US2708171A - Method of controlling coating thickness in continuous galvanizing - Google Patents

Method of controlling coating thickness in continuous galvanizing Download PDF

Info

Publication number
US2708171A
US2708171A US297697A US29769752A US2708171A US 2708171 A US2708171 A US 2708171A US 297697 A US297697 A US 297697A US 29769752 A US29769752 A US 29769752A US 2708171 A US2708171 A US 2708171A
Authority
US
United States
Prior art keywords
strip
coating
bath
portions
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US297697A
Inventor
Jr Charles L Inglefield
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
United States Steel Corp
Original Assignee
United States Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by United States Steel Corp filed Critical United States Steel Corp
Priority to US297697A priority Critical patent/US2708171A/en
Application granted granted Critical
Publication of US2708171A publication Critical patent/US2708171A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C2/00Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14Removing excess of molten coatings; Controlling or regulating the coating thickness
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S118/00Coating apparatus
    • Y10S118/19Wire and cord immersion

Definitions

  • An object of the present invention is to provide an improved method of preventing the zinc coating from attaining excessive thickness adjacent the strip edges, which method involves mechanically blowing molten zinc from the edge portions while applying heat thereto and is applicable to conventional existing lines and enables them to operate at higher speeds.
  • a more specific object is to provide improved methods of preventing the coating adjacent the strip edges from attaining an excessive thickness by the action of gas flames which mechanically blow away the excess and at the same time heat the strip surface near its edges only and thus maintain these edges for a longer time at the temperature at which they emerge from the bath without appreciably raising their temperature.
  • a further object is to provide improved methods of preventing the coating adjacent the strip edges from becoming excessively thick by the combined mechanical action and heating effect of gas jet flames directed downwardly against the surface of the strip adjacent its edges.
  • Figure 1 is a top plan view of a galvanizing pot of a continuous line equipped with heating means in accordance with the present invention
  • Figure 2 is a sectional view taken on line Il--II of Figure 1;
  • Figure 3 is a top plan view similar to Figure 1 but showing a modification
  • Figure 4 is a sectional view taken on line IVlV of Figure 3.
  • Figure 5 is a diagrammatic plan view on a larger scale of the modification of Figure 3 showing more clearly the relative positions of the gas jets and the strip.
  • Figures 1 and 2 show somewhat diagrammatically a portion of a continuous galvanizing line which includes a galvanizing pot 10, a sink roll 12 in the lower portion of said pot, a support 13 for said sink roll, and a pair 2,708,17 1 Ce Patented May 10, 1955 of grooved coating rolls 14 and 15.
  • the pot contains molten zinc at a temperature of 800 to 875 F. to a level about as indicated in Figure 2, which is approximately the diametric plane of the two coating rolls.
  • a continuous steel strip S is led from an annealing furnace, not shown, through an enclosing snout 16, into the pot, around the sink roll and up between the coating rolls.
  • the strip surface picks up a zinc coating, the thickness of which is controlled by the coating rolls. After leaving these rolls, the strip passes upward to the top of a cooling tower, not shown, and thence downward to subsequent treating equipment.
  • the equipment and process thus far described are well known and therefore are not shown nor described in detail.
  • gas burners 17, equipped with control valves 17a are directed downwardly against the strip edges just above the coating rolls. These burners are positioned so that the gas jets emerging therefrom impinge on both faces of the strip adjacent the edges. The flow of gas actually impinges on the coating before combustion takes place. Consequently the gas velocity has a mechanical effect of blowing excess molten zinc downwardly off the strip surface.
  • the flames are regulated not to heat the surface of the strip adjacent the edges appreciably above the temperature at which the edges emerge from the coating rolls, but merely to maintain them at this temperature longer than the remainder of the strip.
  • the resultant heating of the edge portions prevents formulation of a cobweb structure while maintaining a spangled appearance in the finished product. It is possible also that the heating alone may cause some run ofi of the excess coating adjacent the strip edges and thus combine with the mechanical effect of the jets in eliminating this excess.
  • the gas flames do not appreciably raise the temperature of the strip and its coating, or else a nonuniform product would result.
  • a nonspangled galvanized product can be produced by heating the strip across its full width to temperatures around 1000" F. as it leaves the bath, which heating alloys the coating with the strip surface.
  • the burners do not heat the strip sufiiciently to cause this alloying eiiect.
  • Figures 3, 4 and 5 show a modification in which gas burners 18 equipped with control valves 18a are directed downwardly and outwardly against both sides of the strip. This modification enhances the mechanical effect of the jets in blowing away the molten zinc, and also furnishes better control in heating both sides of the strip uniformly.
  • a method of controlling the coating thickness and yet maintaining a uniformly Spangled surface across the width of the strip comprising mechanically blowing away excess molten zinc from the portions of the strip surfaces immediately adjacent the side edges as the strip emerges from the coating rolls before the coating solidifies, and simultaneously heating the same portions of the strip, such heating being confined to these portions and controlled to maintain them at the temperature at which they leave the bath for a longer time than the portion of the strip inwardly of. the side edges without appreciably raising the temperature of any portion of the strip above that of the galvanizing bath.
  • a method of preventing the zinc coating on the strip from attaining excessive thickness immediately adjacent the side edges of the strip and yet maintaining a uniformly spangled surface across the width of the strip comprising directing gas fiames downwardly against the portions of the strip surface immediately adjacent the side edges as the strip emerges from the coating rolls before the coating solidifies, and thereby both mechanically blowing away excess zinc and heating these portions of the strip, such heating being confined to these portions and controlled to maintain them at the temperature at which they leave the bath for a longer time than the portions of the strip inwardly of the side edges without appreciably raising the temperature of any portion of the strip above that of the galvanizing bath.

