US3738861A - Method of wiping galvanised wire or strip - Google Patents

Method of wiping galvanised wire or strip Download PDF

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Publication number
US3738861A
US3738861A US00805145A US3738861DA US3738861A US 3738861 A US3738861 A US 3738861A US 00805145 A US00805145 A US 00805145A US 3738861D A US3738861D A US 3738861DA US 3738861 A US3738861 A US 3738861A
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US
United States
Prior art keywords
bed
gas
wiping
chamber
wires
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Expired - Lifetime
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US00805145A
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English (en)
Inventor
J Sciffer
H Roxby
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AUSTRALIAN WIRE IND PTV Ltd
AUSTRALIAN WIRE IND PTV LTD AU
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AUSTRALIAN WIRE IND PTV Ltd
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/22—Removing excess of molten coatings; Controlling or regulating the coating thickness by rubbing, e.g. using knives, e.g. rubbing solids

Definitions

  • the invention relates to the operation of wiping galvanised wires or strips immediately after they are withdrawn from the galvanisiug bath.
  • the wires or strips are drawn upwardly through a bed of washed and graded river gravel or of nodules or like bodies composed of other suitable inert material having a specific gravity lower than that of molten zinc.
  • the bed is preferably contained within a chamber which is open at its upper and lower ends and the latter preferably projects into the molten zinc bath.
  • the interstices of the bed and the space immediately above it are filled with a non-oxidising gas which excludes air and this gas preferably contains H 8.
  • This gas enters the chamber close to the surface of the molten metal and is preferably preheated by heat exchange from the interior of the chamber before it enters the latter.
  • a wiping bed according to the invention requires replacement less frequently than the conventional charcoal bed so that labour costs are reduced and also that the throughput speeds of the wires or strips may be substantially increased.
  • This invention relates to the continuous galvanising of wire or strip by the hot dip process and more particularly to the operation of Wiping the wire or strip immediately following its withdrawal from the bath of molten zinc in order to ensure that the zinc coating is continuous, uniform and smooth.
  • This wiping operation is usually effected by passing the wire or strip vertically upwards through a bed of powdered charcoal which floats on thesurface of the molten zinc bath and which usually requires to be replaced at intervals of about two to four hours.
  • Another specific object is to provide an improved wiping method and apparatus which permit of a significantly increased speed of operation.
  • the invention includes the method of continuously wiping hot dipped galvanised wire, strip or the like, comprising passing the latter immediately following its withdrawal from the bath of molten zinc, through a bed comprising relatively movable nodules, granules or other like bodies composed of hard, substantially inert material which is substantially unaffected by temperatures up to about 450500 C. and has a lower specific gravity than molten zinc.
  • the material is preferably of a composition such that it is not wetted by molten zinc, its specific gravnited States Patent 0" 3,738,861 Patented June 12, 1973 ity is preferably within the range 2.0 to 4.5, and the nodules, granules or the like are preferably within the size range of about one eighth to one quarter of an inch, though the invention is not limited to nodules or granules of this order of size.
  • the material is approximately spherical in form, but washed and graded river gravel has proved to be very satisfactory for the purpose and is relatively inexpensive and readily obtainable.
  • a suitable non-oxidising gas and preferably an appropriate reducing gas, such as a suitable town gas, liquid petroleum gas, blast furnace gas or annealing furnace atmosphere gas, is continuously passed through the wiping bed so as to fill the interstices thereof.
  • an appropriate reducing gas such as a suitable town gas, liquid petroleum gas, blast furnace gas or annealing furnace atmosphere gas
  • the said wiping bed is confined within a chamber which preferably dips at its lower end into the bath of molten metal and which is provided, near its lower end with a gas inlet opening, and at or near its upper end, with a discharge opening through which the galvanised wires or strips emerge and where the escaping gas is preferably burned.
  • An important feature of the preferred form of the invention resides in using a reducing gas containing a suitable proportion of hydrogen sulphide, for example between and 1000 grains (sulphur content) per 100 cubic feet of gas at atmospheric pressure through the invention is not limited to proportions of this order.
  • Wiping apparatus comprises a generally vertical chamber open at its upper and lower ends and arranged with its lower end dipping into the surface of a bath of molten zinc, and a bed of graded gravel or other suitable inert material in nodular or similar form in the chamber, said bed forming material having a lower specific gravity than zinc whereby the bed floats on the molten metal, and means for moving the wire strip or the like upwardly through the chamber from the bath.
