US3808029A - Lead-zinc wet-flux galvanizing process - Google Patents

Lead-zinc wet-flux galvanizing process Download PDF

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Publication number
US3808029A
US3808029A US00182809A US18280971A US3808029A US 3808029 A US3808029 A US 3808029A US 00182809 A US00182809 A US 00182809A US 18280971 A US18280971 A US 18280971A US 3808029 A US3808029 A US 3808029A
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Prior art keywords
aluminum
bath
lead
lead bath
galvanizing
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Expired - Lifetime
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US00182809A
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English (en)
Inventor
A Marks
G Harvey
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John Lysaght Australia Pty Ltd
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John Lysaght Australia Pty 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
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00—Thermal insulation in general
    • F16L59/14—Arrangements for the insulation of pipes or pipe systems
    • F16L59/16—Arrangements specially adapted to local requirements at flanges, junctions, valves or the like

Definitions

  • the lead bath contains sufficient aluminum to prevent the formation of brittle iron-zinc alloy layers on the steel surface, so that an adherent zinc or zinc alloy coating is formed.
  • the amount of aluminum in the lead is kept at a higher level than normally results from solution of some of the aluminum from the molten zinc containing aluminum floating on the exit section, and is controlled in various ways, such as by a separate molten zinc-aluminum alloy on the lead bath or external to the bath, or by solid aluminum or aluminum alloy bodies submerged in the lead bath.
  • PATENTEUAPR 30 1914 sum 2 or 2 Fi .3c
  • This invention relates to the galvanizing of steel articles, that is to say the coating of the articles with a zinc or zinc alloy layer.
  • coating metal is usedhereinafter and is intended to refer not only to zinc but also to the zinc alloys commonly used in conventional galvanizing practice.
  • galvanizing bath is used hereinafter and is intended to refer to a bath or pool of molten coating metal.
  • the usual way of galvanizing steel articles is to immerse them in or direct them through a galvanizing bath. In that process a certain amount of alloying of the two metals occurs, and this is manifested as an ironzinc alloy layer sandwiched between the steel base and the coating metal layer.
  • the presence of the alloy layer is detrimental, as it is relatively brittle and hence is not readily amenable to cold working.
  • Ability to withstand cold working is particularly desirable where the galvanized articles are in the form of sheets or strip which, or parts of which, are required to be worked by roll-forming, crimping, lockseaming, or in other ways necessitating sharp-cornering or small-radius bending.
  • the alloy layer is sufficiently thin it is better able to deform in a pliant manner; but upon cold working, even a thin alloy layer frequently fails under the loads so imposed upon it thus to cause flaking, cracking or peeling of the coating metal layer.
  • the cleaned sheet is passed into a galvanizing bath through a fenced-in layer of molten, or wet, flux, the common fluxes being chlorides. It is not possible to add aluminum to these baths in sufficient quantities to suppress the growth of undesirable iron-zinc alloy layers, because of rapid reactions between the aluminum and the flux.
  • the Lead-Zinc method consists in directing an article to be galvanized downwardly through a suitable fenced-in pool of, commonly, liquid chloride-bearing flux which floats on a bath of molten lead; then through the lead bath, and then upwardly through a fenced-in pool of molten coating metal which also floats on the molten lead.
  • the lead which does not readily form a coating on steel, acts as a separating medium between the flux and galvanizing bath, and the actual galvanizing (or most of it) is effected in the galvanizing bath. In this last connection it is found that the galvanizing process starts in the lead bath due to migration thereinto of a small proportion of the zinc with which the lead bath is in contact.
  • This migration is usually such that the zinc dissolves into the lead to about 1.0 2.0 percent concentration, but this is sufficient to initiate galvanizing and is one of the factors resulting in an undesirably thick iron-zinc alloy layer in the finished article when the process goes forward in the manner conventional heretofore.
  • the invention consists in a process of galvanizing ferrous articles comprising the step of directing the articles into a molten lead bath containing aluminum and from the lead bath upwards through a galvanizing bath containing aluminum floating on the lead bath.
  • the method of the invention includes the steps of pretreating and fluxing the article before it enters the lead bath, and the step of stripping molten coating metal from the article after it leaves the galvanizing bath to control the thickness of the finished coating.
  • the fluxing may be effected by directing the article into the lead bath through a pool of flux floating thereon.
  • FIG. I is a schematic diagram of a preferred apparatus for effecting the method of the invention.