Description

y 1955 c. L. INGLEFIELD JR ,708,171
ETHOD OF CONTROLLING COATIN THICKNESS IN CONTINUOUS GALVANIZING Filed July 8, 1952 3 Sheets-Sheet 1 IN V EN TOR.
CHARL ES L.|NGLEF|ELD,JR.
HIS ATTORNEY.
y 1955 c. L. INGLEFIELD JR 8, 71
METHOD OF CONTROLLING COATIN THICKNESS IN CONTINUOUS GALVANIZING Filed July 8, 1952 3 Sheets-Sheet 2 IN V EN TOR.
CHARL S L.|NGLEFlE-LD,JR.
HIS ATTORNEY.
May 10, 1955 Filed July 8, 1952 c. L. INGLEFIELD JR METHOD OF CONTROLLING coA'rm THICKNESS m commuous GALVANIZING 5 Sheets-Shoat 3 INVENTOR. CHARLES L lNGLEFIELD, JR.
HIS ATTORNEY United States Patent METHOD OF CONTROLLING COATING THICK- NESS IN CONTINUOUS GALVANIZING Charles L. Inglefield, Jr., Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Application July 8, 1952, Serial No. 297,697
3 Claims. (Cl. 117-46) at a temperature of about 800 to 875 F. A continuous steel strip is led into the pot, passes around a sink roll at the lower portion thereof and emerges between a pair of grooved coating rolls at the bath surface. It is known that at higher speeds the coating rolls tend to draw out the coating near the strip edges so that the coating attains a greater thickness adjacent the edges than in the central part of the strip. This tendency produces undesirable variations in both the final strip thickness and its corrosion characteristics, which variations must be minimized to make an acceptable product. This tendency has limited the speed at which such lines can operate to about 100 feet per minute.
An object of the present invention is to provide an improved method of preventing the zinc coating from attaining excessive thickness adjacent the strip edges, which method involves mechanically blowing molten zinc from the edge portions while applying heat thereto and is applicable to conventional existing lines and enables them to operate at higher speeds.
A more specific object is to provide improved methods of preventing the coating adjacent the strip edges from attaining an excessive thickness by the action of gas flames which mechanically blow away the excess and at the same time heat the strip surface near its edges only and thus maintain these edges for a longer time at the temperature at which they emerge from the bath without appreciably raising their temperature.
A further object is to provide improved methods of preventing the coating adjacent the strip edges from becoming excessively thick by the combined mechanical action and heating effect of gas jet flames directed downwardly against the surface of the strip adjacent its edges.
In accomplishing these and other objects of the invention, I have provided improved details of structure, preferred forms of which are shown in the accompanying drawings, in which:
Figure 1 is a top plan view of a galvanizing pot of a continuous line equipped with heating means in accordance with the present invention;
Figure 2 is a sectional view taken on line Il--II of Figure 1;
Figure 3 is a top plan view similar to Figure 1 but showing a modification;
Figure 4 is a sectional view taken on line IVlV of Figure 3; and
Figure 5 is a diagrammatic plan view on a larger scale of the modification of Figure 3 showing more clearly the relative positions of the gas jets and the strip.
Figures 1 and 2 show somewhat diagrammatically a portion of a continuous galvanizing line which includes a galvanizing pot 10, a sink roll 12 in the lower portion of said pot, a support 13 for said sink roll, and a pair 2,708,17 1 Ce Patented May 10, 1955 of grooved coating rolls 14 and 15. The pot contains molten zinc at a temperature of 800 to 875 F. to a level about as indicated in Figure 2, which is approximately the diametric plane of the two coating rolls. A continuous steel strip S is led from an annealing furnace, not shown, through an enclosing snout 16, into the pot, around the sink roll and up between the coating rolls. The strip surface picks up a zinc coating, the thickness of which is controlled by the coating rolls. After leaving these rolls, the strip passes upward to the top of a cooling tower, not shown, and thence downward to subsequent treating equipment. The equipment and process thus far described are well known and therefore are not shown nor described in detail.
Also as known in the art, at line speeds greater than about feet per minute the zinc bath reaches higher levels adjacent the ends of the bite of the coating rolls than it does in the central part. This difference in bath level causes more zinc to be deposited on the strip adjacent the edges than at the central part. Various remedial measures have been proposed to overcome this tendency. For example, it is possible to use rolls which have grooves of greater cross sectional area at the central part than near the end, whereby more zinc can flow up between them at the central part. However, such rolls are difficult and costly to machine.
