Magnesium alloy die casting dust removal method and dust removal agent for passivation

Abstract

The invention discloses a magnesium alloy die casting dust removal method which comprises the following steps: firstly, dissolving sodium hydroxide, potassium hydroxide, sodium carbonate, sodium nitrate and sodium citrate in water to prepare a dust removal agent, then putting the dust removal agent into a dust removal tank, heating the dust removal tank, finally immersing the magnesium alloy die casting to be subjected to dust removal into the dust removal agent for 1-5 minutes, and finally taking out and cleaning. And sodium citrate is supplemented into the ash removal groove in stages in the continuous ash removal operation period of the magnesium alloy die casting. The invention has the remarkable effects of longer service life and low use cost; the ash removal time is short and the efficiency is high; the use temperature is low, energy consumption is low, and volatilization is little.

Description

Technical Field

[0001] The invention relates to the surface treatment of materials, in particular to a chemical treatment method for the surface of materials and treatment raw materials. Background Art

[0002] After the magnesium alloy die castings are pickled to remove the surface release agent and oxides, a layer of insoluble black ash composed of organic acid salts such as magnesium, aluminum, manganese, and zinc will be produced on the surface. These black ashes need to be treated with chemical methods before passivation. The magnesium alloy die casting deashing agents currently circulating on the market usually need to be heated to above 75°C (such as Gu-M204 deashing agent, JT-JB6 deashing agent) to achieve a good deashing effect. The higher use temperature will not only increase energy consumption, but also cause the solution evaporation to increase, pollute the workshop environment, and increase the cost of use. Summary of the invention

[0003] The invention provides a magnesium alloy die casting deashing method and a magnesium alloy die casting deashing agent which can be used under relatively reduced temperature (55-65°C).

[0004] The dust removal methods used are:

[0005] A method for removing ash from magnesium alloy die castings, the key of which is to follow the following steps:

[0006] Step 1: Dissolve sodium hydroxide, potassium hydroxide, sodium carbonate, sodium nitrate and sodium citrate in water to prepare a deashing agent, wherein:

[0007] The concentration of sodium hydroxide is: 40-50g / l;

[0008] The concentration of potassium hydroxide is: 40-60g / l;

[0009] The concentration of sodium carbonate is: 10-20g / l;

[0010] The concentration of sodium nitrate is: 10-20g / l;

[0011] The concentration of sodium citrate is: 0.1-0.2g / l;

[0012] Step 2: Add the deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 55-65℃:

[0013] Step 3: Immerse the magnesium alloy die casting to be deashed in the deashing agent for 1-5 minutes, and finally take it out and wash it;

[0014] Step 4: Repeat step 3 to perform continuous ash removal operation on the magnesium alloy die castings, during which sodium citrate is periodically added to the ash removal tank.

[0015] The deashing agent used is: in the deashing agent: the concentration of sodium hydroxide is: 40-50g / l; the concentration of potassium hydroxide is: 40-60g / l; the concentration of sodium carbonate is: 10-20g / l; the concentration of sodium nitrate is: 10-20g / l; the concentration of sodium citrate is: 0.1-0.2g / l.

[0016] The process temperature of the present invention only needs to be 55-65°C, which reduces energy consumption, reduces volatilization, and reduces the cost of magnesium alloy deashing; the present invention uses a strong alkaline solution as a carrier to prevent the magnesium alloy matrix from being corroded; the added sodium nitrate is an activator, and ammonium citrate is a coordination agent to maintain the balance of anions and cations in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1a This is a photograph of the appearance of the workpiece before dust removal on the second day using the method of Example 5;

[0018] Figure 1b This is a photograph of the appearance of the workpiece after deashing using the method of Example 5 on the second day;

[0019] Figure 2a This is a photograph of the appearance of the workpiece before dust removal on the 10th day using the method of Example 5;

[0020] Figure 2b This is a photograph of the appearance of the workpiece after deashing using the method of Example 5 on the 10th day;

[0021] Figure 3a This is a photograph of the appearance of the workpiece before deashing using the method of Example 5 on the 20th day;

[0022] Figure 3b This is a photograph of the appearance of the workpiece after deashing using the method of Example 5 on the 20th day;

[0023] Figure 4a This is a photograph of the appearance of the workpiece before deashing on the 120th day using the method of Example 5;

[0024] Figure 4b This is a photograph of the appearance of the workpiece after deashing using the method of Example 5 on the 120th day;

[0025] Figure 5 This is a photo of the appearance of the workpiece after deashing on the 20th day using the method of comparative test 1;

[0026] Figure 6a This is a photo of the appearance of the workpiece after low-temperature deashing using the commercially available Gu-M204 deashing agent on the first day;

[0027] Figure 6bThis is a photo of the appearance of the workpiece after high-temperature deashing on the first day using the commercially available Gu-M204 deashing agent;

[0028] Figure 7a This is a photo of the appearance of the workpiece after low-temperature deashing using the commercially available JT-JB6 deashing agent on the first day;

[0029] Figure 7b This is a photo of the appearance of the workpiece after high-temperature deashing using the commercially available JT-JB6 deashing agent on the first day;

[0030] Figure 8 This is a photo of the appearance of the workpiece after high-temperature deashing on the 50th day using the commercially available JT-JB6 deashing agent. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with embodiments and drawings.

