WO2007058598A1

WO2007058598A1 - Heat treatment and finishing of tools

Info

Publication number: WO2007058598A1
Application number: PCT/SE2006/001306
Authority: WO
Inventors: George Berge
Original assignee: Iut Industriell Ugnsteknik Ab
Priority date: 2005-11-21
Filing date: 2006-11-17
Publication date: 2007-05-24
Also published as: SE0502547L; SE529331C2

Abstract

The invention intends to accomplish heat treatment and finishing of extrusion tools (1) at a common stage. This is attained by a method for providing high surface finish and/or high rate of production of aluminium profiles and other light-metal profiles by means of the tool (1) that said pro- files is formed by via extrusion and which tool (1) is finished by nitriding/nitro-carburizing. According to the invention, said method is effected by, in connection with preheating of the tool (1) and the surrounding tool ring (3) to an intended temperature in a common furnace and with subsequent cooling of the surrounding tool ring (3) only, accomplishing said nitriding/nitro-carburizing of the tool (1) in connection with the preheating of the tool (1). Said preheating is accomplished in an inert atmosphere.

Description

Heat Treatment and Finishing of Tools

The present invention relates to a method for provid- ing high surface finish and/or high rate of production of aluminium profiles and other light -metal profiles by means of the tool that said profiles are formed by via extrusion and which tool is finished by nitriding/nitro-carburizing.

Within aluminium-profile plants, extrusion tools are used through which heated aluminium ingots of high temperature and high pressure, by a speed of between 10 and 50 m/min, are extruded into intended aluminium profiles by the hole shape of the tool. In order to achieve optimum function, the tool is preheated before it is put into the intended extrusion press with the purpose of preventing the emergence of the changes which otherwise would arise as for the quality of the extruded profiles, while the tool was heated from the normal room temperature thereof to the so-called steady-state temperature it reaches because of the friction heat from the preheated ingot. An extrusion tool consists of two or more parts, which, before effecting the preheating, are assembled into a common unit, viz . the proper tool, as well as a surrounding tool ring. By the fact that said two parts are assembled into a common unit in the form of the proper tool as well as the surrounding tool ring, before effecting the preheating, the entire composed unit obtains a common temperature upon the preheating. In a so-called steady-state operation of the press, the tool has a temperature of approx. +550-600 ⁰C while the surrounding ring has a temperature that is substantially lower, between +300 and +400 ⁰C. During the time that the combined tool/ring unit is being adapted to the steady-state temperature, quality changes of the profile arise in the same way as has been indicated above, and which result in a high scrap portion with accompanying high costs.

At present, the composed tool unit is heated to approx. +450 ⁰C, since at a higher starting temperature, the ring does not manage to conduct the heat away from the proper tool sufficiently fast so that the same should not reach temperatures higher than +600 ⁰C with accompanying melting of the extruded profile as a consequence.

By JP 9174145 and JP 5031528, respectively, methods are previously known to finish, among other things, moulding tools by thermal and gas treatment of the same. However, the temperature that it is heated up to is too low in order to obtain the desired result.

In order for the manufactured extruded alumin- ium profiles to achieve a suitable desired surface finish or, alternatively, a higher rate of production, the tools that the profiles are extruded out from are treated with a known technique in a separate nitriding/nitro-carburizing furnace. This known treatment has to be remade from time to time because of the wear of the tools. Said nitriding process is carried out in an inert atmosphere and at a temperature of between +500 ⁰C and +600 ⁰C.

Therefore, the main object of the present invention is primarily to solve, among other things, the above- mentioned problems so that everything becomes much simpler and more inexpensive.

Said object is attained by means of a method according to the present invention that substantially is characterized in that, in connection with preheating of the tool and the surrounding tool ring to an intended temperature in a common furnace and with subsequent cooling of the surrounding tool ring only, said nitriding/nitro-carburizing of the tool is accomplished in connection with the preheating of the tool and said preheating and possibly also the cooling being accomplished in an inert atmosphere.

