CN109679420B

CN109679420B - Double-layer solid film pre-coated on surface of stamping forming plate and preparation method thereof

Info

Publication number: CN109679420B
Application number: CN201811612621.XA
Authority: CN
Inventors: 段海涛; 凃杰松; 李健; 詹胜鹏; 贾丹; 顾卡丽; 魏雷
Original assignee: Wuhan Research Institute of Materials Protection
Current assignee: Wuhan Research Institute of Materials Protection
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2020-09-08
Anticipated expiration: 2038-12-27
Also published as: CN109679420A

Abstract

The invention discloses a double-layer solid film precoated on the surface of a stamping forming plate and a preparation method thereof. The double-layer solid film comprises an organic lubricating layer coated on the surface of the aluminum alloy plate and a protective layer coated on the surface of the organic lubricating layer, wherein the organic lubricating layer comprises a lubricating property endowing agent A, an organic coating B serving as a lubricating property endowing agent binder and a wetting dispersant C for improving the dispersibility of the lubricating property endowing agent A; the protective layer is an organic coating D for improving the acid and alkali corrosion resistance of the organic lubricating layer. Adding the lubricating property endowing agent A and the wetting dispersant C into the organic coating B, uniformly mixing, coating on the surface of a material to be lubricated, naturally drying to form an organic lubricating layer, and coating the organic coating D on the organic lubricating layer to form a double-layer solid film. The invention has good acid and alkali corrosion resistance and weather resistance, good lubricating property, easy removal after stamping, and protection of the surfaces of the plate and the die, and the formed piece has excellent surface quality.

Description

Double-layer solid film pre-coated on surface of stamping forming plate and preparation method thereof

Technical Field

The invention belongs to the technical field of aluminum alloy plate stamping forming processing assistance, relates to a surface lubricating film for aluminum alloy plate stamping forming processing, and particularly relates to a double-layer solid film pre-coated on the surface of a stamping forming processing plate and a preparation method thereof.

Background

Because of the special requirements of the automobile aluminum plate covering part on the aspects of strength, formability, surface precision, baking hardening and the like, the lubricating process is easy to generate defects in the simple transplanting of the original steel plate stamping forming, not only can the manufacturing requirements not be met, but also the problems of resource waste and environmental pollution can be brought. At present, all countries in the world are researching basic problems of strengthening surface treatment and lubricating materials of aluminum alloy plates for vehicles, and form a series of lubricating material products with intellectual property rights. The forming technology of the aluminum alloy covering piece sheet has a large difference with the average level of developed countries, and only individual research and patents are available in the aspect of directly carrying out surface treatment and lubricating material coating on the tail end of the aluminum plate rolling process, so that large-scale production is not suitable.

The solid lubricant can reduce the forming force of the aluminum alloy plate, reduce defects, improve the smoothness of a stamping part, prolong the service life of a die, avoid pollution and failure caused by volatilization of the lubricating oil, realize clean production of a stamping workshop, and is used for stamping the automobile body covering part on a certain scale. However, in large scale industrial applications, aluminum alloy stamping lubricants must meet several requirements: 1. has good weather resistance and acid and alkali corrosion resistance. In the industrial production process, the stamped aluminum plates purchased in the same batch are required to meet the continuous production requirement of several months, so the service life of the lubricating layer coated on the aluminum plates must be ensured to be more than several months; 2. the preparation process cannot be excessively complicated. Too complicated coating process not only increases the cost of industrial application, but also easily causes various defects in the coating process; 3. the lubricating medium should have excellent dispersibility in the solid binder. Research results of a plurality of scholars show that the dispersion of a lubricating medium in a solid lubricant can generate difference on the stamping lubricating effect, and the difference can directly influence the forming performance of the aluminum alloy plate; 4. it is necessary to have good easy-to-remove properties after the stamping is finished. The stamping production is an intermediate process of the manufacture of the automobile body covering parts, and in order not to influence the quality of subsequent processes such as paint spraying, welding and the like, the applied lubricant must be conveniently and quickly removed without residue.

