GB2209178A - Improved hot-dip galvanized coating for steel - Google Patents
Improved hot-dip galvanized coating for steel Download PDFInfo
- Publication number
- GB2209178A GB2209178A GB8813623A GB8813623A GB2209178A GB 2209178 A GB2209178 A GB 2209178A GB 8813623 A GB8813623 A GB 8813623A GB 8813623 A GB8813623 A GB 8813623A GB 2209178 A GB2209178 A GB 2209178A
- Authority
- GB
- United Kingdom
- Prior art keywords
- zinc
- coating
- particles
- metal
- phosphide
- 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.)
- Granted
Links
- 238000000576 coating method Methods 0.000 title claims abstract description 33
- 239000011248 coating agent Substances 0.000 title claims abstract description 28
- 229910000831 Steel Inorganic materials 0.000 title claims description 26
- 239000010959 steel Substances 0.000 title claims description 26
- 239000002184 metal Substances 0.000 claims abstract description 40
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 39
- 229910052751 metal Inorganic materials 0.000 claims abstract description 39
- 239000011701 zinc Substances 0.000 claims abstract description 36
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 35
- 239000002245 particle Substances 0.000 claims abstract description 24
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000003466 welding Methods 0.000 claims abstract description 15
- 229910001297 Zn alloy Inorganic materials 0.000 claims abstract description 11
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 8
- 229910052718 tin Inorganic materials 0.000 claims abstract description 8
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 7
- 239000000758 substrate Substances 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 239000010949 copper Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 239000011733 molybdenum Substances 0.000 claims description 3
- 229910052715 tantalum Inorganic materials 0.000 claims description 3
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 3
- 239000011135 tin Substances 0.000 claims description 3
- 239000010936 titanium Substances 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 238000003618 dip coating Methods 0.000 claims 1
- 239000002923 metal particle Substances 0.000 claims 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims 1
- 230000015572 biosynthetic process Effects 0.000 abstract description 8
- 229910001335 Galvanized steel Inorganic materials 0.000 abstract description 7
- 239000008397 galvanized steel Substances 0.000 abstract description 7
- 239000013078 crystal Substances 0.000 abstract description 6
- 238000002844 melting Methods 0.000 abstract description 5
- 230000008018 melting Effects 0.000 abstract description 5
- 238000010899 nucleation Methods 0.000 abstract description 4
- 230000006911 nucleation Effects 0.000 abstract description 2
- 239000000049 pigment Substances 0.000 description 11
- 238000005260 corrosion Methods 0.000 description 7
- 230000007797 corrosion Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 229910001369 Brass Inorganic materials 0.000 description 5
- 239000010951 brass Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 4
- 238000007598 dipping method Methods 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- 239000011574 phosphorus Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005246 galvanizing Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- -1 iron phosphide compound Chemical class 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 239000003595 mist Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000010961 commercial manufacture process Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- VAKIVKMUBMZANL-UHFFFAOYSA-N iron phosphide Chemical group P.[Fe].[Fe].[Fe] VAKIVKMUBMZANL-UHFFFAOYSA-N 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000003380 propellant Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000001039 zinc pigment Substances 0.000 description 1
- NDKWCCLKSWNDBG-UHFFFAOYSA-N zinc;dioxido(dioxo)chromium Chemical compound [Zn+2].[O-][Cr]([O-])(=O)=O NDKWCCLKSWNDBG-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D15/00—Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
- C25D15/02—Combined electrolytic and electrophoretic processes with charged materials
-
- 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
- C23C2/26—After-treatment
- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
-
- 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
- C23C2/26—After-treatment
- C23C2/265—After-treatment by applying solid particles to the molten coating
Abstract
A hot-dip galvanized coating for improved resistance welding of galvanized steel parts or sheets for use in the automative and appliance industries includes particles of a metal phosphide, and preferably ferrophosphorus particles, having a particle size of from 0.1 to 30 mu m, such particles being included in the galvanized coating while the zinz or zinc alloy is still molten. This causes nucleation of zinc crystals to occur. Since the melting point of the phosphide is substantially higher than that of zinc this permits the formation of a satin finish instead of the normal spangle finish. The phosphide particles may be present in an amount of 0.1-50% by weight of the zinc. The coating may be 0.08-2.8 mu m thick. The coating can also include up to about 40% by weight of the metal phosphide of an additional metal such as nickel, tin, aluminum or lead, which can be incorporated in the coating as discrete particles or deposited onto the surface of the metal phosphide particles.