[0032] Embodiment 1:

[0033] A deashing agent for passivation of magnesium alloy die castings, comprising the following raw materials: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium nitrate, and water;

[0034] The concentration of each raw material in the deashing agent is shown in Table 1:

[0035]

[0036] Embodiment 4:

[0037] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0038] Step 1, dissolving sodium hydroxide, potassium hydroxide, sodium carbonate and sodium nitrate in water to prepare deashing agents according to Examples 1, 2 and 3 respectively;

[0039] Step 2: Add the deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 55-65℃:

[0040] Step 3: Immerse the magnesium alloy die casting to be deashed in the deashing agent for 1-5 minutes, and finally take it out and wash it;

[0041] Step 4: Repeat step 3 to perform continuous ash removal operation on the magnesium alloy die castings, during which sodium citrate is periodically added to the ash removal tank.

[0042] Embodiment 5:

[0043] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0044] Step 1, dissolving sodium hydroxide, potassium hydroxide, sodium carbonate and sodium nitrate in water to prepare a deashing agent according to Example 3;

[0045] Step 2: Pour 500L of deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 55-65℃:

[0046] Step 3: immerse the magnesium alloy die-casting to be deashed in the deashing agent, apply 25-30W / l ultrasonic waves to the magnesium alloy die-casting in the deashing tank, soak for 30-70s, then take it out and wash it;

[0047] Step 4: Repeat step 3 to continuously remove ash from magnesium alloy die castings. During this period, sodium citrate is added to the ash removal tank in stages to maintain the concentration of sodium citrate at 0.1-0.2 g / l. The effects of removing black ash from the surface of magnesium alloy die castings before and after the removal of ash on the 2nd, 10th, 20th, and 120th days are recorded. The results are as follows: Figure 1a , Figure 1b , Figure 2a , Figure 2b , Figure 3a , Figure 3b , Figure 4a , Figure 4b shown.

[0048] Comparative test:

[0049] Comparative test 1:

[0050] Step 1, dissolving sodium hydroxide, potassium hydroxide, sodium carbonate and sodium nitrate in water to prepare a deashing agent according to Example 3;

[0051] Step 2: Pour 500L of deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 55-65℃:

[0052] Step 3: Immerse the magnesium alloy die casting to be deashed in a deashing agent for 5 minutes, take it out, and wash it;

[0053] Step 4: Repeat step 3 to continuously remove the ash from the magnesium alloy die castings. During this period, sodium citrate is added to the ash removal tank in stages to maintain the concentration of sodium citrate at 0.1-0.2 g / l. Record the effects of removing the black ash from the surface of the magnesium alloy die castings before and after the ash removal on the 20th day. The results are shown in Figure 5 .

[0054] Comparative test 2:

[0055] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0056] Step 1: Put 500L of commercially available Gu-M204 deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 65-70°C (low temperature):

[0057] Step 2: Immerse the magnesium alloy die casting to be deashed in the deashing agent, soak for 3-5 minutes, then take it out and clean it; record the deashing effect on the first day. Figure 6a .

[0058] Comparative test three:

[0059] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0060] Step 1: Put 500L of commercially available Gu-M204 deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 75-85°C (high temperature):

[0061] Step 2: Immerse the magnesium alloy die casting to be deashed in the deashing agent, soak for 3-5 minutes, then take it out and clean it; record the deashing effect of the appearance on the first day, see Figure 6b .

[0062] Comparative test 4:

[0063] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0064] Step 1: Put 500L of commercially available JT-JB6 deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 65-70℃ (low temperature):

[0065] Step 2: Immerse the magnesium alloy die casting to be deashed in the deashing agent, soak for 3-5 minutes, then take it out and clean it; record the deashing effect on the first day. Figure 7a .

[0066] Comparative test five:

[0067] A method for removing ash from magnesium alloy die castings is carried out according to the following steps:

[0068] Step 1: Put 500L of commercially available JT-JB6 deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 75-85℃ (high temperature):

[0069] Step 2: Immerse the magnesium alloy die casting to be deashed in the deashing agent, soak for 3-5 minutes, then take it out and clean it; record the deashing effect on the first day and the 50th day, and the results are shown in Figure 7b and Figure 8 .

[0070] Effect comparison interpretation:

[0071] from Figure 1a , 1b , 2a, 2b, 3a, 3b, 4a, 4b comparison shows that:

[0072] ①. This method has a good ash removal effect, and there is no black ash residue on the surface of the magnesium alloy die-casting.

[0073] ②. During long-term (120 days) use, the dust removal agent can maintain a long-term dust removal effect.