However, in the present invention, the solid lubricant for aluminum alloy sheet pressing does not take these problems into full consideration. For example, CN100509181C discloses a resin lubricating film containing polyethylene glycol and paraffin wax, which can provide good stamping lubricating performance, but the preparation process is complicated, which is not suitable for large-scale industrial production, and the resin must be removed with alkali solution after stamping. Aluminum alloy is easy to react with alkali solution, so that the surface of a formed part is corroded, and the surface quality of the formed part is influenced. In addition, the patent does not describe the dispersion of the lubricant. CN102808169A discloses a lubricating method for aluminum alloy, which is characterized in that on the basis of aluminum alloy phosphating, a sodium stearate layer is formed in fatty sodium to serve as a lubricating effect, although the method improves the bonding force between a phosphating layer and a substrate, the processing method is complex and tedious, and meanwhile, the stamping lubricating performance of the processed aluminum alloy is not deeply evaluated.

Disclosure of Invention

The invention aims to solve the problems in the background art, and provides a double-layer solid film precoated on the surface of a stamping forming plate and a preparation method thereof, aiming at the stamping forming of an aluminum alloy plate, the double-layer solid film can be stored for a long time and is resistant to acid and alkali corrosion, and meanwhile, the lubricant also has the advantages of simple preparation, uniform dispersion of a lubricating medium and excellent lubricating property, and the double-layer solid film has excellent acid and alkali corrosion resistance, weather resistance, stamping lubricating property and forming property, can effectively protect the surface of a formed part, and can be conveniently removed after the stamping forming is finished.

The technical scheme of the invention can be realized by the following technical measures:

a double-layer solid film precoated on the surface of a stamping forming processing plate is characterized in that: the lubricating property endowing agent comprises an organic lubricating layer coated on the surface of an aluminum alloy plate and a protective layer coated on the surface of the organic lubricating layer, wherein the organic lubricating layer comprises a lubricating property endowing agent A, an organic coating B serving as a lubricating property endowing agent binder and a wetting dispersant C for improving the dispersibility of the lubricating property endowing agent A, and the lubricating property endowing agent A, the organic coating B and the wetting dispersant C in the organic lubricating layer are respectively as follows in parts by weight: 10-30 parts, 70-90 parts and 0.2-2 parts; the protective layer is an organic coating D for improving the acid and alkali corrosion resistance of the organic lubricating layer.

Preferably, the lubricating property endowing agent A is selected from one or any combination of polytetrafluoroethylene particles, molybdenum disulfide particles and high molecular weight polyethylene particles.

Preferably, the lubricating property imparting agent A has an average particle diameter of 0.5 to 3 μm.

Preferably, the organic coating material B is polyvinyl butyral.

Preferably, the wetting dispersant C is any one or a combination of several of macromolecular carboxylic acid, modified polysiloxane and macromolecular surfactant.

Preferably, the wetting and dispersing agent C is selected from any one of Disponer904S, Disponer903 manufactured by hainshen specialty chemicals.

Preferably, the organic coating material D is a butadiene-styrene copolymer.

A preparation method of a double-layer solid film pre-coated on the surface of a stamping forming processing plate is characterized by comprising the following steps:

adding a lubricating property endowing agent A and a wetting dispersant C into an organic coating B according to a proportion, adding a diluent for dilution, and mixing in a mechanical stirring manner to uniformly and fully disperse the lubricating property endowing agent A to obtain a precursor fluid;

and (2) spraying or brushing the precursor fluid obtained in the step (1) on the surface of the material to be lubricated, and forming an organic lubricating layer after the natural surface of the material is dried.

And (3) adding the organic coating D into a diluent, fully stirring to completely dissolve the organic coating D, coating the diluted organic coating D on the surface of the organic lubricating layer prepared in the step (2) by spraying or brushing, and forming the double-layer solid film after the organic coating D is naturally dried.

Preferably, the diluent is an organic solvent, and the ratio of the addition amount of the diluent to the total mass of the components of the double-layer solid film is 0.6-1.1: 1.

Preferably, the coating thickness of the organic lubricating layer is 5-35 microns, and the coating thickness of the diluted organic coating D is 5-15 microns.

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

(1) the double-layer solid film has simple raw materials and very simple and convenient coating process.

(2) The lubricant medium has the best dispersibility in the adhesive and basically has no agglomeration phenomenon.

(3) The double-layer solid film is resistant to strong acid and alkali corrosion, has good weather resistance and can be stored for a long time.

