CN105803298B - A kind of method that blister steel is prepared with pore creating material - Google Patents

Abstract

A kind of method that blister steel is prepared with pore creating material, using straight iron powder and pore creating material as raw material, suppressed after mixing, under argon atmosphere, open-cell formed steel is prepared in sintering；The present invention is on the basis of powder sintering, pore creating material is used as using different-grain diameter, dextrin powder of different shapes and various starch powders etc., it is easily obtained and cheap, without any residual after being thermally decomposed, finally give the block foam steel of Different Pore Structures and porosity, hole parameter is controllable, stable mechanical property, and industrialized production can be achieved.

Description

A method for preparing foamed steel with pore-forming agent

technical field

The invention belongs to the field of porous metal foam manufacturing, in particular to a method for preparing foam steel with a pore-forming agent.

Background technique

Foamed steel is a structure-function integrated material with a large number of connected or disconnected holes evenly distributed in the steel matrix. As a functional material, it has various properties such as sound absorption, heat insulation, flame retardancy, and electromagnetic shielding. As a structural material, by changing the porosity and pore structure, the steel density, elastic modulus and yield strength can be changed. In the case of the same amount of steel, a reasonable design can effectively improve the overall stability and local stability of structural members, thereby increasing the bearing capacity and achieving the purpose of saving steel. Under the action of strong earthquake or impact load, the plastic compression of pores can absorb a large amount of energy and avoid brittle damage to the structure, so it has broad applications in light steel structures, energy dissipation and shock absorbing structures, seismic structures, impact and riot-proof structures, etc. Application prospects.

At present, the preparation methods of foam steel mainly include molten metal foaming method, metal deposition method, hollow ball sintering method, infiltration method and powder sintering method. The melt metal foaming method cannot make the foaming agent evenly dispersed into the melt, the size and uniformity of the bubble distribution are difficult to control, and the mechanical properties of the obtained material are poor; the hollow sphere method has difficulties in preparing hollow spheres and requires high process equipment. Insufficient; the percolation process is long and the precursor is difficult to completely remove. The powder sintering method is a preparation method with simple process and low cost, and its porosity, pore size and pore size distribution can be effectively controlled.

Chinese patent 201410181538.7 discloses a powder sintering method for preparing foamed steel. In this method, steel alloy powder is used as raw material, and potassium carbonate particles are used as a pore-forming agent. The two are mixed uniformly and pressed into a green body, and then the green body is sintered. . However, in this technology, potassium _carbonate may remain in the steel matrix after thermal decomposition of potassium carbonate, which affects the ductility and energy dissipation capacity of the foamed steel.

Contents of the invention

In order to overcome the above-mentioned shortcoming of the prior art, the object of the present invention is to provide a kind of method for preparing foamed steel with pore-forming agent, on the basis of powder sintering method, use the dextrin powder of different particle size, different shape and various starch Powder is used as a pore-forming agent, which is easy to obtain and low in price. After thermal decomposition, there is no residue. Finally, block foam steel with different pore structures and porosity is obtained. The pore parameters are controllable and the mechanical properties are stable, which can realize industrial production.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The invention discloses a method for preparing foamed steel with a pore-forming agent. Pure iron powder and a pore-forming agent are used as raw materials, mixed, pressed, and sintered in an argon protective atmosphere to prepare the open-celled foamed steel.

The pore forming agent is pea powder, corn powder, wheat powder, dextrin powder or cellulose acetate powder.

The volume ratio of pure iron powder to pore former is 4:1, 3:2 and 2:3.

The particle size of the pure iron powder is 400 mesh, and the purity is 98%; the particle size range of the pore-forming agent is 5-30 μm, the pure iron powder is mixed with the pore-forming agent in the particle size range, put into a ball mill tank, and add The graded iron balls were fully mixed for 12 hours to form a mixed powder.

The pressing is to put the mixed pure iron powder and pore-forming agent into a pressing mold, pressurize 90-120 MPa bidirectionally at room temperature, and press for 1 minute to make a green body.

Described sintering process is:

Put the pressed green body directly into the controllable atmosphere furnace. After vacuuming, argon gas is introduced, and the temperature is raised to 500°C at a rate of 1°C/min and kept for 1 hour, so that the pore-forming agent is fully decomposed and volatilized and discharged out of the furnace; Then raise the temperature to 1100°C at a rate of 8°C/min and keep it warm for 2 hours. After the sintering is completed, it is cooled to room temperature with the furnace, and the foamed steel is obtained after taking it out.

Compared with the prior art, the invention has simple process, readily available raw materials, low cost, no residue after thermal decomposition of the product, controllable pore parameters, stable mechanical properties, and can realize industrial production.