  • FIG. 2 is a schematic diagram of an alternate apparatus for effecting the method of the invention.
  • FIG. 3 are drawings of photomicrographs of cros sections of galvanized coatings.
  • sheet or sheets refers to flat rolled products in which the rolled thickness of the product is substantially less than either its length or width.
  • strip refers to a similar product to sheets, but where the length is such that the product must usually be coiled up for convenience in storage, for instance lengths measured in thousands of feet.
  • uncoated sheets of a ferrous base material may be pretreated by well known means, for example, by pickling in acid followed by water rinsing, and then passed individually along pass line 4 into a molten lead bath 5 contained in a kettle 6 via a flux cover 7 which, as is known, prepares the strip for coating.
  • the flux cover 7 is contained by weirs 8.
  • the sheets are guided through the lead bath 5 by means of guide rolls 9 and I and other means not shown.
  • the sheets, following pass line 4, are guided upwards into a galvanizing bath 11 from which the sheets emerge between coating weight controlling rolls 12. Thereafter the sheets may be cooled by natural or forced convection, chemically treated to prevent corrosion of the coating and stacked.
  • detectable amounts of aluminum are provided within the lead bath 5. It has been found that, for normal coating metal compositions, containing less than 0.5 percent aluminum, the aluminum diffusing from the galvanizing bath 11 into the lead bath is insufficient for alloy suppression and that other means are necessary. Still referring to FIG. I, a molten aluminum-zinc alloy pool 13 is maintained in direct contact with the lead bath 5 by containment by weirs 14 similar to those containing the flux cover 7. The weirs 14 exclude any excess zinc from the alloy pool 13.
  • the aluminum concentration in the alloy pool 13 may be varied up to about preferably 02-20 percent, depending on requirements and the ratio of the interfacial surface area to the volume of lead present.
  • the selection of the concentration of aluminum in the alloy pool 13 is effected by the desired level of aluminum in the lead bath 5 since an equilibrium will eventuate between these two molten phases, and control of the composition of the lead bath 5 is achieved by varying the composition of the alloy pool 13 according to the results of regular analyses of the lead bath 5.
  • the melting point of alloys with greater aluminum concentrations than 20 percent is likely to be higher than the operating temperature of the bath.
  • the preferred proportion of aluminum in the lead bath 5 is somewhat more than the level normally reached by dissolution of the aluminum from the galvanizing bath and not greater than that needed to provide a saturated solution (about 0.06 percent). That is, the preferred aluminum concentration in the lead bath is between 0.0005 percent and 0.06 percent. It has been found that, under normal operation conditions, aluminum concentrations between 0.001 percent and 0.008 percent are usually satisfactory.
  • FIG. 2 displays a lead bath 15 in a kettle 16 supporting a galvanizing bath l7 and a flux cover 18 contained by weirs 19 all much the same as the corresponding components displayed by FIG. 1.
  • the means for feeding a strip or other article through the cover 18 and baths l5 and 17 have been omitted.
  • FIG. 2 illustrates alternative means for controlling the aluminum percentage in the lead bath.
  • Those means comprise a first molten metal pump 20, operated by a drive rod 21 and immersed in the lead bath 15, which delivers lead bath material into an alloying kettle 22 which contains a lead pool 23 with a molten aluminum-zinc alloy layer 24 floating on it which contains from 0.2l00 percent aluminum.
  • the temperature of the metals 23 and 24 in the alloying kettle 22 may be increased considerably above that of the lead bath 15 to increase the rate of dissolution of aluminum into the lead pool 23. This dissolution rate may be further assisted by any of several conventional means of agitating the lead pool 23 and alloy layer 24.
  • the lead enriched in aluminum is then pumped by a second pump 25, driven by rod 26 via conduit 27 back into lead bath IS.
  • the composition of the alloy layer 24 may be varied depending on those factors mentioned in the first described example of the invention, although in this case, with increased temperatures possible, the alloy cover 24 may contain up to aluminum depending on the actual temperature.
  • the pumping operations, from the kettle 16 to the alloying kettle 22, and return, may be either continuous or intermittent.
  • Control of the aluminum concentration in the lead bath 15 is achieved by adjusting the pumping rate and the factors mentioned above viz: temperature of the lead pool 23, composition of the alloy layer 24 and agitation, these adjustments depending on regular analysis of the lead bath 15.
  • Aluminum additions to the galvanizing bath are made in well known manner to control its composition.
  • the preferred concentration of aluminum in the galvanizing bath is from 0. l40.30% by weight, as is usually used in the large-scale and expensive processes referred to above.