Description
IMPROVED HOT-DIP GALVANIZED COATING FOR STEEL
The present invention relates to improved hot-dip galvanized (zinc or zinc alloy) steel parts or sheets obtained by including a metal phosphide pigment, and preferably a ferrophosphorus pigment, in the hot-dip galvanized layer. The welding improvements realized by practicing the present invention are improved weldability lobes and dynamic resistance curves for better welding control for resistance welding systems, as well as increased electrode life and improved appearance and paintability.
The use of galvanized steel sheets in the automotive industry has become increasingly popular in recent years due to the increase in concern for corrosion protection for automobile body panels.
Corrosion problems are particularly severe in environments where salt is used for preventing the icing of snow on highway roads.
Although efforts have been made to enhance the corrosion-resistance of steel sheets, such as by using various chemical conversion treatments and paint coatings, the corrosion protection method of choice currently is galvanized steel, with the galvanized coating formed by either hot-dipping or electrodeposition.
Hot-dip galvanized coatings are applied by dipping or immersing the steel sheet or part in molten zinc to produce a coating having a thickness typically of about 0.003 to 0.15 mm. In a typical modern industrial process, the steel surface is preoxidized at 650 C and then hydrogen-reduced at 8500C to 9500C.
The temperature is lowered to 400 C with the strip still protected in hydrogen until it enters the zinc bath. In this way, flux at the entrance to the bath is avoided and small amounts of aluminum are used to inhibit formation of zinc-iron intermetallic intermediate layers. The bath temperature is maintained at 450-4600C by the sensible heat of the incoming strip.
The strip can then be jet-finished at line speeds of up to 185 m/min. During this process, the strip rises vertically out of the zinc bath, carrying an entrained viscous layer of molten zinc. A row of horizontal jets of air junpinge perpendicularly on one side of the strip, and cause a return flow of liquid metal into the bath. Sensors above the row of air jets meter the thickness of the coating and adjust the velocity of air flow by electronic feedback circuits so that the desired thickness on each side can be maintained continuously throughout the run.
The characteristic spangle of galvanized steel sheets results from the rate of crystallization of the molten zinc, which depends on the condition of the starting steel and the presence of minor additions to the melt. The latter lower the melting point of the zinc and, thereby, lower the cooling rate of the molten layer.
Paint adherence on a galvanized sheet depends on the orientation of the zinc crystals in the spangle, but, in general, adherence tends to be not as good as on bare steel. The spangle can be controlled by blowing zinc dust on the molten zinc surface and producing multi-nucleation sites for crystal formation to provide a highly nucleated, satin finish. However, this does not improve the poor resistance weldability of such coatings due to brass formation as discussed below.
Resistance spot welding is used to form joints between two materials. The process uses a set of electrodes to apply pressure to the weld area, to maintain the components in position, and to pass current through the weld. As the current flows, joule heating of the substrate occurs. Due in part to the cooling effects of the electrodes, a molten nugget eventually develops at the weld centerline or faying surface but not at the electrode contact. On cooling, this nugget resolidifies and effects a joining between the two materials. Some of the problems encountered during spot welding of galvanized steel sheets or parts include reduced weldability lobe widths, the absence of a dynamic resistance "beta peak", and decreased electrode life.
When resistance welding uncoated or bare steels, a single set of copper welding electrodes can be expected to make approximately 50,000 welds. When spot welding electrogalvanized steels, however, the zinc forms alloys with the copper electrode tip, forming a brass in situ. The brass sticks to the weld, rapidly eroding the welding tip which must then be replaced or refinished. This, in turn, reduces electrode life to about 1000-2000 welds or less.
