JPS63317655A - Hot immersion-coated wire material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Summary of the Invention A gas wiping die for wiping wire drawn from a molten metal coating bath has a die angle, a die orifice length and thickness,
Provide critical parameters for orifice side relationship, die throat diameter and height above the molten bath surface. The thickness of the molten coating on the wire wiped with the combination die can be controlled very accurately by varying the wipe gas pressure.

BACKGROUND OF THE INVENTION The present invention relates to the coating of narrow rectilinear materials, such as strips and especially wires, with metallization materials in molten metallization baths. More particularly, the present invention provides for the use of a protective atmosphere and gas wipes when processing straight materials exiting a molten metal coating bath in order to establish an accurate and uniform thickness of coating on the surface of the straight materials. This relates to the combined use of

For example, metal straight materials such as strip and wire have been coated economically for many years by passing the straight materials through baths of molten metal, such as molten zinc or aluminum. Typically, the straight material was a ferrous material, such as steel. Aluminum or zinc or often e.g. tin or turn alloys (lead and
Coatings of other metals or alloys, such as alloys with up to 5% tin) impart corrosion resistance to the basic ferrous metal.

Straight material exiting a molten metal coating bath typically does not have a satisfactory vine layer of molten coating metal on its surface. The molten metal coating is always too thick, uneven, or both, or has some other drawback that prevents the molten metal from solidifying to a satisfactory metal coverage on the base metal. As a result, after the straight material exits the molten coating bath, it has been common to wipe the coating in some way to smooth it and/or reduce its thickness or thickness. Various wiping devices are used to wipe the coating while it is still molten, including soft wipers such as asbestos wipers, hard wipers such as rolls and scrapers, and in some cases Semi-rigid wipers constructed from stones of various materials, such as charcoal or gravel, are included, through which the coated straight material is passed. Recently, gas wipers or gas doctors have been used to force a gas such as air, water vapor, or an inert or reducing gas onto the surface of a straight material coated with molten metal, thereby removing excess metal. and smooth the molten metal coating.

To achieve good adhesion of the coating metal to the substrate metal, it is necessary to clean the surface of the substrate before passing it through the molten coating bath. Therefore, the straight material must be cleaned prior to coating to provide a suitably clean and active substrate surface for contact with the molten coating bath. Once the base metal has been purified,
It must remain active or oxide-free until immersed in the molten coating bath. It is therefore necessary to protect the base metal after cleaning by coating with flux or by placing it in an inert or reducing atmosphere or by continuous immersion.

Thus, ferrous straight materials are often introduced into the melt bath from a protective or oxygen-barring atmosphere of some nature. The protective atmosphere typically consists of either an effectively inert gas or a reducing gas.

An inert or reducing atmosphere is also maintained around the straight material as it exits the melt bath to prevent undue or adverse effects on the surface of the coating while it is still hot, before or after solidification. Prevents some oxidation. Typically, the protective atmosphere is contained within some form of protective chamber or hood that extends up to or into the surface of the molten bath.

More recently, gas wipers are often used to smooth and wipe molten coatings, and inert or reducing gases are often employed to wipe the surface of straight materials to prevent surface oxidation of the coated metal. In equipment, especially wire wiping equipment, a wiper is provided in or attached to a chamber containing a protective atmosphere to completely protect the molten coating on the wire from exposure to the atmosphere until it is smoothed and wiped off.

The use of non-oxidizing gases as wiping and protective gases has been found to be particularly desirable for wiping operations of wire material. The oxidized coating particles on the melt coating surface are
It has a tendency to increase the viscosity of the molten metal resulting in the accumulation of a thick viscous oxide coating, which significantly inhibits effective gas wiping. The small circumference of the wire causes a viscous ring of oxide material to form around the wire and penetrate the gas barrier resulting in a thick ring of coating on the wire. The coating contains ring cracks and flakes that occur when the wire is bent after the coating has solidified.

