METHOD FOR HOT-DIP GALVANIZING A MULTITUDE OF FENCE PANELS AND GALVANIZED FENCE PANEL

Abstract

 The invention relates to a method for hot-dip galvanizing in a zinc bath a plurality of parallel positioned fence panels, comprising horizontal and vertical wires, wherein the zinc bath has a depth of at least 1.5 times the height of a fence panel, and the zinc bath has a length of at least 2.5 times the length of a fence panel, wherein a zinc layer with a thickness between 50 and 200 mu is deposited on the wires of the fence panels, the method comprises the steps of: (i) immersing the fence panels in the zinc bath with an inward downward movement at an angle a; (ii) moving the fence panels horizontally in the zinc bath, whereby the fence panels are tilted so that an angle change takes place, and so that the fence panels are placed at an angle β, where the angles α and β are different; and (iii) pulling the fence panels out of the zinc bath with an outward upward movement at the angle β.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for hot-dip galvanizing of a plurality of fence panels. In a second aspect, the invention concerns a galvanized fence panel.

PRIOR ART

[0002] Hot-dip galvanizing is a commonly used method of galvanizing, intended to protect steel or iron against corrosion. Galvanizing provides a protective layer of zinc that protects the metal against corrosion. If this layer is broken, the zinc acts as a sacrificial anode, so that the iron is protected by the zinc. Hot-dip galvanizing is often carried out by immersing metal in a zinc bath with liquid zinc.

[0003] Good resistance to corrosion and rust is essential for fence panels, especially when the fence panels are intended as an outdoor fence.

[0004] Fence panels are manufactured in known methods, such as WO2021165058, by galvanizing the wires of a fence panel before welding. They are then joined in their perpendicular form by welding horizontal wires to vertical wires. However, the welding process destroys the galvanized coating on the steel in the welded area, leaving the areas where the wires are joined vulnerable to corrosion.

[0005] Instead of welding the galvanized wires, non-galvanized wires can also be welded and the entire panel can be galvanized after welding. Galvanizing a complete panel is much more laborious and difficult than galvanizing lengths of wires. Moreover, when galvanizing a panel, some parts of the panel will remain in the zinc bath longer than others, meaning that the zinc layer applied during galvanizing is not uniformly distributed over the fence panel.

[0006] The present invention aims to find a solution for at least some of the above problems.

SUMMARY OF THE INVENTION

[0007] The invention concerns a method for hot-dip galvanizing of a plurality of fence panels according to claim 1. Preferred forms of the method are shown in claims 2 up to and including 14. In a second aspect, the invention concerns a galvanized fence panel according to claim 15.

[0008] It is an objective of the invention to make the zinc layer on a fence panel as uniform as possible. Moreover, the invention is aimed at galvanizing fence panels as quickly as possible. To this end, it is also an objective of the invention to maximize and optimize the dripping off of the liquid zinc from the fence panel.

[0009] A further objective of the invention is to minimize the formation of membranes or collars on the wires of the fence panel, and to ensure that the membranes or collars only occur at the corner points of the fence panel. The further aim of the invention is to minimize the thickness of the membranes or collars as much as possible.

[0010] The method is advantageous because the method ensures the application of a uniform zinc layer over the entire fence panel. The method avoids the problems related to variations in the thickness of the zinc layer due to temperature differences in the zinc bath. The method ensures that a uniform zinc layer is obtained with minimal variation due to membrane and collar formation. The change in angle from angle α to angle β minimizes membrane and collar formation on the wires of the fence panel. Moreover, the change in angle is also advantageous because the membrane and collar formation only occurs at the intersections in the fence panel. The angle β, different from angle α, ensures optimal dripping off of the liquid zinc from the fence panels when pulling the fence panels out of the zinc bath, which reduces the variation in the thickness of the zinc layer on the fence panels and increases uniformity. The dimensions of the zinc bath allow entire fence panels to be galvanized and to be tilted during immersion.

[0011] A specific preferred form is shown in claim 6. The speed at which the fence panels are pulled out of the zinc bath increases as the fence panels are pulled further out of the zinc bath. The variable and increasing speed ensures a thin zinc layer, with minimal variations in thickness over a fence panel. This means that the layer thickness differences are eliminated as much as possible. Increasing the extraction speed also reduces the galvanizing time.

[0012] The galvanized fence panel is characterized by the fact that it contains a uniform zinc layer that shows no damage or thinning at the welding points where the wires of the fence panel are welded together, and which also has few membranes and/or collars.

