35CrMnSi alloy steel phosphating solution, preparation process and alloy steel medium-temperature phosphating pretreatment process

Abstract

The invention relates to the technical field of metal material surface treatment, in particular to a 35CrMnSi alloy steel phosphating solution, a preparation process and an alloy steel medium-temperature phosphating pretreatment process, firstly, the 35CrMnSi alloy steel phosphating solution is prepared, 35CrMnSi alloy steel is pretreated through the prepared 35CrMnSi alloy steel phosphating solution, on the premise that a common medium-temperature phosphating process route is not changed, the 35CrMnSi alloy steel is subjected to phosphating treatment through the prepared 35CrMnSi alloy steel phosphating solution, and then the 35CrMnSi alloy steel is subjected to phosphating treatment through the prepared 35CrMnSi alloy steel phosphating solution. According to the method, the adverse effects of various metal elements and high carbon content in the 35CrMnSi alloy steel on chemical conversion in the prior art are reduced, compactness, completeness and uniformity of a phosphating film on the surface of a base material are guaranteed, and the technical problem that the consistency and stability of the phosphating film of the 35CrMnSi alloy steel are difficult to control is solved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material surface treatment, and in particular to a 35CrMnSi alloy steel phosphating solution, a preparation process and a medium-temperature phosphating pretreatment process for the alloy steel. Background Art

[0002] With the development of industry, the demand for high-strength and high-wear-resistant alloy steels is increasing. As a low-alloy ultra-high-strength steel containing metal elements such as chromium (Cr), manganese (Mn), and silicon (Si), 35CrMnSi has excellent properties such as high strength, high toughness, good hardenability, and weldability, and is widely used in the aerospace field and the defense military industry. However, due to the presence of multiple alloying elements, 35CrMnSi alloy steel is more sensitive to corrosion in specific environments, which reduces its service life and overall performance. A series of pre-treatment processes are required to improve the oxidation resistance and corrosion resistance of the alloy steel.

[0003] At present, phosphating is a common process to improve the corrosion resistance of steel surface. The traditional phosphating process removes oxides, dirt and grease on the surface of steel by pickling or alkali washing, and then immerses the neutralized steel in a phosphorus-containing bath to chemically react with the steel surface to form a phosphating layer. The phosphating process usually needs to be carried out within a specific temperature range to ensure the best treatment effect.

[0004] For 35CrMnSi alloy steel, it is more difficult to control the phosphating film formation, because different treatment formulas and different process parameters will lead to changes in the organizational structure, thickness and quality of the coating; medium-temperature phosphating pre-treatment involves a complex chemical reaction process, and 35CrMnSi alloy steel contains a variety of metal elements. These metal elements will affect the formation and quality of the coating, making the consistency and stability of the coating difficult to control. Summary of the invention

[0005] The purpose of the present invention is to provide a 35CrMnSi alloy steel phosphating solution, a preparation process and a medium-temperature phosphating pretreatment process for alloy steel, aiming to solve the technical problem in the prior art that 35CrMnSi alloy steel contains multiple metal elements, which will affect the formation and quality of the coating, making the consistency and stability of the coating difficult to control.

[0006] To achieve the above purpose, the present invention adopts a 35CrMnSi alloy steel phosphating solution, which includes 4% to 7% of zinc dihydrogen phosphate, 16% to 20% of zinc nitrate, 2% to 3% of Marib salt, 0.2% to 0.6% of sodium fluorosilicate, 0.3% to 0.5% of citric acid, 0.1% to 0.15% of ferric nitrate, 0.2% to 0.25% of sodium m-nitrobenzene sulfonate and 0.25% to 0.3% of nickel nitrate, and the balance is water.

[0007] The present invention also provides a process for preparing alloy steel phosphating solution, which is used to prepare the 35CrMnSi alloy steel phosphating solution as described above.

[0008] The following steps are involved:

[0009] Step 1: Add 500 ml of pure water into a 1000 ml process tank and start magnetic stirring;

[0010] Step 2: Add zinc dihydrogen phosphate, zinc nitrate and Marif salt into the process tank in proportion and order, and continue stirring until the materials are completely dissolved;

[0011] Step 3: Add sodium fluorosilicate, citric acid, ferric nitrate, sodium m-nitrobenzene sulfonate and nickel nitrate into the process tank in proportion and in order, and stir until the materials are completely dissolved to obtain the 35CrMnSi alloy steel phosphating solution.

[0012] Wherein, in step 1, the stirring speed is 500 rpm.

