CN112522694A

CN112522694A - Foamed aluminum sandwich plate surface blackening foaming method based on rapid heat transfer

Info

Publication number: CN112522694A
Application number: CN202011287013.3A
Authority: CN
Inventors: 祖国胤; 孙溪; 黄鹏; 冯展豪; 韩楠丁
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2021-03-19
Anticipated expiration: 2040-11-17
Also published as: CN112522694B

Abstract

A foamed aluminum sandwich plate surface blackening foaming method based on rapid heat transfer is carried out according to the following steps: (1-6) preparing a prefabricated plate blank; (7) carrying out single-side blackening treatment on the prefabricated plate blank; (8) carrying out double-sided blackening treatment on the prefabricated plate blank subjected to the single-sided blackening treatment; (9) and (3) heating the resistance heating furnace to 580-630 ℃, then placing the blackened prefabricated plate blank into the resistance heating furnace for foaming treatment, taking out and cooling to normal temperature to obtain the foamed aluminum sandwich plate. The method can realize the rapid heating process of the foaming prefabricated blank under the environment of lower foaming temperature, the expansion rate of the obtained foam core layer can reach more than 800 percent, the dependence on a large-size heat transfer mold is reduced, the mold does not need to be preheated before foaming, and the industrial production efficiency is greatly improved.

Description

Foamed aluminum sandwich plate surface blackening foaming method based on rapid heat transfer

Technical Field

The invention belongs to the technical field of material processing, and particularly relates to a foamed aluminum sandwich plate surface blackening foaming method based on rapid heat transfer.

Background

The foamed aluminum sandwich board as a novel porous composite metal material has the characteristics of light weight, high specific stiffness, high specific strength, excellent energy absorption, excellent noise reduction, excellent electromagnetic shielding performance and the like; the material integrates the structure and the functionality, is not only in lightweight design in the field of aerospace and transportation, but also applied to urban construction and noise elimination structures of engine partitions, can be applied to energy absorption designs of vehicle anti-collision beams and armored vehicle chassis, and has high application value and development prospect; as people pay more attention to the technology, a more mature industrial production process is extremely important.

The prior preparation process of the foamed aluminum sandwich plate mainly comprises two process routes of a melt foaming method and powder metallurgy; the melt foaming method is relatively mature, and although the melt foaming method is widely applied to the industrial production of the foamed aluminum sandwich panel, the realization of the large-area high-strength metallurgical bonding of the foamed core layer and the panel is difficult, and the powder metallurgy process is favorable for realizing the industrial preparation of the metallurgical bonding of the core layer and the panel due to the advantages of the process route of the powder metallurgy process, and is the key point of scientific research at present.

For the powder metallurgy foaming process, the factors which can determine the quality of the final product are many, and the factors mainly comprise the matching of powder components, the change of rolling process parameters, the control of various parameters of the foaming environment and the like; there is currently little literature on the impact of heat transfer patterns on foam quality in a foaming environment; the early stage of the foamed aluminum preparation process (from the beginning of titanium hydride decomposition to the liquefaction of the base alloy to a certain extent) needs to have a sufficient temperature rise rate, otherwise the gas accumulated continuously by the decomposition of the internal foaming agent titanium hydride can guide the formation of early-stage through holes and crack defects, and the gas can reduce the foaming expansion rate if overflowing.

In order to improve the heat transfer efficiency in the early stage of foaming, the preset furnace temperature is usually increased in combination with the mold heat transfer, but the following problems are faced:

in the foaming and heating process of the foamed aluminum sandwich board, a certain temperature gradient exists between the outer layer panel and the foam of the sandwich layer, and the magnitude of the gradient is in a direct proportion relation with the preset furnace temperature and the real-time temperature difference of the surface of the panel of the foamed aluminum sandwich board; although the temperature rise rate in the early foaming stage can be increased by increasing the temperature of the preset furnace, the actual temperature of the panel is inevitably far higher than the foam temperature of the core layer in the later foaming stage; if the actual temperature of the foam of the core layer is too low to ensure the strength of the panel, the expansion rate is reduced; if the expansion rate is increased to ensure the temperature of the core layer, the panel is overheated and overburnt, and the mechanical property of the panel is reduced; the temperature gradient of the foam core layer in the prefabricated blank can reduce the uniformity of the foam holes in the foaming process, and simultaneously, the stability of the prepared product is reduced along with the shortening of the allowable time in the later foaming period; in addition, as the preset furnace temperature increases, the difficulty of controlling the uniformity of the temperature field in the furnace increases, so that the large-size foamed aluminum sandwich plate is difficult to prepare, and a large amount of energy is wasted.

