阅读说明：本技术 一种用于铝合金铸造模具的防腐涂层及其制备工艺 (Anticorrosive coating for aluminum alloy casting mold and preparation process thereof ) 是由 叶亚平 许国华 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种用于铝合金铸造模具的防腐涂层,所述防腐涂层为利用水热法工艺在铝合金铸造模具表面反应生成的一种致密的无机硅酸盐矿物涂层,本发明所述的用于铝合金铸造模具表面强化的无机硅酸盐防腐涂层耐熔融铝合金腐蚀、抗热震性能好、制备工艺简单、成本较低,适合型腔复杂的压铸模具。(The invention discloses an anticorrosive coating for an aluminum alloy casting mold, which is a compact inorganic silicate mineral coating generated by reaction on the surface of the aluminum alloy casting mold by utilizing a hydrothermal process.)

1. An anti-corrosion coating for an aluminum alloy casting mold is characterized in that the anti-corrosion coating is a compact inorganic silicate mineral coating generated by reaction on the surface of the aluminum alloy casting mold by using a hydrothermal method process.

2. The corrosion-resistant coating for the aluminum alloy casting mold as recited in claim 1, wherein the thickness of the corrosion-resistant coating is 1-10 μm.

3. The corrosion protective coating for aluminum alloy casting molds according to claim 1, wherein the inorganic silicate mineral coating is a pyroxene group silicate.

4. A process for preparing an anti-corrosive coating for an aluminum alloy casting mold according to any one of claims 1 to 3, comprising the steps of:

(1) placing the pretreated aluminum alloy casting mold in an alkaline solution containing silicon dioxide, and reacting for a period of time at a high temperature;

(2) naturally cooling to room temperature, taking out the aluminum alloy casting mold, washing with deionized water, and naturally drying.

5. The preparation process of the anti-corrosion coating for the aluminum alloy casting die as claimed in claim 4, wherein the concentration of the alkaline solution in the step (1) is 0.1-10M.

6. The preparation process of the anti-corrosion coating for the aluminum alloy casting mold as claimed in claim 4, wherein the mass ratio of the silicon dioxide to the water in the step (1) is 0.1-2.

7. The preparation process of the anti-corrosion coating for the aluminum alloy casting mold as claimed in claim 4, wherein the reaction temperature in the step (1) is 80-280 ℃ and the reaction time is 12-96 h.

Technical Field

The invention relates to the technical field of die casting, in particular to an anticorrosive coating for an aluminum alloy casting die and a preparation process thereof.

Background

Aluminum alloy die casting is a casting method in which molten aluminum alloy is pressed into a precise metal mold cavity at high speed by using high pressure, and aluminum alloy liquid is solidified under the action of the pressure to form a casting. The die-casting die is used as key equipment for die-casting production, and the performance and the service life of the die-casting die directly influence the quality and the cost of an aluminum alloy casting. However, the aluminum alloy die-casting mold has very severe working conditions, and is easy to be in direct contact with molten aluminum alloy to cause corrosion, or the aluminum alloy die-casting mold is repeatedly heated by hot metal and cooled by cooling medium to cause thermal fatigue to generate cracks in the working process of the aluminum alloy die-casting mold, and the corrosion and the cracks are the most common failure modes of the die-casting mold. Although the performance and service life of the die can be improved by adjusting the alloy composition of the die material, the performance and service life of the die are still to be further improved.

Most common failure modes of the die-casting die are failure modes of the working surface of the die, and if the aluminum alloy die-casting die is subjected to proper surface treatment, the corrosion resistance and the thermal fatigue resistance of the die can be greatly improved, so that the quality of the die can be improved, and the service life of the die can be prolonged. At present, aluminum alloy die-casting dies basically need to be subjected to nitriding treatment, and the nitriding treatment improves the corrosion resistance and the thermal fatigue resistance of the working surface of the die to a certain extent, but the service life of the die still needs to be further improved, so that the die-casting production cost is further reduced.

Therefore, how to provide a process for improving the quality and prolonging the service life of an aluminum alloy casting mold at low cost is a problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present invention aims to solve the technical problems of the existing aluminum alloy casting mold that the corrosion resistance is not ideal and the mold surface is prone to generate microcracks due to frequent cold and hot cycles in the die casting process, and in order to achieve the above object, the present invention provides a preparation process for preparing an inorganic silicate anticorrosive coating on the working surface of an aluminum alloy casting mold and the anticorrosive coating, and the present invention adopts the following technical scheme:

an anti-corrosion coating for an aluminum alloy casting mold is a compact inorganic silicate mineral coating generated by reaction on the surface of the aluminum alloy casting mold by utilizing a hydrothermal method process.

Preferably, in the anti-corrosion coating for the aluminum alloy casting die, the thickness of the anti-corrosion coating is 1-10 μm.

The beneficial effects of the above technical scheme are: the anticorrosive coating with the thickness can effectively prevent the corrosion and the erosion of the aluminum liquid, and the excessively thin coating cannot sufficiently protect the mold from being corroded; coatings that are too thick are susceptible to thermal shock and delamination during use.

Preferably, in the above-mentioned corrosion-resistant coating for aluminum alloy casting molds, the inorganic silicate mineral coating is pyroxene silicate such as neon (NaFeSi)₂O₆) Calspodumene (CaFeSi)₂O₆) And the like.

The beneficial effects of the above technical scheme are: iron element of a mould material reacts with dissolved silicon dioxide on the surface of the mould under the alkaline oxidation condition to generate a pyroxene group silicate film, the hardness of the silicate film is 6 grades, and the density of the silicate film is 3.2-3.6g/cm³。

The invention also discloses a preparation process of the anticorrosive coating for the aluminum alloy casting die, which comprises the following steps of:

(1) placing the pre-treated aluminum alloy casting mold in an alkaline solution containing silicon dioxide, completely contacting the pre-treated surface with a reaction solution, and reacting for a period of time at a high temperature;

(2) naturally cooling to room temperature, taking out the aluminum alloy casting mold, washing with deionized water, and naturally drying.