(4) The stamping lubricating property is excellent, the stamping force can be effectively reduced, and the die abrasion is reduced.

(5) The protective agent has excellent protective capability on the surface of the aluminum alloy plate, and the formed piece has higher surface quality.

(6) After the forming is finished, the double-layer solid film is easy to remove and basically has no residue.

Drawings

The invention is further illustrated by means of the attached drawings, the examples of which are not to be construed as limiting the invention in any way.

FIG. 1 is a schematic structural diagram of an aluminum alloy cup specimen coated with a double-layer solid film according to the present invention;

FIG. 2 is a dispersion of the lubricating property imparting agent A in the solid lubricating layer of comparative example 2;

FIG. 3 is a graph showing the distribution of the lubricating property imparting agent A in the cross section of the solid lubricating layer of comparative example 2 (agglomeration is clearly visible);

FIG. 4 is a dispersion of the lubricating property imparting agent A in the solid lubricating layer of example 1 of the present invention;

FIG. 5 is a view showing the distribution of the lubricating property imparting agent A in the cross section of the solid lubricating layer in example 1 of the invention (which is smooth as a whole);

FIG. 6 is a graph showing the press force stroke curves of the lubricants obtained in comparative example 1, comparative example 2 and example 1.

Reference numerals: 1-protective layer, 2-organic lubricating layer, 3-aluminum alloy plate and 4-lubricating property endowing agent A.

Detailed Description

The following will explain in detail the specific embodiment and the operation principle of the double-layer solid film formed by stamping the pre-coated aluminum alloy plate according to the present invention with reference to the attached drawings. The selection of testing equipment and materials and the formulation of testing parameters are only used to illustrate the technical solution of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The double-layer solid film pre-coated on the surface of a stamping forming processing plate comprises an organic lubricating layer 2 coated on the surface of an aluminum alloy plate 3 and a protective layer 1 coated on the surface of the organic lubricating layer 2, wherein the organic lubricating layer 2 comprises a lubricating property endowing agent A4, an organic coating B serving as a lubricating property endowing agent binder and a wetting dispersant C for improving the dispersibility of the lubricating property endowing agent A4, and the lubricating property endowing agent A4, the organic coating B and the wetting dispersant C in the organic lubricating layer 2 are respectively in parts by weight: 10-30 parts, 70-90 parts and 0.2-2 parts; the protective layer 1 is an organic coating D for improving the acid and alkali corrosion resistance of the organic lubricating layer 2.

The lubricating property endowing agent A4 is selected from one or the combination of any more of polytetrafluoroethylene particles, molybdenum disulfide particles and high molecular weight polyethylene particles; the average particle size is 0.5-3 microns; the organic coating B is polyvinyl butyral; the wetting dispersant C is any one or combination of a plurality of polymer carboxylic acid, modified polysiloxane, a mixture of the two and a polymer surfactant; the wetting dispersant C is any one of Disponer904S and Disponer903 manufactured by Haimax specialty Chemicals; the organic coating D is butadiene-styrene copolymer.

Preparation of a bilayer solid film

Degreasing, cleaning and drying the surface of the aluminum alloy cup sample plate.

After the lubricating property endowing agent A and the wetting dispersant C are added into the organic coating B, a diluent is added for dilution, and the components are mixed by mechanical stirring, wherein the weight percentage of each component meets the range of the invention. The coating method of the organic lubricating layer 2 of the present invention is not particularly limited, and dipping, spraying and other methods can be used, and it is noted that the coating thickness is between 5 and 35 μm. After coating, the lubricating layer is naturally dried for 10 minutes at normal temperature, namely dried and solidified. And then adding the organic coating D into another diluent, completely dissolving the organic coating D by mechanical stirring, uniformly coating the organic coating D on the surface of the prepared solid lubricating layer by an immersion method, a spraying method or other methods to form a protective layer 1, wherein the coating thickness of the protective layer 1 is 5-15 micrometers, and naturally drying the protective layer 1 for 10 minutes at normal temperature to obtain the double-layer solid film.

Acid and alkali corrosion resistance and weather resistance test

Respectively dripping 34% concentrated hydrochloric acid and 20% sodium hydroxide solution on the surfaces of the two aluminum alloy wafers coated with the double-layer solid film through a dropper, standing for 15 minutes, washing away strong acid or strong base on the surfaces with clear water, and observing the state of the surface of the solid film through naked eyes.