Besides the temperature rise, people can still realize the rapid temperature rise of the blank through an infrared radiation furnace, a salt bath furnace, a mold heat conduction mode and the like; although the infrared radiation equipment can meet the requirement of high-efficiency temperature rise of the foam prefabricated blank plate, the temperature in the foaming process is difficult to control, and the stability and uniformity of a foam cell structure in the foaming process are difficult to ensure; although the salt bath heating mode can realize the rapid temperature rise of the plate and the temperature control is extremely stable, the salt bath has high danger and pollutes the environment, and the industrialized production is difficult to be promoted; the most common heat transfer process applied to the production of the foamed aluminum sandwich plate is mold heat transfer at present, and although a large-size foamed aluminum plate can be prepared, the production has many limitations including the need of a higher heat transfer mold size, and the heat transfer mold needs to be preheated in advance to ensure the sufficiency of heat transfer; for the foaming prefabricated blank with larger size, preheating treatment is also needed, so that the influence of the excessive temperature drop of the heat transfer mold on the foaming effect is avoided, and even if the requirements are met, the expansion rate of the foam core layer which can be obtained in a laboratory is generally not more than 500 percent under the foaming temperature environment of lower than 630 ℃.

Disclosure of Invention

The invention aims to provide a foamed aluminum sandwich board surface blackening foaming method based on rapid heat transfer, which is characterized in that the surface of a prefabricated plate blank is subjected to blackening treatment, a conventional heating furnace is adopted for foaming, the ultrahigh expansion rate can be obtained at a lower temperature, and the foamed aluminum sandwich board surface blackening foaming method is suitable for large-size foamed aluminum sandwich boards, improves the quality of foam holes of the sandwich layer and reduces the equipment requirement.

The method of the invention is carried out according to the following steps:

1. uniformly mixing aluminum powder/aluminum alloy powder, silicon powder, copper powder, magnesium powder, zinc-white copper powder and a foaming agent to obtain core layer mixed powder; the core layer mixed powder comprises 5-10% of Si by mass percent; 1-8% of Mg, 1-6% of Cu, 0-2% of Zn, 0.5-2% of foaming agent and the balance of Al; the foaming agent is titanium hydride powder;

2. adopting 3000 series aluminum alloy or 6000 series aluminum alloy pipe or plate; annealing the pipe at 400 +/-10 ℃ for 1-3 h, flattening by using a press machine, and rolling into a tubular cavity by using a rolling mill; or sealing two side edges of two plates which are placed in parallel to form a tubular cavity; the tubular cavity is composed of an upper plate, a lower plate and a connecting part between the upper plate and the lower plate, the upper plate and the lower plate are parallel to each other, and the distance between the upper plate and the lower plate is 20-30 mm; the width of the tubular cavity is 40-1200 mm, and the wall thickness is 2-8 mm;

3. pretreating the inner surface of the tubular cavity, wherein during pretreatment, firstly, oil stain is removed by alkali washing, then, impurities are removed by acid washing, then, acid liquor is removed by water washing, and finally, water is removed by drying;

4. taking one end of the tubular cavity subjected to surface pretreatment as a front end and the other end as a tail end; fixing the upper plate and the lower plate together by rivets at the front ends, and taking a gap between adjacent riveted parts as a reserved exhaust hole; placing asbestos or sponge into the tubular cavity from the tail end, filling the mixed powder of the core layer into the tubular cavity from the tail end, and reserving a riveting fixing distance of 30-60 mm at the tail end; adding asbestos or sponge into the tubular cavity from the tail end; the asbestos or sponge added twice covers the core layer mixed powder at the front end and the tail end, and is used for preventing the core layer mixed powder from being discharged along with airflow in the rolling process; then flattening the tail end, fixing the upper plate and the lower plate together through rivets, and taking a gap between adjacent riveted parts as a reserved exhaust hole to manufacture a prefabricated part; the front end and the tail end of the prefabricated part are the front end and the tail end of the tubular cavity;

