IE44962B1 - The manufacture of steel wires - Google Patents

Abstract

A nozzle for the production of steel wires having a small diameter by the extruding of a molten steel under pressure through the nozzle is made essentially of zirconia(ZrO2), possibly containing a small amount of magnesia and/or a rare earth oxide selected in such a manner that, in the presence of silicon and/or silica, it does not give rise to silicates of low melting point, said oxide preferably being yttrium oxide (Y2O3).

Description

This invention relates to the manufacture of steel wires, to spinnerets through v/hich a jet of liquid steel can be projected to give the wires upon cooling, and apparatus which includes such a spinneret, Apparatus for making steel wires or filaments, hereinafter referred to as wires for simplicity, is shown, by way of example, in the accompanying drawing.

The apparatus includes a fluid-tight chamber 1 enclosing a crucible 2 for the molten steel 4. Around the crucible is a heating element 3 for keeping the steel molten and possibly for melting the steel. Into the base 5 of the crucible is a spinneret or die 6, hereinafter called simply a spinneret for simplicity.

A jet 7 of molten steel is forced from the crucible 2 through an orifice 9 of the spinneret 6 into a cooling chamber 8 where a wire solidifies. The jet 7 is forced to pass through the orifice 9 by introducing a pressurized gas through an inlet 10 into the fluid-tight chamber 1 enclosing the crucible 2.

To obtain continuous, small diameter, steel filaments -2which are of constant section; such as those- which are used in cords for the reinforcing of pneumatic tyres, we have found, as described in flo. 36357 , tha ft is advantageous tc use steei having an unusually high silicon content sc that a silicon dioxide coating is formed on the jet of liquid steel projected into the cooling chamber, trie median! which is contained in this chamber obviously having a suitable oxygen content. However, v/e have obss-'-ved that the section of steel wire as thus produced had a tendency to increase during use of ths s Ρ ί ibis rat ins s,:ir.neret is subject to a nin>b?<· yt simultaneous and ciscevantagcoui e.'i'ects. Thus, the moisteel is at a ii'gn A:., ...tore, the fives at SGiSds which can reach scv-rxi i.ciis of «itres per Xsccnd, rf su it has an ev’ceixp actic-r, there it a : corroding : i ty reducing siemerts, such _ carbon, silicon and c iun;iπiirrn, end hy the irides t;h ich .-..: present or which are being forced 'n the steel psssiny through the spinneret, -'.ti. S’O^ arc Al«0.,.i. G ώ A spinn-sret consisting of .-::: «iuminiura ·: xl.; {ftlgOj}» CihtEinid by h j t-s i η ter i ng under high pressure has been suggested, Hiicr this is used for extruding molten steel -3at a flow rate of lOm/second, the steel being at a temperature of 1500°C and having contents of the following elements: Si 3.5%, C 0.38%, Mn 0.07%, Cr 0,8% and Al 0.010%, it was found that there was a variation in the extruded wire>diameter of the order of 10 micrometres per hour. -The initial diameter of the wire was about 160 micrometers, and h^nce there was a relative variation in diameter of more than 6% per hour.

It has also been proposed to use certain other sintered 10 refractory oxides for making the spinneret. However, the refractory oxides involved were based on radioactive elements and so the formation of the spinnerets from such oxides involved the use of protective means and therefore the industrial use of such spinnerets is expensive.

Therefore there is a need to find a refractory material which is both resistant to the attacks of the steel and capable of being used and formed in a simple and safe manner into spinnerets for use in the production of filaments of steel having such a high silicon content.

According to the invention there is provided a method of manufacturing high silicon content, steel wires, in which molten steel, having a high silicon content (as defined herein) is extruded by pressure through an orifice in a 4^9 6 3 spinneret comprising a major amount of zirconium dioxide and a minor amount of a stabilizer for the zirconium dioxide, the stabilizer being magnesium oxide and/or an oxide of a rare earth element which in the presence of silicon and/or allies will not produce silicates which are molten at the extrusion temperature of the highsilicon content steel.

References to steel having a high silicon content herein - =/er to tho silicon being present in the liquid steel in an amount sufficient to ensure that the oxidation product, which forms during the solidification of the steel after extrusion, is silica, as described in fata-it Specification i»O, 35157.

Tho invent lea a Iso extends to apparatus when used in the above process of tha invention, which comprises a crucible for ths mo Veen steel and a cpinnsrat in the wall of the crucible 'laying an orifice threugh which the &o]ten steel is forced by excess pressure applied fo the molten steel, the spinneret comprising a major amount of zirconium dioxide and a mino:’ amount of a stabilizer for tha zirconium dioxide, tho stabilizer being magnesium oxide »nd/cr an oxide of a rare earth element which In tha presence of silicon and/or silica will co·; produce silicates which are molten at the extrusion temperature of the high-silicon content steel. -5449®s The invention also extends to a spinneret when used in the process of the invention, the spinneret comprising a major amount of zirconium dioxide and a minor amount of a stabilizer for the zirconium dioxide, the stabilizer being magnesium oxide and/or an oxide of a rare earth element which in the presence of silicon and/or silica will not produce silicates which are molten at the extrusion temperature of the high-silicon content steel.

