CN111763907A - Salt bath nitriding agent for metal workpiece surface treatment and metal workpiece surface treatment method - Google Patents
Salt bath nitriding agent for metal workpiece surface treatment and metal workpiece surface treatment method Download PDFInfo
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- CN111763907A CN111763907A CN202010805838.3A CN202010805838A CN111763907A CN 111763907 A CN111763907 A CN 111763907A CN 202010805838 A CN202010805838 A CN 202010805838A CN 111763907 A CN111763907 A CN 111763907A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
- C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
- C23C8/48—Nitriding
- C23C8/50—Nitriding of ferrous surfaces
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
- C23C8/58—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions more than one element being applied in more than one step
Abstract
The invention relates to the technical field of metal surface treatment, in particular to a salt bath nitriding agent for metal workpiece surface treatment and a metal workpiece surface treatment method. The salt bath nitriding agent for the surface treatment of the metal workpiece comprises the following components in percentage by mass: 30-40% of sodium cyanate, 15-20% of sodium carbonate, 8-10% of potassium chloride, 8-10% of sodium chloride, 15-20% of potassium carbonate, 2-5% of cerium carbonate, 8-15% of lithium carbonate, 2-5% of sodium sulfite and 2-5% of potassium sulfite. The salt bath nitriding agent for surface treatment of the metal workpiece provided by the invention can effectively improve the wear resistance and corrosion resistance of the metal workpiece.
Description
Technical Field
The invention relates to the technical field of metal surface treatment, in particular to a salt bath nitriding agent for metal workpiece surface treatment and a metal workpiece surface treatment method.
Background
The powder metallurgy brake pad steel backing is a part for braking of the motor train unit, and the surface of the steel backing used by the powder metallurgy brake pad has no defects of oil stain, oxide skin, rust and the like according to the technical specification requirements of the powder metallurgy brake pad industry, so the surface of the steel backing used by the powder metallurgy brake pad is treated before use.
The surface treatment technology is a process method for artificially forming a surface layer with mechanical, physical and chemical properties different from those of a substrate on the surface of a substrate material. The existing metal surface treatment technology mainly comprises chemical plating and salt bath compounding technology.
Chemical plating is a common surface treatment mode for rust prevention and corrosion prevention of the back surface of the prior powder metallurgy brake pad steel, and is a method for reducing metal ions into metal and depositing the metal ions on the surface of a material to form a compact layer by utilizing a strong reducing agent in a solution containing the metal ions according to the principle of redox reaction. Taking a copper plating process as an example, the copper plating process mainly comprises pre-plating treatment, copper plating and post-plating treatment, and a layer of plating layer is formed on the surface of the powder metallurgy brake pad steel back in a chemical plating mode to achieve the effects of wear resistance and corrosion resistance. However, the chemical plating process has a slow plating speed and a long production period, and the production process generates waste liquid to pollute the environment, the service life of the plating liquid is short, and the treatment of the production waste liquid increases the production cost.
The salt bath compounding technology is one kind of pollution-free metal surface treating process combining thermochemical diffusion, passivation and precise treatment in salt bath furnace, and the metal part is set inside two kinds of salt baths with different properties and compounded with several kinds of compounds to form compound permeated layer. The salt bath compounding technology is technically the combination of a heat treatment technology and an anti-corrosion technology, two salts with different properties are used as media, no pollution is generated under the mutual action of the salts of two components in the using process, and harmful substances such as heavy metal and the like are not contained, so that the environment pollution problem caused by chemical plating can be effectively improved while the surface treatment requirement of a steel backing is met; in addition, the service life of the molten salt used by the salt bath compound technology is longer than that of the plating solution used by chemical plating, the salt bath compound technology does not produce harmful waste liquid, the cost for treating the harmful waste liquid can be reduced, and the used equipment is simpler, so that the investment cost and the energy cost in the production process can be reduced by the salt bath compound technology compared with the chemical plating.