5. performing cold rolling on the prefabricated member for 3-7 times, wherein the reduction rate of each time is 3-8%, so that the mixed powder of the core layer and the tubular cavity can achieve primary densification, and preparing a blank; the cold rolling direction is from the tail end to the front end or from the front end to the tail end, and the cold rolling directions of two adjacent passes are opposite;

6. hot rolling the blank, wherein the initial rolling temperature is 330-480 ℃, the final rolling temperature is 300-450 ℃, and the total reduction rate is 40-70%, so as to obtain a hot rolled plate blank; carrying out heat treatment on the hot-rolled plate blank at 400-500 ℃ for 1-5 h, then carrying out edge cutting treatment, and removing the riveted part to prepare a prefabricated plate blank;

7. the method for blackening the single surface of the precast slab comprises the following steps: uniformly stirring and mixing graphite powder and a transition coating according to the mass ratio of 1 (1-8) to prepare a sticky blackening coating; coating the blackening coating on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment; or coating black high-temperature-resistant self-spraying paint on one side surface of the prefabricated plate blank to finish single-side blackening treatment; or covering the graphite plate on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment;

8. the method for blackening the two surfaces of the prefabricated plate blank subjected to the single-surface blackening treatment comprises the following steps: coating the blackening coating on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or coating black high-temperature-resistant self-spraying paint on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or covering the graphite plate on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; taking the prefabricated plate blank subjected to the double-sided blackening treatment as a blackening prefabricated plate blank; the other side surface is the surface of the precast slab which is subjected to the single-side blackening treatment and is not subjected to the blackening treatment;

9. and (3) heating the resistance heating furnace to 580-630 ℃, then placing the blackened prefabricated plate blank in the heated resistance heating furnace for foaming treatment for 10-20 min, and then taking out and cooling to normal temperature to obtain the foamed aluminum sandwich plate.

In the step 9, in order to ensure that the foamed aluminum sandwich panel has uniform thickness during foaming, a limiting mold is arranged above the blackened prefabricated slab, or the foamed material is taken out and pressed to a target thickness by a pressing plate.

The expansion rate of the core layer of the foamed aluminum sandwich plate is 600-900%.

In the step 7, the upper and lower surfaces of the slab are washed with water, air-dried, and then subjected to blackening treatment.

In the step 7, the granularity of the graphite powder is 2500-10000 meshes.

In the step 7, the transition coating is a ZS-1011 transition coating or a high-temperature anti-oxidation coating liquid.

In the

steps

7 and 8, the black high-temperature-resistant self-spray paint is resistant to 800 ℃.

In the

steps

7 and 8, when the graphite plates are used for covering, one side or two side surfaces of the prefabricated plate blank are tightly and completely attached to the graphite plates.

In the step 7, after the blackening coating is coated on one side surface of the prefabricated plate blank, air-drying in the air, and then performing the step 8; after the blackening paint is coated on the other side surface of the preform slab, air-drying is performed, and then step 9 is performed.

In the step 9, the cooling method is air cooling, water cooling or spray cooling.

The method adopts surface blackening treatment to ensure that the graphite plate, the high-temperature-resistant self-painting paint or the graphite powder coating is used as a heat transfer medium, when the surface evenness of the prefabricated slab is poor, the method of coating the self-painting paint or the coating is better, and when the surface evenness of the prefabricated slab is better, the method of covering the graphite plate can be adopted; and controlling the foaming temperature to be 580-630 ℃ according to the porosity and pore diameter requirements of the target product, and selecting the foaming temperature within 10-20 min to prepare the foamed aluminum sandwich board with high expansion rate.

The method adopts a common heating furnace to heat, can effectively reduce the reduction of the comprehensive performance of the outer layer panel, obviously improve the foaming capacity of the core layer, and is obviously higher than the expansion rate range of 400-500% which can be achieved under the heat transfer process of the die, thereby further expanding the advantages of the foamed aluminum sandwich plate in light weight design compared with the traditional metal material.

