CN116043314A - Chromium-free electrochemical polishing solution and polishing treatment method - Google Patents

Abstract

The invention provides a chromium-free electrochemical polishing solution and a polishing treatment method, wherein the polishing solution comprises phosphoric acid, sulfuric acid and glycerol as raw materials, and H ₃ PO ₄ The addition amount is as follows: 400ml/l to 500ml/l; h ₂ SO ₄ The addition amount is as follows: 200ml/l to 400ml/l; c (C) ₃ H ₈ O ₃ The addition amount is as follows: 160ml/l to 320ml/l; a chromium-free electrochemical treatment method, S1 preparing the chromium-free electrochemical polishing solution of claim 1; s2, taking the pretreated workpiece to be polished as an anode, taking an electrochemical reaction tank body as a cathode, immersing the workpiece to be polished into a chromium-free electrochemical polishing solution, and adjusting the reaction temperature and the current density to carry out electrochemical polishing; s3, passivating and drying the polished workpiece to obtain the polished workpiece, wherein the chromium-free electrochemical polishing treatment of the stainless steel material is realized through researching the electrochemical polishing process parameters and related operating conditions of the stainless steel part.

Description

A chromium-free electrochemical polishing solution and polishing method

Technical Field

The invention belongs to the technical field of stainless steel material polishing, and in particular belongs to a chromium-free electrochemical polishing solution and a polishing treatment method.

Background Art

Traditional stainless steel polishing methods include mechanical polishing, chemical polishing and electrochemical polishing. Mechanical polishing is labor-intensive and not suitable for the processing of small precision parts such as screws, nuts, pins, rollers, etc. Chemical polishing has a simple process but poor polishing effect. Electrochemical polishing has the characteristics of fine surface, long solution life and low cost. However, the commonly used electrochemical polishing methods contain a large amount of chromium trioxide. On the one hand, it is highly polluting, toxic and difficult to treat wastewater. On the other hand, it has poor polishing effect on martensitic nickel-free stainless steel, which is easy to cause corrosion of workpieces and low yield.

Therefore, the current stainless steel polishing method has the disadvantages of high pollution, high toxicity, high processing difficulty, long cycle, unstable quality or easy corrosion of workpieces, and cannot meet the requirements of mass processing.

Summary of the invention

In order to solve the problems existing in the prior art, the present invention proposes a chromium-free electrochemical polishing solution and a polishing treatment method. By studying the electrochemical polishing process parameters and related operating conditions of stainless steel parts (nickel-containing stainless steel, nickel-free stainless steel), the chromium-free electrochemical polishing treatment of stainless steel materials is achieved.

To achieve the above object, the present invention provides the following technical solution: a chromium-free electrochemical polishing solution, the raw materials include phosphoric acid, sulfuric acid and propylene _glycol , the addition amount of _H3PO4 is: 400ml/l~500ml/l; the addition amount _{of H2SO4} is: 200ml/l~400ml/l; _the addition amount _{of C3H8O3 is} : 160ml/l~320ml/l.

Furthermore, phosphoric acid, sulfuric acid and glycerol were all of analytical grade.

The present invention also provides a chromium-free electrochemical treatment method, the specific steps are as follows:

S1 preparing the chromium-free electrochemical polishing solution according to claim 1;

S2 uses the pretreated workpiece to be polished as an anode and the electrochemical reaction tank as a cathode, immerses the workpiece to be polished in a chromium-free electrochemical polishing solution, adjusts the reaction temperature and current density, and performs electrochemical polishing;

S3 passivates and dries the polished workpiece to obtain a polished workpiece.

Furthermore, in S2, the pretreatment is ultrasonic degreasing of the workpiece to be polished. Specifically, a pure water solution containing a 3% to 5% concentration of a metal cleaning agent is used to ultrasonically clean the workpiece to be polished for 3 minutes to 5 minutes.

Furthermore, in S2, the pretreated workpiece to be polished is mounted on a hanger and immersed in a chromium-free electrochemical polishing solution, and both the workpiece to be polished and the hanger are immersed in the chromium-free electrochemical polishing solution.

Furthermore, in S2, the reaction temperature is 70°C to 80°C.

