Cannon steel surface Cr coating and preparation method thereof

Abstract

The invention relates to the technical field of gun steel surface Cr coatings, and discloses a preparation method of a gun steel surface Cr coating, which comprises the following steps: S1, gun steel material selection: selecting high-strength and low-alloy gun steel with excellent mechanical property and good hardenability; s2, a Cr coating preparation process: S21, pretreatment; s22, electrochemical plating of Cr is carried out; s3, post-treatment is carried out; and S4, coating performance evaluation. The overall service life of gun steel is prolonged, and maintenance cost is reduced; the Cr coating greatly improves the corrosion resistance and the wear resistance of the gun steel; the adopted electrochemical Cr plating process is environment-friendly, and the solution can be recycled; according to the gun steel surface Cr coating prepared through the technical scheme, the use performance of gun steel can be obviously improved, the service life of the gun steel can be obviously prolonged, a new process choice is provided for application of gun steel materials, and very high economic benefits and market application prospects are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of Cr coating on the surface of gun steel, and in particular to a Cr coating on the surface of gun steel and a preparation method thereof. Background Art

[0002] In the field of artillery manufacturing, the performance of gun steel is crucial, which is directly related to the shooting accuracy, life and safety of the gun. Traditional surface treatment methods for gun steel, such as chrome plating and nickel plating, can indeed improve the performance of gun steel to a certain extent.

[0003] However, these methods also have some obvious disadvantages. First, the process is complicated, requiring multiple steps and strict operating conditions, which increases the difficulty and cost of production. Secondly, the cost is high because it involves expensive materials and complex process flows. In addition, these methods may also cause environmental pollution and do not meet modern environmental protection requirements.

[0004] In view of these problems, it is of great practical significance and application value to develop a new method for preparing the surface coating of gun steel. This new method should be able to overcome the shortcomings of the traditional method and provide better performance improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a Cr coating on the surface of artillery steel and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology. Specifically, the new preparation method should have the following characteristics: 1. Simple process: reduce the operating steps, reduce the production difficulty and cost. 2. High cost-effectiveness: use more economical materials and simplified processes to reduce overall costs. 3. Environmental protection: avoid or reduce pollution to the environment. 4. Significantly improve the hardness, corrosion resistance and wear resistance of artillery steel: to meet the use requirements of artillery under various harsh conditions. By developing such a new method for preparing artillery steel surface coating, the performance and reliability of artillery can be improved, while reducing production costs and environmental impact. This has an important driving role in the development of the artillery manufacturing industry.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a Cr coating on the surface of a gun steel, comprising the following steps:

[0007] S1. Gun steel material selection:

[0008] High-strength, low-alloy gun steel is selected, which has excellent mechanical properties and good hardenability;

[0009] S2. Cr coating preparation process:

[0010] S21, pre-processing:

[0011] Surface cleaning: Use organic solvent to clean the surface of the gun steel to remove oil, dust and impurities;

[0012] Surface activation: Soak in concentrated nitric acid at 5060°C for 3040 minutes to remove the oxide layer and enhance the bonding strength between the coating and the substrate;

[0013] S22, electrochemical Cr plating:

[0014] Electroplating was performed using an electrolyte containing 0.50.8M CrO and 0.010.02M H SO ;

[0015] Set the current density to 2025A / dm 2 , the temperature is maintained at 4550℃, and the electroplating time is 2030 minutes;

[0016] Use intermittent current electroplating to improve the microstructure and adhesion of the coating;

[0017] S3, post-processing:

[0018] Heat treatment: Heat treatment was performed at 400450°C for 1.52 hours to form a more uniform crystal structure of the Cr coating;

[0019] Cooling: Cool naturally to room temperature to avoid stress cracks in the coating;

[0020] S4. Coating performance evaluation:

[0021] Hardness test: Use Vickers hardness tester to test the coating hardness, which is expected to reach HV1000~1200;

[0022] Corrosion resistance test: The treated samples were exposed to 5% salt water spray for 720 hours to detect the corrosion of the coating;

[0023] Wear test: The wear rate of the coating was tested by a standard sliding wear tester and was reduced by more than 50% compared to untreated gun steel.