The method adopts the heat transfer mode of the blackening coating, is simple and convenient to operate, namely the prefabricated blank is directly placed in a conventional heating furnace at room temperature, the limitation of the size of a heat transfer mold is thoroughly eliminated, the foaming preparation period is shortened, and the actual production efficiency is greatly improved; due to the high efficiency of heat transfer, even if the temperature of the foaming preset furnace can be further reduced to below 600 ℃, the expansion capacity of the foaming preset furnace can still reach more than 600 percent; compared with the foaming mode with higher preset furnace temperature, the heating rate is slow and stable in the temperature interval after the graphite is coated. In the temperature range, the foam of the core layer is basically in a semi-solid state, and although the liquid phase proportion is slowly increased in the temperature rise process, the foam matrix can still keep a certain viscosity. The growing and merging of the foam holes require time, and the temperature interval is naturally used as the optimal temperature interval for adjusting the pore diameter and the roundness of the foam holes of the core layer; for a sample without graphite treatment, the transition time at the stage is longer, the proportion of the matrix from solid to liquid is higher, and meanwhile, the combined liquid causes the bubble wall to become thinner under the influence of self weight, the supporting capacity is weakened, and the bubble holes are easy to collapse; the lower furnace temperature is favorable for the uniformity of heat transfer in the later foaming period, the defects of core layer through holes in the foamed aluminum sandwich board are effectively reduced, the comprehensive quality of core layer foam holes is improved, the utilization rate of energy is greatly improved, and the use requirement of equipment is reduced.

The method can realize the rapid heating process of the foaming prefabricated blank by utilizing the high-efficiency absorption of the aluminum alloy panel subjected to the surface blackening treatment on the radiation heat source in the environment of lower foaming temperature, thereby not only effectively reducing the energy consumption, but also effectively shortening the foaming time and improving the production efficiency; the expansion rate of the obtained foam core layer can reach more than 800 percent, the advantage of lightweight design is favorably expanded, and the roundness and the uniformity of foam holes of the core layer are greatly improved; the stability of the foaming process of the foam holes of the core layer is improved again, and due to the high-efficiency heat transfer rate, the lowest foaming furnace temperature is allowed to be further reduced on the premise that the foaming time and the expansion rate are not changed, so that the possibility of overheating and overburning of the aluminum alloy panel is avoided. The low-temperature foaming environment is favorable for improving the temperature uniformity of the foam core layer, reducing the defect forming probability and facilitating the regulation and control of the quality of the final product; the size of the foaming sample can be further increased, the dependence on a large-size heat transfer mold is reduced, the mold does not need to be preheated before foaming, the industrial production efficiency is greatly improved, and the industrial production difficulty is reduced.

Description of the drawings:

FIG. 1 is a schematic flow chart of a method for blackening and foaming the surface of a foamed aluminum sandwich panel based on rapid heat transfer in an embodiment of the present invention;

FIG. 2 is a photograph showing the external appearance of a prefabricated slab and an aluminum foam sandwich panel in example 4 of the present invention; in the figure, the upper layer is a prefabricated plate blank, and the lower layer is a foamed aluminum sandwich plate;

FIG. 3 is a photograph showing the appearance of an aluminum foam sandwich panel according to example 1 of the present invention; in the figure, the upper layer is a foam sandwich board which is not subjected to blackening treatment foaming, the middle layer is a foam aluminum sandwich board which is subjected to blackening treatment foaming on one side, and the lower layer is a foam aluminum sandwich board which is subjected to blackening treatment foaming on two sides;

FIG. 4 is a photograph showing the appearance of the aluminum foam sandwich panel in example 2 of the present invention;

FIG. 5 is a photograph showing the appearance of the cross section of an aluminum foam sandwich panel in example 2 of the present invention;

FIG. 6 is a photograph showing the appearance of an aluminum foam sandwich panel in example 3 of the present invention;

FIG. 7 is a photograph showing the appearance of the cross section of the aluminum foam sandwich panel in example 3 of the present invention. .

