DE1236542B - Furnace for annealing castings - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY Int. Cl .:

C21d

GERMAN

PATENT OFFICE

PATENT LETTERING

German class: 18 c - 5/00

Number: 1236 542

File number: L 41886 VI a / 18 c
Filing date: May 2, 1962
Opened on: March 16, 1967
Issue date: October 19, 1967
The patent specification corresponds to the patent specification

Furnaces for annealing castings are known in various embodiments. In particular, those are known which are used for annealing malleable cast iron in a decarburizing atmosphere. The annealing of castings, especially those made of white malleable cast iron, is increasingly taking place in a controlled atmosphere, which has a strong decarburizing effect but still prevents scaling. This atmosphere is z. B. generated by the fact that air enriched with water vapor is blown into the furnace chamber heated by radiant tubes or electrical heating elements. The oxygen contained in it combines with the carbon emerging from the castings and results in reaction gases which contain considerable proportions of carbon monoxide and hydrogen and have a chemically combined heat of about 1250 kcal / Nm ³ . The decarburizing annealing of white malleable cast iron is a process which requires a lot of heating energy because the annealing material has to be heated at almost 1100 ° C. for long periods of 50 to often over 100 hours. In order to improve the economy, various attempts have therefore been made which attempt to utilize the reaction gas which is formed during tempering in a controlled atmosphere. In this respect, furnaces for annealing castings and in particular malleable castings with devices for utilizing the heat of the reaction gas produced are known. In particular, it is known, for example, to burn part of the reaction gas in jet pipes which have an injector with the aid of which the reaction gas is sucked into the burner. The reaction gases are generated by pre-combustion of luminous gas. However, these measures are not free from drawbacks. It can be seen immediately that the coupling of different processes - here heating and decarburization - cause very great technical difficulties. In addition, measures must be taken to prevent the reaction gases from escaping when the burner is switched off. Because of these difficulties, the last-described measures for utilizing the heat from such reaction gases have not been implemented in practice. According to another proposal, attempts are made to improve the cost-effectiveness of the annealing of castings and, in particular, malleable castings, in that some of the reaction gases are used to generate just reaction gas; In order to work with maximum efficiency, only a small part of the furnace available in the reaction gases can be used for annealing castings

Patented for:

Matthias Ludwig, industrial furnace construction,
Essen, Alfredstr. 72

chemical and sensible heat can be used.

It is also important in such furnaces to reduce gas losses during loading and unloading of the goods to be treated known to carry out the loading by means of entry and exit sluices. In another known furnace for low-scale heating of rod-shaped and sheet-metal Rolling stock is known to divide the channel-shaped furnace by means of an intermediate wall and in the Pre-combustion in the first chamber and post-combustion in the second chamber by supplying additional air the usual combustion gases that are used to heat the furnace. Here The formation of gases and, above all, hot water vapor can be prevented, particularly during post-combustion do not avoid. This is therefore known for the scaling-free heating of malleable castings Oven not suitable.

The invention has the task of providing a furnace for annealing castings, in particular Malleable cast iron pieces, in which a complete utilization of the heat of the easy way reaction gases arising during the glow is possible.

The invention relates to a furnace for annealing castings, in particular malleable castings, in Decarburizing atmosphere with an annealing room heated by radiant tubes and / or electrical heating elements and associated devices for introducing treatment gas and devices to utilize the heat of the corresponding reaction gases. The invention consists in that the Devices for utilizing the heat of the reaction gas from one or more of the annealing material preheating or aftertreatment serving special furnace chambers separated by doors from the furnace and that in the area of the Doors between the annealing room and upstream or downstream furnace chambers outlet or overflow openings for the reaction guests and in their vicinity facilities for the addition of combustion air are arranged, in which the reaction gases are burned with admixture of air. Further can annealing room and upstream or downstream

709 696/44

Furnace chambers through glow rails with guided on them Boxes for receiving the material to be annealed be connected, while it is recommended that the front or downstream furnace chambers with an explosion flap, to provide. According to a special proposal of the invention are to ignite the gas-air mixture Electric ignition coils or pilot burners are arranged in the antechambers.

The advantages achieved by the invention are primarily to be seen in the fact that in the case of the invention Furnace for annealing castings and especially malleable castings in the simplest possible way an arbitrarily complete utilization of the Heat of the reaction gases formed in the glow space is possible, with both the chemical heat as also the sensible heat for preheating the material to be annealed, for setting a certain final temperature used for the purpose of heat treatment of the annealing material, to cover wall losses, etc. can be.