[0024] Preferably, the material of the high-strength, low-alloy gun steel is: 42CrMo4 steel, 34CrNiMo6 steel or AISI4140 steel.

[0025] Preferably, the 42CrMo4 steel contains 0.38%-0.45% carbon, 0.90%-1.20% chromium, and 0.15%-0.30% molybdenum;

[0026] The 34CrNiMo6 steel contains 1.3%-1.7% nickel, 0.30%-0.50% molybdenum and 0.9%-1.2% chromium;

[0027] The AISI 4140 steel contains 0.38%-0.43% carbon, 0.8%-1.1% chromium, 0.15%-0.25% molybdenum.

[0028] Preferably, the organic solvent is a hydrocarbon solvent, and the concentration of isopropanol or butanone is above 70%;

[0029] Temperature: Keep the ambient temperature between 20℃ and 30℃ when using the solvent;

[0030] Soaking time: 10-15 minutes;

[0031] Stirring speed: 100 rpm to ensure full contact.

[0032] Preferably, the electroplating uses a metal salt solution, and the composition of the metal salt solution is as follows:

[0033] Ingredients: Nickel sulfate, nickel chloride;

[0034] Nickel sulfate concentration: 240350g / L;

[0035] Nickel chloride concentration: 4060g / L;

[0036] Additive dosage:

[0037] Brightening additive: 13mL / L;

[0038] Wetting agent: 0.10.5mL / L;

[0039] Grading agent: 0.52mL / L.

[0040] Preferably, the parameters during electroplating are as follows:

[0041] Current type: pulsed DC current;

[0042] Peak current density: 200220A / m 2 ;

[0043] Basic current density: 5055A / m 2 ;

[0044] Pulse duration: 1015ms;

[0045] Interval duration: 2025ms;

[0046] Current duty cycle: 3033%, that is, in each cycle, the activation time of the pulse current should account for one third of the total cycle.

[0047] Preferably, the temperature and pH control during electroplating:

[0048] pH range: 3.8-4.8;

[0049] Electroplating temperature: 4555℃.

[0050] Preferably, the specific steps of cooling are: cooling by using a gradual cooling channel;

[0051] The channel uses a step-down temperature gradient to control the cooling rate;

[0052] Temperature gradient: starting at 5055°C, gradually decreasing to room temperature 2225°C in the channel;

[0053] Length and time: The channel length is set to 1015 meters, and the entire cooling process is controlled to be completed within 3035 minutes;

[0054] Humidity control: Keep relative humidity between 50% and 60% to avoid excessive dryness or moisture that may affect coating performance.

[0055] The present invention proposes a Cr coating on the surface of gun steel and a preparation method thereof, which have the following beneficial effects: improving the overall life of the gun steel and reducing maintenance costs; the Cr coating greatly improves the corrosion resistance and wear resistance of the gun steel; the adopted electrochemical Cr plating process is environmentally friendly and the solution can be recycled; the Cr coating on the surface of gun steel prepared by the present technical solution can significantly improve the performance and service life of the gun steel, providing a new process option for the application of gun steel materials, and has very high economic benefits and market application prospects. DETAILED DESCRIPTION

[0056] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] The present invention provides a technical solution: a method for preparing a Cr coating on the surface of a gun steel, comprising the following steps:

[0058] S1. Gun steel material selection:

[0059] High-strength, low-alloy gun steel is used, which has excellent mechanical properties and good hardenability;

[0060] The material of the high-strength, low-alloy gun steel is: 42CrMo4 steel, 34CrNiMo6 steel or AISI 4140 steel;

[0061] The 42CrMo4 steel contains 0.38%-0.45% carbon, 0.90%-1.20% chromium, and 0.15%-0.30% molybdenum;

[0062] The 34CrNiMo6 steel contains 1.3%-1.7% nickel, 0.30%-0.50% molybdenum and 0.9%-1.2% chromium;

[0063] The AISI 4140 steel contains 0.38%-0.43% carbon, 0.8%-1.1% chromium, 0.15%-0.25% molybdenum.

