阅读说明：本技术 一种气体渗氮炉炉壁长效保护涂料及其制备方法 (Long-acting protective coating for furnace wall of gas nitriding furnace and preparation method thereof ) 是由 乔琛 张炼 于 2021-01-22 设计创作，主要内容包括：本发明提出了一种气体渗氮炉炉壁长效保护涂料及其制备方法,所述保护涂料包括粘合剂、二氧化硅、硼酐、氧化钙、氧化铜和钾盐,作为优选的,还包括防渗剂,本发明通过调整玻璃体涂层的熔点,使得涂层在高温下为玻璃熔融态结构,具有良好的粘滞和密封效果,在冷却至常温后又转变为固态玻璃,从而能够在温差冲击下保持结构完整,同时涂料内还包括功能性元素,如硼、硅、铜和钾,能够提升涂料层的物理化学性能,具有良好的应用前景。(The invention provides a long-acting protective coating for a furnace wall of a gas nitriding furnace and a preparation method thereof, wherein the protective coating comprises an adhesive, silicon dioxide, boric anhydride, calcium oxide, copper oxide, potassium salt and preferably an anti-seepage agent.)

1. A long-acting protective coating for the wall of gas nitriding furnace is characterized by comprising an adhesive, silicon dioxide, boric anhydride, calcium oxide, copper oxide and potassium salt.

2. The gas nitriding furnace wall long-acting protective coating according to claim 1, characterized by comprising, in 100% by weight, 15-35% of a binder, 30-40% of silica, 20-35% of boric anhydride, 5-10% of calcium oxide, 2-5% of copper oxide and 2-4% of a potassium salt.

3. The gas nitriding furnace wall long-acting protective coating according to claim 1, characterized in that the binder is sodium silicate.

4. The gas-nitriding furnace wall long-acting protective coating according to claim 1, wherein the potassium salt is one or a combination of potassium fluoroborate and potassium carbonate.

5. The gas nitriding furnace wall long-acting protective coating according to claim 1, further comprising a barrier agent in an amount of 1 to 3 times the sum of the amounts of the binder, silica, boron anhydride, calcium oxide, copper oxide and potassium salt.

6. The gas nitriding furnace wall long-acting protective coating according to claim 5, characterized in that the barrier agent is one or a mixture of several of alumina, silicon carbide and tin.

7. A method for producing a gas nitriding furnace wall long-acting protective coating according to any one of claims 1 to 6, characterized by comprising the steps of:

step one, mixing sodium silicate, silicon dioxide, boric anhydride, calcium oxide, copper oxide, potassium salt and an anti-seepage agent according to a ratio, adding a solvent, mixing and stirring uniformly to obtain a mixed slurry;

and step two, spraying or brushing the mixed slurry on the surface of the inner wall of the nitriding furnace, and drying to obtain the protective coating after brushing.

8. The method for producing a gas nitriding furnace wall long-acting protective coating according to claim 7, wherein the solvent is water.

Technical Field

The invention relates to the technical field of material science, in particular to a long-acting protective coating for a furnace wall of a gas nitriding furnace and a preparation method thereof.

Background

The metal is easy to be oxidized at high temperature, in order to overcome the problem, the surface of the metal material is usually protected by using a coating, the bonding capability of the conventional coating structure and the metal is poor, after repeated thermal expansion and cold contraction, the adhesive force between the coating and the metal layer is reduced, even cracks or peeling can occur, and in order to overcome the problem, a high-temperature resistant layer can be compounded on the surface of the metal.

However, in the field of metal processing, a nitriding furnace not only experiences high temperature repeatedly, but also is filled with gas containing nitrogen, so that the inner wall of a furnace pipe is also repeatedly coated with nitrogen in the nitriding process, thereby causing over-nitriding, and even if a high-temperature-resistant metal layer is used, the furnace pipe which is over-nitrided is easy to crack and scrap, so that the technical problem which needs to be solved at present is to provide a long-acting protective coating for the furnace wall of the nitriding furnace, which has the advantages of anti-nitriding and high-temperature resistance.