Description of drawings

Fig. 1 is a pore size distribution diagram of foamed steel prepared by sacrificial template method with 20vol.% dextrin as a pore-forming agent by volume ratio.

Fig. 2 is a scanning electron micrograph of a foamed steel prepared by a sacrificial template method with dextrin at a volume ratio of 20 vol.% as a pore-forming agent.

Fig. 3 is a pore size distribution diagram of foamed steel prepared by sacrificial template method with 40vol.% dextrin as a pore-forming agent by volume.

Fig. 4 is a scanning electron micrograph of a foamed steel prepared by a sacrificial template method with 40 vol.% dextrin as a pore-forming agent.

Figure 5 is the XRD pattern of the sintered product.

detailed description

The implementation of the present invention will be described in detail below in conjunction with the drawings and examples.

A method for preparing foamed steel of the present invention, using pure iron powder and pore-forming agent powder as raw materials, adopts argon protection sintering to prepare open-celled foamed steel, the specific steps and process conditions are:

(1) Uniform mixing of pure iron powder and pore-forming agent

Mix the pure iron powder with a particle size of 400 mesh and the above-mentioned pore-forming agents with different particle sizes respectively, put them into a ball mill jar, add graded iron balls, and mix thoroughly for 12 hours to form a mixed powder.

(2) suppression

Put the mixed powder obtained in the step (1) into a pressing mold, pressurize bidirectionally at 90-120 MPa at room temperature, and press for 1 minute to make a green body.

(3) Gas protection sintering

The green body obtained in step (2) is directly placed in a controlled atmosphere furnace, and argon gas is introduced after vacuuming. First raise the temperature to 500°C at a rate of 1°C/min and keep it warm for 1 hour, so that the pore-forming agent is fully decomposed and volatilized and discharged out of the furnace. Then the temperature was raised to 1100°C at a rate of 8°C/min and kept for 2 hours. After the sintering is completed, it is cooled to room temperature with the furnace, and the foamed steel can be obtained by taking it out.

Based on above-mentioned technology, the present invention provides following embodiment:

Example 1

(1) The pore-forming agent is dextrin powder.

(2) Mix the pore-forming agent with iron powder according to the volume fraction of 20%, 40% and 60%, put it into a ball mill jar, add graded iron balls, and mix thoroughly for 12 hours to form a mixed powder.

(3) suppression

Put the mixed powder obtained in the step (2) into a pressing mold, pressurize bidirectionally at 90-120 MPa at room temperature, and press for 1 minute to make two kinds of green bodies, cylindrical and long.

(4) Gas protection sintering

The green body obtained in step (3) is directly placed in a controlled atmosphere furnace, and argon gas is introduced after vacuuming. First raise the temperature to 500°C at a rate of 1°C/min and keep it warm for 1 hour, so that the pore-forming agent is fully decomposed and volatilized and discharged out of the furnace. Then the temperature was raised to 1100°C at a rate of 8°C/min and kept for 2 hours. After the sintering is completed, it is cooled to room temperature with the furnace, and the foamed steel can be obtained by taking it out.

(5) The main characteristics of the obtained foam steel: the porosity of the sintered product corresponding to the volume fraction of pore-forming agent of 20%, 40% and 60% is 41%±1%, 46%±1% and 56%±1% respectively , The quasi-static compressive yield strengths were 69±3MPa, 41±2MPa and 25±2MPa, respectively, and the tensile breaking strengths were 51±1MPa, 37±1MPa and 22±1MPa, respectively.

Example 2

The pore-forming agent is corn flour. Then, according to the steps of Example 1, the main characteristics of the obtained foamed steel: the porosity of the sintered product corresponding to the volume fraction of pore-forming agent of 20%, 40% and 60% is 42% ± 1%, 48% ± 1% respectively and 57%±1%, the quasi-static compressive yield strengths are 50±2MPa, 34±2MPa and 22±2MPa respectively, and the tensile breaking strengths are 43±2MPa, 29±1MPa and 18±1MPa respectively.

Example 3

The pore-forming agent is wheat powder. Then, according to the steps of Example 1, the main characteristics of the obtained foamed steel: the porosity of the sintered product corresponding to the volume fraction of the pore forming agent of 20%, 40% and 60% is 44% ± 1%, 48% ± 1% respectively and 55%±1%, the quasi-static compressive yield strengths are 44±3MPa, 33±2MPa and 25±2MPa respectively, and the tensile breaking strengths are 47±2MPa, 31±1MPa and 21±1MPa respectively.