  • Higher aluminum levels are not normally employed since, in these large scale processes, they are not necessary to prevent undesirable alloy growth, and further, they interfere with certain properties of the finished coating, such as solderability. However, if such properties are not required in the final product, or under other circumstances, higher aluminum concentrations ifdesircd may be used in the galvanizing bath,
  • the aluminum content of the galvanizing bath may be from l-20 percent by weight. Aluminum contents below 0.14 percent are within the range of the invention, since they have been found to produce the desired effect of suppression of the alloy layer.
  • the galvanizing bath may contain other alloying elements which are added for special purposes well known to those skilled in'the art and such bath compositions are within the spirit of this invention.
  • FIG. 3 demonstrates the effectiveness of the aluminum in the lead bath in suppressing the alloy growth between the ferrous base and the galvanized coating.
  • Table 1 showscompositions of the galvanizing bath and the lead bath under the conditions corresponding to the three photomicrographs of representative cross sections of galvanized coatings shown in FIG. 3, together with the results of adherence tests carried out on each of the coatings illustrated.
  • FIGS. 3A, 3B and 3C clearly demonstrate the alloy suppression properties of the aluminum in the lead bath and that an aluminum concentration in the galvanizing bath is only slightly effective in this regard.
  • the adherence rating of the coatings associated with the structures shown inFIGS. 3A, 3B and 3C is shown in Table l;
  • the adherence test used is one commonly employed, whereby a sample of the galvanized sheet is bent through 180 over a number of other, flat, pieces of the same sheet. The galvanized coating on the outside of the bend is then examined to see if it remains adherent. The testis repeated as many times as necessary,
  • OTf means that the coating is adherent when the sample is bent 180 on itself; this represents the severest bend possible with this test; 1T that the coating is adherent when the sheet is bent over one thickness of its own gauge, and
  • a method of galvanizing ferrous articles which I comprises pretreating the said articles for the galvanizing operation, fluxing and then directing the said articles into a molten lead bath and thence upwards through a galvanizing bath containing aluminum floating on the lead bath; the aluminum content of the lead bath being higher than it would be due to dissolution of some of the aluminum from the galvanizing bath, said aluminum content of the lead bath being maintained and controlled by circulating the lead in the lead bath through an alloying kettle containing a molten lead pool upon which floats a molten aluminum-zinc alloy layer.
  • a method according to claim 1 wherein the aluminum concentration in the lead bath is controlled by varying the composition of the molten aluminum-zinc alloy layer.
  • molten aluminum-zinc layer comprises from between 0.2 to percent aluminum by weight, the remainder, excluding impurities, being zinc.
  • a method of galvanizing ferrous articles which comprises pretreating the said articles for the galvanizing operation, fluxing and then directing the said articles into a molten lead bath and thence upwards through a galvanizing bath containing aluminum floating on the lead bath; the aluminum content of the lead bath being higher than it would be due to dissolution of some of the aluminum from the galvanizing bath and being maintained and controlled by floating a molten aluminum zinc alloy pool on the lead bath, said concentration of aluminum in the lead bath being controlled by varying the composition of the molten aluminumzinc alloy pool.
  • molten aluminum-zinc alloy pool comprises from between 0.2 percent to percent aluminum by weight; the remainder, excluding impurities, being zinc.
  • a method of galvanizing ferrous articles which comprises pretreating the said articles for the galvanizing operation, fluxing and then directing the said articles into a molten lead bath and thence upwards through a galvanizing bath containing aluminum floating on the lead bath; the aluminum content of the lead bath being higher than it would be due to dissolution of some of the aluminum from the galvanizing bath, said aluminum content in the lead bath is maintained by holding a solid aluminum or aluminum alloy body immersed in the lead bath.
  • a method according to claim 8 wherein said body is of an alloy of aluminum and zinc.
  • composition of the body alloy includes no more than 10 percent zinc by weight.
  • a method of galvanizing ferrous articles which comprises pretreating the said articles for the galvanizing operation, fluxing and then directing the said articles into a molten lead bath and thence upwards through a galvanizing bath containing aluminum floating on the lead bath; the aluminum content of the lead bath being higher than it would be due to dissolution of some of the aluminum from the galvanizing bath, said aluminum content in the lead bath is maintained by adding pigs or ingots of aluminum enriched lead to the lead bath.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)
US00182809A 1970-09-25 1971-09-22 Lead-zinc wet-flux galvanizing process Expired - Lifetime US3808029A (en)

