracking after delivery.

Korean Patent Registration No. 10-0316343 discloses a method of producing a piezoelectric ceramic composition comprising 38 to 75 wt% of Al ₂ O ₃ , 20 to 48 wt% of SiO ₂ , 10 wt% or less of MgO, and other impurities (Fe ₂ O ₃ , CaO, Na ₂ O, K ₂ O) is disclosed, and it is possible to prevent the molten flux from overflowing through the improvement between the base materials when welding in a vertical-up posture In addition, there is an advantage that the back-bead adhesion of the spatter generated when welding at high voltage and high current can be suppressed. This welding support is SiO ₂ -MgO-Al ₂ O ₃ -based oxide ceramics, and its refractivity is exceeded by SK 14, so that the arc is unstable due to incomplete slag generation and the welding part is not easily protected by slag, May occur.

Therefore, the inventors of the present invention have been continuously studying the technology for preventing the occurrence of overexposure and defects of the backside bead, and thus, in order to prevent excessive moisture absorption and welding defect, SiO ₂ -MgO-Al ₂ O ₃ -CaO The inventors of the present invention have developed a more economical, usable and competitive invention by deducing and inventing a method characteristic of manufacturing a welded support as an oxide ceramic raw material.

Korean Patent Registration No. 10-0316343

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a ceramic welded support which can prevent overexposure of a backside bead and defects and reduce a manufacturing cost.

Another object of the present invention is to provide a method for manufacturing a ceramic welded support which can improve the strength of a welded portion by preventing excessive moisture absorption.

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a ceramic material, comprising: mixing an oxide ceramic powder raw material comprising kaolin, talc, feldspar, and calcium carbonate; Filling the oxide ceramic powder raw material into a die for molding at a filling density of 50% to 80%, and then molding a molded product having a molding density of 1.5 g / cm 2 to 2.0 g / cm 2; And firing the molded product at 1200 ° C to 1350 ° C to form a ceramic welded support having a plastic density of 2.0 g / cm 2 to 2.4 g / cm 2 and a water absorption rate of less than 3.0% to provide.

Here, in the step of molding the molded article, a pressure of 300 kgf / cm 2 to 700 kgf / cm 2 is applied to mold the molded article.

The oxide ceramic powder raw material has an average size of 10 탆 to 500 탆.

The refractory strength of the ceramic welded area is SK8 ~ 12.

As described above, in the present invention, by manufacturing the ceramic welded support with the SiO ₂ -MgO-Al ₂ O ₃ -CaO based oxide ceramic raw material, the refractivity is reduced to SK _{8 to} SK 12 to prevent the occurrence of over- And the manufacturing cost can be reduced.

According to the present invention, by producing a ceramic welded support using an oxide ceramic raw material, dispersibility at the time of wet mixing is good, powder for forming is easy to manufacture, and molding strength at the time of molding is excellent.

In the present invention, a ceramic welding support region is realized by using kaolin, talc, feldspar, and calcium carbonate which are raw materials of oxide ceramics existing in a natural state, and it is advantageous in that the supply and demand is smooth and the cost is low, .

According to the present invention, it is possible to improve the strength of a welded portion by manufacturing a welded support having an absorption rate of less than 3% and preventing excessive moisture absorption.

According to the present invention, it is possible to provide a welded support member capable of performing a stable welding operation and generating a beautiful backside bead.

1 is a flow chart of a method of manufacturing a ceramic welded support according to an embodiment of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 is a flow chart of a method of manufacturing a ceramic welded support according to an embodiment of the present invention.

In the method of manufacturing a ceramic welded support according to an embodiment of the present invention, an oxide ceramic raw material composed of kaolin, talc, feldspar, and calcium carbonate is mixed (S100).

Here, the oxide ceramic raw material composed of kaolin, talc, feldspar, and calcium carbonate is subjected to a forming and firing process to form a mixture of 50 wt% to 70 wt% of SiO ₂ , 15 wt% to 35 wt% of Al ₂ O ₃ , 8 wt% To 15 wt% of MgO, 0.5 wt% to 3 wt% of CaO as main components and other components of Fe ₂ O ₃ , K ₂ O and Na ₂ O in an amount of 0.5 wt% to 5 wt% And a ceramic welded support having a fire resistance of SK8 ~ 12.

