Gas QPQ post-oxidation blackening agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of workpiece surface processing treatment, and discloses a gas QPQ post-oxidation blackening agent as well as a preparation method and application thereof. The gas QPQ post-oxidation blackening agent comprises the following components: 15-30 parts of a rare earth compound, 10-15 parts of citric acid and / or citrate, 5-15 parts of ammonium molybdate, 3-8 parts of ammonium chloride, 15-25 parts of vitamin C, 10-30 parts of formamide, 5-10 parts of manganese dioxide, 5-10 parts of phosphoric acid, 15-30 parts of calcium nitrate, 30-40 parts of ethanol and 5000 parts of water. All the components are matched with one another and act together, so that the treated metal product can fully meet the requirements of the metal product on the corrosion resistance and the color.

Description

Technical Field

[0001] The present invention relates to the technical field of workpiece surface processing, and particularly to a post-oxidation blackening agent for gas QPQ, a preparation method thereof, and an application thereof. Background Art

[0002] Gas nitrocarbooxy-combined nitrocarburizing treatment, also known as gas QPQ, is a process of performing combined nitrocarburizing of nitrogen, carbon, and oxygen on the surface of metal products by placing the metal products in a special furnace for gas QPQ. After the current gas QPQ process is used to treat workpieces, the corrosion resistance time of the workpieces in the neutral salt spray test is about 60 hours, which cannot meet the anti-corrosion ability of metal products in harsh environments. Moreover, the surface of the treated workpieces is gray, dark gray, light black-gray, or light black-blue, and cannot be presented as black. That is, the current QPQ process cannot meet the requirements of metal products for anti-corrosion ability and color.

[0003] In order to meet the above requirements, it is necessary to perform secondary treatment of coupling and oil immersion on the metal products after they are taken out of the furnace. However, on the one hand, in this process, the metal products need to be soaked in the coupling box for at least 30 minutes, the treatment time is long, and a large amount of grease will adhere to the surface of the soaked metal products, making the subsequent cleaning very difficult. On the other hand, the color adhesion of the surface of the metal products after secondary treatment is poor, and the color will be washed off when encountering high-pressure flushing, revealing the gray or gray-blue substrate, and the corrosion resistance is also poor.

[0004] Therefore, how to improve the corrosion resistance and color adhesion performance of metal products is an urgent problem to be solved. Summary of the Invention

[0005] In view of this, the present invention provides a post-oxidation blackening agent for gas QPQ, a preparation method thereof, and an application thereof, so as to solve the defects in the existing gas QPQ process. The existing gas QPQ process often requires a long-time secondary treatment to meet the requirements of metal products for anti-corrosion ability and color adhesion. However, after the secondary treatment, a complex subsequent cleaning process is required, and the color of the workpieces after the secondary treatment still cannot meet the requirements.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a post-oxidation blackening agent for gas QPQ, which, by weight, comprises the following components: 15-30 parts of rare earth compound, 10-15 parts of citric acid and / or citrate, 5-15 parts of ammonium molybdate, 3-8 parts of ammonium chloride, 15-25 parts of vitamin C, 10-30 parts of formamide, 5-10 parts of manganese dioxide, 5-10 parts of phosphoric acid, 15-30 parts of calcium nitrate, 30-40 parts of ethanol, and 5000 parts of water.

[0008] Preferably, the rare earth compound is rare earth chloride and / or rare earth oxide.

[0009] Preferably, the citrate includes one or more of sodium citrate and potassium citrate.

[0010] On the other hand, the present invention provides a preparation method of the post-oxidation blackening agent for gas QPQ described in any one of the above, including the following steps: mixing a rare earth compound, citric acid and / or citrate, ammonium molybdate, ammonium chloride, vitamin C, formamide, manganese dioxide, phosphoric acid, calcium nitrate, ethanol and water to obtain the post-oxidation blackening agent for gas QPQ.

[0011] In addition, the present invention also provides an application of the post-oxidation blackening agent for gas QPQ described in any one of the above or the post-oxidation blackening agent for gas QPQ prepared by the above method in gas nitrocarbo-oxidation treatment.