Detailed Description

The granularity of the aluminum powder/aluminum alloy powder, the silicon powder and the magnesium powder in the embodiment of the invention is 100-400 meshes; the granularity of the copper powder, the zinc white copper powder and the titanium hydride powder is 400-1000 meshes.

The core layer mixed powder in the embodiment of the invention comprises 5-10% of Si by mass percent; 1-8% of Mg, 1-6% of Cu, 0-2% of Zn, 0.5-2% of foaming agent and the balance of Al;

pipes or plates made of 3003 aluminum alloy, 6061 aluminum alloy or 6063 aluminum alloy are adopted in the embodiment of the invention; annealing the pipe at 400 +/-10 ℃ for 1-3 h, flattening by using a press machine, and rolling into a tubular cavity by using a rolling mill; or sealing two side edges of two plates which are placed in parallel to form a tubular cavity; the tubular cavity is composed of an upper plate, a lower plate and a connecting part between the upper plate and the lower plate, the upper plate and the lower plate are parallel to each other, and the distance between the upper plate and the lower plate is 20-30 mm; the width of the tubular cavity is 40-1200 mm, and the wall thickness is 2-8 mm;

the titanium hydride powder in the embodiment of the invention is pre-oxidized for 1-4 hours at the temperature of 420-520 ℃ before use.

The mixing time for obtaining the core layer mixed powder in the embodiment of the invention is 1-4 h.

The method for sealing the two side edges in the embodiment of the invention adopts one of the following modes: 1. respectively bending two side edges of the upper plate and the lower plate, wherein the included angle between the bent part and the horizontal plane is 30-60 degrees, so that the end parts of the two side edges of the upper plate and the lower plate are contacted, and then welding and sealing; 2. folding two sides of the upper plate and the lower plate twice respectively to form a flat plate part and V-shaped parts at two sides, and then stacking the V-shaped parts of the upper plate and the lower plate together to form sealing; 3. placing a flexible metal plate on each of two side edges of the upper plate and the lower plate, and respectively welding the two side edges of the upper plate and the lower plate to the flexible metal to form sealing; the flexible metal is 1050 aluminum alloy, 1060 aluminum alloy or 1100 aluminum alloy, and the thickness is 3-10 mm.

In the embodiment of the invention, the alkali liquor adopted for alkali washing is NaOH aqueous solution with the concentration of 25-45 g/L, and the tubular cavity is soaked in the alkali liquor for 10-40 min; the acid liquor adopted by acid washing is hydrochloric acid with the mass concentration of 30%, and the acid washing mode is that the tubular cavity after alkali washing is placed in the acid liquor to be soaked until the surface of the tubular cavity is smooth.

In the embodiment of the invention, when the front end or the tail end is fixed by the rivets, the rivets are uniformly distributed along the width direction of the tubular cavity, the distance between every two adjacent rivets is 10-100 mm, and gaps among the rivets are used as exhaust holes.

The aluminum powder/aluminum alloy powder, the silicon powder, the copper powder, the magnesium powder and the zinc-copper powder adopted in the embodiment of the invention have the purity of more than 99 percent, and the foaming agent TiH₂The purity is more than 99.5%.

The aluminum alloy powder in the embodiment of the invention is the aluminum alloy powder containing silicon, copper, zinc and/or magnesium.

In the embodiment of the invention, the three-dimensional mixer is adopted as the metal powder mixing equipment.

In the embodiment of the invention, 3-7 cold rolling passes are carried out, the reduction rate of each pass is 3-8%, and the total reduction rate of the cold rolling is less than or equal to 25%.

In the embodiment of the invention, when the front end or the rear end is fixed by the rivets, the rivets are made of pure aluminum, and the number of the rivets is more than 2.

In the embodiment of the invention, the deformation of the rivet part is enlarged during cold rolling, and the exhaust function is completed.

In the embodiment of the invention, the initial rolling temperature of hot rolling is 330-480 ℃, the final rolling temperature is 300-450 ℃, the total reduction rate is 40-70%, and the hot rolled plate blank is obtained.

In the embodiment of the invention, the hot rolled plate blank is subjected to heat treatment at 400-500 ℃ for 1-5 h.