In accordance with the present invention, gas burners 17, equipped with control valves 17a, are directed downwardly against the strip edges just above the coating rolls. These burners are positioned so that the gas jets emerging therefrom impinge on both faces of the strip adjacent the edges. The flow of gas actually impinges on the coating before combustion takes place. Consequently the gas velocity has a mechanical effect of blowing excess molten zinc downwardly off the strip surface. The flames are regulated not to heat the surface of the strip adjacent the edges appreciably above the temperature at which the edges emerge from the coating rolls, but merely to maintain them at this temperature longer than the remainder of the strip. The resultant heating of the edge portions prevents formulation of a cobweb structure while maintaining a spangled appearance in the finished product. It is possible also that the heating alone may cause some run ofi of the excess coating adjacent the strip edges and thus combine with the mechanical effect of the jets in eliminating this excess.
It is critical that the gas flames do not appreciably raise the temperature of the strip and its coating, or else a nonuniform product would result. For example, it is known in the art that a nonspangled galvanized product can be produced by heating the strip across its full width to temperatures around 1000" F. as it leaves the bath, which heating alloys the coating with the strip surface. In the method of the present invention, the burners do not heat the strip sufiiciently to cause this alloying eiiect.
Figures 3, 4 and 5 show a modification in which gas burners 18 equipped with control valves 18a are directed downwardly and outwardly against both sides of the strip. This modification enhances the mechanical effect of the jets in blowing away the molten zinc, and also furnishes better control in heating both sides of the strip uniformly.
While two embodiments of my invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the appended claims.
I claim:
1. In the high speed continuous galvanizing of steel strip, wherein the strip is led continuously at minimum speeds of about 100 feet per minute through a bath of molten zinc at a temperature of 800 to 875 F. and
emerges between a pair of grooved coating rolls located at the bath surface, a method of controlling the coating thickness and yet maintaining a uniformly Spangled surface across the width of the strip comprising mechanically blowing away excess molten zinc from the portions of the strip surfaces immediately adjacent the side edges as the strip emerges from the coating rolls before the coating solidifies, and simultaneously heating the same portions of the strip, such heating being confined to these portions and controlled to maintain them at the temperature at which they leave the bath for a longer time than the portion of the strip inwardly of. the side edges without appreciably raising the temperature of any portion of the strip above that of the galvanizing bath.
2. In the high speed continuous galvanizing of steel strip, wherein the strip is led continuously at minimum speeds of about 100 feet per minute through a bath of molten zinc at a temperature of 800 to 875 F. and emerges between a pair of grooved coating rolls located at the bath surface, a method of preventing the zinc coating on the strip from attaining excessive thickness immediately adjacent the side edges of the strip and yet maintaining a uniformly spangled surface across the width of the strip comprising directing gas fiames downwardly against the portions of the strip surface immediately adjacent the side edges as the strip emerges from the coating rolls before the coating solidifies, and thereby both mechanically blowing away excess zinc and heating these portions of the strip, such heating being confined to these portions and controlled to maintain them at the temperature at which they leave the bath for a longer time than the portions of the strip inwardly of the side edges without appreciably raising the temperature of any portion of the strip above that of the galvanizing bath.
3. A method as defined in claim 2 in which the flames are directed downwardly and outwardly against the side edge portions of the strip on both faces thereof.
References Cited in the file of this patent UNITED STATES PATENTS 287,076 Young Oct. 23, 1883 794,168 Fellows et al. July ll. 1905 2,034,348 Lytle Mar. 17, 1936 2,332,978 Ahern Oct. 6, 1943