Example 4

The pore-forming agent chooses pea powder. Then, according to the steps of Example 1, the main characteristics of the obtained foamed steel: the porosity of the sintered product corresponding to the volume fraction of the pore forming agent of 20%, 40% and 60% is 46% ± 1%, 51% ± 1% respectively and 56%±1%, the quasi-static compressive yield strengths are 37±2MPa, 30±2MPa and 17±1MPa respectively, and the tensile breaking strengths are 27±2MPa, 22±1MPa and 13±1MPa respectively.

It can be seen from Figures 1 and 3 that when the volume fraction of the pore-forming agent is 20 vol.%, the average pore diameter of the sample is 2 μm; when the volume fraction of the pore-forming agent is 40 vol.%, the average pore diameter of the sample is 3 μm. It can be seen from Figure 2 and Figure 4 that the shape of the pores in the sample retains the shape of the pore-forming agent. The pore shape of the sintered samples did not change much with the increase of the content of the pore former. Using the image analysis software Image Pro-Plus, the average pore diameters of the two samples were 10 μm and 14 μm, respectively. The average pore diameter obtained by scanning electron microscopy is larger than that measured by mercury intrusion porosimetry. This is because the prepared sample contains some closed pores, and the pore diameter measured by mercury porosimetry is only for open pores. In addition, dextrin acts as a pore-forming agent and easily forms "ink bottle-like" pores in the sintered samples. It can also be seen from Figure 2 and Figure 4 that the fracture mode of the sample is mainly transgranular fracture, and the average thickness of the cell walls of the foamed steel prepared with the content of pore-forming agent of 20vol.% and 40vol.% is 9μm and 8μm, respectively.

The XRD of the sintered product is shown in Figure 5. It can be seen from the figure that the sample obtained after sintering at 1100°C and holding for 2 hours only has the typical diffraction peak of Fe, indicating that various pore-forming agents are fully burned during the sintering process, and there is no residual pore-forming agent in the product, only the raw material The matrix Fe in.

Taking dextrin as a pore-forming agent as an example, the porosity of the sintered product corresponding to the volume fraction of 20%, 40% and 60% of the pore-forming agent is 41±1%, 46±1% and 56±1%, respectively, and the average pore diameter is respectively 10 μm, 14 μm, and 19 μm, and the average wall thicknesses are 9 μm, 8 μm, and 7 μm, respectively. Using other pore-forming agents, the corresponding pore parameters were also obtained, and the pore parameters were proved to be stable by repeated experiments.

Taking dextrin as a pore-forming agent as an example, the volume fraction of the pore-forming agent is 20%, 40% and 60%, and the average value of 10 samples is taken in each case. The results of multiple samples prove that the mechanical performance parameters are stable. The corresponding quasi-static compressive yield strengths of sintered products are 69±3MPa, 41±2MPa and 25±2MPa respectively, the tensile fracture strengths are 51±1MPa, 37±1MPa and 22±1MPa respectively, and the Vickers hardness ratio is 28HV/0.05 , 26HV/0.05 and 22HV/0.05. The mechanical properties decrease with the increase of pore-forming agent content, which is also consistent with the results of fracture scanning, that is, with the increase of pore-forming agent content, the average pore diameter increases and the average pore wall becomes thinner. Using other pore-forming agents, the corresponding mechanical property parameters were obtained respectively.

Claims (2)

1. a kind of method that blister steel is prepared with pore creating material, using straight iron powder and pore creating material as raw material, suppressed after mixing, Under argon atmosphere, the blister steel in the hole containing opening and closing is prepared in sintering, it is characterised in that：The pore creating material be pea powder, Corn powder, wheat powder, dextrin powder or cellulose acetate powder；

The pure iron Powder Particle Size is 400 mesh, purity 98%；The pore creating material particle size range is 5~30 μm, by straight iron powder with being somebody's turn to do The pore creating material mixing of particle size range, is put into ball grinder, adds the iron ball of grading, mixed powder is formed after being sufficiently mixed 12 hours End；

The compacting is that the straight iron powder of mixing and pore creating material are loaded into compacting tool set, at room temperature 90~120MPa of Bidirectional-pressure, Press time 1min, is made green compact；

The sintering process is：

The green compact that compacting obtains are placed directly within controlled atmosphere generator, argon gas are passed through after vacuumizing, first with 1 DEG C/min speed liter Temperature is to 500 DEG C and is incubated 1 hour, pore creating material is fully decomposed volatilization and discharges out of the furnace；Then it is warming up to 8 DEG C/min speed 1100 DEG C and be incubated 2 hours, cool to room temperature after the completion of sintering with the furnace, take out and produce blister steel.

2. the method for blister steel is prepared with pore creating material according to claim 1, it is characterised in that the body of straight iron powder and pore creating material Product is than being 4:1、3:2 or 2:3.