Furthermore, in S2, the current density is 30 A/dm ² to 40 A/dm ² .

Furthermore, in S2, the electrochemical polishing is performed for 1 min to 3 min.

Furthermore, in S3, the passivation is to immerse the polished workpiece in a 1:1 nitric acid solution for passivation for 30 min to 60 min.

Furthermore, in S3, the drying is performed for 30 min to 60 min.

Compared with the prior art, the present invention has at least the following beneficial effects:

The present invention provides a chromium-free electrochemical polishing solution, which uses glycerol instead of chromium trioxide, is non-toxic and low-pollution, has simple wastewater treatment, and is not prone to workpiece corrosion. The electrochemical polishing mechanism in the present invention is still the mucosal theory, that is, the stainless steel part is immersed in the polishing liquid as an anode, and under the action of direct current, a mucosa with high resistivity is generated on the surface, which is thinner at the micro-convex part, with a large current density and fast metal dissolution, and thicker at the micro-concave part, with a small current density and slow metal dissolution, thereby achieving a polishing effect. In the present invention, glycerol is used as a high-viscosity non-conductive additive, which increases the viscosity of the solution while also increasing the resistivity of the surface mucosa, expanding the unevenness of the surface viscosity and the surface current density, and plays a role in changing the reaction rate ratio of micro-convexities and micro-concave parts, and improving the micro-leveling degree.

The present invention also provides a chromium-free electrochemical polishing method using the above solution, and by adjusting process parameters, a good polishing effect can be obtained on nickel-containing (austenite) and nickel-free (martensite) stainless steel materials.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graph showing the corrosion rate at different currents.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The invention provides a chromium-free electrochemical polishing solution. The raw materials include analytically pure phosphoric acid _{H3PO4 ,} sulfuric acid _{H2SO4 and glycerol C3H8O3 . The} raw _{material addition amounts are H3PO4: 400ml/l-500ml/l; H2SO4: 200ml/l-400ml/l; C3H8O3 : 160ml / l - 320ml} /l.

This solution requires regular maintenance. Sodium hexametaphosphate and EDTA are used as shielding agents. The acid-base titration method is used to continuously titrate and analyze phosphoric acid and sulfuric acid. Supplements are added according to the analysis results, and propylene glycol is added in proportion at the same time. After a full cycle of replenishment, the entire tank of solution is replaced.

The present invention provides a chromium-free electrochemical treatment method, which is also applicable to an electrochemical polishing method for austenitic and martensitic stainless steel materials, and obtains a good polishing effect on the stainless steel surface. The specific steps are as follows:

1. Prepare some parts or samples;

2. Prepare chromium-free electrochemical polishing solution;

3. Carry out electrochemical polishing process, the specific process is: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 3% to 5% mass concentration of metal cleaning agent to clean for 3 to 5 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 70℃～80℃, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 30A/ ^dm2 ～40A/ ^dm2 for polishing, and the polishing time is 1min～3min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 30 to 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 30min to 60min.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright white.

Embodiment 1:

Parts or samples: 1Cr18Ni9Ti and 0Cr18Ti10Ti stainless steel materials.

The raw materials and proportions of the solution are as follows: phosphoric acid (H ₃ PO ₄ analytical grade): 450 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 350 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 200 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 3% metal cleaning agent to clean for 5 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 75°C, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 30A/ ^dm2 , and the polishing time is 2min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 60 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright white.

Embodiment 2:

Parts or samples: 2Cr13 stainless steel material.

The raw materials and proportions of the solution are as follows: phosphoric acid (H ₃ PO ₄ analytical grade): 450 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 350 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 200 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 5% metal cleaning agent to clean for 3 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 80℃, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 40A/ ^dm2 , and the polishing time is 3min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 50 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright milky white to bright white.

Embodiment 3:

Parts or samples: 0Cr18Ti10Ti stainless steel material.

The raw materials and proportions of the solution are as follows: phosphoric acid (H ₃ PO ₄ analytical grade): 500 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 200 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 300 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 4% metal cleaning agent to clean for 4 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 80°C, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 35A/ ^dm2 , and the polishing time is 1min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 30 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 30 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright white.

Embodiment 4:

Parts or samples: 2Cr13 stainless steel material.