According to the embodiment of the invention, the upper surface and the lower surface of the prefabricated plate blank are cleaned by water, air-dried and then subjected to blackening treatment.

The granularity of the graphite powder in the embodiment of the invention is 2500-10000 meshes.

In the embodiment of the invention, ZS-1011 transition coating or high-temperature anti-oxidation coating liquid is selected as the transition coating。

The black high-temperature-resistant self-painting in the embodiment of the invention is 4SD automobile caliper painting, road-remuneration caliper painting or matte black metal paint brush.

In the embodiment of the invention, when the graphite plate is placed on the prefabricated plate blank for foaming treatment, the thickness of the graphite plate is 1-3 mm; when the graphite plate is positioned below the prefabricated plate blank for foaming treatment, the thickness of the graphite plate is 3-30 mm.

In the embodiment of the invention, when the graphite plate is used for covering, one side or two side surfaces of the prefabricated plate blank are tightly and completely attached to the graphite plate.

In the embodiment of the invention, after the blackening coating is coated on one side surface of the prefabricated plate blank, the prefabricated plate blank is air-dried in the air, and then double-side blackening treatment is carried out; and after the blackening coating is coated on the other side surface of the prefabricated plate blank, air drying is carried out in the air, and then foaming treatment is carried out.

The cooling mode in the embodiment of the invention is air cooling, water cooling or spray cooling.

When the foaming treatment is carried out in the embodiment of the invention, in order to ensure that the thickness of the foamed aluminum sandwich board is uniform, a limiting mould is arranged above the blackened prefabricated board blank, or the foamed material is taken out and pressed to the target thickness by a pressing plate.

The present invention will be described in further detail with reference to examples, which are set forth below as preferred examples of the present invention.

Example 1

The flow is shown in figure 1;

uniformly mixing aluminum powder/aluminum alloy powder, silicon powder, copper powder, magnesium powder, zinc-white copper powder and a foaming agent to obtain core layer mixed powder;

manufacturing a tubular cavity;

pretreating the inner surface of the tubular cavity, wherein during pretreatment, firstly, oil stain is removed by alkali washing, then, impurities are removed by acid washing, then, acid liquor is removed by water washing, and finally, water is removed by drying;

taking one end of the tubular cavity subjected to surface pretreatment as a front end and the other end as a tail end; fixing the upper plate and the lower plate together by rivets at the front ends, and taking a gap between adjacent riveted parts as a reserved exhaust hole; placing asbestos or sponge into the tubular cavity from the tail end, filling the core layer mixed powder into the tubular cavity from the tail end, and reserving a riveting fixing distance at the tail end; adding asbestos or sponge into the tubular cavity from the tail end; the asbestos or sponge added twice covers the core layer mixed powder at the front end and the tail end, and is used for preventing the core layer mixed powder from being discharged along with airflow in the rolling process; then flattening the tail end, fixing the upper plate and the lower plate together through rivets, and taking a gap between adjacent riveted parts as a reserved exhaust hole to manufacture a prefabricated part; the front end and the tail end of the prefabricated part are the front end and the tail end of the tubular cavity;

cold rolling the prefabricated part to make the mixed powder of the core layer and the tubular cavity reach primary densification to prepare a blank; the cold rolling direction is from the tail end to the front end or from the front end to the tail end, and the cold rolling directions of two adjacent passes are opposite;

hot rolling the blank, performing heat treatment and edge cutting treatment, removing the riveted part, and manufacturing a prefabricated plate blank;

the method for blackening the single surface of the precast slab comprises the following steps: uniformly stirring and mixing graphite powder and a transition coating according to the mass ratio of 1 (1-8) to prepare a sticky blackening coating; coating the blackening coating on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment; or coating black high-temperature-resistant self-spraying paint on one side surface of the prefabricated plate blank to finish single-side blackening treatment; or covering the graphite plate on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment;

the method for blackening the two surfaces of the prefabricated plate blank subjected to the single-surface blackening treatment comprises the following steps: coating the blackening coating on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or coating black high-temperature-resistant self-spraying paint on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or covering the graphite plate on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; taking the prefabricated plate blank subjected to the double-sided blackening treatment as a blackening prefabricated plate blank; the other side surface is the surface of the precast slab which is subjected to the single-side blackening treatment and is not subjected to the blackening treatment;