[0012] Preferably, the application of the post-oxidation blackening agent for gas QPQ in gas nitrocarbo-oxidation treatment includes the following steps:

[0013] (1) Placing the workpiece to be treated in a co-permeation furnace for nitrocarburizing treatment to obtain a nitrided workpiece;

[0014] (2) Adding the post-oxidation blackening agent for gas QPQ into the co-permeation furnace for drip infiltration treatment to obtain a treated workpiece.

[0015] Preferably, step (2) specifically includes the following steps:

[0016] A. Lowering the temperature in the co-permeation furnace to 560 °C and then maintaining the temperature for 60 - 90 min, and adding the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a rate of 150 - 180 drops per minute during the constant temperature and heat preservation process;

[0017] B. Continuing to lower the temperature in the co-permeation furnace from 560 °C to 380 °C, and adding the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a rate of 40 - 80 drops per minute during the temperature reduction process.

[0018] Preferably, during the temperature reduction process of step B, the post-oxidation blackening agent for gas QPQ is added into the co-permeation furnace at a decreasing rate, specifically as follows: when the temperature in the co-permeation furnace drops from 560 °C to 450 °C, adding the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a rate of 50 - 80 drops per minute; when the temperature in the co-permeation furnace drops from 450 °C to 380 °C, adding the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a rate of 40 - 50 drops per minute.

[0019] Preferably, the nitrocarburizing treatment in step (1) includes: adding a drip infiltration agent into the co-permeation furnace.

[0020] Preferably, the infiltration agent comprises the following components in parts by weight: 80-100 parts of ethanol, 30-40 parts of triethanolamine, 10-20 parts of citrate, 6-10 parts of rare earth oxide powder, and 1-5 parts of auxiliary agent; the auxiliary agent is selected from one or more of a dispersant, sodium gluconate, and silicate.

[0021] Preferably, before adding the infiltration agent into the co-permeation furnace, it further includes: applying a penetration aid on the surface of the workpiece to be treated.

[0022] Preferably, the penetration aid comprises the following components in parts by weight: 80-100 parts of ethanol, 6-10 parts of activated carbon powder, 10-20 parts of triethanolamine, 2-5 parts of rare earth oxide powder, 1-3 parts of nickel powder, and 1-2 parts of dispersant.

[0023] The present invention provides a gas QPQ post-oxidation blackening agent, its preparation method and application. Compared with the prior art, its beneficial effects are as follows:

[0024] The gas QPQ post-oxidation blackening agent of the present invention uses rare earth compounds, citric acid and / or citrate, ammonium molybdate, ammonium chloride, vitamin C, formamide, manganese dioxide, phosphoric acid, calcium nitrate, ethanol and water as raw materials. Among them, rare earth compounds can effectively increase the anti-corrosion performance of the workpiece. Ammonium molybdate, as a coloring agent, can make the surface of the workpiece present black. Ammonium chloride can increase the depth of the infiltration layer and improve the adhesion ability. Vitamin C can convert the rust on the surface of the workpiece into black to form a multi-component protective film. Each component cooperates with each other and acts together, so that the QPQ process can fully meet the requirements of metal products for anti-corrosion ability and color.

[0025] In addition, the workpiece treated with the gas QPQ post-oxidation blackening agent of the present invention can effectively shorten the coupling time in the coupling box, thereby greatly shortening the subsequent cleaning time, improving the production efficiency. And after the coupling is completed and high-pressure cleaning is carried out, the color on the surface of the workpiece is still uniformly black and will not expose the substrate surface, effectively improving the adhesion of the color. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0027] Figure 1 It is a comparison diagram of the workpieces after cleaning in Embodiment 1 (left) and Comparative Example 1 (right) of the present invention. Detailed Embodiments

[0028] The present invention will be described below through specific embodiments. Those skilled in the art can understand that the following specific embodiments are only for the purpose of illustration and do not limit the scope of the present invention in any way. In addition, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and methods are not clearly described in the following embodiments, the conditions and methods known in the art can be used for processing.

