METHOD FOR PRETREATING MAGNESIUM-ALLOY WASTE MATERIAL

Abstract

A method comprises sorting and removing impurities from magnesium alloy waste material, and cleaning and drying said material, the cleaning being high-pressure rinsing, pickling, and water washing, performed in sequence. The method employs high-pressure rinsing during the pretreatment of magnesium alloy waste material; the cleaning effectiveness is excellent, the effectiveness of the removal of impurities from the surface of the magnesium alloy waste material is much better than in conventional processes, and the amount of clean waste material can exceed 90% of the total amount of processed waste material; the clean magnesium alloy waste material obtained from the pretreatment method may be used as the entire raw materials for casting national-standard alloy ingots, the addition of costly high-purity magnesium is unnecessary, and the amount of alloy raw material that must be added is significantly reduced; during processing, little waste material is lost, costs are low, and efficiency is high.

Claims

1. A method for pretreating magnesium alloy waste material, involving sorting and removing impurities from, cleaning and drying magnesium alloy waste material, wherein the cleaning includes high-pressure cleaning, pickling, and water rinse performed in sequence.

2. The method of claim 1, wherein the pressure of high-pressure cleaning is 5-20 MPa.

3. The method of claim 1, wherein the pressure of high-pressure cleaning is 10-15 MPa.

4. The method of claim 1, wherein the large magnesium alloy waste material is cut into plural smaller pieces of the magnesium alloy waste material before sorted and having impurities removed therefrom.

5. The method of claim 4, wherein the cut magnesium alloy waste material is smaller than 300 mm in all dimensions.

6. The method of claim 1, wherein sorting and removing impurities refers to screening waste with inseparable screws, rubber, or plastic, waste with surface coating, and non-magnesium waste out of the cut waste material.

7. The method of claim 1, wherein the high-pressure cleaning is a primary high-pressure cleaning.

8. The method of claim 1, wherein the high-pressure cleaning includes a primary high-pressure cleaning and a secondary high-pressure cleaning where the magnesium alloy waste material to be treated has its surfaces covered by greasiness or demolding agents,

9. The method of claim 1, wherein the cleaning liquid for high-pressure cleaning is water and/or a cleaning agent.

10. The method of claim 9, wherein the cleaning agent is a degreasing agent.

11. The method of claim 9, wherein the cleaning agent is a water-base metal degreasing agent.

12. The method of claim 9, wherein the cleaning agent is an acid water-base metal degreasing agent.

13. The method of claim 9, wherein the cleaning liquid for the primary high-pressure cleaning is water.

14. The method of claim 9, wherein the cleaning duration for the primary high-pressure cleaning is 10-30 min.

15. The method of claim 9, wherein the cleaning liquid of the secondary high-pressure cleaning is aqueous solution containing a cleaning agent.

16. The method of claim 9, wherein the cleaning liquid temperature of the secondary high-pressure cleaning is 40-70° C.

17. The method of claim 9, wherein the cleaning duration of the secondary high-pressure cleaning is 5-10 min.

18. The method of claim 1, wherein the pickling liquid is one or any mixture solution of hydrochloric acid, nitric acid, sulfuric acid, and oxalic acid.

19. The method of claim 1, wherein the pickling liquid has a pH value of 1-3, and the pickling duration is 30-90s.

20. The method of claim 1, wherein a treatment performed to the waste acid generated after pickling includes but is not limited to neutralizing, filtering, evaporating for crystallization and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0054] While the following description will be made referred to examples and comparative examples for detailing the present invention, nothing therein should form limitation to the present invention. Unless stated defiantly in the context, the reagent(s) or equipment mentioned herein are all commercially available and used as instructed by the manuals.

[0055] 1. Reagent

[0056] Hydrochloric acid having its mass fraction of 0.3%-0.5% being prepared into acid hydrochloric dilute having a pH value of about 1.0;

[0057] An environmentally friendly degreasing agent, modeled LQ-56-CX-TCL from Landnok Chemical (Guangzhou) Co., Ltd., being prepared with a volume fraction of 1.0% in use;

[0058] A magnesium alloy environmentally friendly water-based degreasing agent for ultrasonic use modeled LN-33A-7-45MS from Landnok Chemical (Guangzhou) Co., Ltd., being prepared with a volume fraction of 3.0-5.0% in use.

[0059] 2. Equipment

[0060] A metal crusher modeled PF-J-1000 from Gongyi Xingguang Machinery and Equipment Co., Ltd.;

[0061] A heavy-duty hot-water high-pressure cleaning machine modeled 895-1 from Changsha Hongsen Machinery Co. Ltd.;

[0062] An ultrasonic cleaning machine modeled HCP-4B72 from Zhuzhou Huasheng Electronic Equipment Co., Ltd.; and

[0063] A universal type manual dry sand blasting machine modeled 9060A from Changsha Bai Tong Mechanic Electrical Inc.

