Acid pickling additive for removing nitride film on surface of high-carbon-chromium bearing steel and preparation method of acid pickling additive

Abstract

The invention relates to the technical field of metal surface treatment, in particular to a pickling additive for removing a nitride film on the surface of high-carbon-chromium bearing steel and a preparation method of the pickling additive. The catalyst comprises the following components in percentage by mass: 1.0-4.0% of an oxidizing agent; 0.5 to 2.0 percent of corrosion inhibitor; 0.01%-0.05% of a penetrating agent; 1.5-6.0% of a stabilizer and an auxiliary agent; 15-20% of hydrochloric acid; the additive has the functions of accelerating reaction, wetting the surface, improving seepage force and the like, is suitable for removing a compact nitride film which is generated by a nitrogen protection annealing furnace and is difficult to remove by a common acid pickling method, also has a better effect on removing a black oxide film on the surface of hot-rolled metal, and can reduce the acid pickling temperature, solve the problems of incomplete acid washing and poor corrosion resistance. And the volatilization amount of hydrochloric acid is large. Waste acid does not affect cyclic utilization of acid and waste acid treatment, and no new hidden danger of environmental protection is generated after waste water is treated through a neutralization method.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, in particular to a pickling additive for removing a nitride film on the surface of a high-carbon chromium bearing steel and a preparation method thereof. Background Art

[0002] In order to ensure that the product structure and decarburization layer depth of the bearing steel wire meet the technical standards, the applicant used a nitrogen-protected heat treatment furnace produced by Austrian EBNER Company for spheroidizing annealing. When the temperature reaches above 770°C, nitrogen will react with the metal / metal oxide film to generate a metal nitride layer (nitride film). This nitride film has high density and corrosion resistance, is firmly bonded to the metal matrix, and reacts very slowly with normal temperature hydrochloric acid solution. It is difficult to remove it even after more than 2 hours, so that the subsequent coating treatment cannot form a uniform and continuous lubricating film layer. After entering the wire drawing process, the surface of the steel wire will be scratched. Due to the high tolerance requirements and large mold consumption, frequent mold replacement affects production efficiency.

[0003] In order to improve production efficiency and product quality, only high-temperature pickling at 55℃~65℃ and a time of 80 minutes to 100 minutes can be performed. However, under this process condition, the amount of hydrochloric acid volatilization is large, and the sodium hydroxide consumption for acid mist spray absorption reaches 200Kg~250Kg / day. However, the current technology can only improve production efficiency, but cannot reduce the pickling temperature. Therefore, in order to reduce production costs, shorten production cycles, and improve product quality, it is necessary to develop a low-temperature environmentally friendly pickling additive. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a pickling additive for removing the nitride film on the surface of high-carbon chromium bearing steel and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A pickling additive for removing nitride film on the surface of high carbon chromium bearing steel, the mass percentage composition of which is as follows:

[0007]

[0008] The stabilizer and auxiliary agent are selected from a mixture of ethanol and n-propanol in any proportion.

[0009] Furthermore, the oxidant is selected from sodium persulfate, potassium persulfate or a mixture of the two in any proportion.

[0010] Furthermore, the corrosion inhibitor is selected from one of 2-benzoyl-3-hydroxy-1-propylene and sodium molybdate, or a mixture of the two.

[0011] Furthermore, the corrosion inhibitor is a mixture of 2-benzoyl-3-hydroxy-1-propylene and sodium molybdate, and the mass ratio of 2-benzoyl-3-hydroxy-1-propylene to sodium molybdate is 1:10.

[0012] Furthermore, the penetrant is fatty alcohol polyoxyethylene ether.

[0013] A method for preparing a pickling additive for removing a nitride film on the surface of a high-carbon chromium bearing steel, the preparation method comprising the following steps:

[0014] 1) Add penetrant and corrosion inhibitor to stabilizer and additive, dissolve them and add water to make the additive for use;

[0015] 2) When using, take the required amount of oxidant and the additive prepared in step 1), dissolve them in water, add them into the acid solution, and stir evenly.