[0064] S2. Cr coating preparation process:

[0065] S21, pre-processing:

[0066] Surface cleaning: Use organic solvent to clean the surface of the gun steel to remove oil, dust and impurities;

[0067] The organic solvent is a hydrocarbon solvent, and the concentration of isopropanol or butanone is above 70%;

[0068] Temperature: Keep the ambient temperature between 20℃ and 30℃ when using the solvent;

[0069] Soaking time: 10-15 minutes;

[0070] Stirring speed: 100 rpm, ensuring full contact;

[0071] Surface activation: Soak in concentrated nitric acid at 5060°C for 3040 minutes to remove the oxide layer and enhance the bonding strength between the coating and the substrate;

[0072] S22, electrochemical Cr plating:

[0073] Electroplating was performed using an electrolyte containing 0.50.8M CrO and 0.010.02M H SO;

[0074] Set the current density to 2025A / dm 2 , the temperature is maintained at 4550℃, and the electroplating time is 2030 minutes;

[0075] Use intermittent current electroplating to improve the microstructure and adhesion of the coating;

[0076] Electroplating uses a metal salt solution, the composition of which is as follows:

[0077] Ingredients: Nickel sulfate, nickel chloride;

[0078] Nickel sulfate concentration: 240350g / L;

[0079] Nickel chloride concentration: 4060g / L;

[0080] Additive dosage:

[0081] Brightening additive: 13mL / L;

[0082] Wetting agent: 0.10.5mL / L;

[0083] Grading agent: 0.52mL / L;

[0084] The parameters for electroplating are as follows:

[0085] Current type: pulsed DC current;

[0086] Peak current density: 200220A / m 2 ;

[0087] Basic current density: 5055A / m 2 ;

[0088] Pulse duration: 1015ms;

[0089] Interval duration: 2025ms;

[0090] Current duty cycle: 3033%, that is, in each cycle, the activation time of the pulse current should account for one third of the total cycle;

[0091] Temperature and pH control during electroplating:

[0092] pH range: 3.8-4.8;

[0093] Electroplating temperature: 4555℃;

[0094] S3, post-processing:

[0095] Heat treatment: Heat treatment was performed at 400450°C for 1.52 hours to form a more uniform crystal structure of the Cr coating;

[0096] Cooling: Cool naturally to room temperature to avoid stress cracks in the coating;

[0097] The specific steps of cooling are: cooling by using a gradual cooling channel;

[0098] The channel uses a step-down temperature gradient to control the cooling rate;

[0099] Temperature gradient: starting at 5055°C, gradually decreasing to room temperature 2225°C in the channel;

[0100] Length and time: The channel length is set to 1015 meters, and the entire cooling process is controlled to be completed within 3035 minutes;

[0101] Humidity control: Keep relative humidity between 50% and 60% to avoid excessive dryness or moisture that may affect coating performance.

[0102] S4. Coating performance evaluation:

[0103] Hardness test: Use Vickers hardness tester to test the coating hardness, which is expected to reach HV1000~1200;

[0104] Corrosion resistance test: The treated samples were exposed to 5% salt water spray for 720 hours to detect the corrosion of the coating;

[0105] Wear test: The wear rate of the coating was tested by a standard sliding wear tester and was reduced by more than 50% compared to untreated gun steel.

[0106] Embodiment 1:

[0107] Gun steel material selection: 42CrMo4 steel is selected.

[0108] Cr coating preparation process:

[0109] Pretreatment: Use 70% isopropanol as organic solvent, soak for 10 minutes at 20°C ambient temperature, stirring speed is 100 rpm. Then soak in concentrated nitric acid at 50°C for 30 minutes for surface activation.

[0110] Electrochemical Cr plating: using an electrolyte containing 0.5M CrO and 0.01M HSO, the current density is 20A / dm 2 , the temperature is maintained at 45°C, and the electroplating time is 20 minutes. The intermittent current electroplating method is used. The nickel sulfate concentration in the metal salt solution used for electroplating is 240g / L, the nickel chloride concentration is 40g / L, the brightening additive is 1mL / L, the wetting agent is 0.1mL / L, and the grading agent is 0.5mL / L. The parameters during electroplating are pulsed DC current, and the peak current density is 200A / m 2 , the basic current density is 50A / m 2 , the pulse duration is 10ms, the interval duration is 20ms, the current duty cycle is 30%, the pH range is 3.8, and the plating temperature is 45℃.