heating the resistance heating furnace to 620 ℃, then placing the blackened prefabricated plate blank in the heated resistance heating furnace for foaming treatment for 16min, taking out and cooling to normal temperature to obtain a foamed aluminum sandwich plate with the thickness of 35mm, wherein the appearance is shown as the lower layer in figure 3, and the final expansion rate of the sandwich layer is 880%;

directly foaming the same prefabricated plate blank in the above manner without blackening to perform a comparative test, wherein the appearance of the obtained foamed aluminum sandwich panel is shown as the upper layer in fig. 3;

the same preform slab was directly foamed in the above manner under the condition of single-sided blackening treatment to perform a comparative test, and the appearance of the foamed aluminum sandwich panel obtained was as shown in the middle layer of fig. 3.

Example 2

The method is the same as example 1, except that:

(1) coating black high-temperature-resistant self-spray paint on one side surface of the prefabricated plate blank to finish single-side blackening treatment; covering the graphite plate on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment;

(2) heating a resistance heating furnace to 610 ℃; controlling the core layer expansion rate of the blackened prefabricated plate blank to be 810% and the foaming time to be 20 min; obtaining the foamed aluminum sandwich board with the thickness of 32.5mm, wherein the appearance is shown in figure 4, and the final core layer expansion rate is 810%; the appearance of the cross section of the aluminum foam sandwich panel after the edge portion is cut is shown in fig. 5.

Example 3

The method is the same as example 1, except that:

(1) coating black high-temperature-resistant self-spray paint on one side surface of the prefabricated plate blank to finish single-side blackening treatment; coating black high-temperature-resistant self-spray paint on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment;

(2) heating a resistance heating furnace to 630 ℃; controlling the core layer expansion rate of the blackened prefabricated plate blank to be 850% and the foaming time to be 18 min; obtaining a foamed aluminum sandwich panel with the thickness of 34mm, wherein the appearance is shown in figure 6, and the final expansion rate of the sandwich layer is 850%; the appearance of the cross section of the aluminum foam sandwich panel after the edge portion is cut is shown in fig. 7.

Example 4

The method is the same as example 1, except that:

(1) stirring and mixing graphite powder and transition coating uniformly according to the mass ratio of 1:8 to prepare sticky blackened coating; coating the blackening coating on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment; coating black high-temperature-resistant self-spray paint on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment;

(2) heating a resistance heating furnace to 600 ℃; controlling the core layer expansion rate of the blackened prefabricated plate blank to be 800% and the foaming time to be 16 min; obtaining a foamed aluminum sandwich plate with the thickness of 32mm, wherein the final expansion rate of the sandwich layer is 800%; a photograph of the appearance of the same preform slab in comparison to a sandwich of foamed aluminum sandwich panels is shown in fig. 2.

Claims

1. A foamed aluminum sandwich plate surface blackening foaming method based on rapid heat transfer is carried out according to the following steps:

(1) uniformly mixing aluminum powder/aluminum alloy powder, silicon powder, copper powder, magnesium powder, zinc-white copper powder and a foaming agent to obtain core layer mixed powder; the core layer mixed powder comprises 5-10% of Si by mass percent; 1-8% of Mg, 1-6% of Cu, 0-2% of Zn, 0.5-2% of foaming agent and the balance of Al; the foaming agent is titanium hydride powder;

(2) adopting 3000 series aluminum alloy or 6000 series aluminum alloy pipe or plate; annealing the pipe at 400 +/-10 ℃ for 1-3 h, flattening by using a press machine, and rolling into a tubular cavity by using a rolling mill; or sealing two side edges of two plates which are placed in parallel to form a tubular cavity; the tubular cavity is composed of an upper plate, a lower plate and a connecting part between the upper plate and the lower plate, the upper plate and the lower plate are parallel to each other, and the distance between the upper plate and the lower plate is 20-30 mm; the width of the tubular cavity is 40-1200 mm, and the wall thickness is 2-8 mm;