[0029] In one aspect of the present invention, a post-oxidation blackening agent for gas QPQ is proposed. Calculated by weight parts, it includes the following components: 15 - 30 parts of rare earth compound, 10 - 15 parts of citric acid and / or citrate, 5 - 15 parts of ammonium molybdate, 3 - 8 parts of ammonium chloride, 15 - 25 parts of vitamin C, 10 - 30 parts of formamide, 5 - 10 parts of manganese dioxide, 5 - 10 parts of phosphoric acid, 15 - 30 parts of calcium nitrate, 30 - 40 parts of ethanol, and 5000 parts of water.

[0030] Among them, the molecular diameter of rare earth elements is larger than that of cast iron workpieces. In particular, the rare earth molecules after high-temperature decomposition can fill the defects caused by the lower density of cast iron workpieces. Specifically, by adding an appropriate amount of rare earth compounds, the oxidation layer of the workpiece can be strengthened, and the anti-corrosion performance of the workpiece can be increased. Ammonium molybdate can play a role in coloring, making the surface of the workpiece black; ammonium chloride can increase the depth of the infiltration layer, but excessive ammonium chloride will damage the oxidation layer; vitamin C can convert the red and yellow rust on the surface of the workpiece into black, forming a multi-component protective film.

[0031] In some embodiments of the present invention, the rare earth compound is rare earth chloride and / or rare earth oxide, such as lanthanum chloride, cerium chloride, lanthanum oxide, cerium oxide, etc.

[0032] In some embodiments of the present invention, the citrate includes one or more of sodium citrate and potassium citrate. Citric acid and / or citrate can play a role in catalyzing the decomposition of rare earth.

[0033] In another aspect of the present invention, a preparation method of the post-oxidation blackening agent for gas QPQ described in any one of the above is provided, including the following steps: mixing the rare earth compound, citric acid and / or citrate, ammonium molybdate, ammonium chloride, vitamin C, formamide, manganese dioxide, phosphoric acid, calcium nitrate, ethanol, and water to obtain the post-oxidation blackening agent for gas QPQ.

[0034] In some embodiments of the present invention, after mixing the above raw materials, it further includes: fully stirring and then standing for a period of time, for example, it can stand for 24 hours, and then filtering to obtain the gas QPQ post-oxidation blackening agent. Among them, the filtering can be carried out through a sieve with a mesh size of more than 200 meshes to remove impurities. There is no special limitation on the mesh number of the sieve, and it can be adjusted according to the actual situation.

[0035] In another aspect of the present invention, the present invention also provides an application of the gas QPQ post-oxidation blackening agent described in any one of the above or the gas QPQ post-oxidation blackening agent prepared by the above method in gas nitrocarbo-oxidation treatment.

[0036] In some embodiments of the present invention, the application of the gas QPQ post-oxidation blackening agent in gas nitrocarbo-oxidation treatment includes the following steps:

[0037] (1) Place the workpiece to be treated in a co-permeation furnace for nitrocarburizing treatment to obtain a nitrided workpiece;

[0038] (2) Add the gas QPQ post-oxidation blackening agent into the co-permeation furnace for drip infiltration treatment to obtain the treated workpiece.

[0039] In the present invention, first place the workpiece to be treated in a co-permeation furnace for nitrocarburizing treatment to obtain a nitrided workpiece.

[0040] In some embodiments of the present invention, the co-permeation furnace used is the gas nitrocarbo-oxidation QPQ co-permeation furnace for cast iron products disclosed in the patent with the application number 202020931189.7, and its structure will not be elaborated here.

[0041] In some embodiments of the present invention, the nitrocarburizing treatment includes: adding a drip infiltration agent into the co-permeation furnace.

[0042] Among them, the drip infiltration agent includes the following components by weight: 80-100 parts of ethanol, 30-40 parts of triethanolamine, 10-20 parts of citrate, 6-10 parts of rare earth oxide powder, 1-5 parts of an auxiliary agent, and the auxiliary agent is selected from one or more of a dispersant, sodium gluconate, and silicate. Specifically, the drip infiltration agent used in the present invention is the gas QPQ multi-component composite drip infiltration agent for cast iron products disclosed in the patent with the application number 202010466263.7.

