US3759756A - Weld thru primer - Google Patents

Weld thru primer Download PDF

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Publication number
US3759756A
US3759756A US00232980A US3759756DA US3759756A US 3759756 A US3759756 A US 3759756A US 00232980 A US00232980 A US 00232980A US 3759756D A US3759756D A US 3759756DA US 3759756 A US3759756 A US 3759756A
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coating
weld
metal
silicate
properties
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US00232980A
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H Lomasney
W Lomasney
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/226—Non-corrosive coatings; Primers applied before welding
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
    • C09D1/02—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances alkali metal silicates
    • C09D1/04—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances alkali metal silicates with organic additives

Definitions

  • the present invention pertains to a novel coating system for application to carbon steel substrates.
  • the coating provides exceptional arc behavioral properties during the metal joining by fusion or resistance welding of such substrates, via its metallurgical influence on the weld zone.
  • the functional elements of this colating basically comprise a carefully balanced mixture of a sacrificial or anodic metal and a metal alloy such as chromium or nickel which significantly affects the weldability and weld properties of the coating.
  • the powdered metals or pigments are attached to the carbon steel substrates via any of a number of liquid silicate binders, the use of which is well established in the prior art.
  • Preferred embodiments include various additional constituents, e.g. materials such as boron or magnesium to increase Rockwell hardness and susceptibility to high temperature creep.
  • additional constituents e.g. materials such as boron or magnesium to increase Rockwell hardness and susceptibility to high temperature creep.
  • the unique features and advantages of the present coating is the realization of an unusual balance of functional properties, the most significant of which are the beneficial contribution to the metallurgical properties of the finished weld, while actually improving the stable electrical arc discharge normally associated with resistance welding.
  • a further advantage of this coating concept is that it allows arrangement of selected metallic constituents within the coating in such a manner as to assure optimum silicate to silicate bonding when overcoating with a conventional inorganic zinc coating after fabrication of the structure is completed.
  • the novel thin film covering provided by Way of the present invention which favorably influences the metallic structure at the interface (heat affected zone) of the parent metal and the filler metal.
  • This can be achieved while maintaining stable arc initiation and discharge and smooth weld behavior and its attendant effects encountered in the welding of steel substrates that have been pre-coated.
  • this invention provides a coating which constitutes a satisfactory primer for subsequent heavy duty metal/silicate coating systems with, for example, the primers ductile alloying powder constituent achieving a specially shaped non-ferrous metal surface which will afford attractive bonding sites for subsequently applied silicate compounds.
  • An optional mechanical flaking of the alloy powder may be implemented to improve film continuity and coverage of blast produced anchor-profile With a relatively thin film.
  • the present invention provides a weld thru coating formulation which enhances the subsequent weldability and physical properties of welds applied to a base substrate coated therewith.
  • the coating basically comprises a sacrificial or anodic metal selected from the group of metals having an oxidation potential greater than that of iron; a liquid binder; and a metal-alloy constituent agent.
  • Preferred embodiments include, in addition, metallic adhesion promoting agents, degassing agents, thickening agents, and hydrolytic catalysts, either alone or in combination.
  • the present invention provides a process for enhancing the subsequent weldability of a steel surface by improving the metallurgical phenomena within the weld zone. Additionally, the generation of toxic and other harmful fumes,
  • the present pre-weld coating basically comprises a sacrificial or anodic metal, selected from the group con sisting of zinc and other metals having an oxidation potential greater than that of iron; a liquid binder; and one or more metal alloy constituents.
  • Preferred embodiments include the addition of other materials such as degassing agents, thickening agents, all as hereinafter defined.
  • the sacrificial or anodic agent described above must have an oxidation potential greater than +0.44 Eox (value in volts, referred to the hydrogen-hydrogen ion couple as zero) Which is that of iron, the base substrate.