[0013] The present invention also provides a medium-temperature phosphating pretreatment process for alloy steel, using the 35CrMnSi alloy steel phosphating solution prepared by the above-mentioned 35CrMnSi alloy steel phosphating solution preparation process,

[0014] The following steps are involved:

[0015] Step 1: Degreasing: Add 500ml of pure water to a 1L beaker, use a water bath to heat the water to 55°C, then add a degreasing agent and a surfactant, use a glass rod to stir the tank liquid manually until the material is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total alkalinity to 4.0-7.0pt, the temperature to 50-60°C, use tweezers to clamp the product, put it in the beaker and move it up and down 15 to 20 times, then completely immerse the product in the solution and let it stand for 15 minutes;

[0016] Step 2: Hot water washing: Add pure water to the working liquid level in a 1L beaker, use a water bath to heat the water to 55°C, then use tweezers to hold the degreased product, put it in the beaker and move it up and down 10 to 15 times, then completely immerse the product in the solution and let it stand for 30 seconds;

[0017] Step 3: Wash with water at room temperature: Add pure water to a 1L beaker to the working liquid level, keep the temperature at room temperature, use tweezers to clamp the product after hot water washing, put it into the beaker and move it up and down 10 to 15 times, then immerse the product completely in the solution and let it stand for 30 seconds;

[0018] Step 4: Activation: Add 500ml of pure water to a 1L beaker, then add 25g of activator, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 5.0-7.0pt. The temperature is room temperature. Use tweezers to hold the product washed with room temperature water, put it into the beaker and move it up and down 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes;

[0019] Step 5: Repeat step 3 to wash with water at room temperature;

[0020] Step 6: Surface adjustment: Add 500ml of pure water and 3g of surface adjustment agent to a 1L beaker, stir the materials with magnetic stirring until they are completely dissolved, then add pure water to adjust the liquid level to the working level, and adjust the total acidity to 3.5-7.0pt. The temperature is room temperature. Use tweezers to hold the product washed in step 5, put it in the beaker and move it up and down for 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes.

[0021] Step 7, phosphating: add 500ml pure water to a 1L beaker, use a water bath heating box to heat the water to 55°C, then add 85g of 35CrMnSi alloy steel phosphating solution, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 25-35pt, the free acid to 1.2-2.5pt, the accelerator concentration to 2.5-4.0pt, and the acid ratio to 14-20; during production, use tweezers to clamp the surface-adjusted product, put it in the beaker and move it up and down 15 to 20 times, and then immerse the product completely in the solution and let it stand for 8 minutes;

[0022] Step 8. Repeat step 3 to wash with water at room temperature and then use an electric heating box to dry the product.

[0023] In step 1, the amounts of degreasing agent and surfactant added are 40 g and 10 g respectively. After degreasing, the degreasing condition of the product surface is checked. The product surface is required to be completely degreased and visually the product surface can be completely wetted by water.

[0024] In step 2, after the hot water washing is completed, check the cleaning condition of the product surface. It is required that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤2000μs / cm.

[0025] In step three, after the normal temperature water washing is completed, the cleaning condition of the product surface is checked. It is required that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤500μs / cm.

[0026] In step 4, after activation is completed, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete;

[0027] In step 5, after the water washing is completed, check the surface cleaning condition of the product. The surface of the product should be smooth, rust-free, with a uniform and complete liquid film, and the dripping water conductivity ≤500μs / cm;

[0028] In step six, after the surface adjustment is completed, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete.

[0029] In step 7, after phosphating, check the surface condition of the product. The phosphating film should be gray, complete, continuous, and dense, without serious floating dust and yellowing defects.

[0030] In step eight:

[0031] After washing, check the surface cleaning condition of the product. The surface of the product should be smooth, rust-free, with a uniform and complete phosphate film, and the dripping water conductivity should be ≤30μs / cm;

[0032] The temperature and time of drying the product in an electric heating box are 110-120°C and 10-15 minutes respectively.

[0033] The invention discloses a 35CrMnSi alloy steel phosphating solution, a preparation process and a medium-temperature phosphating pretreatment process for alloy steel. The 35CrMnSi alloy steel phosphating solution is firstly prepared by optimizing a formula, and the 35CrMnSi alloy steel is pretreated by the prepared 35CrMnSi alloy steel phosphating solution. Without changing the common medium-temperature phosphating process route, the technical problem that the 35CrMnSi alloy steel contains a variety of metal elements in the prior art, and these metal elements affect the formation and quality of the coating, making the consistency and stability of the coating difficult to control is solved; the adverse effects of the 35CrMnSi alloy steel containing a variety of metal elements and a high carbon content on chemical conversion in the prior art are reduced, and the density, integrity and uniformity of the phosphating film on the surface of the substrate are ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a schematic diagram of the SEM morphology of the phosphating film of the present invention.