The main processes of the existing salt bath compounding technology comprise cleaning, preheating, nitriding, oxidizing and other processes before treatment, wherein nitriding is a core process of the salt bath compounding technology. The prior art CN108251788A discloses a tufftride treatment method for a brake steel backing of a motor train unit, wherein tufftride is disclosed, and the tufftride contains 40-60% of sodium cyanate, 5-10% of sodium carbonate, 5-10% of potassium carbonate, 5-15% of sodium hydroxide, 5-10% of sodium chloride, 3-5% of lithium carbonate, 1-3% of potassium sulfide and 1-3% of cerium trichloride. However, the steel backing is subjected to surface treatment by the soft nitrified salt, the improvement of the wear resistance and the corrosion resistance of the steel backing is limited, and the requirements of the related performances of the powder metallurgy brake pad steel backing of the motor train unit cannot be effectively met.
Disclosure of Invention
The invention aims to overcome the defect that the wear resistance and corrosion resistance of a steel back are improved to a limited extent by adopting the existing soft nitriding salt to carry out surface treatment on the steel back, and further provides a salt bath nitriding agent for surface treatment of a metal workpiece and a surface treatment method of the metal workpiece.
In order to achieve the purpose, the invention adopts the following technical scheme:
a salt bath nitriding agent for surface treatment of a metal workpiece comprises the following components in percentage by mass: 30-40% of sodium cyanate, 15-20% of sodium carbonate, 8-10% of potassium chloride, 8-10% of sodium chloride, 15-20% of potassium carbonate, 2-5% of cerium carbonate, 8-15% of lithium carbonate, 2-5% of sodium sulfite and 2-5% of potassium sulfite.
Preferably, the composition comprises the following components: 35% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 15% of potassium carbonate, 3% of cerium carbonate, 10% of lithium carbonate, 3% of sodium sulfite and 3% of potassium sulfite.
The invention also provides a metal workpiece surface treatment method, which comprises the following steps:
1) cleaning the metal workpiece to obtain a cleaned metal workpiece;
2) preheating the cleaned metal workpiece to obtain a preheated metal workpiece;
3) performing salt bath nitriding on the preheated metal workpiece to obtain a metal workpiece subjected to salt bath nitriding treatment; the salt bath nitriding agent used in the salt bath nitriding treatment is selected from the salt bath nitriding agent for the surface treatment of the metal workpiece;
4) and (3) performing salt bath oxidation on the metal workpiece subjected to the salt bath nitriding treatment to obtain the metal workpiece subjected to salt bath oxidation.
Preferably, in the step 3), the salt bath nitriding temperature is 500-.
Preferably, in the step 4), the oxidizing salt used in the salt bath oxidation treatment comprises the following components in percentage by mass: 10-20% of sodium hydroxide, 10-20% of potassium hydroxide, 20-30% of sodium carbonate, 20-30% of potassium carbonate, 10-15% of potassium permanganate, 10-15% of sodium nitrate and 10-15% of potassium nitrate.
Preferably, in the step 4), the salt bath oxidation temperature is 350-450 ℃, and the salt bath oxidation time is 1-2 h.
Preferably, in the step 1), the cleaning treatment is ultrasonic cleaning, the ultrasonic frequency is 50-120KHz, and the ultrasonic time is 30-60 min. The ultrasonic cleaning of the present invention may be carried out with a water-based cleaning agent.
Preferably, in the step 2), the preheating temperature is 300-450 ℃, and the preheating time is 1-2 h.
Preferably, in step 3), the salt bath nitriding treatment is performed in a nitriding furnace, and a nitride analyzer is arranged in the nitriding furnace and used for monitoring CNO-And adding or adjusting the corresponding salt component at an appropriate timing to prevent CNO-Too much or too little of the content affects the nitriding effect.
Preferably, in the step 3), the salt bath nitriding treatment step comprises melting the salt bath nitriding agent at 500-.
Preferably, in the step 4), the salt bath oxidation treatment step includes melting an oxide salt at 350-.
Preferably, the step 4) further comprises the step of washing the metal workpiece oxidized by the salt bath with water and then soaking the metal workpiece in oil.
Preferably, the metal workpiece is a brake pad steel backing.