The invention is described with reference to the appended drawings, in which Fig. 1 shows a schematic section view of an extrusion tool in a heating furnace, and

Fig. 2 shows the extrusion tool in a furnace for the cooling of the tool.

Primarily, extrusion and thermoforming of plas- tic semi-manufactures of aluminium are intended, but also other light-metal materials such as brass, copper, and magnesium or alloys of the same may be a possibility for the application of the invention.

According to the present invention, the same relates to a method for providing high surface finish and/or high rate of production of aluminium profiles and other light- metal profiles by means of the tool 1 that said profiles are formed by via the extrusion of a heated metal mass contained in a cylinder through a formed nozzle 2 that gives the extruded string the corresponding cross-section shape thereof. Said tool 1 is finished by nitriding/nitro-carburizing in order to achieve high wear resistance of the tool.

The new and characteristic of the present invention is that said heating and finishing of the proper extrusion tool 1, the so-called tool, as well as of the surrounding holder 3, the tool ring, is carried out in a common step and that the heating continues to an intended temperature of preferably approx. +580 ⁰C in a common furnace 4. Next, subsequent cooling of the surrounding tool ring 3 only to between +300 and +400 ⁰C, preferably approx. +350 ⁰C, is effected while the tools retain the previously obtained temperature thereof. Said nitriding/nitro-carburizing of the tool 1 is accomplished in connection with the preheating of the tool 1. In that con- nection, said preheating is accomplished in an inert atmosphere .

Said method allows to combine the preheating of tools to several temperature zones and nitriding/nitro-carbur- izing in a furnace in order to ensure that the tool always has the same or better surface finish and wear resistance as it has today after the undergone separate nitriding/nitro-carburizing.

Suitably, the tool ring 3 is cooled in a cold- storage chamber 5 while heat insulation is provided by suitable heat insulation means 6, 7 of the extrusion tool 1 just before the same is mounted in an extrusion press and starting to extrude the ingot preheated therein through the tool 1 and the nozzle 2 thereof. In that connection, the use of gases is controlled from just normal preheating in nitrogen gas to complete nitriding/nitro-carburizing.

Thanks to the invention, among other things it is attained that :

- The investment in a separate nitriding furnace is avoided.

- The major part of the cooling phase of the nitriding process is avoided since only the ring of the tool is cooled directly after the treatment to the temperature it should have upon the introduction into the press.

- As a natural part of the production process, it can be ensured that the tool is nitrided according to requirements. The use of gases is controllable from just normal preheating in nitrogen gas to complete nitriding/nitro-carburizing.

- Energy is saved by the fact that one heating cycle is omitted.

Naturally, the invention is not limited to the embodiment described above and shown in the accompanying drawings. Modifications are feasible, particularly as for the nature of the different parts, or by using an equivalent tech- nique, without departing from the protection area of the invention, such as it is defined in the claims.

Claims

C l a i m s

1. A method for providing high surface finish and/or high rate of production of aluminium profiles and other light-metal profiles by means of the tool (1) that said profiles is formed by via extrusion and which tool (1) is finished by nitriding/nitro-carburizing, characterized in that, in con- nection with preheating of the tool (1) and the surrounding tool ring (3) to an intended temperature in a common furnace and with subsequent cooling of the surrounding tool ring (3) only, said nitriding/nitro-carburizing of the tool (1) is accomplished in connection with the preheating of the tool (1) and said preheating and possibly also the cooling being accomplished in an inert atmosphere.

2. Method according to claim 1, characterized in that the tool ring (3) is cooled in a cold-storage chamber (5) under heat insulation of the extrusion tool (1) just before the same is mounted in the extrusion press and extrusion through the tool (2) is started.

3. Method according to any one of the preceding claims, characterized in that the use of gases is controlled from just normal preheating/cooling in nitrogen gas to complete nitriding/nitro-carburizing using ammonia.

4. Method according to any one of the preceding claims, characterized in that the tool (1) and the surrounding tool ring (3) is preheated to approx. +580 ⁰C.

5. Method according to claim 4, characterized in that the tool ring (3) is cooled to approx. +350 ⁰C.