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AUPA265070 1970-09-25

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US (1) US3808029A (sv)
JP (1) JPS4942575B1 (sv)
BE (1) BE773078A (sv)
BR (1) BR7106372D0 (sv)
CA (1) CA966765A (sv)
FI (1) FI51498C (sv)
FR (1) FR2093906B1 (sv)
GB (1) GB1324478A (sv)
MY (1) MY7400073A (sv)
NL (1) NL153275B (sv)
PH (1) PH9519A (sv)
ZA (1) ZA716217B (sv)
ZM (1) ZM13671A1 (sv)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103540885A (zh) * 2013-09-30 2014-01-29 河北钢铁股份有限公司唐山分公司 镀锌锌锅的节能装置和方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
PL97845B1 (pl) * 1975-08-15 1978-03-30 Politechnika Slaska Im Sposob wytwarzania warstw z olowiu,i jego stopow na wyrobach ze stopow zelaza
EP0037143B1 (fr) * 1980-03-25 1985-03-20 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Procédé de revêtement à chaud
US4526817A (en) * 1982-11-01 1985-07-02 Material Sciences Corporation Process for surface diffusing steel products in coil form

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US645520A (en) * 1899-12-23 1900-03-13 New Process Coating Company Process of galvanizing metals.
US943264A (en) * 1909-03-11 1909-12-14 Alexander Niedringhaus Galvanizing sheet metal.
US1741388A (en) * 1926-09-13 1929-12-31 American Rolling Mill Co Metal coating metal sheets
GB362683A (en) * 1930-12-16 1931-12-10 Harry Charles Lancaster Improvements in or relating to lead alloys
US2428523A (en) * 1942-04-21 1947-10-07 American Rolling Mill Co Apparatus for and method of coating metal strip at high speeds
US2703766A (en) * 1951-01-25 1955-03-08 Armco Steel Corp Process of continuously galvanizing with control of spangle and corrosion
US2721813A (en) * 1951-09-26 1955-10-25 Berndt Gronblom Galvanizing method, including a removal of metallic iron from zinc-containing materials such as metallic zinc and iron-zinc compounds
US3383189A (en) * 1964-04-16 1968-05-14 Sendzimir Inc T Prevention of white rust on galvanized sheets
US3681118A (en) * 1965-06-08 1972-08-01 Hitachi Ltd Method of removing excess molten metal coatings by employing low pressure gas streams

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US645520A (en) * 1899-12-23 1900-03-13 New Process Coating Company Process of galvanizing metals.
US943264A (en) * 1909-03-11 1909-12-14 Alexander Niedringhaus Galvanizing sheet metal.
US1741388A (en) * 1926-09-13 1929-12-31 American Rolling Mill Co Metal coating metal sheets
GB362683A (en) * 1930-12-16 1931-12-10 Harry Charles Lancaster Improvements in or relating to lead alloys
US2428523A (en) * 1942-04-21 1947-10-07 American Rolling Mill Co Apparatus for and method of coating metal strip at high speeds
US2703766A (en) * 1951-01-25 1955-03-08 Armco Steel Corp Process of continuously galvanizing with control of spangle and corrosion
US2721813A (en) * 1951-09-26 1955-10-25 Berndt Gronblom Galvanizing method, including a removal of metallic iron from zinc-containing materials such as metallic zinc and iron-zinc compounds
US3383189A (en) * 1964-04-16 1968-05-14 Sendzimir Inc T Prevention of white rust on galvanized sheets
US3681118A (en) * 1965-06-08 1972-08-01 Hitachi Ltd Method of removing excess molten metal coatings by employing low pressure gas streams

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103540885A (zh) * 2013-09-30 2014-01-29 河北钢铁股份有限公司唐山分公司 镀锌锌锅的节能装置和方法

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NL7113207A (sv) 1972-03-28
JPS4942575B1 (sv) 1974-11-15
BR7106372D0 (pt) 1973-04-19
ZM13671A1 (en) 1972-09-21
FR2093906B1 (sv) 1974-05-31
DE2146914B2 (de) 1975-08-07
DE2146914A1 (de) 1972-04-13
ZA716217B (en) 1972-05-31
CA966765A (en) 1975-04-29
FI51498C (sv) 1977-01-10
NL153275B (nl) 1977-05-16
GB1324478A (en) 1973-07-25
BE773078A (fr) 1972-01-17
PH9519A (en) 1976-01-09
FI51498B (sv) 1976-09-30
MY7400073A (en) 1974-12-31
FR2093906A1 (sv) 1972-02-04

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