The invention has the beneficial effects that:
1) the salt bath nitriding agent for the surface treatment of the metal workpiece comprises the following components in percentage by mass: 30-40% of sodium cyanate, 15-20% of sodium carbonate, 8-10% of potassium chloride, 8-10% of sodium chloride, 15-20% of potassium carbonate, 2-5% of cerium carbonate, 8-15% of lithium carbonate, 2-5% of sodium sulfite and 2-5% of potassium sulfite. The sodium sulfite and the potassium sulfite are added into the salt bath nitriding agent, and are favorable for improving the active ingredient CNO in the salt bath nitriding process-The active S element generated by the reaction can permeate into the surface of the metal workpiece, the wear resistance and the corrosion resistance of the metal workpiece can be greatly improved by utilizing the antifriction effect of the S element, and simultaneously, the addition of the sodium sulfite and the potassium sulfite can also regulate and control CN in the salt bath nitriding process-So as to adjust the carburizing effect of the metal workpiece; the addition of lithium carbonate can stabilize the active ingredient CNO in the salt bath nitriding process-The research shows that the nitriding speed can be accelerated, the nitriding quality can be improved, and the microhardness of a surface treatment layer can be improved to a certain extent, so that the salt bath environment can be purified.
The salt bath nitriding agent provided by the invention can effectively improve the wear resistance and corrosion resistance of the metal workpiece through the mutual matching and combined action of the components, and compared with a process for carrying out surface treatment on the metal workpiece by adopting chemical plating, the salt bath nitriding agent can greatly improve the production efficiency, reduce the production cost and reduce the environmental pollution in the production process on the premise of meeting the technical specification requirement of the powder metallurgy brake pad industry.
2) According to the metal workpiece surface treatment method provided by the invention, the metal workpiece is sequentially cleaned to remove oil stains on the surface of the treated workpiece, and the condition that the oil stains on the surface pollute a salt bath to influence the process and effect of the salt bath is prevented; the preheating step has the function of drying the moisture on the surface of the metal workpiece, so that the cold workpiece enters the nitriding furnace after being heated, and the problem that the temperature in the nitriding furnace is reduced too much due to the moisture on the surface of the metal workpiece or the low temperature, so that the salt bath nitriding process is influenced is avoided; the salt bath oxidation step can decompose harmful substances brought by the previous process of the workpiece and eliminate pollution on one hand, and can form a layer of oxidation film on the surface of the workpiece to improve corrosion resistance and wear resistance on the other hand; the salt bath nitriding agent is adopted in the salt bath nitriding process, so that the wear resistance and the corrosion resistance of a metal workpiece can be effectively improved. The surface treatment method for the metal workpiece is suitable for carrying out surface treatment on the powder metallurgy brake lining steel back of a 350Km/h non-dovetail (TS355) motor train unit at the speed per hour.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
The embodiment provides a surface treatment method for a powder metallurgy brake pad steel back of a motor train unit, which comprises the following steps:
1) putting the brake pad steel back into ultrasonic equipment for ultrasonic cleaning, and removing oil stains on the surface of the steel back under the action of ultrasonic waves, wherein the ultrasonic frequency is 100KHz, and the ultrasonic time is 50 min;
2) preheating the ultrasonically cleaned steel back in an air furnace at 400 ℃ for 1.2 h;
3) putting the salt bath nitriding agent into a nitriding furnace, melting the salt bath nitriding agent at 550 ℃ to form a nitriding salt bath, then putting the steel back preheated in the step 2) into the nitriding salt bath in the nitriding furnace, and nitriding the steel back for 3 hours in the salt bath at 550 ℃; the salt bath nitriding agent comprises the following components in percentage by mass: 35% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 15% of potassium carbonate, 3% of cerium carbonate, 10% of lithium carbonate, 3% of sodium sulfite and 3% of potassium sulfite;
4) putting oxide salt into an oxidation furnace, melting the oxide salt at 400 ℃ to form an oxide salt bath, then putting the steel back subjected to the salt bath nitriding treatment in the step 3) into the oxide salt bath in the oxidation furnace, and carrying out salt bath oxidation treatment on the steel back at 400 ℃ for 1.5 hours; the oxidizing salt comprises the following components in percentage by mass: 10% sodium hydroxide, 10% potassium hydroxide, 20% sodium carbonate, 30% potassium carbonate, 10% potassium permanganate, 10% sodium nitrate, 10% potassium nitrate;
5) and after the salt bath oxidation treatment is carried out on the steel back, the steel back is cleaned by water, and after the cleaning is finished, the steel back is placed in engine oil to be soaked for 30min, and after the soaking is finished, the steel back is taken out to finish the surface treatment of the brake pad steel back.