Preferably, in the above-mentioned one preparation process for an anticorrosive coating of an aluminum alloy casting mold, the concentration of the alkaline solution in step (1) is 0.1-10M, and the alkaline solution is a sodium hydroxide or calcium hydroxide solution.

The beneficial effects of the above technical scheme are: the concentration of the alkaline solution is low, the reaction is slow, but the surface of the generated silicate coating is smooth; the concentration of the alkaline solution is high, the reaction is fast, the granularity of silicate crystals is large, the surface is rough, and the concentration of the alkaline solution can be adjusted within the range according to actual conditions in the actual application process.

Preferably, in the above-mentioned process for preparing an anticorrosive coating for an aluminum alloy casting mold, the mass ratio of the silica to the water in the alkaline solution in step (1) is 0.1 to 2,

the beneficial effects of the above technical scheme are: the silicon dioxide required by the reaction can be effectively dissolved under the condition of the technical scheme, and the smooth reaction is facilitated.

Preferably, in the preparation process for the anti-corrosion coating of the aluminum alloy casting die, the reaction temperature in the step (1) is 80-280 ℃, and the reaction time is 12-96 hours.

The beneficial effects of the above technical scheme are: in the reaction temperature range, the mold material cannot generate high-temperature deformation, the iron element in the material can be oxidized in an alkaline solution and migrates to the surface of the mold, and pyroxene group silicate generated by reaction with dissolved silicon dioxide is deposited on the surface of the mold to form a protective coating. The lower the temperature, the longer the reaction time, the higher the temperature, and the shorter the reaction time. The temperature is lower than 80 ℃, the silicon dioxide is almost insoluble, and the reaction can not be carried out; if the temperature is higher than 280 ℃, the surface smoothness cannot be ensured, the pressure is too high, the requirement on equipment is too high, and the production cost is increased.

According to the technical scheme, compared with the prior art, the preparation process for the anti-corrosion coating of the aluminum alloy casting die has the following advantages:

(1) aiming at the phenomenon that a metal mold casting mold is corroded by molten aluminum alloy liquid in an aluminum alloy casting process to cause product galling, a compact inorganic silicate mineral coating is generated on the surface of the metal mold casting mold by a hydrothermal method process, so that the surface of the casting mold is effectively protected from corrosion of the aluminum alloy liquid.

(2) The inorganic silicate anti-corrosion coating for strengthening the surface of the aluminum alloy casting die disclosed by the invention is resistant to corrosion of molten aluminum alloy, good in thermal shock resistance, simple in preparation process and low in cost, a die cavity of the die casting die is generally complex, other surface treatment processes such as chemical vapor deposition, physical vapor deposition, thermal spraying and the like have deposition directionality, uniformity of a complex surface is difficult to guarantee, the process is carried out in a water medium, and the inorganic silicate anti-corrosion coating is more suitable for the die casting die with the complex die cavity.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention discloses an anticorrosive coating for an aluminum alloy casting die, which has good corrosion resistance and thermal fatigue resistance and effectively prolongs the service life of the die.

Example 1

And (2) placing the pretreated steel workpiece in NaOH solution containing silicon dioxide, wherein the concentration of NaOH is 2M, the mass ratio of silicon dioxide to water is 1, reacting for 96 hours in a closed container at 220 ℃, naturally cooling to room temperature, taking out the workpiece, washing with deionized water, and naturally drying to obtain the workpiece with the average thickness of the anticorrosive coating being 8.9 mu M.

Example 2

And (2) placing the pretreated steel workpiece in NaOH solution containing silicon dioxide, wherein the concentration of NaOH is 2M, the mass ratio of silicon dioxide to water is 1, reacting for 48 hours in a closed container at the temperature of 200 ℃, naturally cooling to room temperature, taking out the workpiece, washing with deionized water, and naturally drying to obtain the workpiece with the average thickness of the anticorrosive coating of 5.6 microns.

Example 3

And (2) placing the pretreated steel workpiece in NaOH solution containing silicon dioxide, wherein the concentration of NaOH is 1M, the mass ratio of silicon dioxide to water is 1, reacting for 48 hours in a closed container at the temperature of 200 ℃, naturally cooling to room temperature, taking out the workpiece, washing with deionized water, and naturally drying to obtain the workpiece with the average thickness of the anticorrosive coating being 4.8 mu M.

Example 4

Placing the pretreated steel workpiece in Ca (OH) containing silica₂In solution, Ca (OH)₂The concentration of the silicon dioxide is 1M, the mass ratio of the silicon dioxide to the water is 1.5, the reaction is carried out for 96 hours in a closed container at the temperature of 220 ℃, the workpiece is taken out after the temperature is naturally reduced to the room temperature, the workpiece is washed by deionized water and naturally dried, and the workpiece with the average thickness of the anticorrosive coating of 6.8 mu M is obtained.

Example 5

Placing the pretreated steel workpiece in Ca (OH) containing silica₂In solution, Ca (OH)₂Is 1M, the mass ratio of silicon dioxide to water is 1.5, the reaction is carried out for 48 hours in a closed container at the temperature of 180 ℃, and after the temperature is naturally reduced to the room temperature, the mixture is cooledAnd taking out the workpiece, washing with deionized water, and naturally drying to obtain the workpiece with the average thickness of the anticorrosive coating being 1.9 mu m.

Table 1: examples 1-5 Effect on coating formation and Corrosion protection

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.