[0043] In some embodiments of the present invention, the nitrocarburizing treatment further includes: applying a penetration aid on the surface of the workpiece to be treated. Specifically, after applying the penetration aid on the surface of the workpiece to be treated, place the workpiece to be treated with the penetration aid in the co-permeation furnace, and add a drip infiltration agent into the co-permeation furnace for nitrocarburizing treatment.

[0044] Among them, the penetration aid includes the following components by weight: 80-100 parts of ethanol, 6-10 parts of activated carbon powder, 10-20 parts of triethanolamine, 2-5 parts of rare earth oxide powder, 1-3 parts of nickel powder, and 1-2 parts of dispersant. Specifically, the penetration aid adopted in the present invention is the gas nitrogen-carbon-oxygen QPQ multi-component composite penetration aid for cast iron products disclosed in the patent with the application number 202010466704.3.

[0045] In some embodiments of the present invention, the process of nitrogen-carbon co-permeation treatment using the penetration aid and the drip penetration agent may refer to the drip penetration process of the multi-component composite drip penetration agent for cast iron products disclosed in the patent with the application number 202010466704.3, which will not be elaborated here. Specifically, in the specific embodiment of the present invention, the process of nitrogen-carbon co-permeation treatment using the penetration aid and the drip penetration agent refers to Example 1 of the patent with the application number 202010466704.3.

[0046] In the present invention, the gas QPQ post-oxidation blackening agent is added into the co-permeation furnace for drip penetration treatment to obtain the treated workpiece. Specifically, the gas QPQ post-oxidation blackening agent is added into the co-permeation furnace for high-temperature decomposition, and after standing, the gas QPQ post-oxidation blackening agent after high-temperature decomposition penetrates into the surface layer of the nitrided workpiece to obtain the treated workpiece.

[0047] In some embodiments of the present invention, the drip penetration treatment specifically includes the following steps:

[0048] A. The temperature in the co-permeation furnace is reduced to 560 °C and kept constant for 60-90 min. During the constant-temperature holding process, the gas QPQ post-oxidation blackening agent is added into the co-permeation furnace at a rate of 150-180 drops per minute; among them, the holding time can be 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, etc., and the dropping rate can be 150 drops per minute, 160 drops per minute, 170 drops per minute, 180 drops per minute, etc.

[0049] B. The temperature in the co-permeation furnace is further reduced from 560 °C to 380 °C, and during the temperature reduction process, the gas QPQ post-oxidation blackening agent is added into the co-permeation furnace at a rate of 40-80 drops per minute.

[0050] Specifically, in step A, the temperature in the co-permeation furnace can be 560 °C cooled by air cooling. After the constant-temperature holding time reaches 60-90 min, the heating is turned off, and the furnace is cooled to 380 °C, and then the addition of the gas QPQ post-oxidation blackening agent is stopped.

[0051] In some embodiments of the present invention, during the cooling process of step B, the post-oxidation blackening agent of gas QPQ is added to the co-permeation furnace at a decreasing rate, specifically as follows: during the process when the temperature in the co-permeation furnace drops from 560 °C to 450 °C, the post-oxidation blackening agent of gas QPQ is added to the co-permeation furnace at a rate of 50 - 80 drops per minute; during the process when the temperature in the co-permeation furnace drops from 450 °C to 380 °C, the post-oxidation blackening agent of gas QPQ is added to the co-permeation furnace at a rate of 40 - 50 drops per minute.

[0052] Among them, during the process when the temperature in the co-permeation furnace drops from 560 °C to 450 °C, the post-oxidation blackening agent of gas QPQ can be added to the co-permeation furnace at a rate of 50 drops per minute, 60 drops per minute, 65 drops per minute, 70 drops per minute, 75 drops per minute, or 80 drops per minute. As the temperature continues to drop to 380 °C, the dropping amount decreases. For example, the post-oxidation blackening agent of gas QPQ can be added to the co-permeation furnace at a rate of 40 drops per minute, 45 drops per minute, or 50 drops per minute.