DETAILED DESCRIPTION

[0013] The invention concerns a method for hot-dip galvanizing of a plurality of fence panels.

[0014] Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as commonly understood by a person skilled in the art to which the invention pertains. For a better understanding of the description of the invention, the following terms are explained explicitly.

[0015] In this document, "a" and "the" refer to both the singular and the plural, unless the context presupposes otherwise. For example, "a segment" means one or more segments.

[0016] The terms "comprise," "comprising," "provided with," "contain," "containing," "include," "including" are synonyms and are inclusive or open-ended terms that indicate the presence of what follows, and which do not exclude or prevent the presence of other components, characteristics, elements, members, steps, as known from or disclosed in the prior art.

[0017] The terms "consist of," "consisting of," "being composed of," "composed of," are synonyms and are exclusive or closed-ended terms indicating the presence of what follows, and excluding or precluding the presence of other components, features, elements, members, steps known or described in the art.

[0018] Quoting numeric intervals by the endpoints includes all integers, fractions, and/or real numbers between the endpoints, including those endpoints.

[0019] In a first aspect, the invention concerns a method for hot-dip galvanizing in a zinc bath a plurality of parallel positioned fence panels, comprising horizontal and vertical wires.

[0020] In this aspect, the invention preferably concerns a method for hot-dip galvanizing in a zinc bath a plurality of parallel positioned fence panels, comprising horizontal and vertical wires, wherein a zinc layer with a thickness between 50 and 200 mu is deposited on the wires of the fence panels.

[0021] In a preferred embodiment, the zinc bath has a depth of at least 1.5 times the height of a fence panel, and a length of at least 2.5 times the length of a fence panel.

[0022] In a further preferred embodiment, the method comprises the steps of:

i. immersing the fence panels in the zinc bath with an inward downward movement;

ii. moving the fence panels horizontally in the zinc bath; and

iii. pulling the fence panels out of the zinc bath with an outward upward movement.

[0023] In a further preferred embodiment, the method comprises the steps of:

i. immersing the fence panels in the zinc bath with an inward downward movement at an angle α;

ii. moving the fence panels horizontally in the zinc bath, whereby the fence panels are tilted so that an angle change takes place, and so that the fence panels are placed at an angle β, where the angles α and β are different; and

iii. pulling the fence panels out of the zinc bath with an outward upward movement at the angle β.

[0024] The method is advantageous because the method ensures the application of a uniform zinc layer over the entire fence panel. The method avoids the problems related to variations in the thickness of the zinc layer due to temperature differences in the zinc bath. The method ensures that a uniform zinc layer is obtained with minimal variation due to membrane and collar formation. The change in angle from angle α to angle β minimizes membrane and collar formation on the wires of the fence panel. Moreover, the change in angle is also advantageous because the membrane and collar formation only occurs at the intersections in the fence panel. The angle β, different from angle α, ensures optimal dripping off of the liquid zinc from the fence panels when pulling the fence panels out of the zinc bath, which reduces the variation in the thickness of the zinc layer on the fence panels and increases uniformity. The dimensions of the zinc bath allow entire fence panels to be galvanized and to be tilted during immersion.

[0025] In an embodiment, the hot-dip galvanizing is applied to a plurality of fence panels. In a preferred form, between 2 and 100 fence panels are galvanized at the same time, preferably between 10 and 90, more preferably between 20 and 80, even more preferably between 30 and 70, most preferably between 40 and 60.

[0026] In another embodiment, hot-dip galvanizing is applied to only one fence panel.

[0027] In an embodiment, the fence panel is made of unalloyed steel, low-alloy steel or high-alloy steel. The fence panel can be manufactured from high or low carbon steel.

[0028] Unalloyed steel contains a maximum of 1.5% of alloying elements (excluding carbon (C)). Unalloyed steel has a carbon percentage of 0.5% to 2%. Low-alloy steel contains between 1.5 and 5% alloying elements (excluding carbon). High-alloy steel contains more than 5% of alloying elements. The fence panel is preferably made of unalloyed steel. The term "alloying elements" refers to the elements that are present in the alloy in addition to iron and carbon. In a preferred form, the fence panel is made of an alloy comprising iron (Fe), carbon (C) and alloying elements. Preferably, the alloy comprises a maximum of 1.5% alloying elements, more preferably a maximum of 1.4%, even more preferably a maximum of 1.3%, even more preferably a maximum of 1.2%, most preferably a maximum of 1.1%. Preferably the alloy comprises at least 0.5% alloying elements, more preferably at least 0.6%, even more preferably at least 0.7%, even more preferably at least 0.8%, even more preferably at least 0.9%, most preferably at least 1%. In another preferred embodiment, the alloy comprises between 0.5 and 1.5% alloying elements, preferably between 0.6 and 1.5%, more preferably between 0.7 and 1.4%, even more preferably between 0.8 and 1.3%, even more preferably between 0.9 and 1.2%, most preferably between 1 and 1.1%.

