JPS6244506A - Manufacture of porous sintered body of stainless steel powder - Google Patents

Abstract

PURPOSE:To easily manufacture a porous sintered body of stainless steel powder by mixing stainless steel powder with silicic acid sol, molding the mixture in a frame, drying and taking out the molded body and sintering it in vacuum or a nonoxidizing atmosphere. CONSTITUTION:Stainless steel powder is mixed with silicic acid sol, poured into a frame in the form of slurry, dried and taken out of the frame. The resulting molded body is sintered at about 1,100-1,300 deg.C in vacuum or a nonoxidizing atmosphere under ordinary pressure to obtain a porous sintered body of stainless steel powder. The porosity of the sintered body can be regulated within the range of about 60-10% according to gas permeability and strength required by selecting the particle size of stainless steel powder and the sintering conditions.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is a method for producing a porous sintered body of stainless copper powder, which is suitable for use as a sound absorbing material that can withstand high temperatures, filters, molds for small injection machines, etc. Regarding.

BACKGROUND OF THE INVENTION It has been known for some time to produce porous sintered bodies of stainless steel powder. There is also a method of manufacturing a porous sintered body by molding stainless steel powder in a state where it remains porous without being completely compressed.

As a method for manufacturing porous sintered bodies of stainless steel powder without applying pressure, the powder is uniformly dispersed in a container of the desired shape, and then heated in a furnace in a vacuum or non-oxidizing atmosphere. There is also a method of sintering inside.

Problems to be Solved by the Invention Among the conventional methods described above, in the method in which stainless steel powder is molded in a porous state without being completely compressed, a hard oxide film exists on the powder surface. If the oxide film on the surface of the stainless steel powder is not broken by rolling, the shape obtained by compression molding cannot be maintained, and even if the powder is sintered in this way, the porous structure with many pores will not be maintained. Hard to get. In this case, it was necessary to use particles with a relatively coarse particle size.

In the method of obtaining a porous sintered body of stainless steel powder without pressure, it is necessary to use a container that is resistant to high temperatures, and there are restrictions on the size of the container, making it possible to create large or complex-shaped containers. There are difficulties in this case.

Means for Solving the Problems The present invention is an attempt to solve the problems in the above-mentioned conventional methods.The present invention is made by mixing silicic acid sol with stainless steel powder, pouring it into a mold as a slurry, removing it from the mold after drying, and This is a method for producing a porous sintered body of stainless steel powder, which is characterized by sintering the powder in a vacuum or in a non-oxidizing atmosphere.

In other words, since the present invention uses slurry casting, it can be sintered without pressure, and the grain size can be freely selected from coarse to fine. can be tied. Furthermore, since the powder is bonded with silicate sol, the molded shape can be maintained without breaking the oxide film. Sintering conditions are 1100~
A range of 1300'C is good. In addition, by selecting the particle size and sintering conditions according to the purpose of air permeability and strength, the porosity can be increased to 6.
It can be manufactured freely from 0 to 10%.

Stainless steel is martensitic, austenitic,
Any ferrite type material may be used.

Since the molded container itself does not need to be put into the sintering furnace at the same time, the material of the container does not need to be heat resistant, and it is possible to manufacture containers of any shape or size.

In the case of ordinary plaster casting, moisture absorption is required, so a material with a high moisture absorption rate such as a plaster mold is used as the mold, but in the case of the present invention, silicate sol is used as the hardening agent. Because of the use of aluminum, the curing speed is fast, and all types of frame materials can be used, including wooden frames and metal frames.

In the case of the present invention, if fine grain size (400 mesh or less) is used, transferability is good, and minute patterns such as leather wood grain can be transferred, and vacuum forming, which was conventionally performed by die engraving, etc.
It can be used as a mold for pressure molding, etc., or as a durable, heat-resistant, breathable mold, and is also effective as a mold for a small injection machine.

Conventionally, injection molding machines require a gas center blower.
For this reason, I have been trying my best to attach air vents, etc. to the mold. In this case, there is an effect of making the air wider than the entire surface of the mold, and as described above, the transferability is also good, so there is an advantage that machining such as electric discharge machining when die-sinking a complicated shape can be omitted.

When used in injection molds, it is necessary to use stainless steel powder whose strength can be improved by post-treatment after sintering. For example, precipitation hardening type 5US630, quenching,
Use temperable material such as 5US440.

Example 5US630 powder is used as stainless steel powder.

The particles used had an average particle size of 400 mesh.

A silicic acid sol obtained by mixing ethyl silicate with an acid (e.g., HCI) or a basic organic substance (e.g., triethanolamine) is mixed with the above powder in an amount of 15 to 30% by weight based on the powder amount, and the mixture is slurried on a vibrator. Pour this into the desired mold, degas it in a vacuum while applying vibration, and then
After drying in an o'c room, the mold was demolded and sintered in a vacuum. Thereafter, solution treatment was performed at 1040°C for 1/2 hour, and 48°C
Precipitation hardening treatment was performed at 0'C for 4 hours.

The table below shows the characteristics for each sintering temperature.

When the above stainless steel powder was used, solution treatment was performed, but at this time, clogging caused by machining such as polishing after sintering caused a thermal etching effect at the solution treatment temperature.
Subsequent chemical polishing and electrolytic polishing were able to restore the vent holes in a short period of time.

Also, EP shows where the residual 3iQ2 remains after sintering.
When inspected by MA, it was found that it was attached to the wall of the hole. It is thought that this 5iQ2 prevents the reduction of holes due to sintering, and it is presumed that the porous state is more effective.

Effects of the Invention According to the present invention, stainless steel powder sintered bodies can be sintered without pressure, and objects of any shape and size can be sintered with varying degrees of air permeability and
Depending on the purpose of strength, it is possible to obtain a product with a desired porosity within the range of 60 to 10%.

Claims (1)

[Claims] Porous sintering of stainless steel powder, which is characterized by mixing silicic acid sol with stainless steel powder, pouring it into a mold as slurry, removing it from the mold after drying, and sintering it in a vacuum or in a non-oxidizing atmosphere. How the body is manufactured.