[0074] from Figure 1b , 2b , 3b, 4b and Figure 5 The comparison shows that:

[0075] Ultrasonic-assisted ash removal can improve the effect of removing black ash from the surface of magnesium alloy die-castings.

[0076] from Figure 6a-6b , Figure 7a-7b The comparison shows that:

[0077] The traditional deashing agent has little deashing effect below 75°C (low temperature); it needs to be heated to above 75°C (high temperature) to achieve a better deashing effect.

[0078] from Figure 1b , 2b , 3b, 4b and Figure 6b , 7b The comparison shows that:

[0079] The optimal ash removal effect of this method is similar to the optimal ash removal effect of the traditional ash removal agent, and both can achieve obvious ash removal effects under suitable conditions.

[0080] from Figure 4b , Figure 6b and Figure 8 The comparison shows that:

[0081] ① After 50 days of continuous use, the traditional Gu-M204 deashing agent has reduced its effect on removing black ash on the surface of high-magnesium alloy die castings, and it is necessary to consider replacing it with a new deashing agent.

[0082] ②. The dust removal agent / dust removal method of the present invention can still achieve excellent removal effect on the black dust on the surface of high-magnesium alloy die castings after continuous use for 120 days, and has a longer service life.

[0083] The ash removal mechanism of this scheme is:

[0084] ① In a hot solution above 55°C, the insoluble magnesium salt produced by pickling on the surface of the magnesium alloy die casting is dissolved in the strong alkaline solution under the activation of nitrate ions, reacts with hydroxide ions to produce slightly soluble magnesium hydroxide precipitates, and is separated from the magnesium alloy matrix under the cavitation and shock impact of ultrasonic waves (the comparison with and without ultrasonic waves is shown in Figures 3 and 4), thereby achieving the purpose of quickly removing black ash;

[0085] ② Due to the slight solubility of magnesium hydroxide, concentration polarization is generated at the solid-liquid interface, which greatly delays the reaction between the strong alkali and the magnesium alloy matrix, resulting in the magnesium alloy matrix being almost not corroded in the strong alkali solution;

[0086] ③. As the concentration of magnesium ions entering the solution increases, hydroxide is consumed, and anions without side effects need to be introduced into the solution system to release the hydroxide. When ammonium citrate is added to a strong alkaline solution, it will immediately decompose and release ammonia, which reacts with magnesium ions to form magnesium citrate precipitate, thereby ensuring the balance of anions and cations in the solution.

[0087] Beneficial effects: The deashing method and deashing agent of the present invention add a ligand to the deashing agent, which can maintain the anion-cation balance in the solution system. Compared with traditional commercially available deashing agents, the deashing agent has a longer service life and a lower cost; the deashing time is short and the efficiency is high; the operating temperature is low, the energy consumption is low, and the volatilization is less.

[0088] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A method for removing ash from magnesium alloy die castings, characterized in that Follow these steps: Step 1: dissolving sodium hydroxide, potassium hydroxide, sodium carbonate, sodium nitrate and sodium citrate in water to prepare a deashing agent, wherein: The concentration of sodium hydroxide is: 40-50g / l; The concentration of potassium hydroxide is: 40-60g / l; The concentration of sodium carbonate is: 10-20g / l; The concentration of sodium nitrate is: 10-20g / l; The concentration of sodium citrate is: 0.1-0.2g / l Step 2: Add the deashing agent into the deashing tank, heat the deashing tank and maintain the temperature at 55-65℃: Step 3: Immerse the magnesium alloy die casting to be deashed in the deashing agent for 1-5 minutes, and finally take it out and wash it; Step 4: Repeat step 3 to perform continuous ash removal operation on the magnesium alloy die castings, during which sodium citrate is periodically added to the ash removal tank.

2. The method for removing ash from magnesium alloy die castings according to claim 1, characterized in that: In the step three, 25-30W / l ultrasonic waves are applied to the magnesium alloy die castings in the ash removal tank, and the magnesium alloy die castings are taken out and cleaned after being immersed for 30-70 seconds.

3. The method for removing ash from magnesium alloy die castings according to claim 1 or 2, characterized in that: In the step 4, sodium citrate is added to the ash removal tank in stages, and the concentration of sodium citrate is maintained at 0.1-0.2 g / l.

4. A deashing agent for passivation of magnesium alloy die castings, characterized in that The raw materials include: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium nitrate, sodium citrate, water; In the deashing agent: The concentration of sodium hydroxide is: 40-50g / l; The concentration of potassium hydroxide is: 40-60g / l; The concentration of sodium carbonate is: 10-20g / l; The concentration of sodium nitrate is: 10-20g / l; The concentration of sodium citrate is: 0.1-0.2g / l.

5. The deashing agent for passivation of magnesium alloy die castings according to claim 4, characterized in that In the deashing agent: The concentration of sodium hydroxide is: 45g / l; The concentration of potassium hydroxide is: 50g / l; The concentration of sodium carbonate is: 15g / l; The concentration of sodium nitrate is: 15g / l; The concentration of sodium citrate is: 0.1-0.2g / l.

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