[0036] Figure 2 It is a schematic diagram of the energy spectrum analysis and P value of the phosphating film of the present invention. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0038] See also Figure 1 and Figure 2 ,in Figure 1 Schematic diagram of the SEM morphology of the phosphating film of the present invention, Figure 2 It is a schematic diagram of the energy spectrum analysis and P value of the phosphating film of the present invention.

[0039] The invention provides a 35CrMnSi alloy steel phosphating solution, which comprises 4% to 7% of zinc dihydrogen phosphate, 16% to 20% of zinc nitrate, 2% to 3% of Marib salt, 0.2% to 0.6% of sodium fluorosilicate, 0.3% to 0.5% of citric acid, 0.1% to 0.15% of ferric nitrate, 0.2% to 0.25% of sodium m-nitrobenzene sulfonate and 0.25% to 0.3% of nickel nitrate, and the balance is water.

[0040] The present invention also provides a process for preparing alloy steel phosphating solution, which is used to prepare the 35CrMnSi alloy steel phosphating solution as described above.

[0041] The following steps are involved:

[0042] Step 1: Add 500 ml of pure water into a 1000 ml process tank and start magnetic stirring at a stirring speed of 500 rpm;

[0043] Step 2: Add 50g of zinc dihydrogen phosphate, 180g of zinc nitrate and 20g of Marif salt into the process tank in proportion and order, and continue stirring until the materials are completely dissolved. The stirring speed is 500rpm;

[0044] Step 3: Take 5g of sodium fluorosilicate, 3g of citric acid, 1.5g of ferric nitrate, 2g of sodium m-nitrobenzene sulfonate and 3g of nickel nitrate in proportion and add them into the process tank; stir until the materials are completely dissolved to obtain the 35CrMnSi alloy steel phosphating solution.

[0045] During this process, pay attention to the order and proportion of addition to avoid precipitation and crystallization.

[0046] from Figure 1 It can be seen that the phosphating film is uniform and dense, the crystal shape is columnar, the crystal size is 2-6um, and the phosphating film completely covers the substrate, which can effectively prevent the corrosion of the corrosive medium on the substrate, thereby improving the corrosion resistance of the substrate metal.

[0047] from Figure 2Energy spectrum analysis of the phosphating film shows that the main components of the phosphating film are zinc phosphate and zinc iron phosphate; zinc phosphate has good corrosion resistance, and zinc iron phosphate is beneficial to improving the overall corrosion resistance of the film due to its good stability; at the same time, by immersing the sample in 3% NaCl solution for 1 hour, there is no rust on the surface of the sample. It can be seen that the corrosion protection performance of the steel substrate is significantly improved after phosphating treatment.

[0048] In step 1, the stirring speed is 500 rpm.

[0049] The present invention also provides a medium-temperature phosphating pretreatment process for alloy steel, using the 35CrMnSi alloy steel phosphating solution prepared by the above-mentioned 35CrMnSi alloy steel phosphating solution preparation process,

[0050] The following steps are involved:

[0051] Step 1: Degreasing: Add 500ml of pure water to a 1L beaker, use a water bath to heat the water to 55°C, then add 40g of degreasing agent and 10g of surfactant, use a glass rod to stir the tank liquid manually until the material is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total alkalinity to 4.0~7.0pt, the temperature to 50~60°C, use tweezers to clamp the product, put it in the beaker and move it up and down 15 to 20 times, then immerse the product completely in the solution and let it stand for 15 minutes; after degreasing is completed, check the degreasing condition of the product surface, the product surface must be completely degreased, and the product surface must be completely wetted by water.

[0052] Step 2: Hot water washing: Add pure water to the working liquid level in a 1L beaker, use a water bath to heat the water to 55°C, then use tweezers to clamp the degreased product, put it into the beaker and move it up and down 10 to 15 times, then immerse the product completely in the solution and let it stand for 30 seconds; after the hot water washing is completed, check the cleaning condition of the product surface, requiring that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤2000μs / cm.

