JPS58164701A - Manufacture of sintered hard alloy - Google Patents

Abstract

PURPOSE:To manufacture economically a sintered hard alloy with high molding and working efficiency by mixing carbide or nitride powder and powder of an iron group metal with microcrystalline cellulose as a binder, wet-grinding the mixture together with an org. solvent, mixing them, and carrying out proper treatments. CONSTITUTION:Powder of an iron group metal as a binding metal and 0.1- 1wt% microcrystalline cellulose as a binder are added to carbide or nitride powder as the principal component of a sintered hard alloy, and they are mixed. After adding an org. solvent, the mixture is wet-ground and mixed. The solvent is then removed, and the dried powder is press-molded to manufacture a molded body of simple shape. The molded body is preliminarily sintered, worked to a prescribed shape with a diamond tool, and sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing cemented carbide and extra-large shaped cemented carbide.

Cemented carbide mainly contains one or more carbides and nitrides.
It is manufactured from powder raw materials using iron group metals as a binder metal, and has high hardness and excellent wear resistance, so it is widely used in wear-resistant tools such as cutting tools and dies. For this purpose, products of various shapes are required. When pressing with a normal mold, only a simple shape can be obtained, so we first create a molded product with a simple shape, intermediate sintering at SOO~800°C, and then use a diamond tool. The usual method is to mold it into a predetermined shape and sinter it.

Since the raw material powder is a fine powder of several microns or less and is press-molded, it is essential to mix therein an organic binder (binder) that has lubricating properties and serves as a powder binder. This binder is removed during the intermediate sintering or the pre-sintering stage.

Paraffin, polyethylene glycol, camphor, stear monophosphate, etc. have traditionally been used as organic binders.
~896 (by weight) is added.

The effect of this binder is to prevent slippage during press molding, reduce friction with the wall surface of the mold, and equalize the density of the molded product, but it also has the effect of preventing tool blindness during molding and reducing machining efficiency. This will have an adverse effect, such as a decrease in

Particularly in the case of large-sized products, it is economically disadvantageous to newly install a large debinding furnace to remove the binder, and the product must be molded with the binder still inside. At this time, conventional organic binders have the problem of causing cracks during molding, which significantly reduces the processing effect. This seems to be because paraffin wax, for example, is softened by the heat generated during the molding process and becomes a welding liquid, clogging the blade and making it harder to cut, which in turn generates more heat.

To solve this problem (after various studies, it was found that using microcrystalline cellulose as an organic binder not only solves the above problems but also has a surprising effect. 0 for raw material powder
．． 1 to 1.0% by weight is added, wet-pulverized and mixed with an organic solvent such as alcohol or acetone in a ball mill, etc., the organic solvent is removed by a normal method, the powder is press-molded, and the molded body is molded into a predetermined shape and then baked. It was found that molded body 1: □ − can be processed efficiently even when the binder is present, depending on the results. Microcrystalline cellulose has the chemical formula (C6Ht
o 05 ) n is a chain-linked cellulose, and by thermal decomposition (C611005) n −* COg + agO + CxH
This is thought to be because it does not exist in liquid form and does not clog the cutter during molding. Although the purpose of the present invention is to improve the efficiency of the above-mentioned molding process,
In addition, the following effects were also achieved.

One of these is that it has good lubricity and good press moldability despite the small amount of %-Vxo added, and also because it has low solubility in solvents such as water, alcohol, acetone, etc. during wet mixing. , it is possible to homogeneously disperse it between powders, and there are fewer oxidation problems due to moisture absorption during the process.

Furthermore, carbon contour sealing in the alloy has become possible by utilizing the thermal decomposition of the microcrystalline cellulose. There is a great advantage in that it is now possible to mold long products and products with complex shapes by omitting one step of removing the binder.

, :1″ Next, an example will be explained.

Example
2% crystalline cellulose (several 100μ) for a powder with a composition of 1wcss%-Co15% by weight! :, 0.4% added,
This was wet-pulverized and mixed with acetone using an attritor.

This was dried to remove acetone in a vacuum dryer, and then cold isostatically pressed (CIP) to a diameter of 20G1131φ.
A molded body with a length of 200 m (m) was obtained. This was molded using a diamond tool on a lathe to a size of 180 hiro φ x 190 m (m), and sintered in hydrogen for 2 hours. It was completed in about an hour without any problems.

If 5% paraffin wax is added to the same raw material, 2
Machining became impossible in 0 minutes, and some cracks appeared in the molded body.

5-

Claims (1)

[Claims] In the manufacturing method of cemented carbide, carbide, nitride powder, and iron group metal powder are mixed with α1% or more and 1% by weight of microcrystalline steel as a binder, wet-pulverized and mixed with an organic solvent, and then A method for manufacturing cemented carbide, which comprises press-molding a powder that has been dried by removing only an organic solvent, and sintering the molded body into a predetermined shape.