Cup test

Before the cup punching test is carried out, the outermost protective layer 1 needs to be removed. And (3) immersing the whole aluminum alloy wafer coated with the double-layer solid film into a dimethylbenzene solvent, standing for 10 minutes at room temperature, taking out, and naturally airing for 5 minutes to perform a subsequent cup punching test.

Carrying out cup punching test on a sample to be tested by using a GBW-50 cup punching testing machine, wherein the test parameters are as follows: comparative example 1 (commercial liquid aluminum alloy stamping lubricant), comparative example 2 (single layer polyurethane solid lubricant film) and example (double layer solid film described in the present invention), both were applied by brush coating under the same conditions. The cup punching speed value is set to 20mm/min, and the blank holder force is set to 30 KN. The aluminum alloy plate enters the female die under the action of the male die of the cup punching testing machine and gradually forms a cylindrical cup shape. The smaller punching force shows that the lubricating effect is excellent.

Film removal test

And after the cup punching test is finished, immersing the whole formed piece into absolute ethyl alcohol, standing for 15 minutes at room temperature, taking out the formed piece, naturally drying, and detecting organic residues on the surface of the formed piece by an infrared spectrometer.

Comparative example 1

Aluminum alloy wafers lubricated by commercial punching oil QH-7 are selected for cup punching tests, and the experimental parameters and the experimental method are as described above. The physical and chemical properties of the commercially available QH-7 punching oil are shown in Table 1.

TABLE 1 physical and chemical Properties of commercial QH-7 punching oil

Comparative example 2:

the lubricating endowing agent is made of 10 parts by weight of polytetrafluoroethylene particles with the average particle size of 2.8 microns, the organic coating is made of 88.5 parts by weight of polyurethane, the wetting dispersant is made of Disponer904S and 1 part by weight of defoaming agent, and the defoaming agent is made of 0.5 part by weight of Defom 6500.

Example (b):

in the organic lubricating layer 2, 15 parts by mass of a lubricating endowing agent is selected from polytetrafluoroethylene particles with the average particle size of 2.8 micrometers, 83.5 parts by mass of an organic coating is selected from polyvinyl butyral, 1 part by mass of a wetting dispersant is selected from Disponer904S, 0.5 part by mass of a defoaming agent is selected. The organic coating in the protective layer 1 is butadiene-styrene copolymer, and the mass portion is 100. The prepared solid lubricating film was applied to the same aluminum alloy wafer samples as in comparative examples 1 and 2 to perform a cup punching test. The dispersion condition of the lubricant endowing agent is detected by a Micromeasure2 white light confocal three-dimensional topographer produced by the French STIL company, and the detection parameters are scanning area: 1mm × 1 mm; step length: 2 μm × 5 μm; depth of field of the optical pen: 300 μm, the results are shown in FIGS. 2 to 5, and the press force stroke curves of the present example, comparative example 1 and comparative example 2 are shown in FIG. 6.

The aluminum alloy punching cup sample coated with the double-layer solid film has color similar to that of an original aluminum alloy plate, and the quality of the solid film is obviously superior to that of the sample coated with a single-layer polyurethane lubricating layer.

And respectively dripping concentrated hydrochloric acid with the concentration of 34% and sodium hydroxide with the concentration of 20% on the surfaces of two aluminum alloy cup samples coated with the double-layer solid film, standing for 15 minutes, and washing away the concentrated hydrochloric acid and the sodium hydroxide by using clear water, so that the surface of the double-layer solid film is not damaged and has no gloss change, which shows that the double-layer solid film has excellent acid and alkali resistance.

As can be seen from the results of FIGS. 2 to 5 and Table 2, the agglomerate size and density of the lubricant imparting agent in the examples are smaller than those of comparative example 2, indicating that the dispersibility of the lubricant imparting agent in the examples is significantly better than that of comparative example 2; the results in table 3 show that the solid lubricating layers prepared in the examples have better film-based bonding force than the solid lubricating layer prepared in comparative example 2.