  • Suitable anodic metals, other than zinc, having an oxidation potential greater than iron are for example: vanadium, manganese, titanium, aluminum, and the like. From a chemical standpoint, as well as for economic reasons, zinc or aluminum is preferred.
  • the anodic agent must be present in a finely divided form, e.g. in a powder or dust state, generally of a particle size between about 2 to microns, preferably presenting an average particle size of about 4 to 7 microns.
  • the anodic element of this invention is generally employed in amounts of about to 75%, preferably about 30 to 50%, by weight of the total of the metallic components in the coating.
  • Commercially pure materials i.e. 97% or above, as are readily available in the art, are acceptable. Impurities normally present in such powders normally do not have a deleterious effect on the finished coating.
  • the liquid binder is a silicate material which must be capable of retaining the metal particles in intimate contact with the base substrate after drying (solvent release) or curing.
  • the liquid binder is preferably present in a final weight ratio of about 4 to 19 percent, based on nonvolatiles in the dry film.
  • Suitable silicate binders are the silicates having alkali complexes such as ammonium, sodium, potassium, lithium, non-aqueous ethyl silicates, and related ethoxyethyl esters of silicic acid, and in some cases mixtures thereof.
  • the organic coating vehicles in resinous form cited in prior art technology are generally found to be unacceptable since they provide a source of carbon which is undesirable in the finished weld.
  • the metallic alloy can comprise any metal or combina-v tion thereof selected from those heavy metals which impart favorable or desirable physical properties to a carbonsteel parent metal. These may be used alone or in combination with each other. Preferred metals are chromium, molybdenum and nickel. These alloy metals in order to be effective, must be incorporated as a substantial percentage of the total metal powder. Generally, effective percentages are found to be from about 25 to 70% by weight of the total metallic pigments.
  • the metallic alloy is present in the mixture in a finely divided state of commutation, generally in a size range between about 2 and microns. Generally, the purity of these metals as supplied commercially is considered suitable for this application.
  • Another preferred embodiment of the present invention includes the incorporation of a viscosity agent in the present mixture.
  • the viscosity agent minimizes the settling of the dense metallic particles during storage, and enhances the resistance to flow (sagging) after deposition of the film.
  • Exemplary of the viscosity agents that can be employed are zinc stearate, aluminum stearate, organomontmorillonite, flame blown silica and hydrogenated castor oil.
  • a degassing agent is also preferably incorporated in the present weld thru coating.
  • Suitable materials are silica,
  • the percentage of zinc in such a coating was determined on the basis of corrosion resistance and electrical conductivity, and consequently amounts of to 98% based on the Weight of total metal powder present were found to be the optimum eifective concentrations.
  • a composition of metals wherein the range is from 30% to 75% by weight of metallic zinc, based on total weight of constituent metals, was explored. The most desirable percentages, considering welding properties alone, varied from 30% to 50% depending on density of the metal alloy constituent and other hereinafter mentioned metallurgical considerations.
  • the upper limit or constraint on the amount of such low boiling elements used in a preweld coating is believed to be based on a phase separation (gas pocket), resulting in some boundary layer formation which opposes the smooth and even deposit of molten filler metal. This has been seen during testing of prior-art coatings whose essential constituent comprises a low boiling metal (i.e. elemental zinc).
  • An additional feature incorporated in the design of this coating lies in the formulators flexibility to adjust pigments to affect the alloy composition across the weld joint.
  • Conventional techniques for welding allow control of the alloy structure by selection of the desired filler metal.
  • control of, or introduction of a varying alloy composition across a given weld joint is outside the realm of existing technology.
  • This invention affords the metallurgist an opportunity to introduce alloy constituents such as boron, chromium, or molybdenum into the transition area i.e., the heat affected zone between filler metal and parent metal. Thereby he can control such phenomena as austenitic grain growth in this most critical weld zone.
  • Elemental boron in metals has been found to increase weld ductility of alloy steels, particularly those subject to high temperatures. This element may be added to the coatings of the present invention and thus is introduced into the weld zone. The boron inhibits austenitic grain growth which occurs above the critical temperature with the result that there is a significant improvement in the ductility of the present coatings.
