DD244881A3 - METHOD FOR THE PRODUCTION OF BLANK WIRE OF HIGH-WET COPPER ALLUMINIUM CASTING ALLOY - Google Patents

Abstract

The invention relates to a method for the production of bare wire from copper-aluminum casting alloys with or without zinc content. The aim of the invention is to save energy in the production of bare wire made of Cu-Al cast alloys. The object of the invention is to provide a method which comprises only a few method steps from block casting to transformation to finished wire. The idea of the invention consists of casting bolts from the Cu-Al alloy, which are pressed into round wire in a hydrostatic extruder and subsequently rolled continuously to the finished wire without intermediate treatment. The bare wire produced by the process according to the invention can be used as a special material for wear-resistant and corrosion-resistant construction parts.

Description

Field of application of the invention

The invention relates to a method for producing bare wire from copper-aluminum casting alloys with or without zinc, which are used primarily as a special material for wear-resistant and corrosion-resistant construction parts. The method comprises technological steps from billet casting to finished profiled bare wire.

Characteristic of the known technical solutions

Copper-aluminum casting alloys Different compositions are used for special applications. The alloy compositions adapted to the particular field of application and the corresponding mechanical-technological characteristics of these alloys are described, for example, in DD-PS 128890, DD-PS 159552, DD-PS 155701, DD-PS 155083, DD-PS 1545550, DD-PS 204496, DD-PS 154549 , DD-PS 154548, DE-PS 3123682, GB-PS 1593498, GB-PS 1593497, GB-PS 2066849, GB-PS 1462389 and described in DE-PS 2432947. Typical known applications of these also referred to as "Mn-Al-Mehrstoffbronzen" alloys include medium-stressed construction parts (DD-PS 159552), Um- and Urformwerkzeuge (DD-PS 155701), bells (DD-PS 155083), plain bearings (DD-PS No. 154550), medium-duty and highly stressed structural parts (DD-PS 154549) and ship propellers (DD-PS 154548 and DD-PS 206165) In particular for wear-resistant and corrosion-resistant structural parts, alloys are used according to these patents whose chemical composition is in the following range:

Mn 8.0 to 15.0% Zn 2.0 to 21.0% Fe 2.0 to 6.0% Ni 1.5 to 3.0% Al 1.5 to 10.0%

.C 0.03 to 0.5% '

Pb 0.2 to 16.0% Si 0.15 to 5.0% Cu remainder

This type of alloy represents a characteristic cast alloy with a heterogeneous microstructure, which is easy to cast and process by conventional machining methods, but is difficult to reshape. On this basis, for example, the production of wire-shaped welding rods or welding electrodes for the order and production welding in ship propellers is very expensive. A reduction in cross-section, for example, allows for multiple Zish- or rolling stages or intermediate heat treatment and thereby makes the forming process for wire creation effectively, is in the. not to apply said alloys. Therefore, according to the state of the art for special applications, i.a. for bare welding wires, the following manufacturing processes are used:

1. Preparation of blank wires with a diameter of about 5mm by the sand casting method

2. Preparation of blank wires with a diameter of about 5 mm by the Kokillengußverfahren

3. Production of bare wires with a cross section of about 4 χ 4mm by centrifugal casting.

These wires are machined from bushes with a diameter of 300 to 400mm, tapped, separated and straightened as rings.

These known methods and in particular the production of the welding wires from a centrifugal casting bushing according to variant 3 are very labor-intensive. In addition, the manufactured in sand casting welding rods lead to unsatisfactory results in welding. The existing cast skin on the rod causes a strong slag formation in the welding process and leads to insufficient quality of the weld or the deposition welding. Somewhat better results are achieved with the bars cast in molds, but also the production welds carried out with them are of inadequate quality.

An effective method for producing bare wire from high strength copper-aluminum cast alloys having a heterogeneous structure based on the use of conventional forming processes with overall degrees of deformation of greater than 60% is not known.

Object of the invention

The aim of the invention is, bare wire aus.einer difficult to transform copper-aluminum casting alloy with savings. To produce energy and time while maintaining wire quality and high output.

Explanation of the essence of the invention

The invention has for its object to provide a method for producing bare wire from high-strength copper-aluminum casting alloys with or without zinc, which are difficult to form bar, based on a maximum to be realized deformation of the material in securing the application and the Quality of the finished wire only a few steps from the block casting on the transformation to the finished wire comprises.

According to the invention this is achieved in that the molten copper-aluminum casting alloys at a casting temperature above 1 273 K, but which is only slightly above the liquidus temperature, are poured with a known Kokillengußverfahren to cylindrical bolts. The diameter of the bolts should not exceed 95mm.