At this time, an organic binder and an organic lubricant are added to the kaolin, talc, feldspar, and calcium carbonate to smooth powder formation, improve molding strength, and facilitate mold die release in the process described below.

Polyvinyl alcohol (PVA), acrylic resin, glycol, wax and the like are used for the organic material binder. The organic material binder improves the strength of the powder during powder production to prevent the powder from breaking, .

If the amount of the binder is less than 0.5 wt%, the strength of the powder is weakened, and the mold is not filled with the mold, so that the molding strength is weak and the product is broken. , When the amount of the organic binder is more than 5 wt%, the binder is flowed to the surface of the molded article at high pressure molding, and the product is not easily released into the mold due to reaction with the mold die surface, and unnecessary manufacturing costs are increased.

As the organic lubricant, paraffin, wax fatty acid, and silicone oil can be used. The powder does not adhere to the mold, and the flow of the powder is improved. The organic material lubricant is present in an amount of 0.1 to 1 wt% of the total weight of the mixture. When the amount is less than 0.1 wt%, the molded product is difficult to separate. When the amount is more than 1 wt%, an unnecessary manufacturing cost is increased.

At this time, the oxide ceramic raw material made of kaolin, talc, feldspar, and calcium carbonate is an oxide of SiO ₂ -MgO-Al ₂ O ₃ -CaO system, and the refractory degree is SK8-SK12.

That is, in the present invention, SiO ₂ -MgO-Al ₂ O ₃ -CaO-based oxides in which CaO is added to SiO ₂ -MgO-Al ₂ O ₃ -based oxide ceramics such as cordierite and mullite whose fire resistance is SK 14 or higher By applying it as an oxide ceramic raw material, the fire resistance can be lowered to SK8 to SK12.

Here, refractoriness is an important factor which causes the occurrence of slag, which protects welds from outside air, and an excessive factor, which causes beads. If SK8 is less than SK8, excess slag is generated and the backside bead becomes excessive, And a post-process such as grinding or the like is required, and the gas release from the inside becomes difficult. If the fire resistance exceeds SK 12, slag generation is not smooth and the arc becomes unstable, and protection of the welded portion by slag is not easy, resulting in defects in the welded portion such as pore generation.

As described above, the reason for manufacturing the ceramic welded support using the oxide ceramics raw material in the present invention is that the oxide ceramic raw material is excellent in dispersibility during wet mixing, is easy to produce powder for molding, .

In addition, since the oxide ceramic raw material does not require oxygen control of the calcining furnace at the time of calcination, the manufacturing cost can be reduced, and kaolin, talc, feldspar, and calcium carbonate, which are raw materials of the oxide ceramics of the ceramic welded support of the present invention, And it is economical and easy to use.

Therefore, in the present invention, by manufacturing a ceramic welded support with SiO ₂ -MgO-Al ₂ O ₃ -CaO based oxide ceramic raw material, it is possible to reduce the fire resistance to SK _{8 to} SK 12 to prevent the occurrence of over- There is an advantage that the cost can be reduced.

Thereafter, a molding powder having an average size of 10 탆 to 500 탆 is prepared as an oxide ceramic raw material mixed with an organic binder (S110). At this time, the molding powder can be produced by using a spray dryer.

The size of the molding powder is a factor closely related to the filling rate and the molding property. If the size of the molding powder is less than 10 탆, the powder is not formed and the aggregation during molding is not smooth, If the size of the powder exceeds 500 mu m, the powder is too large to be filled smoothly.

Subsequently, the molding powder is packed in a mold die for molding at a filling density of 50% to 80%, and a pressure of 300 kgf / cm 2 to 700 kgf / cm 2 is applied to form a molding die having a molding density of 1.5 g / cm 3 to 2.0 g / The molded product is molded (S120).