[0029] In an embodiment, the alloy comprises a maximum of 0.1% C, more preferably a maximum of 0.09%, even more preferably a maximum of 0.085%, even more preferably a maximum of 0.08%, most preferably a maximum of 0.075%. Preferably, the alloy comprises at least 0.025% C, more preferably at least 0.03%, even more preferably at least 0.035%, even more preferably at least 0.04%, most preferably at least 0.045%. In another preferred embodiment, the alloy comprises between 0.02 and 0.1% C, preferably between 0.025 and 0.09%, more preferably between 0.035 and 0.085%, even more preferably between 0.04 and 0.08%, most preferably between 0.045 and 0.075%.

[0030] In a preferred embodiment, the alloy comprises alloying elements selected from the list of: manganese (Mn), silicon (Si), sulfur (S), phosphorus (P), nitrogen (N), copper (Cu), chromium (Cr), nickel (Ni), niobium (Nb), tin (Sn), aluminum (Al) or any combination thereof. Preferably the alloy comprises manganese (Mn), silicon (Si), sulfur (S), phosphorus (P), nitrogen (N), copper (Cu), and optionally chromium (Cr), nickel (Ni), niobium (Nb), tin (Sn), aluminum (Al).

[0031] Preferably, the alloy comprises Mn in an amount between 0.3 and 0.5%, more preferably between 0.35 and 0.45%, Si in an amount between 0.05 and 0.25%, more preferably between 0.1 and 0.2%, S in an amount between 0.01 and 0.045%, more preferably between 0.015 and 0.04%, P in an amount between 0.005 and 0.03%, more preferably between 0.005 and 0.025%, Cu in an amount between 0.2 and 0.4%, more preferably between 0.25 and 0.35%, N in an amount between 0.005 and 0.02%, more preferably between 0.005 and 0.015%, and Cr in an amount of up to 0.15%, more preferably up to 0.1%, Ni in an amount up to 0.15%, more preferably up to 0.1%, and Nb in an amount up to 0.005%, more preferably up to 0.002%, Sn in an amount up to 0.05%, more preferably up to 0.03%, and/or Al in an amount up to 0.005%, more preferably up to 0.003%.

[0032] In a preferred form, the fence panel is a twin-wire or double-wire fence panel. With double-wire fence panels, parallel vertical bars (wires) are welded to horizontal bars (wires), whereby the vertical bars are welded at the same height between two horizontal bars. The fence panel preferably has between 50 and 55, preferably 51, vertical bars and between 1 and 20 horizontal bars.

[0033] In an embodiment, the fence panels are pre-treated prior to hot-dip galvanizing. So that the adhesion, integrity and uniformity of the zinc layer is assured.

[0034] Preferably, the pre-treatment includes at least one of the following steps: degreasing, rinsing, pickling, fluxing or drying. An example of a pretreatment is degreasing with subsequent rinsing, subsequent acid pickling with subsequent rinsing and finally a fluxing treatment (i.e. a so-called fluxing) with subsequent drying process. Another example of a pretreatment includes the steps of: pickling, rinsing, fluxing and drying.

[0035] In an embodiment, the vertical wires have a length between 500 and 2500 mm, preferably the vertical wires have a length selected from the list: 606, 608, 630, 806, 808, 830, 1006, 1008, 1030, 1206, 1208, 1230, 1406, 1408, 1430, 1606, 1608, 1630, 1806, 1808, 1830, 2006, 2008, 2030, 2206, 2208, 2230, 2406, 2408, 2430 mm. It will be apparent to one skilled in the art that the length of the vertical wires corresponds to the height of a fence panel. In an embodiment, the horizontal wires have a length between 2000 and 3000 mm; preferably between 2400 and 2600, even more preferably between 2500 and 2550 mm, most preferably 2508 or 2510 mm. It will be apparent to one skilled in the art that the length of the horizontal wires corresponds to the length of a fence panel.