  • the gas is preferably, but not necessarily, preheated before it enters the chamber and for this purpose one side wall of the latter may be hollow and the cavity therein forms a gas passage in which the gas is preheated by heat exchange from the inner section of that wall.
  • the upper end portion of the said cavity is formed with a gas inlet opening, while the lower part of the inner wall section is formed with an elongated horizontal slot or equivalent holes through which the heated gas passes from the cavity into the bottom of the chamber as close as is practicable to the point where the wires emerge from the surface of the zinc.
  • the opposite side of the chamber preferably comprises at least one detachable plate which forms a gas-tight seal with the body of the chamber and which, when detached, permits of the insertion and removal of the wiping bed.
  • a detachable plate which forms a gas-tight seal with the body of the chamber and which, when detached, permits of the insertion and removal of the wiping bed.
  • two such detachable plates are provided, with the one arranged above the other.
  • the bed does not fill the chamber, so that a free gas space is provided within the latter and above the bed and this upper portion of the chamber is preferably upwardly convergent and has a relatively narrow slot in its upper end for the emergence of the wires or strips and the discharge of the gas.
  • wires or strips move upwardly above the chamher, they preferably pass through a jet of water in the usual way in order to solidify the zinc without deformation of the coatings formed thereby.
  • the invention may be used in conjunction with existing continuous hot dip galvanising plants.
  • the strip or wire is usually con tinuously subjected to a series of pretreatment operations before it passes into the bath of molten zinc, such pretreatment operations usually comprising heat treatment, acid cleaning, water washing "and fluxing while some plants employ the well known Sendzimir process.
  • the wire or strip is directed to and around a roller submerged in the bath of molten zinc and then passes vertically upwards from this roller through the surface of the molten metal and then through the aforesaid charcoal wiping bed and a water spray, to and around steadying and tension rolls from which it extends more or less horizontally to a winding or take-up frame.
  • wires or strips are coated simultaneously, such wires or strips being arranged side-byside in spaced parallel relationship.
  • the present invention is concerned primarily with the substitution of an improved wiping bed of discrete inert material for the usual charcoal wiping bed and with the exclusion of air therefrom by continuously passing therethrough a non-oxidising gas which preferably contains a small proportion of hydrogen sulphide.
  • FIG. 1 is a partly broken-away view in front elevation of a wiping chamber according to the invention
  • FIG. 2 is a view in plan and is partly a section on the line 22 of FIG. 1, and
  • FIG. 3 is a view in sectional end elevation taken on the line 33 of FIG. 1.
  • the illustrated wiping chamber or box is of relatively long and narrow rectangular shape when viewed in plan, and is arranged transversely or at right angles to the several wires or strips so that its length is determined by the number of wires or strips which simultaneously pass upwards through it.
  • the chamber which is conveniently fabricated from sheet steel, is open at its upper and lower ends and may conveniently be of the order of fifteen to twenty-four inches in height.
  • the end walls 11 of this chamber are disposed vertically, as also are its front and back walls 12 and 14 respectively with the exception of their upper portions which preferably converge upwardly and inwardly as shown, whereby the chamber is of reduced width at its open upper end which thus has the form of a narrow slot 16 which may for example be about one and a half inches in width.
  • the chamber may be about four inches in width below its converging upper portion, and its lower end dips into the molten Zinc bath 24.
  • the back wall 14, i.e. that wall which is more remote from the winding frame, and also the two end walls 11 preferably extend down into the bath for a depth of the order of six inches to serve as baflles which minimise the effect of surging of the molten metal in the bath and also hold back oxide and fluxing products.
  • the front wall 12 preferably projects only a short distance, e.g. a distance of about one quarter of an inch, into the molten metal in order to permit accumulated dross to be readily scraped out from below the wiping bed together with dross-entangled gravel from the latter. As this wall extends only a short distance into the molten metal, it is necessary to maintain the level of the bath substantially constant.
  • the said front wall 12 preferably consists of two detachable plates 12a and 12b arranged, the one above the other, and which when secured in position, form substantially gastight seals with each other and with the end walls 11.