For example, a combined closed hood that may contain an inert gas;
One problem that has been experienced in combined wiping and protective gas installations, such as that described in U.S. Pat. If one relies solely on the force of the wiping gas to determine the coating thickness, the wiping die tends to provide very poor control over the final coating thickness. This means that even if this type of combined wiping and protective gas system is very efficient and effective in wiping and smoothing excess coating from straight materials, such as wire passing through a die, Even if I did, it would have happened. However, the exact final thickness of the coating was often impossible to adjust without changing the parameters of the wiping die itself. In other words, although coating smoothing is very effective and can remove large excess coating material from the coated object, it is not possible to actually adjust the coating thickness dimensionally by wiping gas. Not successful. Therefore, it has often been necessary to vary the rate of passage of the linear material through the wiping die to effectively control the extent to which the molten coating is wiped from the surface of the linear material. If the melt coating layer was too thick, it was necessary to reduce the rate of passage of the straight material through the die orifice to thin the coating layer. On the other hand, if the coating layer was too thin, it was necessary to increase the velocity of the straight material through the die orifice to increase the thickness. Of course, the need to adjust the speed of the coating line to obtain the desired coating weight is undesirable. This is because such adjustments interfere with other operational and production issues.

A further problem with pre-wiping devices and methods, particularly in the case of coating wire material, has been the poor concentricity of the final coating of the wire. In a "concentric coating", the thickness of the coating is substantially uniform on all sides of the wire, ie around the entire circumference of the wire. In non-concentric coatings, the thickness of the coating on one or more sides of the wire is significantly greater than the thickness of the coating on the diametrically opposite side or side. The coating is concentric in the part where the wire is formed,
It will be non-concentric in the part that touches it. Typically, concentricity varies more or less indiscriminately over a given length of wire. In fact, it is virtually impossible to obtain fully concentric heat-dipped coatings of any significant length, especially with prior known equipment. The importance of concentricity is to truly avoid thin spots in the coating. And it will be clear that thin spots can be caused by other causes of coating deposition besides true non-concentricity, such as out-of-round or elliptical shapes. It is therefore understood that one measure of concentricity is by the number of thin spots in the coating, and that perfect concentricity or the absence of thin spots is virtually impossible in heat-dipped coatings of wire. . For example, it has been our experience with aluminum-zinc hot-dip coatings that the best and most concentric wire coatings obtained using a pre-gas wiper are -
0.0127 mtn for any coverage area as measured by a commercially available non-destructive spot coating weight detector based on a target coverage of 1.5 mils or 0.038 m.
10,0127 ru with a thin coating defined as:
m or less is at least 2.5% of the number of thin spots measured in any given wire length. In other words,
An average of 2.5% or more of all tested spots on any given length of wire, with thin spots defined as approximately 1/3 of the targeted or desired coating thickness. will be at a thin point or below the minimum thickness.

On the other hand, the number of thin spots is an acceptable value for most purposes, especially in sacrificial coatings, e.g. zinc or aluminum-zinc coatings on ferrous substrate materials, where the number of thin spots exceeds the number of rejected thin spots. To avoid this, all parts of the wire must be coated with a somewhat thicker coating, thus representing a waste of coated metal.

SUMMARY OF THE INVENTION The disadvantages of previous combinations of gas wiping dies and protective hoods for wiping wire have now been obviated by the improvements of the present invention. Regardless of the speed at which the wire runs through the wiping die through the use of deterministic die parameters, and also regardless of the presence or absence of a protective chamber or hood cooperating with the wiping die, the gas wiper effectively It has now been found that the weight of the remaining coating can be determined. The critical die parameters are an orifice angle of about 10 to 45 degrees downward, preferably 15 to 30 degrees, with respect to the normal to the surface of the wire material passing through the die, and an orifice width parallel to the direction of the wire running through the die. is about 0.254 to 2.032 m, preferably 508 to 1.27 m, and the minimum length of the orifice along the substantially parallel sides of the orifice and the line of passage of the wiping gas is It is 0.635 an or more. The height of the orifice above the melt coating bath is 1.27-38.
1α, preferably 1.21 to 25.4CIR, most preferably 1.2γ to 10.16α, and the throat of the die should be from 1.27 aR to 3.81 cm, preferably Must be 1.9-3, 175 alt. The optimal orifice angle is the optimal orifice width of about 0.889 to 1
．． 043 order was found to be about 20-25 degrees.