The raw materials and proportions of the solution are as follows: phosphoric acid (H ₃ PO ₄ analytical grade): 400 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 400 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 200 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 5% metal cleaning agent to clean for 3 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 70℃, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 30A/ ^dm2 , and the polishing time is 2min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 60 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright milky white to bright white.

Embodiment 5:

Parts or samples: 1Cr18Ni9Ti and 0Cr18Ti10Ti stainless steel materials.

The solution selected raw materials and proportions: phosphoric acid (H ₃ PO ₄ analytical grade): 500 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 340 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 160 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 3% metal cleaning agent to clean for 5 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 80°C, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 40A/ ^dm2 , and the polishing time is 1min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 60 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright white.

Embodiment 6:

Parts or samples: 1Cr18Ni9Ti and 0Cr18Ti10Ti stainless steel materials.

The solution selected raw materials and proportions: phosphoric acid (H ₃ PO ₄ analytical grade): 450 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 230 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 320 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 3% metal cleaning agent to clean for 5 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 70℃, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 30A/ ^dm2 , and the polishing time is 3min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 60 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright white.

Embodiment 7:

Parts or samples: 2Cr13 stainless steel material.

The raw materials and proportions of the solution are as follows: phosphoric acid (H ₃ PO ₄ analytical grade): 400 ml/L; sulfuric acid (H ₂ SO ₄ analytical grade): 400 ml/L; propylene glycol (C ₃ H ₈ O ₃ analytical grade): 200 ml/L.

Electrochemical polishing process: ultrasonic degreasing → hanging → electrochemical polishing → passivation → drying

1) Ultrasonic degreasing: Use a pure water solution containing 5% metal cleaning agent to clean for 3 minutes; after cleaning, rinse the ultrasonic solution with running tap water;

2) Hanging: Use stainless steel or copper hangers to hang the workpiece to be polished securely;

3) Electrochemical polishing: Heat the polishing solution to 75°C, immerse the firmly mounted workpiece and the hanger into the polishing solution, hang it on the anode, the cathode is a stainless steel tank, adjust the current density to 35A/ ^dm2 , and the polishing time is 1min. After polishing, rinse the surface solution of the parts or samples with running water.

4) Immerse the cleaned parts or samples in a 1:1 nitric acid solution for passivation for 60 minutes, and then rinse with running water.

5) After cleaning, hang it in the oven to dry for 60 minutes.

Polishing results:

After polishing, the surface of the part or sample is uniformly bright milky white to bright white.

Comparative Example

The 2Cr13 stainless steel material is placed in a nickel-containing electrochemical polishing solution and electrochemically polished at 80°C and ^a current density of 20-40A/dm2;

The corrosion rates of the comparative example and the embodiment of the present invention at a given polishing temperature (80° C.) and current density were measured, and the results are shown in Table 1 below:

Table 1 Corrosion rate at given polishing temperature (80℃) and current density

It can be seen from the above table that under the same reaction conditions, the present invention has a stable corrosion rate when polishing, and can perform precision milling of stainless steel parts.

1. Verify the effect of glycerol on polishing effect

According to the actual polishing effect, the influence of the propylene glycol component content on polishing was determined. The results are shown in Table 2 below.

Table 2 Polishing solution component content determination test table

It can be seen from Table 2 that for 1Cr18Ni9Ti stainless steel, the change of the content of the three components has little effect on the polishing effect; for 2Cr13 stainless steel, the change of the additive content has a significant effect on the polishing effect. When the glycerol content is greater than 160ml/l, a better polishing effect is obtained.

2. Influence of polishing parameters on polishing effect

Polishing tests were conducted on screw parts. By adjusting the polishing parameters on different materials (1Cr18Ni9Ti, 2Cr13), good polishing effects were achieved on nickel-containing and nickel-free stainless steels. The results are shown in Tables 4 and 5 below.

Table 4 1Cr18Ni9Ti polishing operation conditions test table

According to Table 4, it can be seen that for 1Cr18Ni9Ti, 1Cr18Ni9Ti and austenitic stainless steel, after polishing under the conditions of current density: 20A/dm2~40A/dm2; temperature: 60℃~80℃; polishing time: 1min~3min, it can be seen that the method of the present invention has good polishing performance, both the appearance quality and the thread quality pass rate are very high, and the changes in polishing temperature, current and time have little effect on the polishing quality.