[0053] In some embodiments of the present invention, the standing time is 10 - 20 min, and for example, it can be 10 min, 12 min, 14 min, 15 min, 18 min, 20 min, etc. During this standing time, the nitrided workpiece can fully absorb the post-oxidation blackening agent of gas QPQ that has decomposed at high temperature.

[0054] The post-oxidation blackening agent of gas QPQ of the present invention has the same components as the drip infiltration agent and the penetration aid, and there will be no mutual repulsion during the treatment of the workpiece in the co-permeation furnace, thereby strengthening the adhesion of the post-oxidation blackening agent of gas QPQ on the surface of the workpiece and enabling the workpiece to have a good rust and corrosion resistance effect; in addition, the process of attaching the post-oxidation blackening agent of gas QPQ to the surface of the workpiece in the present invention is mainly carried out using the remaining temperature of the co-permeation furnace after normal nitriding treatment in the early stage, without generating excessive energy consumption.

[0055] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with specific embodiments. The embodiments of this application are only for illustration. All other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0056] Example 1

[0057] This example provides a post-oxidation blackening agent of gas QPQ. In parts by weight, the specific components are as follows: 15 parts of rare earth lanthanum chloride, 10 parts of sodium citrate, 5 parts of ammonium molybdate, 3 parts of ammonium chloride, 12 parts of formamide, 15 parts of vitamin C, 5 parts of manganese dioxide, 5 parts of phosphoric acid, 15 parts of calcium nitrate, 30 parts of ethanol, and 5000 parts of deionized water.

[0058] The preparation method of the post-oxidation blackening agent for gas QPQ is as follows: Mix the above raw materials, stir well, let stand for 24 h, and filter through a 200-mesh sieve to obtain it.

[0059] The application of the post-oxidation blackening agent for gas QPQ in gas nitrocarbooxy compound treatment is as follows:

[0060] (1) After cleaning the surface of the workpiece to be treated, evenly apply the suspension of the infiltration aid on the surface of the workpiece, then place it in a co-permeation furnace and heat it. The heating temperature is 600 ± 20 °C;

[0061] (2) Add the drip infiltration agent into the co-permeation furnace at a speed of 7 mL / s to form steam, and carry out nitriding treatment on the workpiece in the form of steam. The nitriding treatment time is 2.5 h to obtain a nitrided workpiece;

[0062] (3) Air-cool the co-permeation furnace to 560 °C, keep it at a constant temperature for 90 min. During the constant temperature and heat preservation process, add the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a speed of 150 drops per minute, then turn off the heating and air-cool. During the cooling process, add the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a speed of 70 drops per minute. Stop adding the post-oxidation blackening agent for gas QPQ after the temperature drops to 380 °C, let stand for 10 min to make the nitrided workpiece fully absorb the post-oxidation blackening agent for gas QPQ that has decomposed at high temperature, open the furnace cover and take out the workpiece. The surface of the treated workpiece is uniformly light black;

[0063] (4) Put the treated workpiece into a coupling box filled with grease for coupling treatment (the coupling box is used to remove the residues generated after the decomposition of the solvent during multi-element composite co-permeation and quickly cool the workpiece), and then carry out cleaning. The surface of the workpiece is still uniformly light black.

[0064] Example 2

[0065] This example is basically the same as Example 1, and the only difference lies in the component composition of the post-oxidation blackening agent for gas QPQ.

[0066] In parts by weight, the specific components of the post-oxidation blackening agent for gas QPQ are as follows: 20 parts of lanthanum chloride, 15 parts of sodium citrate, 5 parts of ammonium molybdate, 3 parts of ammonium chloride, 20 parts of formamide, 15 parts of vitamin C, 5 parts of manganese dioxide, 5 parts of phosphoric acid, 25 parts of calcium nitrate, 30 parts of ethanol, and 5000 parts of deionized water.

[0067] Example 3

[0068] This example is basically the same as Example 1, and the only difference lies in the component composition of the post-oxidation blackening agent for gas QPQ.