[0111] Post-treatment: heat treatment at 400℃ for 1.5 hours, then cooling using a gradient cooling channel, with the temperature gradient gradually decreasing from 50℃ to room temperature 22℃. The channel length is 10 meters. The entire cooling process is completed within 30 minutes, and the relative humidity is maintained at 50%.

[0112] Coating performance evaluation: The hardness test reached HV1000. In the corrosion resistance test, the coating showed no corrosion after continuous exposure to 5% salt water spray for 720 hours. In the wear resistance test, the wear rate of the coating was reduced by more than 50% compared with untreated gun steel.

[0113] Embodiment 2:

[0114] Selection of gun steel material: 34CrNiMo6 steel is selected.

[0115] Cr coating preparation process:

[0116] Pretreatment: Use 75% butanone as organic solvent, soak for 12 minutes at 25°C ambient temperature, stirring speed is 100 rpm. Then soak in concentrated nitric acid at 55°C for 35 minutes for surface activation.

[0117] Electrochemical Cr plating: using an electrolyte containing 0.6M CrO and 0.015M HSO, the current density is 22A / dm 2 , the temperature was maintained at 48°C, and the electroplating time was 25 minutes. Intermittent current electroplating was used, and the nickel sulfate concentration in the metal salt solution used for electroplating was 280g / L, the nickel chloride concentration was 50g / L, the brightening additive was 2mL / L, the wetting agent was 0.3mL / L, and the grading agent was 1mL / L. The parameters during electroplating were pulsed DC current, and the peak current density was 210A / m 2 , the basic current density is 53A / m 2 , the pulse duration is 12ms, the interval duration is 22ms, the current duty cycle is 32%, the pH range is 4.2, and the plating temperature is 50℃.

[0118] Post-treatment: Heat treatment at 420°C for 1.8 hours, followed by cooling using a gradient cooling channel, with the temperature gradient gradually decreasing from 52°C to room temperature 23°C. The channel length is 12 meters, and the entire cooling process is completed within 32 minutes, maintaining relative humidity at 55%.

[0119] Coating performance evaluation: The hardness test reached HV1100. In the corrosion resistance test, the coating showed no corrosion after being continuously exposed to 5% salt water spray for 720 hours. In the wear resistance test, the wear rate of the coating was reduced by more than 55% compared with the untreated gun steel.

[0120] Embodiment 3:

[0121] Gun steel material selection: AISI 4140 steel is selected.

[0122] Cr coating preparation process:

[0123] Pretreatment: Use 80% isopropanol as organic solvent, soak for 15 minutes at 30°C ambient temperature, stirring speed is 100 rpm. Then soak in concentrated nitric acid at 60°C for 40 minutes for surface activation.

[0124] Electrochemical Cr plating: using an electrolyte containing 0.8M CrO and 0.02M HSO, the current density is 25A / dm 2, the temperature was maintained at 50°C, and the electroplating time was 30 minutes. Intermittent current electroplating was used, and the nickel sulfate concentration in the metal salt solution used for electroplating was 350g / L, the nickel chloride concentration was 60g / L, the brightening additive was 3mL / L, the wetting agent was 0.5mL / L, and the grading agent was 2mL / L. The parameters during electroplating were pulsed DC current, and the peak current density was 220A / m 2 , the basic current density is 55A / m 2 , the pulse duration is 15ms, the interval duration is 25ms, the current duty cycle is 33%, the pH range is 4.8, and the plating temperature is 55℃.

[0125] Post-treatment: Heat treatment at 450℃ for 2 hours, then cooling using a gradient cooling channel, with the temperature gradient gradually decreasing from 55℃ to room temperature 25℃. The channel length is 15 meters. The entire cooling process is completed within 35 minutes, maintaining relative humidity at 60%.

[0126] Coating performance evaluation: The hardness test reached HV1200. In the corrosion resistance test, the coating showed no corrosion after being continuously exposed to 5% salt water spray for 720 hours. In the wear resistance test, the wear rate of the coating was reduced by more than 60% compared with the untreated gun steel.