Table 5 2Cr13 polishing operation conditions test table

It can be seen from Table 5 that for 2Cr13, 2Cr13 and martensitic stainless steel, after polishing under the conditions of current density: 30A/dm2~40A/dm2; temperature: 70℃~80℃; polishing time: 1min~3min, satisfactory polishing results can be achieved within the surface temperature, current density and polishing time.

3. Determination of polishing corrosion rate

The polishing corrosion rate is calculated by thickness measurement method. Under given temperature (80℃) and current conditions, the sample is polished for 10 minutes, the thickness change of the marked point before and after polishing is measured, and the polishing corrosion rate is calculated. The test results are shown in Table 6 and Figure 1.

Table 4 Corrosion rate determination table

Note: δ-marking point thickness; Δ-marking point corrosion thickness; Υ-marking point corrosion rate; υaverage-average corrosion rate under the temperature condition;

It can be seen from Table 6 and Figure 1 that under given temperature conditions, the corrosion rates of the two steel parts increase with the increase of current. Among them, the nickel-containing (1Cr18Ni9Ti) is relatively stable, and the nickel-free (2Cr13) is slightly larger than the nickel-containing (1Cr18Ni9Ti). The slopes of the two are close, both less than 1, and the corrosion rates are stable and close, which is conducive to production control.

4. Conclusion

Determine the composition of the electrochemical polishing solution as:

H ₃ PO ₄ ：400ml/l～500ml/l

_H2SO4 : 200ml/ _l ～400ml/l

Glycerol: 160ml/l～320ml/l

Determine the process parameters for different types of stainless steel parts:

Table 7 Polishing process parameters for different materials

Claims (10)

1. A chromium-free electrochemical polishing solution, characterized in that the raw materials include phosphoric acid, sulfuric acid and glycerol, the addition amount _{of H3PO4} is: 400ml/l~500ml/l; the addition amount _{of H2SO4} is: 200ml/l~400ml/l; _the addition amount _{of C3H8O3 is} : 160ml/l~320ml/l. 2. A chromium-free electrochemical polishing solution according to claim 1, characterized in that phosphoric acid, sulfuric acid and glycerol are all of analytical grade. 3. A chromium-free electrochemical treatment method, characterized in that the specific steps are as follows: S1 preparing the chromium-free electrochemical polishing solution according to claim 1; S2 uses the pretreated workpiece to be polished as an anode and the electrochemical reaction tank as a cathode, immerses the workpiece to be polished in a chromium-free electrochemical polishing solution, adjusts the reaction temperature and current density, and performs electrochemical polishing; S3 passivates and dries the polished workpiece to obtain a polished workpiece. 4. A chromium-free electrochemical treatment method according to claim 3, characterized in that, in S2, the pretreatment is ultrasonic degreasing of the workpiece to be polished, specifically, the workpiece to be polished is ultrasonically cleaned for 3min to 5min using a pure water solution containing a 3% to 5% concentration of a metal cleaning agent. 5. A chromium-free electrochemical treatment method according to claim 3, characterized in that, in S2, the pretreated workpiece to be polished is hung on a hanger and then immersed in a chromium-free electrochemical polishing solution, and both the workpiece to be polished and the hanger are immersed in the chromium-free electrochemical polishing solution. 6. A chromium-free electrochemical treatment method according to claim 3, characterized in that, in S2, the reaction temperature is 70°C to 80°C. 7 . The chromium-free electrochemical treatment method according to claim 3 , characterized in that in S2 , the current density is 30 A/dm ² to 40 A/dm ² . 8. A chromium-free electrochemical treatment method according to claim 3, characterized in that, in S2, the time for electrochemical polishing is 1 min to 3 min. 9. A chromium-free electrochemical treatment method according to claim 3, characterized in that, in S3, the passivation is to immerse the polished workpiece in a 1:1 nitric acid solution for passivation for 30 minutes to 60 minutes. 10. The chromium-free electrochemical treatment method according to claim 3, characterized in that in S3, the drying is drying for 30 minutes to 60 minutes.

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