[0036] In a preferred embodiment, the distance between two adjacent vertical wires is 40-60 mm c.t.c., more preferably between 45 and 55 mm, even more preferably between 49 and 51, most preferably about 50 mm.

[0037] In another embodiment, the distance between the adjacent horizontal wires is 100-300 mm c.t.c., preferably 150-250 mm, more preferably 180-220 mm, most preferably about 200 mm.

[0038] The term "c.t.c." (center to center) refers to a distance between the center (the heart) of a circular cross-section of one wire and the center (the heart) of a circular cross-section of another wire.

[0039] In an embodiment, a plurality of parallel positioned fence panels, comprising horizontal and vertical wires, are hot-dip galvanized in a zinc bath. The plurality of fence panels are preferably positioned parallel with a space between them, so that the fence panels do not touch each other. This avoids contact points that could cause the zinc layer thickness to deviate.

[0040] In an embodiment, the fence panels are positioned parallel and suspended from a suspension apparatus that allows downward and upward movements, so that the fence panels can be immersed in the suspended condition.

[0041] The plurality of fence panels are immersed (step (i)) in the zinc bath with an inward downward movement at an angle α. The angle α is provided by a tilt in the suspension apparatus. In a preferred form, the angle α is at least 5 degrees, preferably at least 10 degrees, more preferably at least 11 degrees, even more preferably at least 12 degrees, most preferably at least 12.5 degrees. In another or further preferred form, the angle α is a maximum of 20 degrees, preferably a maximum of 16 degrees, more preferably a maximum of 15 degrees, even more preferably a maximum of 14 degrees, most preferably a maximum of 13.5 degrees. In another or further preferred form, the angle α is between 5 and 20 degrees, preferably between 10 and 16 degrees, more preferably between 11 and 15 degrees, even more preferably between 12 and 14 degrees, most preferably between 12, 5 and 13.5 degrees.

[0042] Angle α is an angle measured with respect to a horizontal line parallel to the liquid surface.

[0043] The inward downward movement should be understood as a movement in the z-direction perpendicular to the xy-plane, with the horizontal liquid surface lying in the xy-plane. By definition, the z-direction and the inward downward movement are parallel to gravity. The length of the zinc bath is preferably in the x-direction, and the width of the zinc bath is preferably in the y-direction.

[0044] The angle α is the angle by which the fence panels are tilted in the xz-plane, which is perpendicular to the liquid surface, during the inward downward movement. Angle α is therefore the angle at which the vertical wires (transverse bars) of the fence panels enter the liquid surface. The angle α is the angle measured between the liquid surface and the vertical wires (transverse bars) of the fence panels during the inward downward movement. It will be apparent to a person skilled in the art that this angle is always between 0 and 90°, as the suspension system would not allow angles greater than 90°.

[0045] It is clear that the angle α can be measured at different locations, both at the liquid surface and with respect to a horizontal plane parallel to the liquid surface that intersects the fence panel.

[0046] In a preferred form, the zinc bath has a depth of at least 1.5 times the height of a fence panel. This depth is necessary so that the fence panel can be immersed in the zinc bath at an angle α in step (i). Moreover, the depth is necessary so that the tilt (angle change) in step (ii) can be carried out without touching the bottom of the zinc bath.

[0047] In a preferred form, the depth of the zinc bath is at least 1 m, preferably at least 1.5 m, more preferably at least 2 m, even more preferably at least 2.5 meters, even more preferably at least 3 m, most preferably at least 3.5 m. In another or further preferred form, the depth of the zinc bath is a maximum of 7 m, preferably a maximum of 6.5 m, more preferably a maximum of 6 m, even more preferably a maximum of 5.5 meters, even more preferably a maximum of 5 m, most preferably a maximum of 4.5 m. In another or further preferred form, the depth of the zinc bath is 1-7 m, preferably 1.5-6.5 m, more preferably 2-6 m, even more preferably 2.5-5.5 m, even more preferably 3-5 m, most preferably 3.5-4.5 m.

[0048] In a preferred form, the zinc bath has a length of at least 2.5 times the length of a fence panel. This length is necessary so that the fence panel can be moved horizontally in the zinc bath in step (ii). In addition, the length is necessary so that the tilt (angle change) in step (ii) can be carried out without hitting the sides of the zinc bath.