Example 1

[0064] The present example uses discarded magnesium alloy products imported by Hunan S.R.M. Technology CO., Ltd. from Sweden with a batch number of 2013-10-05-A as the feedstock for the process. The batch of magnesium alloy waste material sums 5000 tons. Waste having its surface carrying greasiness and demolding agents takes about 10% of the entire batch. The producing steps are as follows:

[0065] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to small waste pieces whose maximum dimension is 100 mm;

[0066] (2) Sorting and removing impurities: screening waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by organic coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0067] (3) Primary high-pressure cleaning: performing primary high-pressure cleaning on the magnesium alloy waste material that has been sorted and has impurities removed using a heavy-duty hot-water high-pressure cleaning machine modeled 895-1, wherein the cleaning liquid is water, the pressure is 10 MPa, and the cleaning duration is 20 min;

[0068] (4) Secondary high-pressure cleaning: performing secondary high-pressure cleaning on the magnesium alloy waste material that have received the primary high-pressure cleaning using the heavy-duty hot-water high-pressure cleaning machine modeled 895-1, wherein the cleaning liquid is aqueous solution containing an acid water-based metal degreasing agent, in which the aqueous solution prepared according to its formula has a pH value of 5.5, and for the cleaning, the aqueous solution temperature is 55±5° C., the pressure is 10 MPa, and the cleaning duration is 10 min;

[0069] (5) Pickling: placing the magnesium alloy waste material that has received the secondary high-pressure cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, and when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0070] (6) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0071] (7) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0072] (8) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material;

[0073] Results of the pretreatment of Example 1 are shown in Table 1:

Example 2

[0074] The present example is similar to Example 1 except that the pressure for primary high-pressure cleaning is 20 MPa.

[0075] Results of the pretreatment of Example 2 are shown in Table 1:

Example 3

[0076] The present example is similar to Example 1 except that the pressure for secondary high-pressure cleaning is 20 MPa.

[0077] Results of the pretreatment of Example 3 are shown in Table 1:

Example 4

[0078] The present example is similar to Example 1 except that the cleaning liquid for secondary high-pressure cleaning is aqueous solution containing neutral water-based degreasing agent. The aqueous solution prepared according to its formula had a pH value of 7.

[0079] Results of the pretreatment of Example 4 are shown in Table 1:

Example 5

[0080] The present example is similar to Example 1 except that the cleaning liquid for secondary high-pressure cleaning is aqueous solution containing alkaline water-based degreasing agent. The aqueous solution prepared according to its formula had a pH value of about 10.

[0081] Results of the pretreatment of Example 5 are shown in Table 1:

Example 6

[0082] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0083] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to small waste pieces whose maximum dimension is 100 mm;

[0084] (2) Sorting and removing impurities: screening waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by organic coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0085] (3) Primary high-pressure cleaning: performing primary high-pressure cleaning on the magnesium alloy waste material that has been sorted and has impurities removed using a heavy-duty hot-water high-pressure cleaning machine modeled 895-1, wherein the cleaning liquid is water, the pressure is 10 MPa, and the cleaning duration is 20 min;

[0086] (4) Pickling: placing the magnesium alloy waste material that has received the high-pressure cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, and when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0087] (5) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0088] (6) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0089] (7) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material.

[0090] Results of the pretreatment of Example 6 are shown in Table 1:

Comparative Example 1

[0091] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0092] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to small waste pieces whose maximum dimension is 100 mm;

[0093] (2) Sorting and removing impurities: screening waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0094] (3) Primary high-pressure cleaning: performing primary high-pressure cleaning on the magnesium alloy waste material that has been sorted and has impurities removed, wherein the cleaning liquid is water, the pressure is 10 MPa, and the cleaning duration is 20 min;

[0095] (4) Secondary high-pressure cleaning: performing secondary high-pressure cleaning on the magnesium alloy waste material that have received the primary high-pressure cleaning using the heavy-duty hot-water high-pressure cleaning machine modeled 895-1, wherein the cleaning liquid is aqueous solution containing an acid water-based metal degreasing agent, in which the aqueous solution prepared according to its formula has a pH value of 5.5, and for the cleaning, the aqueous solution temperature is 55±5° C., the pressure is 10 MPa, and the cleaning duration is 10 min;

[0096] (5) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0097] (6) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material.

