CN110496967B

CN110496967B - Method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion

Info

Publication number: CN110496967B
Application number: CN201910807027.4A
Authority: CN
Inventors: 孙继锋; 李�昊; 杨良良; 孙浩; 杨旗
Original assignee: Shanghai Institute of Materials
Current assignee: Shanghai Material Research Institute Co ltd
Priority date: 2019-08-29
Filing date: 2019-08-29
Publication date: 2021-12-28
Anticipated expiration: 2039-08-29
Also published as: CN110496967A

Abstract

The invention relates to a method for preparing a FeCrAl metal honeycomb carrier for an infrared burner by plasticizing extrusion. The process comprises the following steps: uniformly mixing FeCrAl pre-alloy powder with rare earth additive powder; putting the obtained mixed powder into a kneader, adding a water-based binder, kneading into a briquette, and then uniformly mixing; putting the mixed blank group into an extruder, and extruding a porous blank body through an extrusion die with a plurality of fine needles; and drying the porous blank, heating to remove the binder, and sintering to obtain the integrated FeCrAl metal honeycomb carrier for the infrared burner. The honeycomb material obtained by the invention has excellent metallurgical bonding inside, the hole wall is rich in holes, and the honeycomb material has high hardness and strength and excellent oxidation resistance and thermal shock resistance. Compared with the prior art, the method realizes purification and activated sintering by adding the rare earth element into the FeCrAl powder serving as the raw material on the basis of not changing the existing production line, improves the microstructure and the performance of a sintered body, and is beneficial to industrial popularization.

Description

Method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion

Technical Field

The invention relates to the field of preparation of porous metal materials, in particular to a method for preparing a FeCrAl metal honeycomb carrier for an infrared burner by plasticizing and extruding.

Background

The infrared combustion is an energy-saving and environment-friendly combustion technology, and the core of the infrared combustion technology is an infrared combustion plate, namely a honeycomb carrier. In order to fully exploit the advantages of infrared combustion and ensure a sufficient service life, infrared combustion plates are required: a plurality of communicating holes for gas to flow and burn; the hole wall and the interior are rich in small holes to improve the steady flow, reduce the thermal conductivity (tempering risk) and enhance the adhesion of the catalyst; the plate surface has high compressive strength, high temperature resistance and thermal shock resistance.

At present, the known honeycomb carriers for infrared combustion mainly comprise two types, namely monolithic cordierite ceramic honeycomb carriers and metal foil tape winding type honeycomb carriers. The ceramic carrier has good stability, high cost performance and easy mass production, but has the defects of poor toughness, poor thermal shock resistance and the like, and the ceramic plate is easy to crack in the using process. The FeCrAl metal foil winding type honeycomb carrier has the advantages of high strength, good toughness and the like, but the processing technology is complex, the foil is smooth and not tightly combined with a catalyst, and the combustion airflow cannot be stabilized; in addition, welding points between the foil strips are easy to fall off in a severe use environment, and great hidden danger exists.

The plasticizing extrusion method is characterized in that a plasticizer is added into metal powder, the metal powder is uniformly mixed and then extruded into a porous blank through a die with a plurality of fine steel needles, and the blank is dried, debonded and sintered to obtain the metal honeycomb member. The development of metallic honeycomb supports prepared from FeCrAl and stainless steel powders has been reported for automobile exhaust purification treatment, but the requirements are different from those for infrared combustion. The temperature is higher during infrared combustion, which can reach 1100 ℃, and the alternating stress caused by cold and heat is larger, so the requirements on the oxidation resistance and the thermal shock resistance of the honeycomb material are higher. Moreover, the infrared combustion body requires that the hole wall is rich in small holes to reduce the heat conductivity and the risk of tempering and the like, which is different from the requirement of high heat conductivity of a metal carrier for treating automobile exhaust.

Although the FeCrAl infrared heating carrier prepared by adopting the plasticizing extrusion method reported in the literature (Zhouyu, the research on the process, the performance and the theory of preparing the metal honeycomb material by plasticizing extrusion-sintering of powder, Kunming university, 2007) can be formed, a sample is cracked in an air cooling test after the temperature is kept at 1000 ℃ (the thermal shock property of the plate is not too close), and the analysis shows that Al is formed on the surface of powder particles in the plate₂O₃Resulting in weak bonding between particles. This is mainly because the FeCrAl alloy powder particles are of "egg shell structure", i.e. there is a layer of oxide film on the surface of the powder particles, which strongly hinders the sintering process, so that the original particle boundaries inside the sintered FeCrAl alloy are obvious, and the alloy plasticityPoor, cracking under large stresses induced by rapid cooling and heating. In addition, the use of large amounts of binders in the plasticization and extrusion process, which are mostly organic, leads to decomposition and contamination of the powder particle surfaces, which also hinders subsequent sintering. From the conventional powder metallurgy, loose sintering can be adopted to increase the number of micropores in the material, or the sintering temperature can be reduced to shorten the sintering time, but the bonding force of the powder particles is weak. If the sintering temperature is increased or the sintering time is prolonged, the porosity of the sintered body is reduced although the bonding force of the powder particles is increased.

Disclosure of Invention

The invention aims to overcome the defects and provide an improved method for preparing FeCrAl metal honeycomb carriers for infrared burners by plasticizing extrusion.

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

a method for preparing FeCrAl metal honeycomb carrier for an infrared burner by plasticizing extrusion comprises the following steps:

(1) mixing powder: uniformly mixing FeCrAl pre-alloy powder with rare earth additive powder;

(2) kneading and mixing: putting the mixed powder obtained in the step (1) into a kneader, adding a water-based binder, kneading into a briquette, and then uniformly mixing;

(3) extruding: putting the mixed blank group into an extruder, and extruding a porous blank body through an extrusion die with a plurality of fine needles;

(4) and (3) debonding and sintering: and drying the porous blank, heating to remove the binder, and sintering to obtain the integrated FeCrAl metal honeycomb carrier for the infrared burner.

In one embodiment of the present invention, in the FeCrAl pre-alloyed powder in the step (1), the mass percentages of the elements are Cr: 20-25%, Al: 4.5-5.5%, C: < 0.1%, Si: < 0.7%, Mn: < 0.5%, O < 0.8%, and the balance Fe.

In one embodiment of the invention, the powder particle size is less than 45 μm.

In one embodiment of the invention, the stepsIn the step (1), the rare earth additive powder is selected from Y simple substance or YH₂Or Y with YH₂A mixture of (a).

In one embodiment of the invention, the rare earth additive powder has a particle size of less than 45 μm.

In one embodiment of the present invention, the FeCrAl pre-alloyed powder and the rare earth additive powder in step (1) are mixed while being protected with an inert gas to prevent the rare earth metal from being oxidized, and the FeCrAl pre-alloyed powder and the rare earth additive powder in step (1) are mixed for 0.5 to 1 hour; the addition amount of the rare earth additive is 0.1-0.3 percent of the total weight of the FeCrAl pre-alloy powder and the rare earth additive powder.

In one embodiment of the present invention, the weight formula of the aqueous binder in step (2) comprises: 5-15% of polyethylene glycol, 10-30% of methyl cellulose, 5-10% of glycerol and the balance of water.

In one embodiment of the present invention, in the step (2), the mass ratio of the mixed powder to the aqueous binder is 7:3 to 9: 1.

In one embodiment of the present invention, in the step (2), the kneading time is 30 to 60 min.

In one embodiment of the present invention, in the step (2), the mixing time is 30 to 60 min.

In one embodiment of the present invention, the extrusion ratio at the time of the extrusion in the step (3) is 2 to 10, and the extrusion pressure is less than 100 MPa.

In one embodiment of the present invention, the drying temperature in step (4) is 100-150 ℃ and the drying time is 12-24 h.

In one embodiment of the present invention, the temperature of the binder removal treatment in step (4) is 400 to 800 ℃.

In one embodiment of the present invention, the sintering temperature in step (4) is 1250-.

In one embodiment of the present invention, the heating treatment or the sintering treatment in step (4) is performed under vacuum or under an inert gas atmosphere.

The binder formulation is the core during the molding process. The binder comprises a bonding component, a plasticizer component, a lubricating component and a solvent.

Methylcellulose is selected as a binding and plasticizing component to increase the plasticity of the metal and improve the ability to form porous honeycombs. If the content is too low, the powder is difficult to bond, and the extrusion pressure is extremely high; if the temperature is too high, the blank is easy to have the defects of bubbling, cracking, collapse, deformation and the like in the debonding process, and the appearance of the product are difficult to ensure to be lossless. According to the using effect, the content is selected from 10 to 30 percent, so that a satisfactory extrusion blank and a satisfactory sintered body can be obtained.

Polyethylene glycol is selected as lubricating property, so that the friction force between the blank and the die can be reduced, and the integrity of the wall of the hole of the extruded blank is ensured. In the binder proportion, if the content is too low, the lubricating effect is not obvious; if the content is too high, the content is seriously volatilized in the subsequent debonding process, so that blank defects are caused. According to the using effect, the content is selected from 5 to 15 percent, so that a satisfactory extrusion blank and a satisfactory sintered body can be obtained.

Glycerin is selected as a humectant, so that the surface of a blank cluster after mixing can be prevented from crusting to influence the continuity of the extrusion process, and the surface of an extruded blank can be prevented from being dried and cracked too early. According to the using effect, the content is selected from 5 to 10 percent, and satisfactory extrusion blanks and sintered bodies can be obtained.

Water is selected as a solvent, and the compatibility with methyl cellulose is good; the source is wide, and the cost is low; in addition, water is easy to remove in the subsequent drying process of the extrusion billet and has no pollution.

After the extruded porous blank is formed, the sintering process, including temperature and time, has a significant effect on the final particle-to-particle bond and porosity. The sintering process is generally controlled by diffusion of substances, and increasing the sintering temperature or prolonging the sintering time is beneficial to the diffusion process, and finally can improve the bonding between particles, but at the same time, the porosity of the material is reduced, which is not beneficial to being used as a heating carrier of an infrared burner. To achieve both excellent particle bonding (meaning high strength) and high porosity in the walls and interior of the pores requires that the blank be capable of being sintered in a short time.

According to the invention, a small amount of rare earth element Y is mixed into FeCrAl pre-alloy powder, the egg shell structure of particles is destroyed by utilizing the reaction of Y and surface oxide in the sintering process, and meanwhile, Y and Fe react to generate an instantaneous liquid phase to generate activated sintering, so that the sintering process is promoted. By increasing the content of the rare earth elements, the amount of transient liquid phase sintering can be increased, and then the powder particles form good metallurgical bonding at a low sintering temperature or in a short time, and a large number of holes are reserved.

Compared with the prior art, the honeycomb material prepared by the method has excellent metallurgical bonding inside, the hole wall is rich in holes, and the honeycomb material has high hardness and strength, and excellent oxidation resistance and thermal shock resistance. Compared with the prior art, the method realizes purification and activated sintering by adding the rare earth element into the FeCrAl powder serving as the raw material on the basis of not changing the existing production line, improves the microstructure and the performance of a sintered body, and is beneficial to industrial popularization.

Drawings

FIG. 1 shows the microstructure and fracture characteristics of a FeCrAl honeycomb sintered body in comparative example 1, wherein (a) and (b) are metallographic structures of a honeycomb material, and (c) is fracture morphology, and oxide particles containing a large amount of white aluminum are visible in the fracture; the sintering condition is 1250 ℃, and the time is 0.5 h;

FIG. 2 shows the microstructure characteristics of the FeCrAl honeycomb sintered body in comparative example 2, and the sintering conditions are 1350 ℃ and 0.5 h.

FIG. 3 is a macroscopic view of a FeCrAl honeycomb sintered body containing 0.1% Y prepared in example 1, sintering conditions are 1250 ℃, 0.5 h;

FIG. 4 shows microstructure and fracture characteristics of a FeCrAl honeycomb sintered body containing 0.1% Y prepared in example 1, (a) and (b) are metallographic structures of the honeycomb material, and (c) is fracture morphology;

FIG. 5 shows the microstructure characteristics of a FeCrAl honeycomb sintered body containing 0.3% Y prepared in example 2. The sintering condition is 1250 ℃, and the time is 0.5 h;

FIG. 6 is a microstructure characterization of FeCrAl honeycomb sintered body with 0.3% Y prepared in example 3, using YH₂As a source of the rare earth element Y, the alloy is sintered for 1h at 1250 ℃ in Ar gas atmosphere.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Comparative example 1

(1) Kneading and mixing: FeCrAl pre-alloy powder (the particle size is less than 45 mu m) is put into a kneader, premixed with aqueous binder accounting for 10 percent of the total mass for 30min, and then mixed for 60min on a vacuum pugmill to prepare a blank mass.

(2) Extruding: and putting the blank pellets into an extruder, and extruding the honeycomb material under the pressure of less than 100 MPa.

(3) And (3) debonding and sintering: drying the honeycomb biscuit at 120 ℃ for 12h, slowly heating to about 400 ℃ at a speed of 2 ℃/min in a vacuum furnace, and preserving heat for 1 h; then slowly raising the temperature to 800 ℃ at a speed of 1.5 ℃/min, preserving the temperature for 1h, and removing the binder; finally sintering the mixture in vacuum at 1250 ℃ for 0.5h, and cooling the mixture along with the furnace. The mass formula of the water-based binder is as follows: 10% of polyethylene glycol, 20% of methyl cellulose, 5% of glycerol and the balance of water.

FIG. 1 shows the microstructure and fracture characteristics of FeCrAl honeycomb sintered body, and it can be seen that although the sintered body contains a large amount of pores, the appearance of spherical powder particles still exists, indicating that the neck development is not good and the bonding between particles is weak; the fractures show that the interior of the sintering neck contains aluminum oxide particles. The Hv hardness of the hole wall was 99, and the compressive strength in the direction of the through hole was 45 MPa.

Comparative example 2

The comparative example differs from comparative example 1 in that the sintering temperature was 1350 ℃. From the microscopic structure of fig. 2, the sintering between particles is good, but the internal micropores are few, which is not favorable for the use as the infrared burner carrier.

Example 1

The difference between this example and comparative example 1 is that 0.1% by weight of Y powder (particle size <45 μm) based on the total powder mass was added to FeCrAl pre-alloy powder and the two were Ar-mixed in a V-blender for 60 min.

FIG. 3 is a photomicrograph of a FeCrAl honeycomb sintered body containing 0.1% Y, showing good appearance and metallic luster.

Fig. 4 shows the microstructure and fracture characteristics of the sintered body. It can be seen that the sintering necks between the powder particles develop well; the fracture is clean. The Hv hardness of the sintered body hole wall was 132, and the compressive strength in the through hole direction was 49 MPa.

The material is water quenched after being kept at 1000 ℃, and has no cracking, and no cracking phenomenon after repeated use, which shows that the porous material has excellent oxidation resistance and thermal shock resistance.

Example 2

This example differs from example 1 in that the Y powder accounts for 0.3% of the total mass.

Fig. 5 is a microstructure of a sintered body, the porosity of the sintered body of 0.3% Y is increased and exhibits a communicating character with respect to the sintered body of 0.1% Y, mainly due to the fact that Y and Fe generate more transient liquid phase during sintering, and the liquid phase flows out under gravity (liquid phase condensate is found at the bottom of the sintered body) to form pores.

The Hv hardness of the hole wall was 72, and the compressive strength in the direction of the through hole was 35 MPa. The material is water quenched after being kept at 1000 ℃, and has no cracking, and no cracking phenomenon after repeated use, which shows that the porous material has excellent oxidation resistance and thermal shock resistance.

Example 3

The difference between this example and example 1 is that YH is used₂As a source of the rare earth element Y, Y powder accounts for 0.3% of the total mass. And (3) removing the binder from the extruded blank in an Ar gas environment, and sintering at 1250 ℃ for 1 h.

Fig. 6 is a microstructure of a sintered body, all exhibiting good metallurgical bonding and containing abundant porosity, similar to fig. 5.

The Hv hardness of the hole wall was 74, and the compressive strength in the direction of through-hole was 37 MPa. The material is water quenched after being kept at 1000 ℃, and has no cracking, and no cracking phenomenon after repeated use, which shows that the porous material has excellent oxidation resistance and thermal shock resistance.

Example 4

(1) Mixing powder: the FeCrAl pre-alloy powder was added with Y powder (particle size <45 μm) in an amount of 0.2% by mass of the total powder, and the two were mixed in a V-type mixer with Ar for 0.5 hour. And inert gas is adopted for protection during mixing so as to prevent the rare earth metal from being oxidized.

(2) Kneading and mixing: putting the mixed powder into a kneader, adding a water-based binder, kneading into a blank cluster, and then uniformly mixing on a vacuum pugmill; wherein the water-based binder comprises the following components in percentage by weight: 5% of polyethylene glycol, 30% of methyl cellulose, 10% of glycerol and the balance of water; the mass ratio of the mixed powder to the binder was 7: 3. The kneading time was 60min, and the mixing time was 30 min.

(3) Extruding: putting the mixed blank group into an extruder, and extruding a porous blank body through an extrusion die with a plurality of fine needles; the extrusion ratio of the extrusion is 2, and the extrusion pressure is less than 100 MPa.

(4) And (3) debonding and sintering: drying the honeycomb biscuit at 100 ℃ for 24h, slowly heating to about 450 ℃ at a speed of 2 ℃/min in a vacuum furnace, and preserving heat for 1 h; then slowly heating to 800 ℃ at the speed of 2 ℃/min, preserving the heat for 1h, and removing the binder; finally, sintering at 1350 ℃ for 0.5h in vacuum.

The Hv hardness of the hole wall of the material is 70, and the compressive strength along the direction of the through hole is 36 MPa. The material is water quenched after being kept at 1000 ℃, and has no cracking, and no cracking phenomenon after repeated use, which shows that the porous material has excellent oxidation resistance and thermal shock resistance.

Example 5

(1) Mixing powder: adding YH accounting for 0.25 percent of the total powder mass into FeCrAl pre-alloy powder₂Powder (particle size)<45 μm) were mixed in a V-type blender with Ar for 1 hour. And inert gas is adopted for protection during mixing so as to prevent the rare earth metal from being oxidized.

(2) Kneading and mixing: putting the mixed powder into a kneader, adding a water-based binder, kneading into a blank cluster, and then uniformly mixing on a vacuum pugmill; wherein the water-based binder comprises the following components in percentage by mass: 15% of polyethylene glycol, 10% of methyl cellulose, 5% of glycerol and the balance of water; the mass ratio of the mixed powder to the binder was 9: 1. The kneading time was 30min, and the mixing time was 60 min.

(3) Extruding: putting the mixed blank group into an extruder, and extruding a porous blank body through an extrusion die with a plurality of fine needles; the extrusion ratio of extrusion is 10, and the extrusion pressure is less than 100 MPa.

(4) And (3) debonding and sintering: drying the honeycomb biscuit at 150 ℃ for 12h, slowly heating to about 420 ℃ at 1.2 ℃/min in an Ar atmosphere protection furnace, and preserving heat for 1 h; then slowly heating to 800 ℃ at the speed of 2 ℃/min, preserving the heat for 1h, and removing the binder; finally sintering at 1250 ℃ for 3h in an inert gas atmosphere.

The Hv hardness of the hole wall of the material is 105, and the compressive strength along the direction of the through hole is 45 MPa. The material is water quenched after being kept at 1000 ℃, and has no cracking, and no cracking phenomenon after repeated use, which shows that the porous material has excellent oxidation resistance and thermal shock resistance.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A method for preparing FeCrAl metal honeycomb carrier for an infrared burner by plasticizing extrusion is characterized by comprising the following steps:

(4) and (3) debonding and sintering: drying the porous blank, heating to remove the binder, and sintering to obtain an integrated FeCrAl metal honeycomb carrier for the infrared burner;

in the step (1), the rare earth additive powder is selected from Y simple substance or YH₂Or Y with YH₂The particle size of the rare earth additive powder is less than 45 mu m;

the sintering temperature in the step (4) is 1250-1350 ℃, and the sintering time is 0.5-3 h;

the 'egg shell structure' of the particles is damaged by the reaction of Y and surface oxides in the sintering process, and meanwhile Y and Fe react to generate an instantaneous liquid phase to generate activation sintering, so that the sintering process is promoted, the powder particles form metallurgical bonding, and a certain amount of pores are reserved.

2. The method for preparing the FeCrAl metal honeycomb carrier for the infrared burner by plasticizing and extruding according to claim 1, wherein in the FeCrAl pre-alloy powder in the step (1), the mass percentages of the elements are Cr: 20-25%, Al: 4.5-5.5%, C: < 0.1%, Si: < 0.7%, Mn: < 0.5%, O < 0.8%, and the balance Fe, wherein the particle size of the powder is less than 45 μm.

3. The method for preparing a FeCrAl metal honeycomb carrier for an infrared burner through plasticization and extrusion as claimed in claim 1, wherein the FeCrAl pre-alloy powder is mixed with the rare earth additive powder in step (1) under the protection of inert gas to prevent the rare earth metal from being oxidized, and the FeCrAl pre-alloy powder is mixed with the rare earth additive powder in step (1) for 0.5-1 h; the addition amount of the rare earth additive is 0.1-0.3 percent of the total weight of the FeCrAl pre-alloy powder and the rare earth additive powder.

4. The method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion according to claim 1, wherein the weight formula of the aqueous binder in step (2) comprises: 5-15% of polyethylene glycol, 10-30% of methyl cellulose, 5-10% of glycerol and the balance of water.

5. The method for preparing the FeCrAl metal honeycomb carrier for the infrared burner through plasticizing and extruding according to claim 1, wherein in the step (2), the mass ratio of the mixed powder to the water-based binder is 7: 3-9: 1.

6. The method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion according to claim 1, characterized in that in step (2), the kneading time is 30-60min, and the mixing time is 30-60 min.

7. The method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion according to claim 1, wherein the extrusion ratio in the extrusion in the step (3) is 2-10, and the extrusion pressure is less than 100 MPa.

8. The method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion as claimed in claim 1, wherein the drying temperature in step (4) is 100-150 ℃ and the drying time is 12-24 h;

the temperature of the de-bonding treatment in the step (4) is 400-800 ℃.

9. The method for preparing FeCrAl metal honeycomb carrier for infrared burner by plasticizing extrusion according to claim 1, wherein the de-binding treatment or sintering treatment in step (4) is performed under vacuum or protective atmosphere.