[0049] In a preferred form, the length of the zinc bath is at least 4 m, preferably at least 4.5 m, more preferably at least 5 m, even more preferably at least 5.5 meters, even more preferably at least 6 m, most preferably at least 6.5 m. In another or further preferred form, the length of the zinc bath is a maximum of 10 m, preferably a maximum of 9.5 m, more preferably a maximum of 9 m, even more preferably a maximum of 8.5 meters, even more preferably a maximum of 8 m, most preferably a maximum of 7.5 m. In another or further preferred form, the length of the zinc bath is 4-10 m, preferably 4.5-9.5 m, more preferably 5-9 m, even more preferably 5.5-8.5 m, even more preferably 6-8 m, most preferably 6.5-7.5 m.

[0050] The zinc bath comprises liquid zinc. The zinc bath preferably further comprises at least one of the following components: lead (Pb), nickel (Ni), aluminum (Al), or a combination of these.

[0051] In an embodiment, the zinc bath comprises a combination of zinc, lead, nickel and aluminum. In a further embodiment the zinc bath comprises:

• zinc, in an amount between 95 and 99 m% of the total zinc bath;
• lead, in an amount of a maximum of 5 m% of the total zinc bath, preferably a maximum of 2 m% of the total zinc bath, more preferably a maximum of 1 m% of the total zinc bath;
• nickel, in an amount of a maximum of 1 m% of the total zinc bath, preferably a maximum of 0.1 m% of the total zinc bath, more preferably a maximum of 0.05 m% of the total zinc bath;
• aluminum, in an amount of a maximum of 0.01 m% of the total zinc bath, preferably a maximum of 0.001 m% of the total zinc bath, more preferably a maximum of 0.0007 m% of the total zinc bath.

[0052] In step (ii) the plurality of suspended fence panels are moved horizontally through the zinc bath. The fence panels are tilted so that an angle change occurs, and so that the fence panels are placed at an angle β, where the angles α and β are different.

[0053] In a preferred form, the plurality of fence panels are tilted in step (ii), whereby a first angle change takes place, whereby the fence panels are tilted to a substantially horizontal position. This tilting can take place before or during the horizontal movement through the zinc bath in step (ii), preferably during the horizontal movement. In a subsequent preferred form, the plurality of fence panels are then tilted again, causing a second angle change, where the fence panels are tilted to an angle β. This second tilt can take place during or after the horizontal movement through the zinc bath in step (ii), preferably during the horizontal movement.

[0054] When the fence panels are immersed, the zinc in the zinc bath cools locally. This causes non-uniformity in the zinc layer because more zinc is deposited on the fence panel at a higher temperature than at a lower temperature. The horizontal movement in the zinc bath ensures that the fence panels are moved to a warmer part of the zinc bath, which improves the uniformity of the zinc layer on the wires of the fence panel.

[0055] In a preferred form, the fence panels are moved horizontally at least 0.25 meters in step (ii), preferably at least 0.5 meters, more preferably at least 0.75 meters, even more preferably at least 1 meter.

[0056] The maximum horizontal movement depends on the dimensions of the zinc bath, therefore the horizontal movement will be a maximum of 2 meters, so that the zinc bath does not have to be unnecessarily large.

[0057] In a particularly preferred form, in step (ii) the angle α is adjusted to an angle of approximately 0°C and then to an angle β.

[0058] The plurality of fence panels are pulled out of the zinc bath in step (iii) with an outward upward movement at an angle β. The angle β is provided by a tilt in the suspension apparatus. The angle β preferably has a sign equal to that of angle α. In a preferred form, the angle β is at least 25 degrees, preferably at least 30 degrees, more preferably at least 31 degrees, even more preferably at least 32 degrees, even more preferably at least 33 degrees, most preferably at least 35.5 degrees. In another or further preferred form, the angle β is a maximum of 45 degrees, preferably a maximum of 40 degrees, more preferably a maximum of 39 degrees, even more preferably a maximum of 38 degrees, even more preferably a maximum of 37 degrees, most preferably a maximum of 36.5 degrees. In another or further preferred form, the angle β is between 25 and 45 degrees, preferably between 30 and 40 degrees, more preferably between 31 and 39 degrees, even more preferably between 32 and 38 degrees, even more preferably between 33 and 37 degrees, most preferably between 35.5 and 36.5 degrees.

[0059] Angle β is an angle measured with respect to a horizontal line parallel to the liquid surface.