Example 2
The embodiment provides a surface treatment method for a powder metallurgy brake pad steel back of a motor train unit, which comprises the following steps:
1) putting the brake pad steel back into ultrasonic equipment for ultrasonic cleaning, and removing oil stains on the surface of the steel back under the action of ultrasonic waves, wherein the ultrasonic frequency is 50KHz, and the ultrasonic time is 60 min;
2) preheating the ultrasonically cleaned steel back in an air furnace at the preheating temperature of 300 ℃ for 2 hours;
3) putting the salt bath nitriding agent into a nitriding furnace, melting the salt bath nitriding agent at 500 ℃ to form a nitriding salt bath, then putting the steel back preheated in the step 2) into the nitriding salt bath in the nitriding furnace, and nitriding the steel back for 4 hours in the salt bath at 500 ℃; the salt bath nitriding agent comprises the following components in percentage by mass: 30% of sodium cyanate, 20% of sodium carbonate, 8% of potassium chloride, 10% of sodium chloride, 15% of potassium carbonate, 2% of cerium carbonate, 8% of lithium carbonate, 2% of sodium sulfite and 5% of potassium sulfite;
4) putting oxide salt into an oxidation furnace, melting the oxide salt at 350 ℃ to form an oxide salt bath, then putting the steel back subjected to the salt bath nitriding treatment in the step 3) into the oxide salt bath in the oxidation furnace, and carrying out salt bath oxidation treatment on the steel back at 350 ℃ for 2 hours; the oxidizing salt comprises the following components in percentage by mass: 10% sodium hydroxide, 10% potassium hydroxide, 25% sodium carbonate, 20% potassium carbonate, 10% potassium permanganate, 10% sodium nitrate, 15% potassium nitrate;
5) and after the salt bath oxidation treatment is carried out on the steel back, the steel back is cleaned by water, and after the cleaning is finished, the steel back is placed in engine oil to be soaked for 30min, and after the soaking is finished, the steel back is taken out to finish the surface treatment of the brake pad steel back.
Example 3
The embodiment provides a surface treatment method for a powder metallurgy brake pad steel back of a motor train unit, which comprises the following steps:
1) putting the brake pad steel back into ultrasonic equipment for ultrasonic cleaning, and removing oil stains on the surface of the steel back under the action of ultrasonic waves, wherein the ultrasonic frequency is 120KHz, and the ultrasonic time is 30 min;
2) preheating the ultrasonically cleaned steel back in an air furnace, wherein the preheating temperature is 450 ℃ and the preheating time is 1 h;
3) putting the salt bath nitriding agent into a nitriding furnace, melting the salt bath nitriding agent at 600 ℃ to form a nitriding salt bath, then putting the steel back preheated in the step 2) into the nitriding salt bath in the nitriding furnace, and nitriding the steel back for 2 hours in the salt bath at 600 ℃; the salt bath nitriding agent comprises the following components in percentage by mass: 40% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 15% of potassium carbonate, 2% of cerium carbonate, 8% of lithium carbonate, 2% of sodium sulfite and 2% of potassium sulfite;
4) putting oxide salt into an oxidation furnace, melting the oxide salt at 450 ℃ to form an oxide salt bath, then putting the steel back subjected to the salt bath nitriding treatment in the step 3) into the oxide salt bath in the oxidation furnace, and carrying out salt bath oxidation treatment on the steel back at 450 ℃ for 1 h; the oxidizing salt comprises the following components in percentage by mass: 20% sodium hydroxide, 10% potassium hydroxide, 20% sodium carbonate, 20% potassium carbonate, 10% potassium permanganate, 10% sodium nitrate, 10% potassium nitrate;
5) and after the salt bath oxidation treatment is carried out on the steel back, the steel back is cleaned by water, and after the cleaning is finished, the steel back is placed in engine oil to be soaked for 30min, and after the soaking is finished, the steel back is taken out to finish the surface treatment of the brake pad steel back.