TABLE 2 comparative example 2 and examples lubrication imparting agent agglomerate size

TABLE 3 bonding force between solid lubricant film and aluminum alloy plate in comparative example 2 and example

And (3) immersing the aluminum alloy wafer coated with the double-layer solid film into a dimethylbenzene solvent, standing for 15 minutes, taking out, and performing a cup punching forming test after the aluminum alloy wafer is naturally dried. The results in fig. 6 and table 4 show that the maximum press force of the lubricating layer according to the invention during the cup punching process is significantly lower than in comparative example 1 in all three stages of cup punching, and is comparable to comparative example 2. The result shows that the solid film disclosed by the invention can provide excellent lubricating property for the stamping process of the aluminum alloy plate 3.

The punching test is carried out after the punching sample coated with the double-layer solid film is placed for one month, the punching force is basically unchanged, and the double-layer solid film has good weather resistance.

TABLE 4 maximum press force during cup punching for comparative examples 1, 2 and examples

The roughness of the cup wall surface of the comparative examples 1, 2 and the molded article of example was measured and compared, and the results are shown in table 5. As can be seen from the results of the roughness, in the case of QH-7 punching oil lubrication, the roughness Ra of the cup wall of the formed article was 0.9 μm and Rz was 4.8. mu.m, whereas in the example, the roughness Ra of the cup wall of the formed article was 0.2 μm and Rz was 1.2. mu.m, and the Ra value was reduced by about 77.8% and Rz by about 75.0% with respect to QH-7 punching oil as in comparative example 2. It is understood that the solid film of the present invention has excellent lubricating properties under lubrication, and therefore protects the surface of the plate material during the cup punching process, thereby greatly improving the surface quality of the molded article.

TABLE 5 roughness of cup wall surface of comparative example 1, comparative example 2 and molded article of the present example

And (3) immersing a formed part coated with the lubricating layer into an absolute ethyl alcohol solution after the cup is washed, standing for 15 minutes, taking out and naturally drying, and randomly detecting 5 areas on the surface of the formed part by using an infrared spectrometer, wherein no organic peak appears, so that the lubricating layer is extremely easy to remove and has no residue.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A double-layer solid film precoated on the surface of a stamping forming processing plate is characterized in that: the lubricating property endowing agent comprises an organic lubricating layer coated on the surface of an aluminum alloy plate and a protective layer coated on the surface of the organic lubricating layer, wherein the organic lubricating layer comprises a lubricating property endowing agent A, an organic coating B serving as a lubricating property endowing agent binder and a wetting dispersant C for improving the dispersibility of the lubricating property endowing agent A, and the lubricating property endowing agent A, the organic coating B and the wetting dispersant C in the organic lubricating layer are respectively as follows in parts by weight: 10-30 parts, 70-90 parts and 0.2-2 parts; the protective layer is an organic coating D for improving the acid and alkali corrosion resistance of the organic lubricating layer; the organic coating B is polyvinyl butyral, and the organic coating D is a butadiene-styrene copolymer.

2. The bi-layer solid film of claim 1, wherein: the lubricating property endowing agent A is selected from one or the combination of any more of polytetrafluoroethylene particles, molybdenum disulfide particles and high molecular weight polyethylene particles.

3. The bilayer solid membrane of claim 2, wherein: the lubricating property imparting agent A has an average particle diameter of 0.5 to 3 μm.

4. The bi-layer solid film of claim 1, wherein: the wetting dispersant C is any one or combination of a plurality of polymer carboxylic acid, modified polysiloxane and polymer surfactant.

5. The bi-layer solid film of claim 1, wherein: the wetting dispersant C is any one selected from Disponer904S, Disponer903 manufactured by Haimax specialty Chemicals.

6. A method of preparing a two-layer solid film pre-applied to the surface of a press-formed sheet material according to claim 1, comprising the steps of:

step (2) spraying or brushing the precursor fluid obtained in the step (1) on the surface of a material to be lubricated, and forming an organic lubricating layer after the natural surface of the material is dried;

7. The method of producing a bilayer solid film according to claim 6, wherein: the diluent is an organic solvent, and the ratio of the addition amount of the diluent to the total mass of all components of the double-layer solid film is 0.6-1.1: 1.

8. The method of producing a bilayer solid film according to claim 6, wherein: the coating thickness of the organic lubricating layer is 5-35 microns, and the coating thickness of the diluted organic coating D is 5-15 microns.