[0060] The outward upward movement should be understood as a movement in the z-direction perpendicular to the xy-plane, with the horizontal liquid surface lying in the xy-plane. By definition, the z-direction and the outward upward movement are parallel to gravity. The length of the zinc bath is preferably in the x-direction, and the width of the zinc bath is preferably in the y-direction.

[0061] The angle β is the angle by which the fence panels are tilted in the xz-plane, which is perpendicular to the liquid surface, during the outward upward movement. Angle β is therefore the angle at which the vertical wires (transverse bars) of the fence panels leave the liquid surface. The angle β is the angle measured between the liquid surface and the vertical wires (transverse bars) of the fence panels during the outward upward movement. It will be apparent to a person skilled in the art that this angle is always between 0 and 90°, as the suspension system would not allow angles greater than 90°.

[0062] It is clear that the angle α can be measured at different locations, both at the liquid surface and with respect to a horizontal plane parallel to the liquid surface that intersects the fence panel.

[0063] The angle β is the angle by which the fence panel is tilted in the xz-plane, perpendicular to the liquid surface, during the outward upward movement.

[0064] In a preferred form, the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is between 0.1 and 5 m/min, preferably between 0.1 and 2 m/min, more preferably between 0.4 and 1.55 m/min. In another or further preferred form, the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is constant or increasing, preferably the extraction speed is increasing during extraction. This means that the speed increases the further the fence panel is pulled out of the zinc bath. Preferably, the extraction speed increases in steps.

[0065] In a preferred form, the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is increasing in the range of 0.1 to 5 m/min, preferably in the range of 0.1 to 2 m/min, more preferably in the range of 0.4 to 1.55 m/min.

[0066] The speed at which the fence panels are pulled out of the zinc bath increases as the fence panels are pulled further out of the zinc bath. The variable and increasing speed ensures a thin zinc layer, with minimal variations in thickness over a fence panel.

[0067] When the fence panels are pulled out of the zinc bath, the air mass above the zinc bath becomes warmer. The warm air mass also has an influence on the zinc layer. It has been found that increasing the extraction speed minimizes this influence.

[0068] In a preferred form, the method further comprises the step (iv) of moving air lances between the wires of the fence panels, wherein the air lances blow air under increased pressure between the wires of the plurality of fence panels.

[0069] The air lances blow air under pressure through the openings of the fence panels. Openings are intended to be the grids formed by the horizontal and vertical wires in a fence panel. As a result, the extraction speed in step (iii) may be higher because so-called "membranes" of liquid zinc, which are formed in the openings when pulling the fence panels out of the zinc bath and during the dripping off of the liquid zinc from the fencing panels during extraction, are blown away or blown to pieces.

[0070] The air lances move through the openings of the plurality of fence panels during blowing, so that any membranes formed on each fence panel can be blown apart. In an embodiment, the air lances are movable so that they can move through the plurality of fence panels during blowing. In an embodiment, air lances are moved through all openings simultaneously. In another preferred form, the air lances are moved simultaneously through the openings at the same horizontal height, after which the air lances are then moved simultaneously through the openings at a next equal horizontal height.

[0071] In a preferred form, the air lances move at a speed between 5 and 40 m/min, preferably between 10 and 35 m/min.

[0072] In a preferred form, the air blown from the air lances has a pressure between 2 and 10 bar, preferably between 3 and 7 bar, more preferably between 4 and 6 bar.

[0073] In a preferred form, the air is blown from the air lances at a flow rate between 500 and 1500 m³/hour, preferably between 750 and 1250 m³/hour, more preferably between 850 and 1150 m³/hour, even more preferably between 950 and 1050 m³/hour.

[0074] In a preferred form, the air lances move in a first direction perpendicular to the wires of the fence panels in the plurality of fence panels, preferably at a speed between 5 and 25 m/min, and then back out of the plurality of fence panels in a second direction opposite to the first direction, preferably at a speed between 20 and 40 m/min.

[0075] In a further preferred form, the speed in the first direction is between 10 and 20 m/min, preferably between 11 and 18 m/min, more preferably between 12 and 17 m/min, even more preferably between 13 and 15 m /min.

[0076] In another further preferred form, the speed in the second direction is between 25 and 35 m/min, preferably between 26 and 34 m/min, more preferably between 27 and 33 m/min, even more preferably between 28 and 32 m/min, most preferably between 29 and 31 m/min.