Example 4
The embodiment provides a surface treatment method for a powder metallurgy brake pad steel back of a motor train unit, which comprises the following steps:
1) putting the brake pad steel back into ultrasonic equipment for ultrasonic cleaning, and removing oil stains on the surface of the steel back under the action of ultrasonic waves, wherein the ultrasonic frequency is 80KHz, and the ultrasonic time is 35 min;
2) preheating the ultrasonically cleaned steel back in an air furnace, wherein the preheating temperature is 380 ℃ and the preheating time is 1.3 h;
3) putting the salt bath nitriding agent into a nitriding furnace, melting the salt bath nitriding agent at 600 ℃ to form a nitriding salt bath, then putting the steel back preheated in the step 2) into the nitriding salt bath in the nitriding furnace, and nitriding the steel back for 2 hours in the salt bath at 600 ℃; the salt bath nitriding agent comprises the following components in percentage by mass: 30% of sodium cyanate, 15% of sodium carbonate, 10% of potassium chloride, 8% of sodium chloride, 15% of potassium carbonate, 5% of cerium carbonate, 10% of lithium carbonate, 5% of sodium sulfite and 2% of potassium sulfite;
4) putting oxide salt into an oxidation furnace, melting the oxide salt at 420 ℃ to form an oxide salt bath, then putting the steel back subjected to the salt bath nitriding treatment in the step 3) into the oxide salt bath in the oxidation furnace, and carrying out salt bath oxidation treatment on the steel back at 420 ℃ for 1.1 h; the oxidizing salt comprises the following components in percentage by mass: 10% sodium hydroxide, 20% potassium hydroxide, 20% sodium carbonate, 20% potassium carbonate, 10% potassium permanganate, 10% sodium nitrate, 10% potassium nitrate;
5) and after the salt bath oxidation treatment is carried out on the steel back, the steel back is cleaned by water, and after the cleaning is finished, the steel back is placed in engine oil to be soaked for 30min, and after the soaking is finished, the steel back is taken out to finish the surface treatment of the brake pad steel back.
Example 5
The embodiment provides a surface treatment method for a powder metallurgy brake pad steel back of a motor train unit, which comprises the following steps:
1) putting the brake pad steel back into ultrasonic equipment for ultrasonic cleaning, and removing oil stains on the surface of the steel back under the action of ultrasonic waves, wherein the ultrasonic frequency is 100KHz, and the ultrasonic time is 48 min;
2) preheating the ultrasonically cleaned steel back in an air furnace at the preheating temperature of 410 ℃ for 1.6 h;
3) putting the salt bath nitriding agent into a nitriding furnace, melting the salt bath nitriding agent at 540 ℃ to form a nitriding salt bath, then putting the steel back preheated in the step 2) into the nitriding salt bath in the nitriding furnace, and nitriding the steel back for 3 hours in the salt bath at 540 ℃; the salt bath nitriding agent comprises the following components in percentage by mass: 30% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 20% of potassium carbonate, 2% of cerium carbonate, 13% of lithium carbonate, 2% of sodium sulfite and 2% of potassium sulfite;
4) putting oxide salt into an oxidation furnace, melting the oxide salt at 430 ℃ to form an oxide salt bath, then putting the steel back subjected to the salt bath nitriding treatment in the step 3) into the oxide salt bath in the oxidation furnace, and carrying out salt bath oxidation treatment on the steel back at 430 ℃ for 1.1 h; the oxidizing salt comprises the following components in percentage by mass: 10% sodium hydroxide, 10% potassium hydroxide, 20% sodium carbonate, 20% potassium carbonate, 15% potassium permanganate, 15% sodium nitrate, 10% potassium nitrate;
5) and after the salt bath oxidation treatment is carried out on the steel back, the steel back is cleaned by water, and after the cleaning is finished, the steel back is placed in engine oil to be soaked for 30min, and after the soaking is finished, the steel back is taken out to finish the surface treatment of the brake pad steel back.
Comparative example 1
The comparative example provides a surface treatment method for a powder metallurgy brake lining steel back of a motor train unit, and compared with example 5, the difference is that the salt bath nitriding agent in the step 3) consists of the following components in percentage by mass: 30% of sodium cyanate, 15% of sodium carbonate, 10% of potassium chloride, 10% of sodium chloride, 20% of potassium carbonate, 2% of cerium carbonate and 13% of lithium carbonate.
Comparative example 2
The comparative example provides a surface treatment method for a powder metallurgy brake lining steel back of a motor train unit, and compared with example 5, the difference is that the salt bath nitriding agent in the step 3) consists of the following components in percentage by mass: 30% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 20% of potassium carbonate, 2% of cerium carbonate, 13% of lithium carbonate and 4% of potassium sulfide.
