RU2108534C1 - Method of production of pyrotechnic aluminium powder - Google Patents

Abstract

FIELD: powder metallurgy. SUBSTANCE: the method involves dry grinding of aluminium blank (aluminium powder obtained by spraying of molten metal, ground waste of aluminium foil, chip) in a ball mill. Grinding is accomplished in atmosphere of inert gas - nitrogen with controlled content of oxygen (2 to 10 volume percent). Prior to grinding, fat addition - synthetic fatty acids of group C₁₂-C₁₆ or higher fatty alcohols of group C₁₆-C₂₀,, representing petroleum-refining products, is added to the charge. Use of the above components as fat addition instead of difficulty available (because of finishing of production at enterprises of Russia) and expensive stearin makes the offered method accessible on one hand, and reduces the price of it as compared with the method - prototype, on the other hand. EFFECT: reduced cost of production. 2 cl

Description

 The invention relates to powder metallurgy, and in particular to a group of manufactures manufactured by aluminum powder for pyrotechnics.

 A known method of producing aluminum powder (including pyrotechnic) by wet grinding of an aluminum billet in a liquid medium [1]. The uyat spirit is used as the latter. The disadvantage of this method is its high cost, due to the presence in it of such an expensive component as white spirit.

 There is also a method of producing aluminum powder (including pyrotechnic) by dry grinding of an aluminum billet in an atmosphere of an inert nitrogen gas containing a certain amount of oxygen in the presence of fat additives [2]. The amount of oxygen in the gas mixture is strictly controlled and amounts to 2-8%, because when its content is less than 2%, an intense oxidation of the finished product is observed when it is unloaded from the mill and powder can ignite, and when the oxygen content in the gas mixture is more than 8%, tanning or explosion inside the grinding system. As a fat additive during grinding, stearin is used according to GOST 6434-64, which uniformly covers aluminum particles during the grinding process with a thin film that prevents particles from “welding”. The crushed aluminum particles are transported by a stream of nitrogen into a separator with the return of large flakes to the mill, and the gas-dust mixture enters the classification system with the release of a conditionally sized powder in it.

 The disadvantage of this method is that stearin is currently a scarce product in connection with the termination of its production at the enterprises of the Russian Federation.

 The objective of the invention is the replacement of a deficient fat supplement - stearin, used in the manufacture of pyrotechnic aluminum powder, with a deficient and, in addition, cheaper fat supplement.

 The technical result of the invention is the general availability of the method for the production of pyrotechnic aluminum powder by eliminating the deficient component of stearin during dry grinding of the charge. An additional technical result is a cheaper method by using a cheaper (compared with stearin) fat supplement.

The technical result is achieved as follows. In a method for the production of pyrotechnic aluminum powder, including dry grinding of an aluminum billet in an atmosphere of an inert nitrogen gas with a controlled oxygen content in the presence of fat additives, synthetic fatty acids of group C _12-16 or higher fatty alcohols of group C _16-20 are used as the latter obtained during oil refining.

The method is as follows. An aluminum billet, for example, an aluminum atomizer - a powder obtained by spraying liquid aluminum, is loaded into a ball mill. Grinding is carried out in a nitrogen atmosphere with a controlled oxygen content (2 - 8%). Synthetic fatty acids of group C _12-16 or higher fatty alcohols of group C _16-20 are loaded into the mill as a fat additive to prevent the "welding" of aluminum particles. The aluminum particles ground in the mill are transported by a nitrogen stream to the separator and cyclone. In the separator, the conditioned product is separated from large particles, which are sent through the return pipe to the mill for regrinding. In the cyclone, the finished product is precipitated from the dust-gas mixture, from where it is unloaded into the packaging.

 The optimal content of synthetic fatty acids, higher fatty acids in the production of pyrotechnic aluminum powder is 0.25 - 0.38%. With a decrease in their content in powder less than 0.25%, the process of hardening ("welding") of aluminum particles occurs, which leads to an increase in the particle size distribution of the powder, i.e. to reduce grinding efficiency.

 With an increase in their powder content of more than 0.38%, particles stick together in conglomerates both in the mill and in the separator, which leads to a sharp decrease in grinding efficiency: it is difficult to blow the powder from the mill, the number of clumped powder lumps again returned from the separator increases in the mill, the flowability of the powder is lost.

The applicant has mastered the production of pyrotechnic aluminum powder from a mixture of the following composition:
The composition of the charge N 1 (%):
Aluminum powder - 99.7
Synthetic fatty acids of group C _12-16 TU 38.507-63-285-92 - 0.3
The composition of the charge N 2 (%):
Aluminum powder - 99.7
Higher fatty alcohols of group C _16-20 TU 38.107-119-85 - 0.3.

 Thus, replacing a scarce and expensive component with a scarce and cheaper component — synthetic fatty acids or higher fatty alcohols (oil refined products) - on the one hand, makes the proposed method for producing pyrotechnic aluminum powder by dry grinding of an aluminum billet publicly available, on the other hand, the method itself is also cheaper (the price of 1 ton of stearin is 10.5 million rubles, the price of 1 ton of synthetic fatty acids and higher fatty alcohols is 8 million rubles).

 Sources of information.

 1. Gopienko V.G. and others. Production and use of aluminum powders and powders. - M.: Metallurgy, 1980, p. 38.

 2. The same, p. 38-41, 44.

Claims (2)

1. A method for the production of pyrotechnic aluminum powder, comprising dry grinding an aluminum billet, mainly aluminum powder, in an inert gas atmosphere with a controlled oxygen content in the presence of fat additives, characterized in that the products obtained from oil processing are used as fat additives - synthetic fatty acids groups C _{1 2} - C _{1 6} or higher fatty alcohols of group C _{1 6} - C _{2 0} . 2. The method according to p. 1, characterized in that the synthetic fatty acids of the group C _{1 2} - C _{1 6} or higher fatty alcohols of the group C _{1 6} - C _{2 0} are used in an amount of 0.25-0.38% by weight of the aluminum billet .