[0077] In an embodiment, the zinc layer deposited on the wires of the fence panels has a thickness between 50 and 200 mu.

[0078] The average layer thickness on the fence panel preferably complies with the ISO 1461 standard.

[0079] In a preferred form, the average zinc layer on the wires of the fence panels is between 40 and 120 mu. In a further preferred form, the average thickness of the zinc layer on the wires of the fence panels is between 60 and 80 mu.

[0080] The zinc layer and the average zinc layer on the fence panel can be measured using a gravimetric measurement in accordance with EN ISO 1460 or a magnetic method in accordance with EN ISO 2178.

[0081] In a second aspect, the invention concerns a galvanized fence panel comprising vertical and horizontal wires.

[0082] The galvanized fence panel is advantageous because it contains a thin zinc layer that shows no damage or thinning at the welding points where the wires of the fence panel are welded together.

[0083] In a preferred embodiment, a zinc layer with a thickness between 50 and 200 mu is attached to the wires of the fence panel.

[0084] In a preferred form, the average zinc layer on the wires of the fence panels is between 40 and 120 mu. In a further preferred form, the average thickness of the zinc layer on the wires of the fence panels is between 60 and 80 mu.

[0085] In a preferred form, the galvanized fence panel is obtained according to a method according to the first aspect of the invention.

[0086] In what follows, the invention is described by way of non-limiting examples and figures illustrating the invention, and which are not intended to and should not be interpreted as limiting the scope of the invention.

EXAMPLES AND DESCRIPTION OF THE FIGURES

[0087] 

Figure 1 shows step (i) of a method according to the first aspect.
In step (i) of the method, a plurality of fence panels (5), comprising vertical (1) and horizontal (2) wires are immersed (i) in a zinc bath. The plurality of fence panels are suspended from a suspension apparatus (4) that engages in a suspension point (7) at an angle α. The angle α is an angle measured with respect to a horizontal line (6) through the suspension point (7) parallel to the liquid surface (3) in the zinc bath.

Figure 2 shows step (iii) of a method according to the first aspect.
In step (iii) of the method, a plurality of fence panels (5), comprising vertical (1) and horizontal (2) wires are pulled from the zinc bath (iii). The plurality of fence panels are suspended from a suspension apparatus (4) that engages in a suspension point (7) at an angle β. The angle β is an angle measured with respect to a horizontal line (6) through the suspension point (7) parallel to the liquid surface (3) in the zinc bath.

Figure 3 shows a schematic representation of a method according to the first aspect.
The plurality of fence panels are immersed in the zinc bath at an angle α of 13 degrees. Once the fence panels have been immersed in the zinc bath, the fence panels are tilted during a horizontal movement in the zinc bath to an angle of approximately 0 degrees, after which the fence panels are tilted through a second angle change to an angle β of 36 degrees. The fence panels are then pulled back out of the zinc bath at an angle β of 36 degrees.

Figure 4 shows the gradually increasing extraction speeds (201) in m/min based on the position relative to the liquid surface (202) for Examples 1, 2 and 3, where 5550 is the starting position of the extraction at the liquid surface.
Examples 1, 2 and 3 concern gradually increasing extraction speeds in meters per minute (m/min) for three different fence panels.

[0088] Example 1 concerns the extraction of a plurality of twin-wire fence panels with a height between 1430 and 2430 mm. The vertical and horizontal wires have a diameter of 6 and 8 mm, respectively. Example 2 concerns the extraction of a plurality of twin-wire fence panels with a height between 600 and 1230 mm. The vertical and horizontal wires have a diameter of 6 and 8 mm, respectively. Example 3 concerns the extraction of a plurality of twin-wire fence panels with a height between 600 and 2430 mm. The vertical and horizontal wires have a diameter of 5 and 6 mm, respectively. The extraction speeds are shown in Table 1 and Figure 4.

TABLE 1

Example 1 (Ex. 1)		Example 2 (Ex. 2)		Example 3 (Ex. 3)
position (202)	speed (m/min) (201)	Position (202)	speed (m/min) (201)	Position (202)	speed (m/min) (201)
5550	0.5	5550	0.5	5550	0.55
5000	0.5	4735	0.5	4675	0.55
5000	0.6	4735	0.6	4675	0.85
4200	0.6	4100	0.6	3675	0.85
4200	0.7	4100	0.75	3675	1.15
3700	0.7	3700	0.75	2375	1.15
3700	0.8	3700	0.9	2375	1.45
2300	0.8	3400	0.9	0	1.45
2300	1	3400	1.05	0	1.45
1200	1	985	1.05	0	1.45

[0089] Figure 5 and figure 6 show a double-wire fence panel that can be galvanized according to the method of the first aspect. Figure 5 shows a perspective view of a double-wire fence panel. Figure 6 shows an enlarged perspective view of a double-wire fence panel (section A in Figure 5).