The height above the bath surface appears to depend somewhat on the structure of the die. If the die has a hood or a protective gas chamber or a partial protective chamber, ie the chamber walls only partially enclose the space, at the lower end the die can be located further away from the bath surface. Therefore, if there is no protective chamber, the dies are placed closely together. For example, regarding the bath surface: 1.
The best results are obtained between 27 and 10.16 al.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved gas wiping arrangement for wiping molten metal coated on straight materials, such as wire rods, to smooth the coated surface and determine coating weight and thickness. It provides:

According to the invention, a gas wiping die is provided which is placed in contact with the surface of a molten metal coating bath.

The gas wiping die can be fixed and coupled within or closely adjacent to a hood or protective chamber surrounding the straight material passing from the molten metal coating bath to the gas wiping die.

Alternatively, the gas wiping die can be placed close to the surface of the melt bath without a protective hood. When using a protective hood, an inert or effectively inert gas is applied, which serves to protect the molten coated surface from oxidation until it reaches the gas wipe die. The surface portion of the melt coating bath is also enclosed within the hood to prevent or minimize the formation of an oxide film or scum on the melt bath surface.

It has been found that in order to allow the inert or reducing gas to determine and control the final weight and thickness of the final coating on the wire, the following criteria must be supported. These are: (1) The gas wiping orifice is about 10 to 45 degrees from normal to the surface of the wire, more preferably about 15 to 30 degrees from normal to the surface of the wire passing through the die, and most preferably about 20 to 2 degrees from normal to the surface of the wire passing through the die.
It must be tilted downward at an angle of 5 degrees.

(2) The thickness or width of the orifice parallel to the wire is approximately 0.
254-2.032asa+, preferably 0.508-1
．． 27 ta, and most preferably 0.889-1,
(3) the orifices are parallel to each other and equidistant at all points from the surface of the material being wiped;
The length in the gas flow direction is at least 0.635C
! (4) The height of the die orifice should be approximately 1.27 mm above the surface to be melted.
~38.1α, preferably about 1.27-25.4 cm.

Most preferably it should be about 1.21 to 10.16 ca+; (5) the die throat diameter should be 1.27 ca+ or more 3.81 ca+;
C! R is preferably 1.9 to 3.1751.

A very satisfactory wipe was obtained. For example, the orifice angle is 22.5 degrees and the orifice width is 1.016 am.
, throat diameter 2.54 CIR and 2.54 to 10.1 above the bath surface
It's on 612+. For best results, the inert or reducing gas used as the wiping gas is preferably a "heavy gas." However, in most cases other non-oxidizing gases can be used effectively. Suitable heavy gases include nitrogen, argon, propane, and the like. The term heavy is used in contrast to "light" protective gases such as hydrogen (H2), methane (CH4), natural gas, and helium.
A heavy wiping gas can be defined as a gas having a molecular weight or specific gravity that is substantially the same as the average intermolecular or specific gravity of air. ) When the above die parameters and conditions are strictly followed, the coating thickness and @
It has been surprisingly discovered that good control of the boat can be obtained. On the contrary, for example, U.S. Patent No. 3.707.
If a wiping die is used with a fully enclosed protective chamber from which wiping gas is released, as in No. You can't get it.

It has also surprisingly been found that according to the invention a very good concentric coating for the wire, or in other words a reduction in the number of thin spots in the coating, is obtained. With the improved gas wiping die and manufacturing method of this invention, the inventors have been able to reduce the number of measurement points over any given length of wire to less than 0.3% of the total measurement points when the target coating is 0.038#. is thin or below the minimum thickness; i.e. 0.0127 rrm
It was found that aluminum-zinc coatings could be obtained consistently and uniformly, and this was found to be a particular advantage of the die of the present invention. This was the inventor's previous best experience using conventional gas wipes,
That is, more than 2.5% of the measurement points, which is the best result achieved when the target coating was 0.038 m, had a coating thickness of 0.0 m.
This represents a significant improvement compared to the previous time, which was less than 127m. In other words, if the thin point is considered to be about 173 or less of the target or desired coating thickness, compared to more than 2.5% of the test score for the conventional,
Wire coated according to the present invention will exhibit less than 0.3% of the test score over any given length.

FIG. 1 schematically shows a front sectional view of a gas wiping die according to an embodiment of the present invention. Gas wiping die 11 is spaced a predetermined distance from surface 13 of molten metal coating bath 15 . The die itself consists of an outer cylindrical body 17 having an internal thread 19 at the upper end within the hollow interior of the cylindrical body. The cylindrical body has a lower end 21 in which an orifice 23 is provided which communicates with a gas passage 24 defined within the side wall 25 of the cylindrical gas guiding member 27 . Orifice 23 is
It constitutes the so-called throat part of the wipe die.

