DE2249244A1 - Explosive compaction and hardening of moulding sand - contg. plastics binder, by controlled detonation of gas mixts esp. hydrogen- oxygen - Google Patents

Abstract

Moulding material, incorporating plastics binder can be simultaneously compacted and hardened by the energy generated in the explosive reaction between hydrogen and oxygen (3 vol: 2 vol. originall press. 2-3 atmos) other gas mixts. can be used, incl. CO, CH4, C2H2, C2H4, C2H6, (CH3)2O C2N2 etc.

Description

Process for the simultaneous compaction and hardening of hardenable Molding materials The invention relates to a method for simultaneous compression and curing of curable molding materials.

In addition to the well-known compression methods such as shaking, pressing, shooting or bubbles, it is known from US Pat. No. 3,170,202 and DT-AS 1 242 802, clay-bound To compact sands with the help of explosion pressures. The one released during the explosion Energy is used by a piston to apply the compression forces to the molding material used, whereby heat energy is still lost.

According to Freytag (manual of itaumexplosion, Verlag Chemie GmbH, Weinheim / Bergstrasse) you can with a detonation in closed rooms, z. B. in a molding box or in a core box with molding material, with the introduction of small amounts of gas Reach pressure increase, starting from 1 atü, to 50 atü. The shock waves take care of a directed compression. When the pressure waves hit a wall or here This pressure can double to triple the filled molding material increase and thus become an ideal, economical compaction force.

In addition to the clay-bound molding materials produced by the aforementioned process can be easily compacted, synthetic resin-bound molding sands are known, after compression in the molding box or in a core box in an additional Operation must be cured by heat or by a gas. Because of the poor heat conduction of molding sands and the required reaction time results themselves this results in a relatively long cycle time for production of a molded part.

According to the invention it is now proposed that the additional work gallows to avoid. This is done by the fact that the compression by a necessary Temperature and / or the reaction generating explosion takes place.

In the case of synthetic resin-bonded, thermosetting sand The Verdiclituiig expediently by a braked heat-generating JOetonation. The amount of heat released is used to harden the molding material by shock Experiments used have shown that this is preferably done with the help of an oxyhydrogen chain reaction 2 H2 + 02 - 20 11 + 2 H is possible.

A pure explosion, i. n. an exothermic chain reaction, would be high Generate combustion temperatures that are used for other purposes, e.g. thermal deburring of castings, would be useful, but would never lead to a combustion of the binder would.

For the simultaneous compression and hardening of molding materials under braked heat generation is a reaction process with small, spherical and exothermic Explosion necessary, which after an induction time of a few microseconds in an endothermic detonation with shock waves passes.

The steering of the reaction process is by exact control the Mixture composition, the outlet pressure of the gases and the ignition energy possible. It should be noted that in the Knaligasreaktion by an excess of fuel (H2) this does not come to equilibrium, whereby only part of the available heat of reaction is released.

This excess supply of hydrogen leads to a detonation-like one Process with shock wave emission for compression and a braked energy release in the form of warmth.

It was found that a ratio of 5 parts by volume of hydrogen and 2 parts by volume of oxygen an ideal mixture for solving the task at hand forms.

The premix should have a pressure of about 2-3 atmospheres.

The detonation with oxyhydrogen can be directed so that it as a result of the fuel surplus to a brief high temperature rise in the period of about 20 msec comes up, which is enough to produce thermosetting plastics in this time Bring curing. When the outlet pressure of the gases is low, the temperature rises of the sand is only applied enough to obtain a hardened molding material.

But the compression energy of this oxyhydrogen mixture is all the more so greater.

The short-term combustion heat generated in the cavities of the sand in msec must be dimensioned so that the binder is only thermally shocked, but not yet covered. According to tests, this is in the range between 550 and 650 ° C possible. Compression and curing therefore take place according to this proposal from today 20 - 40 seconds in less than 1 second. One will be this short one though Cycle times cannot be used to the full, since the Trerm processes between The molding material and model require a certain amount of time.

In addition to the described compression and hardening of a synthetic resin-bonded, According to the invention, it is also possible to compress thermosetting molding sand and at the same time harden it to a certain extent by removing the existing water. In tests, it was possible to set an oxyhydrogen gas mixture with such a high O2 content that i.e. to drive so hot that in the same time the water in a wet casting sand evaporated, so that dry castings with very high strength were produced. This type of application, too matters.

A fuel-air mixture is used to carry out the invention This method is less recommended as it is much more difficult to achieve the desired result the endothermic detonation is to be brought. But there are others too Gases can be used as fuel, such as carbon monoxide, ldethane, acetylene, ethylene, Athane, dimethyl ether and dicyanes, which increased according to this order Explosion and detonation pressures result. Also propane gas, gasoline, butane, diesel oil, Kerosene, natural gas and solid explosives can be used.

In the event that the molding material is not affected by the resulting heat but can be cured by a reaction agent such as CO 2 a fuel mixture is to be used, which during the explosion desired reactants generated.

Compaction and curing are when using the invention Process uniformly in all parts of the molding material. The costs the combined treatment are far lower than with conventional procedures.

There is a risk of detonation of the protected system if it is properly operated Execution not.

Claims (1)

Claims 1. Process for the simultaneous thinning and hardening of curable Molding materials indicate that the compaction is achieved one which generates the necessary temperature and / or the necessary reaction product Explosion occurs. 2. The method according to claim 1, d a d u r c h g e k e n nz e i c Ll n e t that the compaction and the simultaneous hardening by a braked heat-generating Chain reaction of oxyhydrogen takes place. 5. The method according to claims 1 and 2, d a d u r c h g e k e n It is noted that the mixture of the oxyhydrogen gas in a ratio of about 3 parts by volume of hydrogen to 2 parts by volume of oxygen. 4. The method according to claims 1 to 5, d a d u r c h g e k e n Note that the premix pressure is about 2-5 atmospheres. 5. The method according to claims 1 to 4, d a d u r c n g e k e n It is not noted that instead of the oxyhydrogen gas mixture, other fuels, such as carbon monoxide, Methane, acetylene, ethylene, ethane, dimethyl ether and dicyanes as well as other common uses Types of gas or solid explosives are used. 6. The method of claim 1, d a d u r c h g e k e n nz e i c h n e t that the compression by the explosion of a strong heat generator, which in the Molding material existing water evaporating fuel mixture takes place. 7. The method of claim 1, d a d u r c h g e k e n nz e i c h n e t that a gas is used as fuel, which after combustion as Reaction product results in a gas acting as a hardener for the binder.