[0098] Results of the pretreatment of Comparative Example 1 are shown in Table 1:

Comparative Example 2

[0099] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0100] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to small waste pieces whose maximum dimension is 100 mm;

[0101] (2) Sorting and removing impurities: screening waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0102] (3) Pickling: placing the magnesium alloy waste material that has received cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, and when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0103] (4) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0104] (5) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0105] (6) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material;

[0106] Results of the pretreatment of Comparative Example 2 are shown in Table 1:

Comparative Example 3

[0107] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0108] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to small waste pieces whose maximum dimension is 100 mm;

[0109] (2) Sorting and removing impurities: screen waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0110] (3) alkali wash: performing degreasing process to the magnesium alloy using alkali wash solution, the proportion of which is: 80 g/L of NaOH, 20 g/L of Na.sub.2CO.sub.3, 10 g/L of Na.sub.3PO.sub.4, 15 g/L of Na.sub.2SiO.sub.3, and the rest being water, and the alkali wash has a washing temperature of 50±5° C. and a washing duration of 2 min;

[0111] (4) Pickling: placing the magnesium alloy waste material that has received cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, and when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0112] (5) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0113] (6) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0114] (7) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material;

[0115] Results of the pretreatment of Comparative Example 3 are shown in Table 1:

Comparative Example 4

[0116] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0117] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to waste pieces whose maximum dimension is 100 mm;

[0118] (2) Sorting and removing impurities: screen waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by organic coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0119] (3) ultrasonic cleaning: cleaning the magnesium alloy waste material with an ultrasonic cleaning machine, wherein the cleaning liquid has a pH value of 4-6, the ultrasonic wave has a frequency of 28 Hz, and the cleaning temperature is 50±5° C. and the cleaning duration is 30 min;

[0120] (4) Pickling: placing the magnesium alloy waste material that has received cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, and when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0121] (5) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0122] (6) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0123] (7) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material;

[0124] Results of the pretreatment of Comparative Example 4 are shown in Table 1:

Comparative Example 5

[0125] The materials used in the present example are identical to those for Example 1. The producing steps are as follows:

[0126] (1) Cutting: cutting the magnesium alloy waste material using a metal crusher to waste pieces whose maximum dimension is 100 mm;

[0127] (2) Sorting and removing impurities: screen waste material containing inseparable screws, rubber or plastic, waste material with its surface covered by organic coating, and non-magnesium material out from the cut magnesium alloy waste material, and reserving the remaining magnesium alloy waste material for later use;

[0128] (3) Sand blasting (bead blasting): processing the magnesium alloy waste material with a sand blasting machine, wherein the sand blasting has a pressure of 1.0 MPa and a duration of 5 min, and the abrasive for sand blasting is cast steel grit.

[0129] (4) Pickling: placing the magnesium alloy waste material that has received the secondary high-pressure cleaning into dilute hydrochloric acid solution having a pH value of 1.0 for pickling, wherein the pickling duration is 40s; before every time of pickling, adding proper amount of acid for ensuring that the pickling liquid is in the pH range, when Mg.sup.2+ concentration in the solution is greater than 2.0 mol/L, the pickling liquid is replaced.

[0130] (5) Water rinsing: combining rinsing and spraying to remove acid liquid and impurities remained on the surface of the obtained magnesium alloy waste material;

[0131] (6) Drying: combining air blowing and hot air drying to remove water remained on the surface of the cleaned magnesium alloy waste material;

[0132] (7) Sorting again: sorting unclean waste material and non-magnesium material out of the dried waste material, thereby finalizing pretreatment for the magnesium alloy waste material;

[0133] Results of the pretreatment of Comparative Example 5 are shown in Table 1:

[0134] Table 1 shows data of pretreatment experiments obtained from the foregoing examples and comparative examples.

TABLE-US-00002 TABLE 1 Clean waste Clean waste material content material content Composition before treatment (%) after treatment (%) Example 1 0 92 Example 2 0 94 Example 3 0 93 Example 4 0 85 Example 5 0 84 Example 6 0 78 Comparative 0 11 Example 1 Comparative 0 46 Example 2 Comparative 0 50 Example 3 Comparative 0 59 Example 4 Comparative 0 62 Example 5

[0135] As can be seen from table 1, Examples 1-6 have obviously better pretreating results than Comparative Examples 1-5. Moreover, Examples 1-3 have excellent pretreating results with clean waste material taking up to 90%. According to the table above, by using high-pressure cleaning to remove impurities from magnesium alloy waste material, the resulting rate of clean waste material is much higher than the prior art, thereby providing significant advancement.

[0136] The present invention has been described with reference to the preferred embodiments and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims.