KR970001003B1 - Forming method for compound particles layer sintered by coating pulverulent body - Google Patents

Abstract

Process for making a powder layer on a metal surface by electrostatic followed by sintering consists of, i)washing to eliminate a contamin-ant from metal surface(1), ii)dring, iii)spraying a mixture(2) of alloy powder, carbon powder and additives on a metal surface(1) under the electrostatic state, iv)sintering it at a predetermined temperatu-re. In the process, mixed powder consists of 6.5 wt.% of Cr, 4.96 wt.% of Mo, 1.25 wt.% of P, 1 wt.% of C, 86.29 wt.% of Fe, and below 0.5 wt.% of additives in which the particle size of componant is below 7 microns.

Description

Formation method of powder sintered layer by powder coating method

1 is an overall process diagram of the present invention.

2 is an installation diagram for the electrostatic spraying process of FIG.

* Explanation of symbols for main parts of the drawings

A: washing process B: drying process

C: electrostatic spraying process D: sintering process

1: target sample 2: mixed powder

3: storage container 4: high pressure hose

5: high voltage current generator 6: electrostatic spraying

7: electrostatic spray room 8 transfer means

9: duct 10: cyclone

11: pipeline 12: pocket filter

13: exhaust fan

The present invention relates to a method of forming a powder layer for forming a powder sintered layer on the metal surface to improve the wear resistance of the metal, in particular an alloy on the surface of the target specimen made of SKD-11 material, which is a special steel that is often used as a base material for molds Powder, carbon powder, and additives are powdered and then formed into a powder layer by using static electricity, and then powder sintered layer by powder coating method to easily obtain powder sintered layer having excellent abrasion resistance by sintering. It relates to a method of forming.

In general, in the parts of automobile parts such as rocker arms, cams, gears, and valves, which require abrasion resistance, various metal surface hardening methods using physical and chemical methods are used to harden the surface of the working part. Among them, the patent application No. 88-13298 filed by the present applicant is made of a solution having an appropriate viscosity to melt and spray the alloy powder and synthetic resin mixture in a solvent and sprayed locally on the metal surface where the powder sintered layer is needed. Next, a method of forming a metal composite carbide having high hardness and high wear resistance by performing liquid phase sintering at a high temperature around 1,100 ° C. is disclosed. In the method of forming the powder sintered layer, carbon is formed in the powder sintered layer. While forming complex carbide, complete metallurgical bonding of metal matrix and powder sintering layer by diffusion Although it plays the most important role, the carbon is mainly mixed with alloy powder, so the specific gravity of carbon is extremely small compared to the metal powder, so it is not sufficiently mixed and floated to the upper part. There was a problem that spraying is difficult.

This problem is not a problem for cast iron containing a large amount of carbon in the base material, but in general low carbon steel containing less carbon, it is necessary to supply a sufficient and stable amount of carbon required to form metal carbide. There was a difficult issue.

In addition, a method for enabling a stable carbon supply by spraying the carbon powder layer separately to compensate for such a problem is disclosed in the patent application No. 92-19780 filed by the present applicant.

However, in the formation of the powder sintered layer by the spray method described above, there are important enumerated problems, namely

1) Problems with the content of resin: Original resin plays the role of giving the initial adhesiveness to bond the metal powders to the surface of the base material, the higher the content of the resin is added, the higher the bonding strength, the higher the spray layer density However, the resin occupies a large volume, and the resin heated at 300 to 400 ° C decomposes by heat to form pores as much as the space occupied by the resin. Therefore, the resin content is preferably minimized. There was a problem that the roughness was poor, and when spraying, the nozzle was clogged or a powder layer of sufficient thickness could not be obtained;

2) Problems caused by the use of solvents: Solvents commonly used for viscosity control for dissolving resins and spraying during ease of spraying are volatile in their physical properties. When a large amount of solvent is contained in a specific portion of the sprayed powder layer during the sintering process, there is a problem that a small explosion occurs, causing damage to the surface of the powder sintered layer, thereby making the material vulnerable;

3) Problems with spray work: In order for the powder layer formed on the base material to have a certain thickness, it must be sprayed several times (at least three times) by a skilled worker or an automated equipment. The powder layer to be formed may easily have a constant thickness, but there is a problem in that the powder layer to be formed is not uniform in cases such as bends and corners;

4) Problems in the reuse of raw powder: In the case of recovering and reusing the mixture sprayed out of the target specimen during the spraying operation, re-introduction of the solvent, control of the resin content, re-introduction of the settling agent and Many processes, such as the control of the content of the alloy powder has to be added, the economical efficiency of the recycling of the raw material powder is considered, the practical reuse is not possible;

5) Problems in SWTTING PROCESS: After the spraying is completed, the mixed powder layer gives the fluidity of air in the static state in the static state in order to induce initial adhesion with the sample and evaporation of the solvent. Although the solvent may evaporate to obtain a good surface roughness, a large amount of space must be secured, a large amount of process energy is required, and during the fixing process, in order to have a large amount of specimens in such a good condition. Gravity was applied to the mixed powder layer attached to the vertical portion of the specimen surface, causing a problem that the thickness between the upper and lower portions of the vertical portion was changed.

Therefore, the present invention was invented to solve the above problems, and the alloy powder and additives in the powder state of 7㎛ or less in the state of eliminating the use of solvents and synthetic resins, and then to the high By adhering and grounding the target specimen, the powder layer can be adhered to the target specimen, and the desired thickness of the powder layer can be obtained even with a single coating to improve the work efficiency, while the arrival efficiency (that is, the powder particles can be applied to the target specimen). It is an object of the present invention to provide a method for forming a powder sintered layer by the powder coating method, which has an increased amount of 95% or more than conventional spray powder particles.

It is also possible to arbitrarily form the powder layer thickness on all or selected portions of the specimen by adjusting the amount of electrostatic charge or the time to impart.The sintering process in the state of static charge causes the powder layer to deflect, ie vertical The purpose is to prevent the thickness of the powder layer of one part from becoming uneven.

The present invention for achieving the above object, the washing step to wash and remove the contaminants stuck to the surface of the target specimen, the drying step to dry it, the alloy powder, carbon powder and additives mixed in an appropriate ratio Electrostatic spraying step of spraying the powder on the surface of the target specimen in the state of electrostatic charge and sintering step of sintering the target specimen in which the mixed powder forms the powder layer at a predetermined temperature in a heating furnace are sequentially It is intended to cure.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing the overall process according to the present invention, Figure 2 is a facility diagram for the electrostatic spraying process of FIG.

In the method of forming the powder sintered layer by the powder coating method of the present invention, after performing the washing step (A) to remove and remove the dust and other contaminants adhering to the surface of the target specimen (1), the target specimen ( Electrostatic spraying is performed by drying the surface (1) to dry the surface of 1) and injecting the mixed powder (2) in which the alloy powder, the carbon powder, and the additive are mixed in an appropriate ratio to the target specimen (1) under the electrostatic state. After the completion of the step (C), the sintering step (D) of sequentially sintering the powder layer formed by mixing the powder (2) electrically on the surface of the target specimen (1) at a predetermined temperature in a heating furnace was sequentially performed. By doing so.

Here, the equipment of the electrostatic spraying step (C) is, as shown in Figure 2, the mixing powder (2) in which the alloy powder, the carbon powder and a very small amount of additives are mixed in an appropriate ratio, the storage container (HOPPER; 3), the high pressure hose (4) is connected to the lower part of the storage container (3), the high-pressure hose (4) is connected to the high-voltage current generator (5) at the front end of the electrostatic injection (6) While the injection chamber 7 is installed to penetrate into the interior, the electrostatic spray chamber 7 is suspended from the specimen 1 vertically into the electrostatic spray chamber 7 via a transfer means 8 such as a conveyor. This target specimen 1 is pointed with the outside. In addition, the lower portion of the electrostatic spray chamber (7) is provided with a duct 9 is connected to the cyclone 10, the lower portion of the cyclone 10 is connected through the storage container 3 and the conduit 11 The upper part is connected to the bag filter 12, the bag filter 12 is connected to the exhaust fan (13).

In the electrostatic spraying step (C), the alloy powder constituting the mixed powder 2 stored in the storage container 3 includes iron (Fe) powder, stainless (SUS 410) powder, iron (Fe) -molybdenum (Mo). ) The powder or iron (Fe) -phosphorus (P) powder, such as powders of one or two and a small amount of additives in an appropriate ratio mixed in one-way and two-way powder, such that the mixed weight ratio (%) is 6.5 It has a chemical composition of% chromium (Cr), 4.96% molybdenum (Mo), 1.25% phosphorus (P), 1% carbon (C), and 86.29% iron (Fe), where 0.5 Less than% of the additives are mixed to form the mixed powder (2).

Therefore, the high pressure current generator 5 is moved to the electrostatic spray event 6 through the high pressure hose 4 through the compressed air pressurized from the outside by the mixed powder 6 of the storage container 3. When a high pressure of 120 Kv is applied to the electrostatic spraying event 6, the mixed powder 2 is electrically attached to the surface of the target specimen 1 suspended from the transfer means 8 in a state where the charge is charged. In this case, since the target specimen 1 is grounded to the outside, the mixed powder 2 first applied to the surface continuously forms a powder layer having the same thickness, and then the target specimen ( When 1) is moved into a heating furnace (not shown), the target specimen 1 in which the powder layer is formed is first preheated at about 300 ° C. and then sintered for a predetermined time at 1,050 ° C. to 1,200 ° C.

On the other hand, of the mixed powder (2) injected through the electrostatic spray event (6) is injected to the periphery of the target specimen (1) and the mixed powder (2) falling to the lower portion of the electrostatic spray chamber (7) is a duct (9) Through the cyclone 10 is introduced through, the cyclone 10 is divided into the mixed powder (2) moved in the state mixed with the compressed air into the centrifugal separation by dividing only the mixed powder (2) pipeline 11 The compressed air is transferred into the storage ware 3), and the remaining compressed air is passed through the bag filter 12 and then discharged into the atmosphere through the exhaust fan 13.

Here, when the mixed powder (2) is injected into the target specimen (1) in the electrostatic spray chamber (7) through the electrostatic spray (6), the transfer of the mixed powder (2) is a high-pressure hose (4) The amount of static charge applied from the high-voltage current generator (5) to the electrostatic injection (6) while adjusting the supply amount of the compressed air through the outside to the maximum 500 ~ 600g / min at the minimum 100 ~ 200g / min (30 ~ 120Kv) or spraying time (min), if appropriately adjusted, the thickness of the powder electrically applied to the target specimen (1) can be arbitrarily adjusted.

Then, when the target specimen (1) having completed the electrostatic spraying step (C) is subjected to the sintering step (D), the alloy powder of the mixed powder (2), which was the first solid state, is iron (Fe) -phosphorus (P) during the sintering process Liquid phase, forming complex carbides, ternary process compounds such as carbon (C), iron (Fe) -molybdenum (Mo) -carbon (C), or iron (Fe) -chromium (Cr) -carbon (C) After cooling, it causes shrinkage to improve density and to form a solid powder sintered layer having good abrasion resistance.

In addition, the powder layer of the mixed powder (2) applied to the target specimen (1) is to maintain the state of static charge continuously while the target specimen (1) is moved into the heating furnace by the transfer means (8) As well as the horizontal and vertical parts of 1), the thickness change of the powder layer formed at the curved or uneven propagation part does not occur, so that the surface roughness in the uneven condition can be maintained.

As described above, according to the method of forming the powder-stripping layer according to the powder coating method of the present invention, a target specimen made of a special steel material such as SKD-11, which is not only high carbon steel or cast iron, but also low carbon steel or carbon carburized with low carbon content (1) ) To remove contaminants stuck to the surface by washing process (A), and then dry the surface by drying process (B), and then iron (Fe) powder, stainless (SUS 410) powder, and iron (Fe) -molybdenum An electrostatic mixture of an alloy powder consisting of mono- and binary powders, such as (Mo) powder, iron (Fe) -phosphorus (P) powder, and a mixed powder (2) in which carbon powder and additives are mixed at an appropriate ratio is applied to the target specimen (1). Sintering step (D) is carried out by spraying at a lower state to form a powder layer on the surface of the target specimen 1 at a predetermined thickness, and then sintering at a high temperature of 1,050 ° C to 1,200 ° C in a heating furnace (D ) By sequentially performing (1) Iron (Fe) -phosphorus (P) -carbon (C), iron (Fe) -molybdenum (Mo) -carbon (C), or iron (Fe) -chromium (Cr) -carbon (C) As the liquid complex carbide, which is a ternary process compound such as), forms a powder-sintered layer having high abrasion resistance, unlike the conventional powder sintering layer formation method, that is, eliminating the use of a solvent and a synthetic resin, It is possible to form a powder sintered layer with the desired thickness by only one spray on the surface of 1), and to control the arrival efficiency of the raw material powder during the spraying while suppressing the damage of the metal surface generated during the sintering process when using the synthetic resin and the solvent. In addition to the increase, there is an advantage that can effectively reuse the excess mixed powder (2).

Claims (3)

Washing process (A) for washing and removing contaminants adhering to the surface of the target specimen (1), drying process for drying it (B), mixed powder in which alloy powder, carbon powder and additives are mixed at an appropriate ratio (2) Electrostatic spraying step (C) for spraying the surface of the target specimen (1) in the state of static charge, and sintering the target specimen (1) in which the mixed powder (2) forms a powder layer at a predetermined temperature in a heating furnace. The powder sintering layer forming method by the powder coating method which consists of a sintering process (D) which hardens the surface of a metal. The method of claim 1, wherein the mixed powder (2) is a member such as iron (Fe) powder, stainless (SUS 410) powder, iron (Fe)-molybdenum (Mo) powder, iron (Fe) -phosphorus (P) powder, etc. A method of forming a powder sintered layer by powder coating, comprising an alloy powder consisting of a system and a binary powder, a carbon powder, and a small amount of additives, the particles having a size of 7 μm or less. The mixed weight ratio (%) of the mixed powder (2) is 6.5% chromium (Cr), 4.96% molybdenum (Mo), 1.25% phosphorus (P), 1% carbon (C) , 86.29% iron (Fe), and the powder sintering method of the powder coating method, characterized in that consisting of less than 0.5%.