(3) pretreating the inner surface of the tubular cavity, wherein during pretreatment, firstly, oil stain is removed by alkali washing, then, impurities are removed by acid washing, then, acid liquor is removed by water washing, and finally, water is removed by drying;

(4) taking one end of the tubular cavity subjected to surface pretreatment as a front end and the other end as a tail end; fixing the upper plate and the lower plate together by rivets at the front ends, and taking a gap between adjacent riveted parts as a reserved exhaust hole; placing asbestos or sponge into the tubular cavity from the tail end, filling the mixed powder of the core layer into the tubular cavity from the tail end, and reserving a riveting fixing distance of 30-60 mm at the tail end; adding asbestos or sponge into the tubular cavity from the tail end; the asbestos or sponge added twice covers the core layer mixed powder at the front end and the tail end, and is used for preventing the core layer mixed powder from being discharged along with airflow in the rolling process; then flattening the tail end, fixing the upper plate and the lower plate together through rivets, and taking a gap between adjacent riveted parts as a reserved exhaust hole to manufacture a prefabricated part; the front end and the tail end of the prefabricated part are the front end and the tail end of the tubular cavity;

(5) performing cold rolling on the prefabricated member for 3-7 times, wherein the reduction rate of each time is 3-8%, so that the mixed powder of the core layer and the tubular cavity can achieve primary densification, and preparing a blank; the cold rolling direction is from the tail end to the front end or from the front end to the tail end, and the cold rolling directions of two adjacent passes are opposite;

(6) hot rolling the blank, wherein the initial rolling temperature is 330-480 ℃, the final rolling temperature is 300-450 ℃, and the total reduction rate is 40-70%, so as to obtain a hot rolled plate blank; carrying out heat treatment on the hot-rolled plate blank at 400-500 ℃ for 1-5 h, then carrying out edge cutting treatment, and removing the riveted part to prepare a prefabricated plate blank;

the method is characterized in that:

(7) the method for blackening the single surface of the precast slab comprises the following steps: uniformly stirring and mixing graphite powder and a transition coating according to the mass ratio of 1 (1-8) to prepare a sticky blackening coating; coating the blackening coating on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment; or coating black high-temperature-resistant self-spraying paint on one side surface of the prefabricated plate blank to finish single-side blackening treatment; or covering the graphite plate on the surface of one side of the prefabricated plate blank to finish single-side blackening treatment;

(8) the method for blackening the two surfaces of the prefabricated plate blank subjected to the single-surface blackening treatment comprises the following steps: coating the blackening coating on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or coating black high-temperature-resistant self-spraying paint on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; or covering the graphite plate on the surface of the other side of the prefabricated plate blank to finish double-sided blackening treatment; taking the prefabricated plate blank subjected to the double-sided blackening treatment as a blackening prefabricated plate blank; the other side surface is the surface of the precast slab which is subjected to the single-side blackening treatment and is not subjected to the blackening treatment;

(9) and (3) heating the resistance heating furnace to 580-630 ℃, then placing the blackened prefabricated plate blank in the heated resistance heating furnace for foaming treatment for 10-20 min, and then taking out and cooling to normal temperature to obtain the foamed aluminum sandwich plate.

2. The foamed aluminum sandwich panel surface blackening foaming method based on rapid heat transfer as claimed in claim 1, wherein the foamed aluminum sandwich panel has a core layer expansion rate of 600-900%.

3. The foamed aluminum sandwich panel surface blackening foaming method based on rapid heat transfer as claimed in claim 1, characterized in that the particle size of the graphite powder is 2500-10000 meshes.

4. The method as claimed in claim 1, wherein the transition coating is selected from a ZS-1011 transition coating or a high temperature anti-oxidation coating liquid.

5. The method for blackening and foaming the surface of the foamed aluminum sandwich panel based on rapid heat transfer as claimed in claim 1, wherein the black high temperature self-painting paint is a black high temperature self-painting paint which can resist 800 ℃ in steps (7) and (8).

6. The foamed aluminum sandwich panel surface blackening foaming method based on rapid heat transfer as claimed in claim 1, wherein in the step (9), the cooling manner is air cooling, water cooling or spray cooling.