[0053] Step 3: Wash with water at room temperature: Add pure water to a 1L beaker to the working liquid level and keep the temperature at room temperature. Use tweezers to clamp the product after hot water washing, put it into the beaker and move it up and down for 10 to 15 times, then immerse the product completely in the solution and let it stand for 30 seconds; after washing with water at room temperature, check the cleaning condition of the product surface. It is required that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤500μs / cm.

[0054] Step 4. Activation: Add 500ml of pure water to a 1L beaker, then add 25g of activator, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 5.0-7.0pt. The temperature is room temperature. Use tweezers to clamp the product washed with room temperature water, put it into the beaker and move it up and down 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes; after activation, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete.

[0055] Step 5. Repeat step 3 to wash at room temperature. After washing at room temperature, check the surface cleaning condition of the product. The surface of the product should be smooth, rust-free, with a uniform and complete liquid film, and the dripping water conductivity ≤500μs / cm.

[0056] Step 6. Surface conditioning: Add 500ml of pure water and 3g of surface conditioning agent to a 1L beaker, use magnetic stirring to stir the materials until they are completely dissolved, then add pure water to adjust the liquid level to the working level, and adjust the total acidity to 3.5-7.0pt. The temperature is room temperature. Use tweezers to clamp the product washed in step 5, put it into the beaker and move it up and down for 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes. After the surface conditioning is completed, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete.

[0057] Step 7, phosphating: add 500ml pure water to a 1L beaker, use a water bath heating box to heat the water to 55℃, then add 85g 35CrMnSi alloy steel phosphating solution, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 25-35pt, the free acid to 1.2-2.5pt, the accelerator concentration to 2.5-4.0pt, and the acid ratio to 14-20; during production, use tweezers to clamp the surface-adjusted product, put it in a beaker and move it up and down 15 to 20 times, then immerse the product completely in the solution and let it stand for 8 minutes; after phosphating, check the surface condition of the product. The phosphating film should be gray, complete, continuous, and fine, without serious floating dust or yellowing defects.

[0058] Step 8: Repeat step 3 to wash with water at room temperature and then use an electric heating box to dry the product;

[0059] In step eight, the drying temperature is 110-120°C for 10-15 minutes. After the room temperature water washing is completed, the surface cleaning condition of the product is checked. The surface of the product should be smooth, rust-free, with a uniform and complete phosphate film, and the dripping water conductivity ≤30μs / cm.

[0060] The 35CrMnSi alloy steel phosphating solution, preparation process and medium-temperature phosphating pretreatment process of the alloy steel of the present invention are used. First, the 35CrMnSi alloy steel phosphating solution is prepared by optimizing the formula, and the 35CrMnSi alloy steel is pre-treated by the prepared 35CrMnSi alloy steel phosphating solution. Without changing the common medium-temperature phosphating process route, the technical problem that the 35CrMnSi alloy steel in the prior art contains a variety of metal elements, and these metal elements affect the formation and quality of the coating, making the consistency and stability of the coating difficult to control is solved; the adverse effects of the 35CrMnSi alloy steel in the prior art containing a variety of metal elements and a high carbon content on chemical conversion are reduced, and the density, integrity and uniformity of the phosphating film on the surface of the substrate are ensured.

[0061] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A 35CrMnSi alloy steel phosphating solution, characterized in that: The invention comprises 4% to 7% zinc dihydrogen phosphate, 16% to 20% zinc nitrate, 2% to 3% Marib salt, 0.2% to 0.6% sodium fluorosilicate, 0.3% to 0.5% citric acid, 0.1% to 0.15% ferric nitrate, 0.2% to 0.25% sodium m-nitrobenzene sulfonate and 0.25% to 0.3% nickel nitrate, and the balance is water.

2. A process for preparing alloy steel phosphating solution, used for preparing the 35CrMnSi alloy steel phosphating solution as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Add 500 ml of pure water into a 1000 ml process tank and start magnetic stirring; Step 2: Add zinc dihydrogen phosphate, zinc nitrate and Marif salt into the process tank in proportion and order, and continue stirring until the materials are completely dissolved; Step 3: Add sodium fluorosilicate, citric acid, ferric nitrate, sodium m-nitrobenzene sulfonate and nickel nitrate into the process tank in proportion and in order, and stir until the materials are completely dissolved to obtain the 35CrMnSi alloy steel phosphating solution.

3. The process for preparing phosphating solution for 35CrMnSi alloy steel according to claim 2, characterized in that: In step 1, the stirring speed is 500 rpm.