Such spinnerets can be manufactured by prolonged sintering of a mixture of zirconium dioxide powder and stabilizer at high temperature; The minor amount of stabilizer for the zirconium dioxide which is present partially or completely stabilizes the zirconium dioxide. Actually, v/ith the heating and the cooling of the pure'zirconium dioxide, the latter shows, in certain temperature ranges, variations in the crystalline lattices which result in stresses and cause cracking and even rupturing. The stabilizer chosen should be an oxide which shows little reaction or no reaction at all with the metallic elements and the metallic oxides which are contained in the steel. This is the reason why, in the case of steels including silicon and containing in particular silica, calcium oxide which is a known stabilizer of zirconium dioxide cannot be used. The same also applies as regards -6certain rate earth oxides. Quite generally, the use of any oxides whicn give, with silicaii; silicates having a low melting poirt, must be avoided.

Yttrium oxide used as an additive to the zirconium dioxide 5 is particularly useful from tins point of view in the formation of spinnerets according to the invention and preferably the yttrium oxide is added in an amount of from 5 to 12 mole %. in the preparation of one spinneret for use in the 1G invention yttrium ox’’de was added to zirconium dioxide at the rate of 6 mole %, i.e. δ moles of yttrium oxide and 94 moles of zirconium dioxide. The powder, of which the grains had an average diameter of 2.2 micrometers, was cold pressed at 10 bg/mm^ pressure and then sintered for 10 hours at s temperature of 17Q0~C. The material as thus obtained had a density of 5.90, A spinneret consisting of zirconium dioxide and yttrium oxide made in this way was used to extrude molten steel at 15OG°C and ai a speed of 15 m/second tod it was found that there was no variation in the initial diameter of the wire (150 micrometers) after· ths spinneret had been in use for 5-J hours. Another spinneret of the same composition, usee for extruding an identical steel, did not result in -7any variation in the initial diameter of the wire after having been used for 9 3/4 hours, the initial diameter of the wire in this case being 190 micrometers for an extrusion speed of 10 m/second.

In each of these examples, the steel had the same composition as that used with the aluminium oxide spinneret described above.

The behaviour of spinnerets used in the invention is all the more surprising, since it is usually advised that zirconium dioxide should not be used for extruding steels which contain silicon and manganese because of their corrosive effect. It seems that this behaviour could be attributed to the fact,that the zirconium dioxide either does not react with the silica or that it forms, with the 1 latter, solid products (silicates of zirconium or zircon), which are refractory at the temperatures at which they are used in the extrusion process. ί Furthermore, in the presence of aluminium ox.ide, caused by the traces of aluminium which are inevitably present industrially in steel, the eutectic is absent below 1750°C from the ternary diagram of ZrOg-SiOg -A12°3· -8The steal wires prepared according to the invention using the zirconium dioxide spinneret are of ssisli diameter and so useful in the making of reinforcements for pneumatic tyres.

Claims (5)

1. WHAT WE CLAIM IS:1. A method of manufacturing high silicon-content, steel wires, in which molten steel, having a high silicon content (as defined herein), is extruded by pressure through an orifice in a spinneret comprising a major amount of zirconium dioxide and a'minor amount of a stabilizer for the zirconium dioxide, the stabilizer being an oxide of a rare earth element which in the presence of silicon and/or magnesium oxide and/or//an oxide of a rare earth such that in the presence of silicon and/or silica will not produce silicates which a're molten at the extrusion temperature of the high-silicon content steel.

2. A method ,as claimed in claim 1 in which the spinneret comprises zirconium dioxide and from 5 to 12 mole 7 of yttrium oxide,

3. A method of manufacturing high-silicon content, steel wires according to Claim 1 and substantially as herein described.

4. Steel, wire when made by a method as claimed in any one of claims 1 to 3. 5. A spinneret when used in the process of Claim 1, the spinneret comprising a major amount of .irconium dioxide and a minor amount of a stabilizer for the zirconium dioxide, -104 4 9 6 3 the stabilizer being magnesium oxide and/or an oxide of a rare earth element which in the presence of silicon and/ or silica will not produce silicates which are molten at the extrusion temperature of the high-silicon content 5 steel. 6. A spinneret as claimed in Claim 5 which comprises zirconium dioxide and from 5 to 12 mole % of yttrium oxide. 7. A spinneret according to Claim 5, and substantially as herein described. 10 3. Apparatus wnen used in the process of Claim 1 comprising a crucible for the molten steel and a spinneret in the wall of the crucible having an orifice through which the molten steel is forced by excess pressure applied to the molten steel, the spinneret comprising « major amount of 15 zirconium dioxide and a minor amount of a stabilizer for ths zirconium dioxide, the stabilizer oeing magnesium oxide and/or an oxide of a rare earth elaineist which in the presence of silicon and/or silica will not produce silicates which are molten at the extrusion temper.”ture of the high20 silicon content steel. 9. Apparatus as claimed in Claim 8 in which the spinneret comprises zirconium dioxide and from 5 to 12 mole % yytrium oxide. 10. Apparatus according to Claim 8 and substantially as herein described with reference to the accompanying

5. Drawings.