The stud cooled down to room temperature is removed by turning the casting skin on the surface. In addition, as viewed in the pressing direction, a cone is turned on at the front end of the bolt. The point angle of this cone must be 50 to 70 °. Subsequently, this so-prepared bolt is superficially a thin film of an oxidation-inhibiting in the preheating to pressing temperature and friction-reducing solid lubricant 'is applied during extrusion. It has been found that after preheating, preferably by means of inductive rapid heating, to a temperature of at least 970 to 1000 K, the bolts of difficult-to-form copper-aluminum casting alloys with a cross-sectional ratio output area to end face up to 150: 1 are deformable, if the hydrostatic extrusion is used and the forming conditions are set according to the invention as follows. The decisive factor is the application of the hydrostatic high-pressure forming process, taking into account the almost adiabatic heating of the material during forming. This must be targeted by the choice of the degree of deformation in realization of a Mindestumformgeschwindigkeit, which in turn prevents excessive cooling of the bolt in the pressure chamber of the hydrostatic extruder and limits the heat transfer between the material and Umformwerkstoff. Held in a certain range. According to the adiabatic temperature increase in the range up to 150K to keep. The degree of deformation should be chosen so that pressing pressures, i. Pressing pressures required to extrude the billet into a round wire in the range of 9 to 13 kbar for hot working the material.

The round wire thus prepared is cooled to room temperature. It can be stored in straight length or wound into a bundle. When winding a federal government from the round wire is to be noted, however, that the introduced by the winding process in the round wire bending stresses below the yield point of the material remain limited. This ensures that without an additional process step in the form of straightening the invention required feeding the round wire for subsequent hot forming can be done by rolling in straight fixed lengths. The cooled round wire is inventively preheated again for further cross-section reduction by rolling. In this case, a temperature in the range of 900 to 1 00OK is observed. This preheating of the round wire is carried out by a rapid heating, preferably in the direct current passage with about 2 to 5Ks ~ ¹ .

According to the invention, the hot forming of the bare, uncoated round wire is carried out continuously in succession by four rolling steps. For this purpose, roll stands arranged one behind the other, preferably 2- or 3-roll rolling stands, which have a stretch caliber row with a minimum degree of deformation of 10%, are used in a rolling line. The rolling takes place continuously without intermediate dressing in the form of heating or cooling between the individual rolling stands at a final rolling speed of up to 20 m / s. The round wire, supplied in straight fixed lengths of the first rolling stand, is stored in straight length after rolling to the finished wire diameter and cooled to still air. This bare finished wire produced by the process according to the invention has a cold workability of up to 60% reduction in cross-section, which can optionally be used for the production of wires with smaller diameters. This can preferably be done by means of a duo-profile rolling mill having a draw caliber row with individual degrees of deformation of 5 to 20%, wherein a number of rolling passes corresponding to the required final diameter of the wire is to be made.

It was not to be assumed that by using the method steps hydrostatic extrusion with simultaneous adiabatic heating and subsequent rolling of the extruded round wire, it will be possible to produce from hard to form copper-aluminum casting alloys with a heterogeneous microstructure blank wires with a cold workability up to 60% reduction in cross section.

The advantage of the method according to the invention consists mainly in that a targeted high deformation of the difficult-to-form copper-aluminum casting alloy is achieved with a heterogeneous structure. As a result, it is possible to produce bare wire effectively starting from billet casting with a few process steps. Therefore, in comparison with known casting methods for producing wire-like products from copper-aluminum casting alloys

saved by the inventive method, in particular by the realization of high Gesamtumformgrade in hydrostatic extrusion, energy and time. Furthermore, the inventive method enables the production of bare wire with different finished diameters adapted to the application. By applying the continuous rolling process, a high quality of the wires is ensured with high material output.

embodiment

The inventive method for producing bare wire from copper-aluminum casting alloys will be explained in more detail below ah two preferred embodiments.