[0127] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Cr coating on the surface of gun steel, characterized in that: The following steps are involved: S1. Gun steel material selection: High-strength, low-alloy gun steel is used, which has excellent mechanical properties and good hardenability; S2. Cr coating preparation process: S21, pre-processing: Surface cleaning: Use organic solvent to clean the surface of the gun steel to remove oil, dust and impurities; Surface activation: Soak in concentrated nitric acid at 5060°C for 3040 minutes to remove the oxide layer and enhance the bonding strength between the coating and the substrate; S22, electrochemical Cr plating: Electroplating was performed using an electrolyte containing 0.50.8M CrO and 0.010.02M H SO ; Set the current density to 2025A / dm 2 , the temperature is maintained at 4550℃, and the electroplating time is 2030 minutes; Use intermittent current electroplating to improve the microstructure and adhesion of the coating; S3, post-processing: Heat treatment: Heat treatment was performed at 400450°C for 1.52 hours to form a more uniform crystal structure of the Cr coating; Cooling: Cool naturally to room temperature to avoid stress cracks in the coating; S4. Coating performance evaluation: Hardness test: Use Vickers hardness tester to test the coating hardness, which is expected to reach HV1000~1200; Corrosion resistance test: The treated samples were exposed to 5% salt water spray for 720 hours to detect the corrosion of the coating; Wear test: The wear rate of the coating was tested by a standard sliding wear tester and was reduced by more than 50% compared to untreated gun steel.

2. The method for preparing a Cr coating on the surface of gun steel according to claim 1, characterized in that: The material of the high-strength, low-alloy gun steel is: 42CrMo4 steel, 34CrNiMo6 steel or AISI 4140 steel.

3. The method for preparing a Cr coating on the surface of gun steel according to claim 2, characterized in that: The 42CrMo4 steel contains 0.38%-0.45% carbon, 0.90%-1.20% chromium, and 0.15%-0.30% molybdenum; The 34CrNiMo6 steel contains 1.3%-1.7% nickel, 0.30%-0.50% molybdenum and 0.9%-1.2% chromium; The AISI 4140 steel contains 0.38%-0.43% carbon, 0.8%-1.1% chromium, 0.15%-0.25% molybdenum.

4. The method for preparing a Cr coating on the surface of gun steel according to claim 3, characterized in that: The organic solvent is a hydrocarbon solvent, and the concentration of isopropanol or butanone is above 70%; Temperature: Keep the ambient temperature between 20℃ and 30℃ when using the solvent; Soaking time: 10-15 minutes; Stirring speed: 100 rpm to ensure full contact.

5. The method for preparing a Cr coating on the surface of gun steel according to claim 4, characterized in that: Electroplating uses a metal salt solution, the composition of which is as follows: Ingredients: Nickel sulfate, nickel chloride; Nickel sulfate concentration: 240350g / L; Nickel chloride concentration: 4060g / L; Additive dosage: Brightening additive: 13mL / L; Wetting agent: 0.10.5mL / L; Grading agent: 0.52mL / L.

6. The method for preparing a Cr coating on the surface of gun steel according to claim 5, characterized in that: The parameters for electroplating are as follows: Current type: pulsed DC current; Peak current density: 200220A / m 2 ; Basic current density: 5055A / m 2 ; Pulse duration: 1015ms; Interval duration: 2025ms; Current duty cycle: 3033%, that is, in each cycle, the activation time of the pulse current should account for one third of the total cycle.

7. The method for preparing a Cr coating on the surface of gun steel according to claim 6, characterized in that: Temperature and pH control during electroplating: pH range: 3.8-4.8; Electroplating temperature: 4555℃.

8. The method for preparing a Cr coating on the surface of gun steel according to claim 7, characterized in that: The specific steps of cooling are: cooling by using a gradual cooling channel; The channel uses a step-down temperature gradient to control the cooling rate; Temperature gradient: starting at 5055°C, gradually decreasing to room temperature 2225°C in the channel; Length and time: The channel length is set to 1015 meters, and the entire cooling process is controlled to be completed within 3035 minutes; Humidity control: Keep relative humidity between 50% and 60% to avoid excessive dryness or moisture that may affect coating performance.