In this process, when a molding die is filled with a molding powder at a filling rate of less than 50%, a molded article having a molding density of less than 1.5 g / cm 3 can not be produced even when molded at a high pressure. It is not preferable because it can not come out.

The molding pressure should be molded at a proper pressure for lowering the water absorption rate and increasing the density of the molded article. If the pressure is less than 300 kgf / cm 2, a molded product having a molding density of less than 1.5 g / cm 3 is produced. If the molding is performed in excess of 700 kgf / cm 2, the upper and lower punches of the mold after molding are not smoothly separated from the mold die, .

Subsequently, the molded product is fired at 1200 ° C to 1350 ° C to form a ceramic welded support having a sintering density of 2.0 g / cm 3 to 2.4 g / cm 3, a water absorption of less than 3.0% and a refractivity of SK 8 to 12 (S 130).

The above-mentioned molding density is closely related to the plastic density, the filling of the raw material, and the delivery of the molding pressure. Therefore, when a molded article having a molding density of 1.5 g / cm 3 or less is fired to form a fired product having a fired density of 2.0 g / cm 3 to 2.4 g / cm 3, the fired article is vitrified and the shape due to excessive shrinkage Resulting in a weld defect in which a spatter occurs on welding and a weld defect on the backside bead shape occurs.

In addition, the molding density can be evaluated in filling the raw material and in transferring the molding pressure. That is, when the molding is performed at a pressure of 300 kgf / cm 2 to 700 kgf / cm 2, if the molding density is less than 1.5 g / cm 3, the raw material filling and molding pressure become uneven and the molding size and mass become uneven, It is impossible to produce a welded support having a density of 2.0 g / cm 3 to 2.4 g / cm 3 and a water absorption of less than 3%.

If the molding density exceeds 2.0 g / cm 3, the molded product must be molded at a pressure exceeding 700 kgf / cm 2, which may result in reduced productivity and breakage of the mold.

The firing temperature is a factor attributable to the density and the water absorption rate of the weld metal, and the firing process should be performed at an appropriate temperature. At this time, when a molded article having a molding density exceeding 1.5 g / cm 3 is formed by molding an oxide ceramic raw material which is SK8-SK12, if the molded article is fired at a temperature lower than 1200 캜, the firing density of the fired article is less than 2.0 g / And the water absorption rate exceeds 3%, and if it is fired above 1350 ° C, shrinkage deformation or melting due to the incompleteness of the fired product may occur.

If the plastic density of the fired product is less than 2.0 g / cm 3, an excessive amount of beads is formed to lower the quality of the weld, and a post-process such as grinding is required. If the plastic density of the fired product exceeds 2.4 g / cm < 3 >, slag generation is not easy and protection of the backside bead from outside air is not easy, and welding defects such as pore generation occur.

Also, if the water absorption rate exceeds 3%, the moisture absorption becomes 0.1% when the welded support is exposed to the external environment, and the strength of the welded portion may be lowered due to the occurrence of blowholes and diffusive hydrogen.

The ceramic welding support according to one embodiment of the present invention can be manufactured from 50 wt% to 70 wt% of SiO ₂ , 15 wt% to 35 wt% of Al ₂ O ₃ , 8 wt% to 15 wt% of MgO, 0.5 by weight, CaO as a main component, and other components composed of Fe ₂ O ₃ , K ₂ O and Na ₂ O in an amount of 0.5 wt% to 5 wt%, and has a fire resistance of SK8 to 12 , A plastic welded support having a plastic density of 2.0 g / cm 3 to 2.4 g / cm 3 and a water absorption of less than 3% is produced.

The impurities of 0.5 wt% to 5 wt% are used as ceramic ceramic raw materials of kaolin, talc, feldspar and calcium carbonate in natural state. Therefore, inevitable Fe ₂ O ₃ , K ₂ O, Na ₂ O are mixed.

Hereinafter, the present invention will be described more specifically with reference to preferred embodiments. Table 1 below shows the compositions of Examples and Comparative Examples of the present invention. Table 2 shows the compositions of Examples and Comparative Examples of the present invention in Table 1, in which the refractoriness, the molding pressure, the molding density, the sintering temperature, And the measured absorption rate after manufacturing the welded support.