Disclosure of Invention

In view of the above, the invention provides a long-acting protective coating for a furnace wall of a gas nitriding furnace, which can effectively prevent the inner wall of the nitriding furnace from being over nitrided and has a more stable structure, and a preparation method thereof.

The technical scheme is realized in such a way that the invention provides a long-acting protective coating for the furnace wall of a gas nitriding furnace, which comprises an adhesive, silicon dioxide, boric anhydride, calcium oxide, copper oxide and potassium salt.

In the technical scheme, the adhesive, the silicon dioxide, the boric anhydride, the calcium oxide, the copper oxide and the sylvite can react to form a glassy protective layer after being subjected to high-temperature treatment in a nitriding furnace, the silicon dioxide, the boric anhydride, the calcium oxide, the copper oxide, the sylvite and the like generate corresponding silicate after being subjected to high temperature treatment, wherein potassium silicate, sodium silicate, calcium silicate, copper silicate, borosilicate glass and the like are all the components of the glass, the potassium silicate-containing potassium glass has the functions of high temperature resistance, high hardness and chemical corrosion resistance, can effectively play a supporting role when being applied in a nitriding furnace, meanwhile, when facing high-temperature corrosive gas, the borosilicate glass can isolate the gas and prevent the gas from directly corroding the furnace wall, has good effect of resisting instant temperature difference, the structural integrity of the glass can still be kept under the action of the instant temperature difference close to 200 ℃.

The metal is easy to oxidize at high temperature, especially the property of the metal material is easy to change by complex chemical atmosphere, and the service performance of the material is influenced.

On the basis of the technical scheme, the adhesive preferably comprises 15-35% of adhesive, 30-40% of silicon dioxide, 20-35% of boric anhydride, 5-10% of calcium oxide, 2-5% of copper oxide and 2-4% of potassium salt by weight of 100%.

On the basis of the above technical solutions, preferably, the binder is sodium silicate, i.e. water glass, and a good binder can be formed after water is added.

On the basis of the technical scheme, preferably, the potassium salt is one or the combination of two of potassium fluoborate and potassium carbonate.

Still further preferably, the anti-seepage agent is used in an amount of 1 to 3 times the total amount of the binder, the silicon dioxide, the boron anhydride, the calcium oxide, the copper oxide and the potassium salt.

On the basis of the technical scheme, preferably, the anti-seepage agent is one or a mixture of more of aluminum oxide, silicon carbide and tin.

The invention also provides a preparation method of the long-acting protective coating for the furnace wall of the gas nitriding furnace, which comprises the following steps:

step one, mixing sodium silicate, silicon dioxide, boric anhydride, calcium oxide, copper oxide, potassium salt and an anti-seepage agent according to a ratio, adding a solvent, mixing and stirring uniformly to obtain a mixed slurry;

and step two, spraying or brushing the mixed slurry on the surface of the inner wall of the nitriding furnace, and drying to obtain the protective coating after brushing.

On the basis of the above technical scheme, preferably, the solvent is water.

On the basis of the technical scheme, preferably, in the second step, the thickness of spraying or brushing is 0.3-0.7 mm.

Compared with the prior art, the long-acting protective coating for the furnace wall of the gas nitriding furnace and the preparation method thereof have the following beneficial effects:

(1) the invention adopts various oxides and inorganic salt as raw materials of a coating, the raw materials are coated on the inner wall of a nitriding furnace, the coating can be converted into a glass state substance under the high-temperature condition, so that the inner wall of the nitriding furnace is isolated, nitrogen-containing gas is prevented from entering the furnace wall, meanwhile, an impermeable material is permeated and wrapped in the glass state substance, so that a metal material is protected from being permeated by nitrogen under the nitrogen-containing atmosphere, the glass is a mixture and does not have a crystalline state, and therefore, the glass does not have a fixed melting point and can be slowly softened in the temperature rising process; (2) the coating contains boric anhydride and sylvite, potassium element can improve the high temperature resistance and chemical stability of the glassy coating, and the addition of the boric anhydride greatly improves the temperature difference resistance of the glassy coating, so that the coating has better stability under temperature difference impact and cannot crack easily;