The cylindrical member 27 is attached by a removable mechanical bolt 41.
It is fixed to the bottom of the cylindrical body 11 of the die 11.

However, it will be appreciated that other suitable connection means may also be used, such as a threaded connection.

Optionally, the member 27 is attached to the bottom or lower end 21 of the die 11.
It may also be constructed from an extension of.

The outer cylinder of die 11 has an inner cylinder 43 screwed into this cylinder. The inner cylinder 43 has an extension or nose 45 which creates an arcuate circumference between its surface and the inner surface of the outer cylinder 17 when the two cylindrical members 17 and 13 are precisely positioned relative to each other. A gas passage 41 is defined. The lower part of this passage constitutes a circumferential gas wipe orifice 49. The central space through which the circumferential gas wiping orifice 49 extends can be considered to constitute an upper extension of the throat 23 of the gas wiping die. The wiping gas is supplied to the circumferential gas passage 47 via the gas inlet pipe 51. The gas inlet pipe is connected to one or more pressurized gas tanks or to a gas generation plant, etc., with a suitable intermediate vibrator and adjustable valve means or, if desired, automatic pressure regulating means (the details of which are known to those skilled in the art and are not shown). ) will be understood to be connected via.

According to the invention, the gas wipe orifice 49 has straight side walls 49a and 49b that are parallel to each other and slope downwardly at an angle of 25 degrees to the normal to the wire surface. The thickness of the wiping orifice in the direction parallel to the surface of the wire, that is, the distance between the parallel side walls 49a and 49b, is 1.0.
It is 16#m. The lengths of the parallel side walls 49a and 49b are:
1.27 as.

The distance between the inner edges of the orifices is 2.54 on.

This last dimension is also the diameter of the die throat 23. The distance from the surface 13 of the coating bath 15 of the gas wiping orifice 49 communicating with the throat 23 is 10.16aI!
It is. The height of the bottom surface of the cylindrical member 27 above the bath surface is 2.5
It is 4ca+.

In operation of the apparatus shown in FIG. 1, the wire 37 passes through the molten metal coating bath in the usual manner, typically traveling downwardly along a lower settling roll or pulley (not shown) and then at the bath surface and gas passage 24. through the orifice or throat 23 to the circumferential gas wipe orifice 4.
9 and finally passes upwardly through the central passage 53 of the inner cylinder to extend out of the gas wiper.

As the wire passes near the circumferential gas wiping orifice 49, it is wiped by a tight, precisely sized gas curtain formed by the critical dimensions of the wiping orifice. This gas curtain wipes and smoothes the molten coating on the wire. Excess coating is effectively returned to the melt coating bath. The gases used are preferably reducing or inert gases and should be heavy gases, such as argon, nitrogen, propane, etc., to achieve optimal control of coated seedlings. Currently considered preferred. This gas curtain is oriented downwardly and inwardly at an angle of about 25 degrees plus or minus a few degrees relative to the wire to achieve a wiping action. The non-oxidizing gas passes downwardly towards the molten bath surface where it additionally serves to protect the molten coating of the wire and the molten surface of the bath from oxidation. Such oxidation has a tendency to form an oxide film on the surface of the bath, which is pulled upwardly with the molten coating on the wire, creating undesirable roughness on the wire and interfering with smooth wiping of the coating. do. Reducing or inert gases protect molten metal from oxidation and are therefore broadly referred to as protective gases or non-oxidizing gases.

Contrary to the state of the art in conventional wiping and guard chamber gas combinations, if the critical parameters of the present invention are strictly adhered to, very effective control of the coating thickness of the wire can be obtained by simply varying the wiping gas pressure. is known.

However, if the critical parameters of the die are not strictly adhered to, gas pressure alone will not be effective unless a critical dimension exhaust orifice in the side of the chamber is used as disclosed in a co-filed application with this application. No wiping control is obtained.

FIG. 2 shows an example of an alternative configuration of a die and a hood for coating the wire. A cylindrical hood 111 is shown in the drawing. Hood 111 has an exit orifice 117 in the center of the top of the hood.