[0090] A twin-wire fence panel (108) consists of parallel vertical wires (104) welded to horizontal wires (101, 102) with the vertical wires welded at any height between two horizontal wires (101, 102) forming a double pair (103). The distance between two adjacent vertical wires (106) is about 50 mm c.t.c. The distance between the adjacent horizontal wires (105) is about 200 mm c.t.c.

Claims

1. A method for hot-dip galvanizing in a zinc bath a plurality of parallel positioned fence panels, comprising horizontal and vertical wires, wherein the zinc bath has a depth of at least 1.5 times the height of a fence panel, and where the zinc bath has a length of at least 2.5 times the length of a fence panel, wherein a zinc layer with a thickness between 50 and 200 mu is deposited on the wires of the fence panels, and wherein the method comprises the steps of:

i. immersing the fence panels in the zinc bath with an inward downward movement at an angle a;

ii. moving the fence panels horizontally in the zinc bath, whereby the fence panels are tilted so that an angle change takes place, and so that the fence panels are placed at an angle β, wherein the angles α and β are different; and

iii. pulling the fence panels out of the zinc bath with an outward upward movement at the angle β.

2. Method according to claim 1, wherein the plurality of fence panels are tilted in step (ii), wherein a first and a second angle change takes place, wherein the fence panels are tilted in a first angle change from an angle α to a substantially horizontal position, and wherein the fence panels are tilted in a second angle change from a substantially horizontal position to an angle β.

3. Method according to claim 1 or 2, wherein the angle α is between 5 and 20 degrees, preferably between 10 and 16 degrees, and wherein the angle β is between 25 and 45 degrees, preferably between 30 and 40 degrees.

4. Method according to any one of the preceding claims, wherein the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is between 0.1 and 5 m/min, preferably between 0.1 and 2 m/min, more preferably between 0.4 and 1.55 m/min.

5. Method according to any one of the preceding claims, wherein the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is constant or increasing, preferably the extraction speed is increasing during extraction.

6. Method according to any one of the preceding claims, wherein the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) is increasing in the range of 0.1 to 5 m/min, preferably in the range of 0.1 up to 2 m/min, more preferably in the range of 0.4 to 1.55 m/min.

7. Method according to any one of the preceding claims, wherein the extraction speed at which the plurality of fence panels are pulled out of the zinc bath in step (iii) increases gradually.

8. Method according to any one of the preceding claims, wherein the method further comprises the step (iv) of moving air lances between the wires of the fence panels, wherein the air lances blow air under increased pressure between the wires of the plurality of fence panels.

9. Method according to claim 9, wherein the air lances move at a speed between 5 and 40 m/min, preferably between 10 and 35 m/min.

10. Method according to any one of claims 9-10, wherein the air blown from the air lances has a pressure between 2 and 10 bar, preferably between 3 and 7 bar, more preferably between 4 and 6 bar.

11. Method according to any one of claims 9-11, wherein the air is blown from the air lances at a flow rate between 500 and 1500 m³/hour, preferably between 750 and 1250 m³/hour.

12. Method according to any one of claims 9-12, wherein the air lances move in a first direction perpendicular to the wires of the fence panels in the plurality of fence panels, preferably at a speed between 5 and 25 m/min, and then back out of the plurality of fence panels in a second direction opposite to the first direction, preferably at a speed between 20 and 40 m/min.

13. Method according to any one of the preceding claims, wherein the average zinc layer on the wires of the fence panels is between 60 and 80 mu, measured according to a gravimetric measurement in accordance with EN ISO 1460.

14. Method according to any one of the preceding claims, wherein the angle α is between 5 and 20 degrees, wherein the angle β is between 25 and 45 degrees, and wherein the fence panels are moved horizontally by at least 0.25 meters in step (ii).

15. A galvanized fence panel comprising vertical and horizontal wires,
characterized in that a zinc layer with a thickness between 50 and 200 mu is attached to the wires of the fence panel.

Drawing