In the following, the invention, also with regard to further features, is merely an exemplary embodiment Illustrative drawing explained in more detail. It shows

F i g. 1 shows a longitudinal section through an inventive Oven,

FIG. 2 shows a section in the direction A -A through the object according to FIG. 1,

F i g. 3 shows a section in the direction BB through the object according to FIG. 1.

The furnace 1 shown in the figures is used for annealing castings and in particular for Annealing of malleable cast iron. This annealing takes place in the annealing chamber 2 of the furnace in a decarburizing atmosphere. For this purpose, radiant tubes 3 and / or electrical heating elements are provided in the glow space 2 of the furnace. In addition, devices 4 for introducing treatment gas are attached in the glow space 2. As treatment gas For example, air enriched with water vapor is introduced.

To utilize the heat of the reaction gases arising in the glow chamber 2, which arise from the reaction of the gas atmosphere mentioned with the carbon emerging from the castings and which contain considerable amounts of carbon monoxide and hydrogen, two in the exemplary embodiment are used, on the one hand, to preheat the glowing goods and, on the other hand, to post-treat the glowing goods Furnace chambers 5, 6 are provided in which the reaction gases are burned with the addition of air. Doors 7 are located between the glow space 2 and the mentioned furnace chambers 5, 6, but they allow the transport of goods, for example as train doors. In the area of the doors 7 between the glow space 2 and upstream or downstream furnace chambers 6.5 there are outlet or transfer openings for the reaction gases. These can be designed like nozzles, and under certain circumstances conveying means for the reaction gases in the form of fans or the like can also be arranged. In addition, in the area of these outlet or overflow openings 8 for the reaction gases, devices 9 for the supply of combustion air are attached. Finally, the glow space 2 and upstream or downstream furnace chambers 5, 6 are connected to one another by slide rails 10. The material is located in annealing boxes 11, which can be moved on these slide rails 10. Finally, explosion flaps 12 are provided on the furnace chambers 5, 6 .

The combustion of the reaction gases in the mentioned furnace chambers 5, 6 can in principle done different ways. For example, it is possible to use the gas in the manner described through several openings 8 made in or near the aforementioned doors 7 the possibility of the exit from the glow chamber 2 into the antechamber 5, 6. In the immediate vicinity of these openings 8 the air is supplied as mentioned. This can e.g. B. done by tubes 9 with small Holes are provided from which the air exits at high speed. That is ignited so formed gas-air mixture by electrical ignition coils or pilot burner 13, which one already ignitable gas mixture is supplied. Are, such as B. in a continuous furnace, several antechambers present, then these various amounts of reaction gases can be supplied by the resulting flue gas z. B. measured with the help of a measuring orifice and the reaction gas feed through an actuator is set individually. In addition, one is of course through suitable Control organs ensure that the combustion devices 8, 9 assigned to the reaction gas Igniter 13 are always in function to prevent an explosive gas-air mixture forms.

Claims (3)

Patent claims: 1. Furnace for annealing castings, especially malleable castings, in decarburizing Atmosphere with glow space heated by radiant tubes and / or electrical heating elements and this associated devices for the introduction of treatment gas and facilities for Utilization of the heat of the resulting reaction gases, characterized in that the facilities for utilizing the heat of the reaction gas from one or more of the Annealing material preheating or post-treatment serving special, through doors (7) from the annealing room separate furnace chambers (5, 6) exist and that in the area of the doors (7) between Annealing room and furnace chambers upstream or downstream of the furnace, outlet or transfer openings (8) for the reaction gases and in their vicinity facilities (9) for the addition of combustion air are arranged, in which the reaction gases are burned with admixture of air. 2. Oven according to claim 1, characterized in that the upstream or downstream Furnace chambers (5, 6) are provided with an explosion flap (12). 3. Furnace according to claims 1 and 2, characterized in that the ignition of the Gas-air mixture in the antechambers (5, 6) electrical ignition coils or pilot burners (13) are arranged. Considered publications:
German Patent Nos. 263 776, 290 254;
"Gießerei" magazine, 1960, pp. 492 to 497. 1 sheet of drawings 709 519/366 3.67 © Bundesdruckerei Berlin