  • the coating is to be used in concert with the welding of medium or high carbon content steel, it has been shown that the metallurgical effect of chromium introduced during welding will improve physical properties of the heat-affected weld zone, such properties being ductility, hardness, and notch sensitivity.
  • the metallurgist can design weld structures showing greater ductility for a given strength or greater strength for a given ductility than for plain carbon steel.
  • Elements such as chromium, nickel, tungsten, silicon, and molybdenum in the coating can be effective in strengthening the ferrite matrix (i.e. in solid solution).
  • the metallic Weld-thru primer developed in this invention exhibits a unique weld structure and thus represents a major contribution to welding technology; at the same time the coating does not significantly compromise the desired corrosion resistant properties afforded by prior-art coatings. This is the first time these two functions have been incorporated into a single vehicle.
  • Example 1 The coating system was prepared from the designated ingredients using high shear mixing procedure.
  • the prehydrolyzed liquid binder solution is weighed directly into a water jacketed stainless steel tank, equipped with a high energy dispersion mixer.
  • the sacrificial-anode metal is added under slow agitation (approximately 2000 to 3000 surface feet per minute).
  • the metallic alloy agent is next added, the speed of the mixer being regulated so as to maintain a continuous vortex to optimize mixing.
  • other additives i.e. thickening agent, degassing agent, or the like
  • the mixer speed is then increased such that the dispersion blade reaches a velocity of approximately 5000 surface feet per minute.
  • Break test A destructive break test is generally recognized by persons schooled in the art of welding over precoated steel, as a method of determining the amount of porosity introduced into the weld by the coating.
  • Samples were prepared using three pairs of V2 inch by 3 inch bar stock (5 feet long). Two pairs were blasted and coated with the mixture outlined above, the other pair remained uncoated.
  • Tests were conducted using a Gelman #GM-4 membrane filter taped inside the welders helmet. This filter has a 0.8 micron pore size, retaining any particle above 0.3 micron. A flow rate of to 12 liters of vapor per minute (approximate human breathing rate) was drawn through the filter. The sample was drawn throughout the duration of Welding (approximately 20 inches length; 10 minute sample time). The welding electrode was type No. 6010.
  • Fume samples were analyzed spectrographically to determine the amount and concentration of metallic elements.
  • Example H The coating system was prepared from the designated ingredients using high shear dispersion equipment normally familiar to paint manufacturers.
  • the liquid binder solution is weighed into a water jacketed stainless steel tank.
  • 0.1 N HCl is slowly added and the resulting mixture agitated for no less than four (4) hours at low speed.
  • the thickening and anti-mud cracking agents are added and dispersed at high speed (5000 surface feet per COMPOSITION OF COATING Parts] Nature Type weight sacrificial/anode metal- Zine dust 500 Liquid bind Cellosolve silicate 680 Metal/alloy agent Chrome flake 363 Modified hydrogenated 25 Anti-mud eraekin agent Tri methyl borate 13.8 Hydrolyzing agent.
  • 0.1 N H01 one tenth normal hydro- 23. 8
  • Cellosolve silicate is a trade name for a commercial preparation of ethoxyethyl silicate.
  • the coating described above was applied to two pieces of /1 plate-6" wide x longV grooved 60 included angle, thickness on face side and /a groove on backside. A pair of identical steel plates were similarly prepared but left uncoated.
  • the plate pairs were welded using a shielded metal arc-7/32 AWS wire #E6011 manufactured by Airco.
  • the welds were examined for welding defects by subject ing the bars to a standard Bend Test consisting of bending a bar of the welded material in the region of the weld zone such that the ends were parallel to each other and at a distance apart of 2 /2". Examination of the welded regions yielded the results shown in Table IV.
  • test bars were also sectioned and three test specimens were removed for Charpy Impact Testing, using standard test specimens 10 mm. square. The results of the weld testing is described in Table IV.
  • Example III The coatings described in Example II were applied at the recommended film thickness and compared to a prior art weldable coating, whose metallic constituents comprised essentially metallic zinc with 5% metallic aluminum at the same film thickness.