Embodiment 1

For the production of bare wire, which is to be used as an additional material for build-up welding on ship propellers, a special material is processed, which consists of a multi-component bronze of the following composition:

Mn 11.3%

Fe 3.2%

Al 7.2%

Ni 1.9%

Cu rest

The goal is the production of a finished wire with a diameter of 5mm. The alloy to be processed is a typical cast material with a heterogeneous microstructure that is difficult to form. The solidus point is about 1 213 K, the liquidus of this alloy at about 1 273 K. The molten alloy is poured at a casting temperature of about 1 350-K using a known Kokillengußverfahrens to a cylindrical bolt with a diameter of 90 mm. By turning to a diameter of 80 mm, the cast skin of the bolt is superficially removed. At the front end of the bolt a cone is worked, which has a point angle of 55 °. Subsequently, the stud is superficially coated with a solid lubricant, preferably white boron nitride, and heated to a temperature of 973 K in a medium frequency induction furnace. This prepared and preheated bolt is pressed by means of a hydrostatic extruder to a round wire of 7.6 mm. The realized forming requires a contact pressure of 9.5kbar. Under these conditions, an almost adiabatic heating of the material by an average of 140K occurs during the forming process. As a result, the forming of the casting alloy is made possible according to the invention. It should be noted that the extrusion process is performed so that an exit velocity of the round wire of 2 m / s is formed.

The extruded round wire is placed in a straight length on a cooling bed and cooled to room temperature. Then it is cut into fixed lengths, brought again by direct current heating to a temperature of 950 K and immediately fed to a rolling mill. This rolling mill consists of four rolling mills arranged one behind the other in a rolling line, each having two rolling disks in alternately horizontal and vertical arrangement. The round wire is rolled in 4 passes continuously without intermediate treatment between the rolling stands with a single cross-section decrease of more than 10% in a series of stretch calibers to a final diameter of 5 mm. The bare finished wire is laid down in a straight length and cooled to room temperature in still air.

Exemplary embodiment 2 -

A multi-component bronze for medium to high-stress corrosion-resistant construction parts of the following composition is to be processed into a bare wire of 4 mm diameter:

Mn 9 to 11% Zn 8 to 10% Fe 2 to 4% al 2 to 4% Cu rest

This hard-to-convert casting alloy is melted in a MF induction coating and poured at a casting temperature of 1 400k using a standard Kokillengußverfahrens to a bolt of 95mm diameter. After cooling to room temperature, this bolt is turned off to a diameter of 90 mm. At the front end of the bolt, seen in the direction of pressing, a cone with a point angle of about 60 ° is applied. As in preferred embodiment 1, boron nitride is then superficially applied as an oxidation-protecting and friction-reducing medium, and the pin is inductively heated to a temperature of 973 K more rapidly. Under hydrostatic pressure of 10 kbar, this bolt is converted to a round wire with a diameter of 8 mm. This results in a temperature increase in the material of about 150K. The round wire obtained by this forming process at an exit velocity from the hydrostatic extruder of 2.5m / s on average is deposited in a straight length and cooled to room temperature. Subsequently, a rapid heating of this round wire to a temperature above the recrystallization takes place. It is immediately fed to a well-known hot rolling mill, where it is continuously rolled with 4 profiled rolling passes in a stretch quilting row to form a 5.5 mm diameter bare wire. The

Single cross section decrease is about 10% on average. This straight-rolled wire, cooled to room temperature, is then formed into a 4mm diameter die at room temperature using a duo-roll mill in 3 single passes.

Claims (4)

Invention claim: 1. A process for the production of bare wire made of high-strength copper-aluminum casting alloys, wherein the molten metal alloys poured at a casting temperature just above the liquidus with a known Kokillen-casting to cylindrical bolts, this after solidification, the Gußhaut be removed, characterized in that the Bolt to a temperature in the range of 970 to 1 000 K, under hydrostatic pressure at a Mindestumformgrad and at a press speed corresponding to an adiabatic temperature increase during the forming in the limited range to 150K, pressed into a round wire and cooled to room temperature and that this round wire again on a temperature above the recrystallization is heated rapidly, then continuously rolled without intermediate treatment at a final rolling speed of up to 20m / s and a minimum degree of deformation of 10% to the finished wire. 2. A process for the production of bare wire copper-aluminum casting alloys according to claim 1, characterized in that the cast-off bolt after removing the cast skin in addition to the seen in the pressing direction front end a cone with a total peak angle in the range of 50 to 70 ° is attached. 3. A process for the production of bare wire from copper-aluminum casting alloys according to claim 1, characterized in that the round wire produced by hydrostatic hot pressing is stored in straight length or in the form of a federal and fed in straight fixed lengths of the arranged in a rolling mill rolling stands. 4. A process for the production of bare wire of copper-aluminum casting alloys according to claim 1 and 3, characterized in that the optionally additionally required after hot rolling of the round wire cold forming   preferably with a known duo-roll mill in 4 passes, which has a draw caliber series with individual cross-section decreases of 5 to 20% is performed.