[0016] The beneficial effects of the technical solution of the present invention are:

[0017] The additive in the present invention has the functions of accelerating reaction, wetting surface, improving permeability, etc., and is suitable for removing dense nitride film produced by nitrogen protection annealing furnace which is difficult to remove by ordinary pickling method, and also has good effect on removing black oxide film on the surface of hot-rolled metal. The present invention can reduce the pickling temperature, solve the problems of incomplete pickling, large amount of hydrochloric acid volatilization, etc. Waste acid does not affect the recycling and treatment of acid, and no new environmental hazards are generated after the waste water is treated by neutralization method. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific implementation methods and description.

[0019] This application is aimed at the most commonly used nitrogen-protected spheroidizing annealing GCr15 material in the bearing steel industry to prevent decarburization. It is heated to 790°C at room temperature for 6 hours, then slowly cooled, and the total time in the furnace is 34 hours. When the temperature reaches above 770°C, nitrogen will react with the metal / metal oxide film to generate a metal nitride layer (nitride film). This nitride film has high density and corrosion resistance and is firmly bonded to the metal matrix. At present, the treatment of this type of material is all done with high-temperature hydrochloric acid, pursuing a short-term temperature of 70-75°C, a pickling time of 20-25 minutes, metal ions in the acid not exceeding 80 grams / liter, and a hydrochloric acid content of 20-25%. Due to the violent reaction and poor surface uniformity, it is easy to over-pickling and produce defective products. For the manual pickling line, hydrogen chloride gas overflows in the factory building, and workers wear gas masks to work. The automatic line uses sodium hydroxide spraying, which consumes a lot of sodium hydroxide, and the loss of transport manipulators and slings doubles.

[0020] The pickling additive for removing the nitride film on the surface of high-carbon chromium bearing steel in the present invention has the following mass percentage composition:

[0021]

[0022] The stabilizer and auxiliary agent are selected from a mixture of ethanol and n-propanol in any proportion, so that the oxidant is slowly released during the pickling process, the life of the pickling solution is extended, the amount of scale treated is increased, and the solubility of insoluble substances is increased.

[0023] The principle of pickling is to use hydrochloric acid as the base liquid to remove the chromium nitride layer. Other additives such as oxidants and penetrants are to speed up the reaction rate at low temperatures. During the heat treatment process, the furnace atmosphere and heat conduction are uneven, and the nitride layer is formed unevenly. In pickling, the dissolution completion time of the nitride layer is different. The surface that has been dissolved in advance is directly in contact with the acid solution. At this time, the useful matrix begins to corrode, and the waste of the pickling reaction - ferrous chloride is produced. This is an ineffective and harmful pickling. The use of a slow-release agent is a corrosion inhibitor to protect the first exposed steel matrix from excessive pickling and pitting defects. Oxidants are used to speed up the reaction rate and reduce the temperature. Penetrants can improve the dispersibility of additives in acid solution, reduce the surface tension of acid solution and steel, increase the contact area between acid solution and steel, and promote the diffusion and penetration of additives and acid solution. Stabilizers can make the oxidant proceed smoothly. The ferrous chloride produced in the reaction is a metal salt with excellent water solubility. At 40°C, 100 ml of water can dissolve 70 grams. Under the synergistic effect of corrosion inhibitors and water, the treatment area can be effectively increased, thereby enhancing the pickling ability.

[0024] The raw material manufacturers in this application are shown in the table below:

[0025]

[0026] Additive formula:

[0027] Oxidant (accelerates reaction speed and lowers temperature): sodium persulfate, potassium persulfate, one or a mixture of the two, with no limit on the mixing ratio of the two.

[0028] Corrosion inhibitor (the dissolution and shedding of scales in the pickling process has a sequence, and the corrosion inhibitor is to protect the first exposed steel substrate from excessive pickling and the formation of pitting defects): 2-benzoyl-3-hydroxy-1-propene, sodium molybdate, one or a mixture of the two. If a mixture of 2-benzoyl-3-hydroxy-1-propene and sodium molybdate is used, the mass ratio is 1:10.

[0029] Penetrant (improve the dispersibility of additives in acid solution, reduce the surface tension between acid solution and steel, increase the contact area between acid solution and steel, and promote the diffusion and penetration of additives and acid solution.): fatty alcohol polyoxyethylene ether.

[0030] Stabilizer and additive (to slowly release the oxidant during the pickling process, extend the life of the pickling solution, increase the amount of scale treated, and increase the solubility of insoluble substances), ethanol and n-propanol, the mixing ratio of the two is not limited.