Claims (1)

  1. 2. IN HIGH SPEED CONTINUOUS GALVANIZING OF STEEL STRIP, WHEREIN THE STRIP LED CONTINUOUSLY AT MIMIMUM SPEEDS OF ABOUT 100 FEET PER MINUTES THROUGH A BATH OF MOLTEN ZINC AT A TEMPERATURE OF 800* TO 875* F. AND EMERGES BETWEEN A PAIR OF GROOVED COATING ROLLS LOCATED AT THE BATH SURFACE, A METHOD OF PREVENTING THE ZINC COATING ON THE STRIP FROM ATTAINING EXCESSIVE THICKNESS IMMEDIATELY ADJACENT THE SIDE EDGES OF THE STRIP AND YET MAINTAINING A UNIFORMLY SPANGLED SURFACE ACROSS THE WIDTH OF THE STRIP COMPRISING DIRECTING GAS FLAMES DOWNWARDLY AGAINST THE PORTIONS OF THE STRIP SURFACE IMMEDIATELY ADJACENT THE SIDE EDGES AS THE STRIP EMERGES FROM THE COATING ROLLS BEFORE THE COATING SOLIDIFIES, AND THEREBY BOTH MECHANICALLY BLOWING AWAY EXCESS ZINC AND HEATING THESE PORTIONS OF THE STRIP, SUCH HEATING BEING CONFINED TO THESE PORTIONS AND CONTROLLED TO MAINTAIN THEM AT THE TEMPERATURE AT WHICH THEY LEAVE THE BATH FOR A LONGER TIME THAN THE PORTIONS OF THE STIP INWARDLY OF THE SIDE EDGES WITHOUT APPRECIABLY RAISING THE TEMPERATURE OF ANY PORTION OF THE STRIP ABOVE THAT OF THE GALVANIZING BATH.
US297697A 1952-07-08 1952-07-08 Method of controlling coating thickness in continuous galvanizing Expired - Lifetime US2708171A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US297697A US2708171A (en) 1952-07-08 1952-07-08 Method of controlling coating thickness in continuous galvanizing

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US297697A US2708171A (en) 1952-07-08 1952-07-08 Method of controlling coating thickness in continuous galvanizing

Publications (1)

Publication Number Publication Date
US2708171A true US2708171A (en) 1955-05-10

Family

ID=23147369

Family Applications (1)

Application Number Title Priority Date Filing Date
US297697A Expired - Lifetime US2708171A (en) 1952-07-08 1952-07-08 Method of controlling coating thickness in continuous galvanizing

Country Status (1)

Country Link
US (1) US2708171A (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894856A (en) * 1956-08-31 1959-07-14 Inland Steel Co Apparatus for and method of controlling the coating thickness in continuous galvanizing
US2964419A (en) * 1958-03-27 1960-12-13 United States Steel Corp Method and apparatus for producing anti-skid tread plate
US2967114A (en) * 1958-07-22 1961-01-03 Nat Steel Corp Coating apparatus and method
US2992941A (en) * 1958-05-07 1961-07-18 Armco Steel Corp Exit machine for coating apparatus and method of controlling coating thickness
US2993804A (en) * 1959-03-13 1961-07-25 Yawata Iron & Steel Co Surface treatment for metal coated objects
US3049441A (en) * 1959-10-09 1962-08-14 United States Steel Corp Method of and apparatus for preventing edge build-up of coating material on dip-coated strip
US3104981A (en) * 1960-11-22 1963-09-24 Nat Steel Corp Hot dip metal coating method
US3260577A (en) * 1961-12-20 1966-07-12 Nat Steel Corp Coated product and its manufacture
US3383239A (en) * 1964-04-01 1968-05-14 Du Pont Air impingement apparatus and process to control edge flow in coating procedures
US3518109A (en) * 1968-01-15 1970-06-30 Inland Steel Co Apparatus and method for controlling thickness of molten metal coating by a moving magnetic field