  • the lower end portion of the lower plate 12b is preferably bent horizontally outwards to form a flange 120.
  • These plates are detachable primarily for the purpose of facilitating the insertion and removal of the gravel or other bed 13 though they also facilitate the setting-up operation which involves passing the several wires upwardly from rollers 30 submerged in the bath and then through the chamber from which they pass in succession to the steadying rollers and the take-up or winding frame which are not shown.
  • the bed may for example consist of washed river gravel which has been graded by passing it through a one-quarter inch screen and by then discarding the grains which pa s through a one-eighth of an inch screen.
  • the gravel is inserted into the latter through the front opening formed preferably by the removal of the upper detachable plate 12a only.
  • this plate is replaced.
  • the bed thereof floats on the molten zinc bath, the depth of this bed being conveniently about six to twelve inches so that a free gas space of substantial depth remains within the chamber above the bed.
  • both of the plates 12a and 12b are preferably detached.
  • the back wall 14 of the chamber is hollow and the lower end of the cavity 18 therein communicates with the interior of the chamber immediately above the surface of the molten zinc, by means of a slot 20 which extends substantially the full length of the wall.
  • the upper end of the cavity 18 is connected, e.g. by a pipe 22, to a source of a suitable reducing gas, e.g. coke oven gas, containing a small proportion of hydrogen sulphide.
  • a suitable reducing gas e.g. coke oven gas
  • the ends of the pipe 22 may be connected to alternative gas supplies, both to ensure continuity in the event that one supply should be interrupted and to obtain more uniform distribution of gas within the chamber.
  • the gas is preheated as it flows downwardly through the hollow back wall from which it passes through the slot 20 into the bottom of the chamber and is uniformly distributed along the full length thereof. This gas then flows upwardly through the interstices of the gravel bed and through the free space thereabove, and is finally discharged through the aforesaid narrow slot 16 at the top of the chamber, where it is preferably burned.
  • the pressure and rate of flow of the gas do not appear to be important though the flow should be steady and uniform and sufficient to exclude all air.
  • the wiping bed ensures that the gas is uniformly distributed over the area of the chamber and in conjunction with the narrow discharge slot at the top of the chamber, it restricts the rate of flow. It has been found unnecessary to install apparatus to measure or control the gas flow, as with experience, the height and character of the exhaust flame provides an effective indication of uniformity of flow and distribution though suitable flow control apparatus may be used to obtain more constant operating conditions.
  • the wiping bed of gravel or the like not only serves to form a continuously self-adjusting and infinitely variable orifice for each wire or strip which extends therethrough, but also it acts as an eflicient vibration damper and so permits of higher throughput speeds than are normally possible without detriment to the quality and uniformity of the zinc coating.
  • the wiping bed may be formed of gravel or any other suitable material in discrete condition.
  • the preferred charactersitics of such material are that it has a specific gravity lower than molten zinc and it should be hard but not so brittle as to powder under the conditions of use and it should be non-wettable and unaffected by molten zinc. Also this material should be unaffected by strongly reducing atmospheres and the granules should have little or no tendency to stick together but should remain free to tumble under the con-' ditions of use.
  • the material is preferably one which is readily available in moderate quantities at a relatively low cost as is usually the case with water washed gravel which satisfies all of the foregoing requirements.
  • the free gas space above the wiping bed should be as high as possible consistent with adequate control of vibration in order to allow sufficient time for the reflow of the zinc to produce a uniform coating.
  • H S is a more effective reducing agent than hydrogen, methane and carbon dioxide, and also that it favourably affects the surface tension of molten zinc.
  • a gravel wiping bed as herein disclosed may normally be used for as much as one week or more with the periodic in-process removal of foreign accumulations from the bottom of the bed and its replacement by clean gravel at the top of the bed, whereas it is usually necessary for a charcoal bed to be adjusted or replaced every two to four hours so that labour costs are significantly reduced by the present invention while also it has been found that throughput speeds may be substantially increased as compared with charcoal beds.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)
US00805145A 1968-03-08 1969-03-07 Method of wiping galvanised wire or strip Expired - Lifetime US3738861A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AU34755/68A AU421751B2 (en) 1968-03-08 1968-03-08 Improved method of and apparatus for wiping galvanised wire or strip