Since the production line must be stopped each time an electrode is replaced, at a considerable expense to the user, the relatively limited electrode life experienced when welding galvanized steels represents a significant economic disadvantage.
The use of ferrophosphorus pigment for both improved corrosion protection and weldability has been suggested in the prior art.
For instance, U.S. Patent 3,884,705, issued May 20, 1975, and U.S.
Patent 4,119,763, issued October 10, 1978, both disclose the use of coatings containing ferrophosphorus and zinc pigments, and a non-metallic corrosion inhibitor such as zinc chromate, as a replacement for zinc-rich coatings. As contemplated in these patents, the ferrophosphorus pigment-containing coating is applied to bare steel panels rather than to galvanized sheets. The ferrophosphorus pigment used in such applications is commercially available from the Occidental Chemical Corporation under the trademark Ferrophos pigment.
A ferrophosphorus pigment dispersed in a resin to bind adjacent steel plates to form a vibration-damping composite suitable for resistance welding is disclosed in Japanese Patent
Application No. 61-41540, published on February 27, 1986.
The use of a coating comprising a resin, ferrophosphorus powder and mica powder applied to a steel sheet having a layer of fused aluminum or an aluminum/zinc alloy is disclosed in Japanese
Patent Application No. 591456884, published August 22, 1984. The steel sheet described in this reference can be subjected to chemical conversion, and is further described as having excellent weldability, processability and corrosion and heat resistance.
The use of an iron layer containing less than about 0.5 weight percent phosphorus applied to a zinc/iron or zinc/nickel alloy electroplated steel sheet for improved surface properties is described by Honjo et al. in Internal Journal of Materials and
Product Technology, Vol. 1, No. 1, pp. 83-114 (1986).
It will be appreciated by those skilled in the art that a continuing need exists for steel sheets or parts which possess the durability and corrosion resistance of galvanized components, but also possess the weldability advantages of bare steel. It would also be desirable to modify an existing coating line in order to accomplish this obJective with minimal expense.
SUMMARY OF THE INVENTION
In accordance with the present invention, a steel sheet or part with improved resistance welding characteristics has a hot-dip galvanized layer containing at least one metal phosphide selected from the group consisting of phosphides of iron, nickel, cobalt, tin, copper, titanium, manganese, molybdenum, tungsten, vanadium, tantalum, and mixtures thereof. Preferably, the metal phosphide is ferrophosphorus pigment having a range of particle sizes of from about 0.1 to about 30 microns, and which is present in the galvanized layer in amounts of from about 0.1X to about 50X by weight of the zinc.
A metal additive for increased electrode life can also be included in the coating in amounts of up to about 40% by weight of the metal phosphide. The metal additive can be added to the coating in particulate form as a separate component, or deposited onto the surface of the metal phosphide particles. Suitable metal additives include nickel, tin, aluminum, lead, and mixtures thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The steel sheets or formed parts which are used in the present invention contain a thin layer of zinc metal or a zinc alloy which is in direct contact with the steel surface. The steel substrate can vary in thickness, and is typically about 30 mils thick. Thin steel sheets of this type are used extensively in the automotive and applicance industries for forming auto and appliance bodies.
The zinc or zinc alloy coating or layer is applied to the steel sheet by a hot-dip galvanizing process where the coating is applied to the substrate by dipping the sheet in molten zinc.
The metal phosphide pigment of the present invention comprises particles having an average size within the range of from about 0.1 to about 30 microns, and is present in the galvanized layer in amounts of from about 0.12 to about 50S by weight of the zinc.
Particles within the desired size ranges are suitably obtained by pulverizing the metal phosphide using conventional techniques.
Suitable metal phosphides include phosphides of iron, nickel, cobalt, tin, copper, titanium, manganese, molybdenum, tungsten, vanadium, tantalum, as well as mixtures of these metal phosphides.