That is, in the embodiment of the present invention, the fire resistance is SK8 to 12, the molding pressure is 300 kgf / cm2 to 700 kgf / cm2, the molding density is 1.5 to 2.0 g / cm3, the firing temperature is 1200 to 1350 deg. And the welded support was manufactured under the conditions of the range of 2.0 g / cm 3 to 2.4 g / cm 3, and the comparative example was manufactured under the conditions of the molding pressure, the molding density, the firing temperature and the plasticity density condition of the embodiment of the present invention, .

In Examples 1, 2, 3, 4 and 5 of the present invention, the water absorption rate was 2.35%, 1.88%, 0.95%, 0.86% and 0.71%, all less than 3.0% , 3 and 4 exhibit absorption rates of 24.28%, 4.02%, 10.53% and 25.42%, respectively, indicating that the weld pool is a poor welded area where excessive moisture can be absorbed.

division SiO ₂ Al ₂ O ₃ MgO CaO Etc Sum Example One 66.93 16.80 12.65 1.97 1.65 100 2 67.14 16.81 12.61 1.78 1.66 100 3 58.02 28.78 8.61 2.61 1.98 100 4 55.39 28.83 11.84 2.56 1.38 100 5 50.55 34.33 12.76 1.65 0.71 100 Comparative Example One 66.93 16.80 13.65 1.97 0.65 100 2 68.09 15.88 7.85 6.67 1.51 100 3 50.83 40.17 6.48 1.54 0.98 100 4 23.05 73.87 1.06 1.56 0.46 100

division Refractory Molding pressure
(kgf / cm2) Forming density
(g / cm3) Firing temperature
(° C) Plastic density
(g / cm3) Absorption rate
(%) Exterior Example One SK8  310 1.53 1220 2.00 2.35 Good 2 SK8  354 1.62 1250 2.08 1.88 Good 3 SK9 450 1.73 1250 2.11 0.95 Good 4 SK11 550 1.78 1270 2.25 0.86 Good 5 SK12 630 　 1.91 1300 2.40 0.71 Good Comparative Example One SK8  155 1.41 1260 1.62 24.28 Good 2 SK6 155 1.40 1270 1.98 4.02 Bad 3 SK15 354 1.59 1310 1.90 10.53 Good 4 SK18 155 1.39 1360 1.54 25.42 Good

The welded support of the examples and comparative examples manufactured under the conditions of the above-mentioned Table 2 was stored for 72 hours in the thermo-hygrostat under the conditions of the following 1, and welding was performed under the following conditions 2 to obtain the moisture absorption rate, diffusible hydrogen Generation, welding results, internal crack points, and impact strength of the base material root were measured.

1. Ceramic storage conditions

   Storage place: Thermo-hygrostat

   Condition: Temperature 25 ° C ± 2 ° C / Humidity 95% ± 2%

   Storage time: 72hr

2. Welding conditions

   Welding method: FCAW - Automatic carrier welding

   Welding position: Flat (Welding position from top to bottom)

   Welding wire: SC-71LH 1.4Ø (Low-hydrogen electrode)

   Welding current voltage: 200A / 24V

   Torch angle: 45 °

   Welding speed: 15cm / min

   Base material and base material thickness: EH 36 / 12mmt

   Welding gap: 10mm

division Moisture absorption rate Diffusibility
Hydrogen
Generation Welding results Internal Crack
Point Base material Root part
Impact strength
(at 0 C) Arc
stability Slag
Peelability Blow
hall Spatters If
Bead If the bead height Example One 0.07% 3.0ml
/ 100g ◎ ◎ ◎ ◎ 　 ◎ 1.54 cm 0 72 Joule 2 0.04% 2.8 ml
/ 100g ◎ ◎ ◎ ◎ ◎ 1.51 cm 0 72 Joule 3 0.02% 2.9 ml
/ 100g ◎ ◎ ◎ ◎  ◎ 1.47 cm 0 72 Joule 4 0.03% 2.8 ml
/ 100g ◎ ◎ ◎ ◎  ◎ 1.44cm 0 75 Joule 5 0.01% 2.5ml
/ 100g ◎ ◎ ◎ ◎ 　 ◎ 1.38cm 0 76 Joule Comparative Example One 0.45% 8.7ml
/ 100g ○ ◎ ◎ ◎ ▲ 3.31cm 2 33 Joule 2 0.13% 5.8ml
/ 100g ▲ ▲ ○ X X 2.23 cm One 45Joule 3 0.23% 6.2ml
/ 100g ▲ X X ▲ ▲ 1.30cm 2 48 Joule 4 0.59% 10.5ml
/ 100g X X X X X 1.00cm 3 42 Joule