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US3738861A true US3738861A (en) 1973-06-12

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US (1) US3738861A (enrdf_load_stackoverflow)
JP (1) JPS5020552B1 (enrdf_load_stackoverflow)
AU (1) AU421751B2 (enrdf_load_stackoverflow)
BE (1) BE729567A (enrdf_load_stackoverflow)
GB (1) GB1256928A (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892894A (en) * 1973-03-16 1975-07-01 Australian Wire Ind Pty Wiping hot dipped galvanized wire or strip
US3914481A (en) * 1973-03-01 1975-10-21 Theodore Bostroem Process of hot dip metallizing of metallic articles
US4107357A (en) * 1975-09-16 1978-08-15 Nippon Steel Corporation Method for effecting one side molten metal plating
US4207362A (en) * 1977-11-21 1980-06-10 Australian Wire Industries Proprietary Limited Method of and apparatus for wiping hot dipped metal coated wire or strip
US4282273A (en) * 1978-04-10 1981-08-04 Messer Griesheim Gmbh Process and apparatus for galvanizing a wire
US4310572A (en) * 1980-04-11 1982-01-12 Bethlehem Steel Corporation Method for wiping hot dip metallic coatings
US4421054A (en) * 1980-04-11 1983-12-20 Bethlehem Steel Corporation Apparatus for preventing surface blemishes on aluminum-zinc alloy coatings
US4664953A (en) * 1984-02-23 1987-05-12 Copas Raymond J Coating of wire or strip
WO2004003250A1 (de) * 2002-06-28 2004-01-08 Sms Demag Aktiengesellschaft Trenngaseinsatz bei der kontinuierlichen schmelztauchveredelung
CN110184554A (zh) * 2019-05-30 2019-08-30 江苏景源泓科技有限公司 一种无需氮气保护的敞开式钢丝热镀锌用电磁抹拭装置

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3631893A1 (de) * 1986-09-19 1988-03-31 Paul Fontaine Verfahren und vorrichtung zum abstreifen von mit schmelzfluessigem material beschichtetem blech
BE1004900A3 (nl) * 1991-05-29 1993-02-16 Bekaert Sa Nv Bedekken van metaaldraden.
GB2281309B (en) * 1993-08-27 1997-04-23 Boc Group Plc A method of galvanising
CN109266987A (zh) * 2018-08-29 2019-01-25 广州倬粤动力新能源有限公司 锌丝的加工设备

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3131093A (en) * 1961-11-08 1964-04-28 Boeing Co Combined cleaning and tinning apparatus

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3914481A (en) * 1973-03-01 1975-10-21 Theodore Bostroem Process of hot dip metallizing of metallic articles
US3892894A (en) * 1973-03-16 1975-07-01 Australian Wire Ind Pty Wiping hot dipped galvanized wire or strip
US4107357A (en) * 1975-09-16 1978-08-15 Nippon Steel Corporation Method for effecting one side molten metal plating
US4207362A (en) * 1977-11-21 1980-06-10 Australian Wire Industries Proprietary Limited Method of and apparatus for wiping hot dipped metal coated wire or strip
US4282273A (en) * 1978-04-10 1981-08-04 Messer Griesheim Gmbh Process and apparatus for galvanizing a wire
US4421054A (en) * 1980-04-11 1983-12-20 Bethlehem Steel Corporation Apparatus for preventing surface blemishes on aluminum-zinc alloy coatings
US4310572A (en) * 1980-04-11 1982-01-12 Bethlehem Steel Corporation Method for wiping hot dip metallic coatings
US4664953A (en) * 1984-02-23 1987-05-12 Copas Raymond J Coating of wire or strip
WO2004003250A1 (de) * 2002-06-28 2004-01-08 Sms Demag Aktiengesellschaft Trenngaseinsatz bei der kontinuierlichen schmelztauchveredelung
US20050233088A1 (en) * 2002-06-28 2005-10-20 Walter Trakowski Use of separation gas in continuous hot dip metal finishing
AU2003219109B2 (en) * 2002-06-28 2009-01-22 Sms Demag Aktiengesellschaft Use of separation gas in continuous hot dip metal finishing
CN110184554A (zh) * 2019-05-30 2019-08-30 江苏景源泓科技有限公司 一种无需氮气保护的敞开式钢丝热镀锌用电磁抹拭装置
CN110184554B (zh) * 2019-05-30 2023-12-22 河北鑫鹏通信设备有限公司 一种无需氮气保护的敞开式钢丝热镀锌用电磁抹拭装置

Also Published As

Publication number Publication date
GB1256928A (enrdf_load_stackoverflow) 1971-12-15
BE729567A (enrdf_load_stackoverflow) 1969-08-18
AU3475568A (en) 1970-09-10
JPS5020552B1 (enrdf_load_stackoverflow) 1975-07-16
AU421751B2 (en) 1972-02-25

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