Performance testing
Test example 1
The corrosion resistance of the brake pad steel backs subjected to surface treatment in examples 1-5 and comparative examples 1-2 is subjected to a salt spray test according to a neutral salt spray test method in GB/T10125 & 2012 salt spray test, and is evaluated according to the rating of a test sample and a test piece after corrosion tests on metal and other inorganic coatings on a GB/T6461 & 2002 metal substrate; the results are shown in Table 1.
TABLE 1 Corrosion resistance of the Steel backing
| Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Comparative example 1 | Comparative example 2 | |
| Corrosion resistance | Grade 9 | Stage 8 | Stage 7 | Stage 8 | Stage 8 | Grade 5 | Grade 6 |
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. A salt bath nitriding agent for surface treatment of a metal workpiece is characterized by comprising the following components in percentage by mass: 30-40% of sodium cyanate, 15-20% of sodium carbonate, 8-10% of potassium chloride, 8-10% of sodium chloride, 15-20% of potassium carbonate, 2-5% of cerium carbonate, 8-15% of lithium carbonate, 2-5% of sodium sulfite and 2-5% of potassium sulfite.
2. The salt bath nitriding agent for surface treatment of metal workpieces according to claim 1, comprising the following components: 35% of sodium cyanate, 15% of sodium carbonate, 8% of potassium chloride, 8% of sodium chloride, 15% of potassium carbonate, 3% of cerium carbonate, 10% of lithium carbonate, 3% of sodium sulfite and 3% of potassium sulfite.
3. A surface treatment method for a metal workpiece is characterized by comprising the following steps:
1) cleaning the metal workpiece to obtain a cleaned metal workpiece;
2) preheating the cleaned metal workpiece to obtain a preheated metal workpiece;
3) performing salt bath nitriding on the preheated metal workpiece to obtain a metal workpiece subjected to salt bath nitriding treatment; the salt bath nitriding agent used in the salt bath nitriding treatment is selected from the salt bath nitriding agent for surface treatment of a metal workpiece according to any one of claims 1 or 2;
4) and (3) performing salt bath oxidation on the metal workpiece subjected to the salt bath nitriding treatment to obtain the metal workpiece subjected to salt bath oxidation.
4. The method for treating the surface of the metal workpiece as recited in claim 3, wherein in the step 3), the salt bath nitriding temperature is 500-.
5. The method for surface treatment of a metal workpiece according to claim 3 or 4, characterized in that in step 4), the oxidizing salt used in the salt bath oxidation treatment comprises the following components in mass fraction: 10-20% of sodium hydroxide, 10-20% of potassium hydroxide, 20-30% of sodium carbonate, 20-30% of potassium carbonate, 10-15% of potassium permanganate, 10-15% of sodium nitrate and 10-15% of potassium nitrate.
6. The method for treating the surface of a metal workpiece according to any one of claims 3 to 5, wherein in the step 4), the salt bath oxidation temperature is 350-450 ℃, and the salt bath oxidation time is 1-2 h.
7. The metal workpiece surface treatment method according to any one of claims 3 to 6, characterized in that in the step 1), ultrasonic cleaning is adopted for the cleaning treatment, the ultrasonic frequency is 50 to 120KHz, and the ultrasonic time is 30 to 60 min.
8. The method as claimed in any one of claims 3 to 7, wherein the preheating temperature in step 2) is 300 ℃ to 450 ℃ and the preheating time is 1 to 2 hours.
9. The method for surface treatment of a metal workpiece according to any one of claims 3 to 8, further comprising the step of washing the metal workpiece oxidized by the salt bath with water and then immersing in oil in step 4).
10. A surface treatment method of a metal workpiece according to any one of claims 3 to 9, characterized in that the metal workpiece is a brake lining steel backing.
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Cited By (2)
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| CN115233150A (en) * | 2022-07-27 | 2022-10-25 | 桂林理工大学 | Formula of rare earth carbonitriding composite salt of Q235 and 9Cr18Mo and QPQ gas carbonitriding salt bath process thereof |
| CN115558879A (en) * | 2022-08-26 | 2023-01-03 | 创斯特精密机械（昆山）有限公司 | Preparation process and application of mold core with high heat conduction and heat dissipation |
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