◎ Excellent, ○ Good, ▲ Normal, X bad

In Table 2, the moisture absorption rates of Examples 1, 2, 3, 4, and 5 of the present invention are 0.07%, 0.04%, 0.02%, 0.03%, and 0.01% The results of the welding, internal crack point and impact strength of the base material root showed excellent results, but in Comparative Examples 1, 2, 3 and 4, the moisture absorption rate was 0.45%, 0.13%, 0.23%, 0.59% , The diffusive hydrogen generation amount, the welding result, the internal crack point, and the impact strength of the base material root portion are generally normal or poor.

That is, in Comparative Example 1, the raw material of the same refractivity as in Example 1 or a product manufactured at a low molding pressure had a high water absorption rate due to high moisture absorption of the product, resulting in a low amount of diffusive hydrogen, The height is more than 2 mm, and a high temperature crack is generated in a part thereof, and there is also a disadvantage that a post-process of grinding is necessary

In Comparative Example 2, a product having a low refractivity was molded at a low molding pressure and fired at a high firing temperature, but the product was warped due to a low molding density. In addition, the surface was vitrified to produce a spatter, The results of the underbody welding were obtained.

Comparative Example 3 is a product molded with a proper molding pressure by applying a raw material having a high refracting power. However, because of high refractivity, slag deterioration is not easy due to the high refractivity, blind holes are generated due to insufficient welding protection, And the impact strength was less than the reference value.

Comparative Example 4 is a product with high refractoriness developed as a conventional ceramic welding support for large heat input. Since the ceramic is not melted, the amount of slag generated is small and the arc is unstable, the blow hole is generated at 3 points, the slag peeling property is lowered, The shape of the backside bead was poor, and the impact strength of the weld portion due to moisture absorption was also lowered.

For reference, the moisture absorption rate in the present invention was measured by the following measurement method.

1) The sample is dried in an oven at 110 ± 5 ° C until it becomes constant, cooled in a desiccator, and then accurately weighed to 0.001 g to measure the mass (D) before moisture absorption.

2) Put the sample in a constant temperature and humidity machine capable of maintaining 95 ± 3% of humidity and 25 ± 2 ℃ of humidity and keep it for 72hr. Then, weigh accurately the sample up to 0.001 g and measure the mass (M) .

The moisture absorption rate A is represented by the mass ratio of the moisture absorbed to the mass of the dry sample. The mass of 1 cm 3 of water is 1.0 g, and the moisture absorption rate is calculated by the following equation.

A = ((MD) / D) X 100

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. Various changes and modifications may be made by those skilled in the art.

Claims (4)

Kaolin, talc, feldspar, and calcium carbonate;
Filling the oxide ceramic powder raw material into a die for molding at a filling density of 50% to 80%, and then molding a molded product having a molding density of 1.5 g / cm 2 to 2.0 g / cm 2; And
And firing the molded product at 1200 ° C to 1350 ° C to form a ceramic welded support having a plastic density of 2.0 g / cm 2 to 2.4 g / cm 2 and a water absorption of less than 3.0%. The method of manufacturing a ceramic welded support according to claim 1, wherein in the step of molding the molded product, a pressure of 300 kgf / cm 2 to 700 kgf / cm 2 is applied to mold the molded product. The method of claim 1, wherein the oxide ceramic powder raw material has an average size of 10 to 500 탆. The method according to claim 1, wherein the ceramic welded support has a fire resistance of SK8 ~ 12.

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