JPS6396201A - Production of dustproof active metal powder - Google Patents

Abstract

PURPOSE:To produce active metal powder which is improved in dustproof and explosionproof characteristics by adding and mixing a specific amt. of granular polytetrafluoroethylene to and with raw material grains of an active metal in the stage of crushing and subjecting the mixture to dry pulverization to a specific grain size in an inert gaseous atmosphere. CONSTITUTION:The granular polytetrafluoroethylene is added and mixed at 0.005-0.1pt.wt. to and with 100pts.wt. raw material grain of the active metal formed to about <=15mm grain size in the stage of the crushing. The active metal includes Ca, Mg, Al, Si, Zr, Ti, Fe, etc. The mixture is then subjected to the dry pulverization continuously in the inert gaseous atmosphere so that >=50% thereof is <=100 mesh fine powder. The fine dustproof powder which is eliminated of the danger of dusting and exploding during handling is thereby obtd. without deteriorating the characteristics of the active metal powder.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a deoxidizing agent for steel manufacturing, a refractory additive, and a paint.

Ca, Mg+ A are widely used as reaction catalysts, metal refining exothermic agents, fireworks, welding rods, etc. 1. ! ；＋ ＋
The present invention relates to a method for producing powders of active metals such as Zr, TL Fe or their alloys with improved dust and explosion resistance without any loss of their properties.

[Conventional technology]

When manufacturing these active metal powders, atomization processing or mechanical pulverization using impellers, stamps, ball mills, etc. are often used, so explosion-proof measures are extremely important in addition to dust-proofing.

Conventional dust-proof and explosion-proof measures taken when processing active metal powders with strong oxidizing power include processing them with liquids such as oil or ethylene glycol, or sufficiently impregnating the treated powder with these liquids. It was common to do so.

However, depending on the purpose of use, there may be cases where it is desired to use dry powder, and for this purpose, a dust-free treatment method was developed using the
As described in Japanese Patent Publication No. 877 and Japanese Patent Publication No. 55-24481, there is a method in which active metal powder is mixed with granular polytetrafluoroethylene (PTFE) resin.

(Problems to be Solved by the Invention) However, in all of the conventional techniques using the above-mentioned PTFE resin powder, the fine powder that has been pulverized is subjected to a dry or wet dustproof treatment, and the following problems have been pointed out. Ru.

(1) There is a high risk of dust explosion during the process of obtaining fine powder, especially during crushing.

(2) The work becomes complicated due to processing after the crushing is completed.

It is necessary to add a large amount of +31 P T F H, which may harm the properties of the active metal powder itself.

Furthermore, there is a high risk of dust explosion during handling until it becomes effective.

+4] In order to reduce the amount of PTFE resin powder added, a double-breasted treatment is required in order to increase the dispersion efficiency of PTFH, and vacuum drying is required as a post-process, resulting in high cost.

The purpose of the present invention is to solve the problems in the dustproofing treatment of the above-mentioned active metal powder by dry processing.
It is an object of the present invention to provide a method of effectively preventing dust explosions and performing dustproof treatment over the entire process of producing fine powder using FB.

[Means for Solving Problem C] The present invention achieves the above object by adding PTFE resin powder at the stage where the active metal is crushed to a coarse particle size, and performing dry crushing and dust-free treatment at the same time. This is what I did.

That is, in order to reduce the risk of dust explosion up to the stage of pulverization that can be made dustproof, PTFE resin powder is mixed with the coarsely crushed active metal raw material, and the raw material is further made dustproof while being crushed. By reducing the amount of resin powder added, we succeeded in developing the effect of PTFE in parallel with the progress of pulverization.

Furthermore, in the present invention, by simultaneously adding a solid fatty acid such as stearic acid or a saponified product thereof together with the PTFE resin powder, PTFE can be removed at the coarse grinding stage.
In addition to the effect of preventing dust explosions during the pulverization process without deteriorating the properties of the active metal itself by adding resin powder, it also prevents the powder from adhering to the pulverizer and preventing particles from colliding with each other. It is also possible to increase the yield of powder by reducing agglomeration.

When the particle size of the crushed active metal raw material particles at the stage of adding PTFE resin powder is 15 mm or less, it is most efficient from the viewpoint of explosion protection (If there are many coarse particles of 15 m1 or more, it is difficult to obtain fine powder of 100 mm or less). The pulverization efficiency is too poor.The preferred raw material particle size depends on the pulverizer selected, but for pulverizers such as impellers, stamps, and ball mills, a particle size of 3 mm or less is most economical.

Next, regarding the amount of PTFE to be added, although the appropriate amount to be added differs slightly depending on the grinding type A and the grinding conditions, PTFE powder and granules with an average particle size of about 500μ are added to the pulverized metal raw material at 0, O1
Add approximately 0.1 part by weight. If the amount is less than 0.01 part by weight, the dust-proofing effect will be weak, and if it is more than 0.1 part by weight, the adhesion will be too strong, making discharge and classification difficult and, in extreme cases, impossible.

In order to improve this, solid fatty acids or their saponified products, such as stearic acid, are added to PTFE and the well.
When 605 to 0.5 parts by weight is added, the dust-proofing effect of PTFH is not impaired to the same extent, and adhesion to the grinder and aggregation of particles among themselves can be effectively prevented and the yield of treated powder can be improved.

Furthermore, regarding the crushing conditions, in the case of the prior art, PT
One of the essential conditions is the presence or absence of fibrillation of FH, but in the method of the present invention, the coarsely crushed raw material of 100 mesh or less is continuously dry-pulverized for a period of time such that at least 50% of the fine powder of 100 mesh or less can be obtained. It is sufficient for dust prevention.

However, in the active metal powder vehicle chassis, which has been found to have a dust-proofing effect even when investigated using a scanning electron microscope,
FE cannot be clearly identified, and the mechanism of its dust-proofing effect is unclear.

The dust-proofing effect of PTFH is related to the grinding time and the amount and timing of addition of PTFE, but the purpose of this process is to obtain fine powder. The timing and timing of PTFE addition, taking into consideration the shearing force and temperature during pulverization, should be determined so as not to interfere with the pulverization process, for example, by adding it during degassing during pulverization.
It can be adjusted according to each process for pulverization.

As for the sorter F7, it is a military standard for crushing that is attached to the mechanism, but in the case of unclassified products to be crushed, it is only necessary to classify them according to the target particle size, and normally industrially dust-proof treated products are
It is possible to classify with a sieve mesh down to about 0 mesh. Since this work is dust-free, it is environmentally friendly and can be carried out safely.

The obtained dust-proof powder has a single particle size of 60 mesh or less and a rounded granule shape, and these particles are weak due to the action of polytetrafluoroethylene (the size of aggregated coarse secondary particles formed by adhesion is The mesh is 60 or less, and 98% or more is 100 or less.

〔Example〕

Example 1 A with a weight Y ratio obtained by melting AA and Mg with a purity of 99% or more
An alloy ingot of 150.3-Mg49.0 was coarsely crushed into 10 or less pieces using a small jaw crane jar to prepare coarsely crushed raw material 4. Next, 2 kg of this Affi-ffg alloy coarse raw material
Next, PTFE (Teflon K manufactured by DuPont Mitsui Fluorochemical Co., Ltd.) granules Log were placed in a porcelain ball mill with an internal volume of 14β, nitrogen gas was introduced, and dry crushing was carried out for 4 hours.

The discharge star from inside the ball mill of this material to be crushed is 1.6k
It was g. Next, this discharge was classified using a 100 mesh sieve, and the product yield of 100 mesh or less was 1.2 kg.
Met. The product was found to be dust-free when measured in accordance with ASTM Comparative Flow Test Y, and furthermore, the obtained AJ-Mg alloy powder had a rounded granular shape when observed with a scanning electron microscope. However, it could not be distinguished from Teflon, let alone fibrillated Teflon.

Example 2 The procedure of Example 1 was repeated except that 524 g of granular stearin was added together with PTFE.

The material to be crushed after crushing was 1.96 kg, and 100 kg
After classification using a mesh sieve, the weight of products with a size of 100 mesh or less was 1.9 kg. It was confirmed that the yield was improved compared to Example 1, the amount of coarse particles present in the product of 100 mesh or less was small, and it was confirmed that the pulverization efficiency was excellent. This product is dust-free as in Example 1, and furthermore, the obtained A7! -The Mg alloy powder was observed under a scanning electron microscope in the same way as in Example 1, and the particle shape was rounded. and stearic acid could not be identified either.

Comparative Example Grinding was carried out in the same manner as in Example 2 under the same conditions except that Teflon K was omitted.

As in Example 2, 1.90 kg of the material to be crushed, which corresponds to almost the entire amount, was discharged from the ball mill, but a large amount of dust was generated during discharge. In addition, 100
The product yield below the mesh was 1.55 kg, but in the comparative flow test, there was no dust resistance at all.

〔Effect of the invention〕

By using the method of the present invention to process the pulverization and dust-free processing of the coarsely crushed raw material in the same process using a dry method, the amount of PTFH used can be reduced and the properties of the active metal powder will not be deteriorated to the same extent.
It is possible to obtain dust-proof fine powder that can completely prevent dust explosions during the manufacturing process and eliminate the risk of dust explosions during handling.

Claims (1)

[Claims] 1. Add and mix 0.005 to 0.1 part by weight of granular polytetrafluoroethylene to 100 parts by weight of active metal raw material grains at the coarse crushing stage, and mix the mixture to 100 mesh or less under an inert gas atmosphere. 1. A method for producing dust-proof active metal powder, which comprises continuously dry-pulverizing until 50% or more of fine powder is obtained. 2. Add and mix 0.005 to 0.1 parts by weight of granular polytetrafluoroethylene and 0.05 to 0.5 parts by weight of solid fatty acids or saponified products thereof to 100 parts by weight of active metal raw material particles at the coarse crushing stage. . A method for producing a dust-proof active metal powder, which comprises continuously dry-pulverizing the powder under an inert gas atmosphere until 50% or more of fine powder of 100 mesh or less is obtained.