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US287076A (en) * 1883-10-23 Art of removing surplus material from articles coated with melted metal
US794168A (en) * 1904-09-29 1905-07-11 Olin S Fellows Method of removing superfluous metallic coating from sheet metal.
US2034348A (en) * 1930-09-03 1936-03-17 Lytle Clark Kenneth Nonspangled galvanized sheet
US2332978A (en) * 1939-11-08 1943-10-26 Frank J Ahern Apparatus for hot dip coating of metals

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US287076A (en) * 1883-10-23 Art of removing surplus material from articles coated with melted metal
US794168A (en) * 1904-09-29 1905-07-11 Olin S Fellows Method of removing superfluous metallic coating from sheet metal.
US2034348A (en) * 1930-09-03 1936-03-17 Lytle Clark Kenneth Nonspangled galvanized sheet
US2332978A (en) * 1939-11-08 1943-10-26 Frank J Ahern Apparatus for hot dip coating of metals

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894856A (en) * 1956-08-31 1959-07-14 Inland Steel Co Apparatus for and method of controlling the coating thickness in continuous galvanizing
US2964419A (en) * 1958-03-27 1960-12-13 United States Steel Corp Method and apparatus for producing anti-skid tread plate
US2992941A (en) * 1958-05-07 1961-07-18 Armco Steel Corp Exit machine for coating apparatus and method of controlling coating thickness
US2967114A (en) * 1958-07-22 1961-01-03 Nat Steel Corp Coating apparatus and method
US2993804A (en) * 1959-03-13 1961-07-25 Yawata Iron & Steel Co Surface treatment for metal coated objects
US3049441A (en) * 1959-10-09 1962-08-14 United States Steel Corp Method of and apparatus for preventing edge build-up of coating material on dip-coated strip
US3104981A (en) * 1960-11-22 1963-09-24 Nat Steel Corp Hot dip metal coating method
US3260577A (en) * 1961-12-20 1966-07-12 Nat Steel Corp Coated product and its manufacture
US3383239A (en) * 1964-04-01 1968-05-14 Du Pont Air impingement apparatus and process to control edge flow in coating procedures
US3518109A (en) * 1968-01-15 1970-06-30 Inland Steel Co Apparatus and method for controlling thickness of molten metal coating by a moving magnetic field

Similar Documents

Publication Publication Date Title
US3056694A (en) Galvanizing process
US2708171A (en) Method of controlling coating thickness in continuous galvanizing
US2914423A (en) Method and apparatus for metallic coating of metallic strands
US2034348A (en) Nonspangled galvanized sheet
US2914419A (en) Method and apparatus for continuously coating a metal strand-like article with molten metal
JPS5835590B2 (en) Finishing method and apparatus for hot-plating ferrous base metal strip with hot-melt coating metal
US3112213A (en) Differentially coated galvanized strip
US3479210A (en) Method and apparatus for controlling coating metal temperature in a hot-dip coating bath
US2992941A (en) Exit machine for coating apparatus and method of controlling coating thickness
US4173663A (en) Dipless metallizing process and apparatus
US3322558A (en) Galvanizing
US3619247A (en) Method of producing thin, bright unspangled galvanized coatings on ferrous metal strips
EP0565272B1 (en) Stripping liquid coatings
US3181963A (en) Alkali metal borate masking in galvanizing process
US2094583A (en) Manufacture of metal coated products
US2160864A (en) Producing galvanized metal sheets or articles
US2172933A (en) Galvanizing process
US3369923A (en) Method of producing heavy coatings by continuous galvanizing
US3322560A (en) Control of spangle in hot dip galvanizing
JP5824905B2 (en) Manufacturing method of molten metal plated steel strip
US2315150A (en) Exit roll for galvanizing pots
JPS6240350A (en) Method for controlling plating deposition of molten metal
US2283109A (en) Bluing steel
US2823641A (en) Apparatus for fluxing and coating metal strip
US1732504A (en) Method and apparatus for coating