[0069] In parts by weight, the specific components of the post-oxidation blackening agent for gas QPQ are as follows: 25 parts of rare earth lanthanum chloride, 15 parts of sodium citrate, 5 parts of ammonium molybdate, 3 parts of ammonium chloride, 30 parts of formamide, 15 parts of vitamin C, 5 parts of manganese dioxide, 10 parts of phosphoric acid, 30 parts of calcium nitrate, 40 parts of ethanol, and 5000 parts of deionized water.

[0070] Example 4

[0071] This example is basically the same as Example 3, and the difference lies only in step (3).

[0072] (3) Cool the co-permeation furnace by air cooling to 560 °C, keep it at a constant temperature for 90 minutes, and add the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a speed of 150 drops per minute during the constant temperature and heat preservation process. Then turn off the heating and cool it by air cooling. During the process of cooling from 560 °C to 450 °C, add the post-oxidation blackening agent for gas QPQ into the co-permeation furnace at a speed of 70 drops per minute. As the furnace temperature continues to decrease from 450 °C to 380 °C, the dropping amount of the post-oxidation blackening agent for gas QPQ is reduced to 45 drops per minute. After the temperature drops to 380 °C, stop dropping the post-oxidation blackening agent for gas QPQ, let it stand for 10 minutes to allow the nitrided workpiece to fully absorb the post-oxidation blackening agent for gas QPQ that has been decomposed at high temperature, open the lid and take out the furnace to obtain the treated workpiece. The surface of the treated workpiece is uniformly dark black.

[0073] Comparative Example 1

[0074] (1) After cleaning the surface of the workpiece to be treated, evenly apply the suspension of the penetration aid on the surface of the workpiece, and then place it in the co-permeation furnace and heat it. The heating temperature is 600 ± 20 °C;

[0075] (2) Add the drip penetration agent into the co-permeation furnace at a speed of 7 mL / s to form steam, and carry out nitriding treatment on the workpiece in the form of steam. The nitriding treatment time is 2.5 h to obtain the nitrided workpiece;

[0076] (3) Put the nitrided workpiece into a coupling box filled with grease for coupling treatment, and then carry out cleaning. The gray and gray-blue matrix is exposed on the surface of the workpiece.

[0077] The coupling time of the workpieces in Examples 1-4 and Comparative Example 1, the color of the workpieces after cleaning, and their corrosion resistance were detected. The results are shown in Table 1. Among them, the corrosion resistance detection includes copper sulfate titration detection and neutral salt spray test.

[0078] Table 1

[0079]

[0080]

[0081] It can be concluded from Table 1 that by using the post-oxidation blackening agent of gas QPQ, the color of the workpiece after treatment can still remain uniformly black after cleaning, effectively improving the color adhesion ability. Moreover, the workpiece can withstand a higher concentration of copper sulfate titration detection, and the salt spray resistance time is significantly increased. The treated workpiece has good corrosion resistance and can meet the requirements of the workpiece for anti-corrosion ability and color.

[0082] By treating the workpiece with the post-oxidation blackening agent of gas QPQ, the coupling time of the workpiece after leaving the furnace is effectively shortened. The coupling time is reduced from 30 minutes to 5 - 8 minutes, effectively improving the workpiece treatment efficiency. And due to the shortening of the coupling time, a large amount of grease attached to the workpiece surface is reduced, greatly shortening the subsequent cleaning time and further improving the production efficiency. It should also be noted that when using Comparative Example 1 to treat the workpiece, 50 - 70 kg of cooling grease needs to be added to the coupling box every day. However, after using the post-oxidation blackening agent of gas QPQ of the present invention to treat the workpiece, only 25 - 50 kg of cooling grease needs to be added to the coupling box every week to meet the coupling requirements, which can effectively reduce costs.

[0083] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A gas QPQ post-oxidation blackening agent, characterized in that: The invention comprises the following components in parts by weight: 15-30 parts of rare earth compound, 10-15 parts of citric acid and / or citrate, 5-15 parts of ammonium molybdate, 3-8 parts of ammonium chloride, 15-25 parts of vitamin C, 10-30 parts of formamide, 5-10 parts of manganese dioxide, 5-10 parts of phosphoric acid, 15-30 parts of calcium nitrate, 30-40 parts of ethanol and 5000 parts of water.