[0031] Hydrochloric acid: 15-20% HCL aqueous solution

[0032] The preparation method comprises the following steps:

[0033] 1) Add penetrant and corrosion inhibitor to stabilizer and additive, dissolve them and add water to make the additive for use;

[0034] 2) When using, take the required amount of oxidant and the additive prepared in step 1), dissolve them in water, add them into the acid solution, and stir evenly.

[0035] Example:

[0036] The percentages in the examples are all mass percentages, the process is the same, the test discs are all 6.5 mm in diameter, and the spheroidizing annealing is performed under nitrogen protection. The final drawing size is 3.5 mm, and the die distribution is: 6.5-5.5-4.7-4.1-3.5.

[0037] Process: loose bundle → loading → water washing → acid washing → high pressure water washing → water washing → surface conditioning → phosphating → saponification → drying → wire drawing

[0038] Example 1

[0039] 1) Acid wash formula: containing 18% HCL aqueous solution,

[0040] 2) Pickling process: temperature 45°C, soaking time 70 minutes.

[0041] Additive usage: sodium persulfate 3.0%; 2-benzoyl-3-hydroxy-1-propylene: sodium molybdate, mass ratio of 1:10, 1.5%; fatty alcohol polyoxyethylene ether 0.03%; ethanol and n-propanol, mixed in a ratio of 3:1, 3%.

[0042] Example 2

[0043] 1) Acid wash solution formula: containing 20% ​​HCL aqueous solution,

[0044] 2) Pickling process: temperature 50°C, soaking time 65 minutes.

[0045] Additive usage: potassium persulfate 4.0%; 2-benzoyl-3-hydroxy-1-propylene: sodium molybdate, the mass ratio of which is 1:10, 1.5%; fatty alcohol polyoxyethylene ether 0.05%; ethanol 5%.

[0046] Example 3

[0047] 1) Acid wash solution formula: containing 15% HCL aqueous solution,

[0048] 2) Pickling process: temperature 45°C, soaking time 60 minutes.

[0049] Additive usage: Sodium persulfate and potassium persulfate mixed in a mass percentage of 1:1, 1.5%; 2-benzoyl-3-hydroxy-1-propylene 2%; fatty alcohol polyoxyethylene ether 0.03%; ethanol and n-propanol mixed in a mass percentage of 1:1, 2%.

[0050]

[0051] In addition, it should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent claim scheme. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A pickling additive for removing the nitride film on the surface of high carbon chromium bearing steel, characterized in that: Its mass percentage composition is as follows: Oxidant 1.0~4.0%; Corrosion inhibitor 0.5~2.0%; Penetrant 0.01~0.05%; Stabilizers and additives 1.5~6.0%; Hydrochloric acid 15-20%; The stabilizer and auxiliary agent are selected from a mixture of ethanol and n-propanol in any proportion.

2. The pickling additive for removing the nitride film on the surface of high carbon chromium bearing steel according to claim 1, characterized in that: The oxidant is selected from sodium persulfate, potassium persulfate or a mixture of the two in any proportion.

3. The pickling additive for removing the nitride film on the surface of high carbon chromium bearing steel according to claim 1, characterized in that: The corrosion inhibitor is selected from 2-benzoyl-3-hydroxy-1-propylene and sodium molybdate, or a mixture of the two.

4. The pickling additive for removing the nitride film on the surface of high carbon chromium bearing steel according to claim 3, characterized in that: The corrosion inhibitor is a mixture of 2-benzoyl-3-hydroxy-1-propylene and sodium molybdate, and the mass ratio of the 2-benzoyl-3-hydroxy-1-propylene to the sodium molybdate is 1:

10.

5. The pickling additive for removing the nitride film on the surface of high carbon chromium bearing steel according to claim 1, characterized in that: The penetrant is fatty alcohol polyoxyethylene ether.

6. A method for preparing a pickling additive for removing nitride film on the surface of high carbon chromium bearing steel according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: 1) Add penetrant and corrosion inhibitor to stabilizer and additives, dissolve them and add water to make the additives ready for use; 2) When using, take the required amount of oxidant and the additive prepared in step 1), dissolve them in water, add them to the acid solution, and stir evenly.

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