The preferred metal phosphide is iron phosphide, which includes various ratios of iron and phosphorus, and particularly ferrophosphorus, which is an iron phosphide compound containing from about 20S to 28% of phosphorus and corresponding chemically to a mixture of Fe2P and FeP. Ferrophosphorus is obtained as a by-product in the commercial manufacture of elemental phosphorus by the electric furnace reduction of phosphate ores, with the iron present in the phosphate ores forming the ferrophosphorus. Ferrophosphorus typically contains impurities, of which silicon and manganese are the major impurities, typically being present in amounts of up to 5S by weight, and is further characterized as being electrically conductive, brittle, and substantially unreactive in water, dilute acidic or alkaline environments.A particularly suitable ferrophosphorus pigment is Ferrophos pigment which is manufactured and sold by the Occidental Chemical Corporation.
The metal phosphide can be advantageously incorporated directly into the zinc metal or zinc alloy galvanized coating by modifying the commercial line to incorporate suitable amounts or the metal phosphide particles. The metal phosphide particles can be sprayed directly onto the molten zinc coating which has been applied to the steel surface by hot-dipping. The metal phosphide particles contact the zinc while it is still molten, thus allowing nucleation of zinc crystals to occur. The melting point of ferrophosphorus is substantially higher than the melting point of zinc, i.e. approximately 1,320"C compared to 420cm, thereby permitting the formation of a satin finish instead of the spangle finish normally present on hot-dip galvanized surfaces.This is accomplished by substituting the metal phosphide for the zinc powder which is used to prevent spangling in hot-dip galvanizing operations. This results not only in improved paintability as would be expected, but also improved resistance welding characteristics as well.
The metal phosphide particles are applied to the molten zinc surface in an amount of from about 0.1X to about 50% by weight of the zinc. The metal phosphide particles are uniformly applied to the zinc surface to insure good adhesion and a smooth finish using well know techniques.
An additional metal, such as nickel, tin, aluminum, lead, and mixtures thereof, can also be incorporated into the molten zinc coating by direct application to the zinc surface. Alternatively, the additional metal can be deposited directly onto the surface of the metal phosphide particles using techniques which are well-known to those skilled in the art, such as by physically grinding or blending mixtures of the metal phosphide and added metal in the desired proportions, or by immersion coating, etc. Amounts of additional metal of up to about 40S by weight, based on the weight of metal phosphide, are suitable.
The following specific examples are provided as exemplary of various embodiments of the present invention, but are not intended to limit the full scope of the invention as defined by the appended claims.
EXAMPLE 1
A 1-1/4" wide by 9" long strip of highly spangled hot-dip galvanized steel was inserted 12" into a 1-1/2" diameter glass tube having a side arm at one end. A rubber stopper was placed in one end of the glass tube, and a slow flow of nitrogen gas was introduced into the side arm. A glass blower's torch having a broad brush flame was used to heat the upper end of the galvanized strip. Melting of the zinc only occurred at the upper end of the strip. The tube was allowed to cool under nitrogen.
A ten (10) power micrograph was made of the interface area between the unmolten and melted areas of the strip. Upon cooling, the crystal structure of the "spangled" hot-dip galvanized surface was observed to be re-established.
EXAMPLE 2
The procedure of Example 1 was repeated. The rubber stopper was removed from the tube and a quick squirt of a mist of Ferrophos particles having an average size of three (3) microns was propelled into the tube using a neutral propellant (Medici Aerosol Universal
Multi-Mist). The stopper was replaced, the flame was removed, and the galvanized strip was allowed to cool under nitrogen.
A ten (10) power micrograph was made of the interface area between the unmolten and melted areas. Upon cooling, there was no spangling, and a satin finish was observed on the strip indicating that micro-nucleation had occurred.
EXAMPLE 3
The procedure of Example 2 was repeated using a 1" by 5" strip of hot-dip galvanized steel. Four (4) inches of the galvanized strip was observed to have a uniform and non-spangled finish.
Under 400 power magnification, the formation of tiny crystals appeared to have occurred on the surface.