2. The gas QPQ post-oxidation blackening agent according to claim 1, characterized in that: The rare earth compound is rare earth chloride and / or rare earth oxide.

3. The gas QPQ post-oxidation blackening agent according to claim 1 or 2, characterized in that: The citrate includes one or more of sodium citrate and potassium citrate.

4. A method for preparing the gas QPQ post-oxidation blackening agent according to any one of claims 1 to 3, characterized in that: The following steps are involved: The rare earth compound, citric acid and / or citrate, ammonium molybdate, ammonium chloride, vitamin C, formamide, manganese dioxide, phosphoric acid, calcium nitrate, ethanol and water are mixed to obtain a gas QPQ post-oxidation blackening agent.

5. Use of the gas QPQ post-oxidation blackening agent according to any one of claims 1 to 3 or the gas QPQ post-oxidation blackening agent prepared by the method according to claim 4 in gas nitrogen, carbon and oxygen composite treatment.

6. The use of the gas QPQ post-oxidation blackening agent in gas nitrogen-carbon-oxygen composite treatment according to claim 5, characterized in that: The following steps are involved: (1) placing the workpiece to be treated in a carbonitriding furnace for carbonitriding treatment to obtain a nitrided workpiece; (2) Add the gas QPQ post-oxidation blackening agent into a co-infiltration furnace and perform a drip infiltration treatment to obtain a treated workpiece.

7. The use of the gas QPQ post-oxidation blackening agent in gas nitrogen-carbon-oxygen composite treatment according to claim 6, characterized in that: Step (2) specifically includes the following steps: A. Lower the temperature in the infiltration furnace to 560°C and keep it at a constant temperature for 60-90 minutes. During the constant temperature and heat preservation process, add gas QPQ and then oxidize the blackening agent into the infiltration furnace at a rate of 150-180 drops / minute; B. Continue to lower the temperature in the co-infiltration furnace from 560°C to 380°C. During the cooling process, add gas QPQ and then oxidize the blackening agent into the co-infiltration furnace at a rate of 40-80 drops / minute.

8. The use of the gas QPQ post-oxidation blackening agent in gas nitrogen, carbon and oxygen composite treatment according to claim 7, characterized in that: Step B During the cooling process, the gas QPQ post-oxidation blackening agent is added into the co-infiltration furnace at a decreasing rate, as follows: When the temperature in the co-infiltration furnace drops from 560°C to 450°C, add gas QPQ and then oxidize blackening agent into the co-infiltration furnace at a rate of 50-80 drops / minute; when the temperature in the co-infiltration furnace drops from 450°C to 380°C, add gas QPQ and then oxidize blackening agent into the co-infiltration furnace at a rate of 40-50 drops / minute.

9. The use of the gas QPQ post-oxidation blackening agent according to any one of claims 6 to 8 in gas nitrogen, carbon and oxygen composite treatment, characterized in that: The nitrocarburizing treatment in step (1) comprises: adding a dripping agent into a nitrocarburizing furnace; The dripping agent comprises the following components by weight: 80-100 parts of ethanol, 30-40 parts of triethanolamine, 10-20 parts of citrate, 6-10 parts of rare earth oxide powder, and 1-5 parts of auxiliary agent; The auxiliary agent is selected from one or more of a dispersant, sodium gluconate and a silicate.

10. The use of the gas QPQ post-oxidation blackening agent in gas nitrogen, carbon and oxygen composite treatment according to claim 9, characterized in that: Before adding the dripping agent into the co-infiltration furnace, the method further includes: applying a penetration-enhancing agent on the surface of the workpiece to be processed; The penetration enhancer comprises the following components in parts by weight: 80-100 parts of ethanol, 6-10 parts of activated carbon powder, 10-20 parts of triethanolamine, 2-5 parts of rare earth oxide powder, 1-3 parts of nickel powder and 1-2 parts of dispersant.

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