(3) the coating forms a glassy substance at high temperature, has viscosity, and can not crack at the position contacted with the furnace wall of the nitriding furnace even if the relative position shifts due to thermal expansion and cold contraction, so that the structural stability is stronger, and the furnace wall can not be subjected to over-nitriding after multiple nitriding treatments, thereby ensuring the long-term continuous use of the nitriding furnace.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

Respectively weighing 15kg of sodium silicate, 36kg of silicon dioxide, 35kg of boric anhydride, 10kg of calcium oxide, 2kg of copper oxide, 1kg of potassium fluoborate and 1kg of potassium carbonate, mixing, adding 100kg of water, mixing and stirring to obtain mixed slurry, spraying the mixed slurry on the surface of the inner wall of a nitriding furnace, wherein the average sprayed thickness is 0.3mm, and drying to obtain the protective coating.

Example 2

Respectively weighing 35kg of sodium silicate, 31kg of silicon dioxide, 20kg of boric anhydride, 5kg of calcium oxide, 5kg of copper oxide, 2kg of potassium fluoborate, 2kg of potassium carbonate and 150kg of silicon carbide, mixing, adding 250kg of water, mixing and stirring to obtain mixed slurry, spraying the mixed slurry on the surface of the inner wall of a nitriding furnace, wherein the average sprayed thickness is 0.4mm, and drying to obtain the protective coating.

Example 3

Respectively weighing 28kg of sodium silicate, 30kg of silicon dioxide, 30kg of boric anhydride, 6kg of calcium oxide, 4kg of copper oxide, 2kg of potassium fluoborate, 100kg of aluminum oxide, 50kg of silicon carbide and 50kg of tin powder, mixing, adding 300kg of water, mixing and stirring to obtain mixed slurry, spraying the mixed slurry on the inner wall surface of a nitriding furnace, wherein the average sprayed thickness is 0.5mm, and drying to obtain the protective coating.

Example 4

Respectively weighing 21kg of sodium silicate, 40kg of silicon dioxide, 25kg of boric anhydride, 7kg of calcium oxide, 5kg of copper oxide, 2kg of potassium carbonate, 150kg of aluminum oxide, 50kg of silicon carbide and 50kg of tin powder, mixing, adding 350kg of water, mixing and stirring to obtain mixed slurry, spraying the mixed slurry on the inner wall surface of a nitriding furnace, wherein the average sprayed thickness is 0.6mm, and drying to obtain the protective coating.

Example 5

Respectively weighing 30kg of sodium silicate, 33kg of silicon dioxide, 23kg of boric anhydride, 8kg of calcium oxide, 3kg of copper oxide, 2kg of potassium fluoborate, 1kg of potassium carbonate, 150kg of aluminum oxide, 100kg of silicon carbide and 50kg of tin powder, mixing, adding 400kg of water, mixing and stirring to obtain mixed slurry, spraying the mixed slurry on the inner wall surface of a nitriding furnace, wherein the average sprayed thickness is 0.3mm, and drying to obtain the protective coating.

Comparative example

A conventional nitriding furnace was used for comparison.

The nitriding furnaces of examples 1 to 5 and the comparative example were each charged with ammonia gas at 700 ℃ for 3 hours per pass to conduct a continuous working performance test, and the number of initial cracks was calculated as follows:

the data show that the protective coating of the invention can keep the coating intact under the condition of continuous operation for a plurality of times, while the conventional nitriding furnace has cracks after continuous operation for 8 times, can not normally operate, needs to be subjected to idle burning to eliminate nitrogen potential, and can continue to operate after the cracks are repaired.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.