The strip was bent in the middle to give a 1" by 2-1/2" sandwich. Nine spot welds were made on the strip using a 5,500 amp, Miller spot-welder, Model M5W-41T, at 15 cycles. The top welds were made on the Ferrophos containing portion of the strip, while the bottom welds were made on the regular hot-dip galvanized portion which did not contain Ferrophos.
Visual inspection of the welds, both without magnification and a 12 power magnification, showed significant brass formation in the bottom spot welds with at crack in the coating around the weld. No brass formation was evident in the top welds.
Although the present invention has been described with respect to several illustrative embodiments, it should not be interpreted as being so limited. As will be evident to those skilled in the art, other substitutions and equivalents are possible without departing from the spirit of the invention or the scope of the claims.
Claims (11)
1. An article having improved resistance welding characteristics comprising a steel substrate having a hot-dip coating of zinc metal or a zinc alloy containing discrete particles of at least one metal phosphide selected from phosphides of iron, nickel, cobalt, tin, copper, titanium, manganese, molybdenum, tungsten, vanadium and tantalum.
2. An article according to claim 1 wherein the coating is 0.08 to 2.8 vm (0.003 to 0.15 mils) thick.
3. An article according to claim 1 or 2 wherein the phosphide particles have an average size of 0.1 to 30 vm.
4. An article according to claim 1, 2 or 3 wherein the phosphide particles are present in the coating in an amount of from 0.1% to 50% by weight of the zinc.
5. An article according to any one of claims 1 to 4 wherein the coating also contains up to 40% by weight, based on the weight of metal phosphide, of particles of at least one additional metal selected from nickel, tin, aluminum and lead.
6. An article according to claim 5 wherein the metal particles have an average size of 0.1 to 30 vm.
7. An article according to any one of the preceding claims wherein the metal phosphide is ferrophosphorus.
8. An article according to claim 7 except when appendant to claim 5 or 6 wherein the ferrophosphorus particles are coated with up to 40t by weight of the
ferrophosphorus with a layer of at least one additional
metal selected from nickel, tin, aluminum and lead.
9. An article according to claim 1 substantially as
described with reference to Example 2 or 3.
10. A process for preparing an article as claimed in any
one of the preceding claims which comprises;
a) immersing a steel substrate in a bath of molten
zinc or zinc alloy to provide a thin coating of zinc or zinc
alloy on the substrate,
b) contacting the coating with discrete particles
of said at least one metal phosphide while the zinc or zinc
alloy is still molten, and
c) allowing the coating to cool and solidify.
11. A process according to claim 10 substantially as
described with reference to Example 2 or 3.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/093,946 US4873153A (en) | 1987-06-25 | 1987-08-28 | Hot-dip galvanized coating for steel |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8813623D0 GB8813623D0 (en) | 1988-07-13 |
| GB2209178A true GB2209178A (en) | 1989-05-04 |
| GB2209178B GB2209178B (en) | 1991-09-11 |
Family
ID=22241858
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8813623A Expired - Fee Related GB2209178B (en) | 1987-08-28 | 1988-06-09 | Improved hot-dip galvanized coating for steel |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2209178B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62224699A (en) * | 1986-03-26 | 1987-10-02 | Nippon Steel Corp | Steel sheet coated with zn-base layer by dispersion plating and having superior weldability |
| EP0174019B1 (en) * | 1984-09-06 | 1989-03-01 | Nippon Steel Corporation | Steel strip plated with a zinc-based coating layer containing an inorganic dispersoid |
-
1988
- 1988-06-09 GB GB8813623A patent/GB2209178B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0174019B1 (en) * | 1984-09-06 | 1989-03-01 | Nippon Steel Corporation | Steel strip plated with a zinc-based coating layer containing an inorganic dispersoid |
| JPS62224699A (en) * | 1986-03-26 | 1987-10-02 | Nippon Steel Corp | Steel sheet coated with zn-base layer by dispersion plating and having superior weldability |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8813623D0 (en) | 1988-07-13 |
| GB2209178B (en) | 1991-09-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19950609 |