  • the coatings were applied to metal plates x 6" x l5"-60 included angle, V grooved. These plates were welded using a shielded metal are 7/32 AWS wire #E6011. During weld deposition the prior art coating was noted to produce irregularity with a slight tendency to fingernail during deposition of weld metal. No such unstable weld arc behavior was reported in the coating prepared per Example III.
  • Example IV The coating system outlined below was prepared from the designated ingredients using high speed shear mixing procedure.
  • the xylene and amine-treated clay are weighed into a water jacketed stainless steel tank, equipped with a high energy dispersion mixer and dispersed at high speed (approximately 5000 surface feet per minute) for 15 minutes. The speed is then reduced to approximately 2000 surface feet per minute and the Cellosolve acetate, zinc dust, chrome flake are mixed with one fourth of the light binder.
  • the hydrolyzing agent required for the entire batch of binder is added slowly and stirring is continued for 20 minutes after this addition. Next the neutralizing and anti-mud cracking agents are added. Slow agitation is continued for four hours.
  • the remaining three quarters of the binder and the modified hydrogenated castor oil are dispersed at high speed for approximately 20 minutes.
  • the pro-thickened Cellosolve silicate is added to the metallic mixture.
  • a final dispersion at 5000 surface feet per minute is made in order to obtain a grind of 4 Hegman.
  • a control sample of the mixture is then evaluated for viscosity, weight per gallon, and drying time. Where required, the viscosity and weight per gallon are adjusted by the addition of a solvent of the ester family.
  • Cellosolve acetate is a trade name for a commercial preparation of ethylene glycol mono-ethyl ether acetate.
  • Shear test-Bars coated with the product outlined above were assembled and welded such that fillet welds could be broken apart in order to examine the weld for porosity and evidence of weld defects. In an analysis of approximately 30 inches of A weld bead, only scattered fine porosity as is normal in hand welding was observed.
  • Example V Adhesion of subsequent coatings-To determine the adhesion properties of the weld-thru primer described herein, three 4" x 8" 14 ga. metal panels were sandblasted to white metal using fine silica sand. Each of the proprietary coatings of Examples II and IV and a commercially available inorganic silicate (2 package type) was applied, one coating to each panel. Coating thickness in each case varied from 0.75 to 1.0 mils dry. The coatings were allowed to cure 24 hours before topcoating.
  • a pre-weld coating composition which enhance the stability of the electrical arc discharge during the welding of metals and improves the physical properties of the heat-affected weld zone comprising:
  • a metal alloy selected from the group consisting of chromium, molybdenum and nickel, and
  • composition of claim 1 wherein the anodic metal is present in an amount of about 30 to 75% by weight and the metal alloy is present in an amount of about 25 to 7o% by weight, based on the total metallic components in the coating.
  • composition of claim 1 wherein the binder material is selected from the group consisting of ammonium silicate, sodium silicate, potassium silicate, lithium silicate, ethyl silicate, and ethoxyethyl silicate.
  • composition of claim 1 wherein the anodic metal is zinc.
  • composition of claim 1 further including a thickening agent.
  • composition of claim 7 wherein the thickening agent is selected from the group consisting of zinc stearate, aluminum stearate, organo-montmorillonite, flame-blown silica and hydrogenated castor oil.
  • composition of claim 1 further including a degassing agent.
  • composition of claim 9 wherein the degassing agent is selected from the group consisting of silica, calcium, calcium oxide and tetraethyl ortho silicate.
  • composition of claim 1 wherein the metal alloy comprises a finely divided chromium powder.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Arc Welding In General (AREA)
  • Nonmetallic Welding Materials (AREA)
US00232980A 1972-03-08 1972-03-08 Weld thru primer Expired - Lifetime US3759756A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2506340A1 (fr) * 1981-05-19 1982-11-26 Nippon Steel Corp Tole d'acier revetue de peinture soudable presentant une excellente resistance a la corrosion

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS511269A (enrdf_load_html_response) * 1974-06-20 1976-01-07 Meito Yushi Kogyo Kk
US4517558A (en) * 1982-05-03 1985-05-14 International Game Technology Three dimensional video screen display effect
JP2598969B2 (ja) * 1988-03-08 1997-04-09 東海ゴム工業株式会社 流体封入式筒型マウント装置

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2506340A1 (fr) * 1981-05-19 1982-11-26 Nippon Steel Corp Tole d'acier revetue de peinture soudable presentant une excellente resistance a la corrosion
US4524111A (en) * 1981-05-19 1985-06-18 Nippon Steel Corporation Weldable paint-coated steel sheets having excellent corrosion resistance

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