4. A medium-temperature phosphating pretreatment process for alloy steel, using the 35CrMnSi alloy steel phosphating solution prepared by the 35CrMnSi alloy steel phosphating solution preparation process as claimed in claim 3, characterized in that: The following steps are involved: Step 1: Degreasing: Add 500ml of pure water to a 1L beaker, use a water bath to heat the water to 55°C, then add a degreasing agent and a surfactant, use a glass rod to stir the tank liquid manually until the material is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total alkalinity to 4.0-7.0pt, the temperature to 50-60°C, use tweezers to clamp the product, put it in the beaker and move it up and down 15 to 20 times, then completely immerse the product in the solution and let it stand for 15 minutes; Step 2: Hot water washing: Add pure water to the working liquid level in a 1L beaker, use a water bath to heat the water to 55°C, then use tweezers to hold the degreased product, put it in the beaker and move it up and down 10 to 15 times, then completely immerse the product in the solution and let it stand for 30 seconds; Step 3: Wash with water at room temperature: Add pure water to a 1L beaker to the working liquid level, keep the temperature at room temperature, use tweezers to clamp the product after hot water washing, put it into the beaker and move it up and down 10 to 15 times, then immerse the product completely in the solution and let it stand for 30 seconds; Step 4: Activation: Add 500ml of pure water to a 1L beaker, then add 25g of activator, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 5.0-7.0pt. The temperature is room temperature. Use tweezers to hold the product washed with room temperature water, put it into the beaker and move it up and down 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes; Step 5: Repeat step 3 to wash with water at room temperature; Step 6: Surface adjustment: Add 500ml of pure water and 3g of surface adjustment agent to a 1L beaker, stir the materials with magnetic stirring until they are completely dissolved, then add pure water to adjust the liquid level to the working level, and adjust the total acidity to 3.5-7.0pt. The temperature is room temperature. Use tweezers to hold the product washed in step 5, put it in the beaker and move it up and down for 15 to 20 times, then immerse the product completely in the solution and let it stand for 1.5 minutes. Step 7, phosphating: add 500ml pure water to a 1L beaker, use a water bath heating box to heat the water to 55°C, then add 85g of 35CrMnSi alloy steel phosphating solution, use magnetic stirring to stir the material until it is completely dissolved, add pure water to adjust the liquid level to the working level, and adjust the total acidity to 25-35pt, the free acid to 1.2-2.5pt, the accelerator concentration to 2.5-4.0pt, and the acid ratio to 14-20; during production, use tweezers to clamp the surface-adjusted product, put it in the beaker and move it up and down 15 to 20 times, and then immerse the product completely in the solution and let it stand for 8 minutes; Step 8. Repeat step 3 to wash with water at room temperature and then use an electric heating box to dry the product.

5. The medium-temperature phosphating pretreatment process for alloy steel according to claim 4, characterized in that: In step 1, the amounts of degreasing agent and surfactant added are 40 g and 10 g respectively. After degreasing, the degreasing condition of the product surface is checked. The product surface is required to be completely degreased and visually the product surface can be completely wetted by water.

6. The medium-temperature phosphating pretreatment process for alloy steel according to claim 5, characterized in that: In step 2, after the hot water washing is completed, check the cleaning condition of the product surface. It is required that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤2000μs / cm.

7. The medium-temperature phosphating pretreatment process for alloy steel according to claim 6, characterized in that: In step three, after the normal temperature water washing is completed, the cleaning condition of the product surface is checked. It is required that the product surface can be completely wetted by water visually, and the dripping water conductivity is ≤500μs / cm.

8. The medium-temperature phosphating pretreatment process for alloy steel according to claim 7, characterized in that: In step 4, after activation is completed, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete; In step 5, after the water washing is completed, check the surface cleaning condition of the product. The surface of the product should be smooth, rust-free, with a uniform and complete liquid film, and the dripping water conductivity ≤500μs / cm; In step six, after the surface adjustment is completed, check the surface condition of the product. The surface of the product should be smooth, rust-free, and the liquid film should be uniform and complete.

9. The medium-temperature phosphating pretreatment process for alloy steel according to claim 8, characterized in that: In step 7, after phosphating, check the surface condition of the product. The phosphating film should be gray, complete, continuous, and dense, without serious floating dust and yellowing defects. In step eight: After washing, check the surface cleaning condition of the product. The surface of the product should be smooth, rust-free, with a uniform and complete phosphate film, and the dripping water conductivity should be ≤30μs / cm; The temperature and time of drying the product in an electric heating box are 110-120°C and 10-15 minutes respectively.

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