The hood also comprises a circumferential bracket 119 with a central opening in the middle, into which is mounted a gas wiping die 121 consisting of an external cylinder 123 with an internal thread 125, into which a central conical throat 127 is attached. An inner cylindrical member 126 having a diameter is screwed into the inner cylindrical member 126. Central conical part 129C
two opposing internal conical portions 129a and 1 connected by
A cylindrical throat member 128 having an internal passageway 129 in the shape of 29b is located at the bottom of the outer cylinder 123 and secured in place by mechanical bolts 131. The cylindrical throat member is preferably made of a wear resistant material such as hard stainless steel. External cylindrical body 123 and internal cylindrical member 12
6 is connected to a circumferential gas wipe orifice 134 leading to the top of the internal passage 129.

Inner cylindrical member 126 includes a short nose 128 having an outer conical surface 128a. Conical surface 128 of nose 128
a is parallel or equidistant to the inner cone 129a, and when the inner cylindrical member is screwed into the outer cylindrical body 123, surfaces 128a and 129a have substantially parallel curved surfaces approximately 0.762 cm apart. The parallel or equidistant portions of each surface 128a and 129a are approximately 0.635z. This provides a gas wipe orifice 134 having a thickness of 0.762 cm and a uniform length of 0.6350. The wiping orifice is inclined downwardly at an angle of 30 degrees with respect to the normal to the wire surface, and the opening of the gas wiping orifice is connected to the molten coating bath 1.
12.7 an above the surface 144 of 45.

Circumferential brackets 1 to 11 supporting the wiping die 121
9, the circumferential hood 111 is connected to the upper chamber 135 and the lower chamber 137.
Divide into. Upper chamber 135 and lower chamber 137 are not in direct communication with each other. Gas inlet pipe 141 is connected to hood 1
11 and is screwed into an opening 142 in the outer cylinder 123 that opens into the annular passage 133.

In order to obtain a more uniform gas pressure in the annular passage 133, several gas inlet tubes 141 may be selectively provided. The lower edge 112 of the hood 111 is preferably spaced a short distance above the bath surface 144. This distance is approximately 0.635 to 1
．． 27α, but it may be more or less than this.

In operation, the wire 143 passes upwardly through the molten coating bath 145 and extends from the bath surface 144 into the lower chamber 137, from where it passes through the wiping die 121 and through the gas wiping orifice 134, where it passes through the circumferential gas wiping orifice. is swept away by a curtain of inert or reducing gas emanating from the upper chamber 131 , from which the wire 143 extends through the orifice 117 .

At least a portion of the wiping gas passes through the internal passageway 129 of the throat member 128 to the confined space of the lower chamber 137 of the hood 111 after wiping and smoothing the coating on the wire as it passes through the circumferential orifice 134. Go inside,
The gas then protects the molten coating on the wire and the molten surface 144 of the coating bath 145 directly below the lower chamber 137. Excess gas escapes from chamber 137 around the lower edge. Optionally, chamber 13
7 is immersed in the molten coating bath to form a substantially completely confined space in the chamber 137, and the excess accumulated protective gas passes through the internal passage 129 and the conical throat 12γ to the upper part. The wire is returned to the chamber 135, and the wire is continued to be protected in this upper chamber.
It could also be discharged via 17. If the wipe protection gas is a flammable reducing gas, the gas is preferably combusted as it passes through the orifice 117.

Another embodiment of the invention is illustrated in FIG. Third
The figure shows a gas wiping die, which is similar to the first
It is substantially the same as the wipe die shown in the figure. Since all parts of the die are substantially the same as the die shown in FIG. 1, the reference numbers identifying the parts shown in FIG. 3 have been the same as those used in FIG. The die has a diameter of 2.
It has a 54 cm throat and the gas wipe orifice is located 3.81 cm above the surface of the melt bath. The other parameters of the die are the same as those of the die shown in FIG. The flow of nitrogen gas from the wiping orifice is combined with a large throat diameter and a die located near the surface of the molten coating bath to very effectively wipe the coating on the wire and regulate the pressure of the wiping gas. Only the coating weight can be determined. By placing the wiping die close to the surface of the molten bath and the large amount of gas passing through the large diameter throat, the coating surface of the wire rod between the surface of the coating bath and the wiping die and the area near where the wire comes out are damaged. The surface portions of the melt coating bath can be filled with a non-oxidizing wipe gas and temporarily protected from oxidation. Generally, the shorter the extension at the bottom of the wiping die, or if there is no extension, the closer it is desirable to have the die closer to the coating bath surface.

FIG. 4 shows a graphical graph of the pressure effect during wiping obtained by plotting the coating thickness against the gas pressure applied to the wiping die.

Plots are approximations and are not intended to represent exact numerical relationships. “Low pressure region” (A) and “high pressure region”
The horizontal portions of the curves labeled (C) indicate the areas where the straight material is wiped and smoothed, respectively. However, the deposited coating weight is not controlled more effectively by varying the pressure. In contrast, the "transition region" (B) is the region where a change in gas pressure results in a change in the thickness or weight of the coating remaining on the wire or other straight material. The exact slope and profile depends on various factors. However, as long as this critical parameter of the present application is strictly adhered to, the general slope of the curve will be maintained and the entire "transition region"
Alternatively, the "intermediate region" can be used to control coating weight by simply adjusting the wiping gas pressure. The wipe coating also has very good concentricity with respect to the surface of the wire.

The exact reason why wiping is improved by using the critical parameters of this invention is not fully understood at this time, but by providing appropriate parameters and conditions, the slope of the curve in the transition region is reduced. , thus effectively extending the area over which changes in gas pressure cause changes in thickness. The relationship between coating thickness, weight, and wiping gas pressure is improved or made more controllable by reducing the amount of change in coating mold 11 for any change in wiping gas pressure. The relatively large throat and wiping orifice of the wiping die with respect to other parameters of the die results in a relatively lower gas wiping rate or "gentler" wiping than a comparative wiping with other dies using the same relative gas pressure. This explains the excellent wiping control and good concentricity of the coating. However, at present this is only speculation and the applicant does not wish to adhere to any particular theory regarding this excellent result, but it is possible to The result can be effectively wiped.

Although the present invention has been described with respect to special gas wiping devices, the critical parameters of the present invention can also be used with other types of appropriately designed wiping devices, and in addition to those expressly disclosed, It will be appreciated that gas can be used.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a wire wiping device for producing the improved wire material of the present invention, FIG. 2 is a sectional view of another type of wiping device for producing the wire material of the present invention, and FIG. 3 is a sectional view of the present invention. FIG. 4 is a sectional view of yet another type of gas wiping device for manufacturing wire materials according to the invention, illustrating the general relationship of gas wiping pressure to coating thickness in a device for manufacturing wire materials constructed according to the invention. It is a curve diagram. 11... Gas wiping die 13... Molten metal coating bath surface 15... Molten metal coating bath 17... External cylindrical body 1
9...Inner thread 21...Lower end 23...
- Throat (orifice) 24... Gas passage 25... Side wall 27...
・Cylindrical gas guiding member 37...Wire rod 41...Machine bolt 43...Inner cylinder 45...Nose part
47... Cylindrical gas passage 49... Cylindrical gas wipe orifice 49a, 49b... Straight side wall
51... Gas inlet pipe 53... Central passage 111... Hood 112... Lower edge 117
...Exit orifice 119...Circumferential bracket 121...Gas wipe die 123...Outer cylindrical body 125...Inner thread 126...Inner cylindrical member 127...Central conical throat 128. ... Cylindrical throat member (nose part) 128a ... External conical surface 129 ... Internal passages 129a, 129b - ... Internal conical part 129C...
Central conical part 131... Machine bolt 133...
Annular passage 134... Circumferential gas wiping orifice 135...
Upper chamber 137... Lower chamber 141... Gas inlet pipe 142... Opening 143... Wire rod
144... Bath surface 145... Melt coating bath

Claims (1)

[Claims] (1) Consisting of a ferrous base material having a circular cross section and a predetermined length and a layer of coating metal surrounding this base material, the layer of coating metal is concentric with respect to the base material over its length, and this coating Concentricity is measured as a function of the number of thin spots in the coating, said thin spots being 1/1/2 of the target or desired coating thickness.
Hot dip coated wire material where the thin point is less than 0.3% of the coating thickness measurement when defined as 3 or less.