Description

Technical Field

[1 ] The invention relates to an elongated zinc coated steel wire for flexible carding clothing.

Background Art

[2] In the production of textiles, the fibres shall be arranged in a uniform state, i.e. uniform density and uniform thickness, and the impurities shall be removed. This is so-called carding process done by means of flexible card clothing.

[3] Flexible card clothing, i.e. flexible fillet, comprises small needles which are set into resilient and multi-ply fabric foundation. The small needles are made of steel wires bent into a II shape and provided with a knee. During the carding process, the needles of the flexible card clothing bend when being subjected to a load and return to their original position when the load disappears.

[4] The steel wire for making the flexible card clothing is coated with zinc coating for corrosion resistance. In case the steel needles are corroded, the strength of the steel needles is reduced because of the iron oxides on the surface of the steel needles, so that the steel needles are weakened and thereby can’t provide the sufficient strength for carding, and this may cause the failure of the needles during the carding process.

[5] The steel wire is also required to have high tensile strength and high bending performance for prolonging the lifetime of the flexible card clothing, and in particular, during the making of flexible carding clothing and the carding process, the high bending performance is beneficial for reducing the risk of wire breaking.

[6] Normally the steel wire for the flexible carding clothing is an oil quenched and tempered steel wire. The oil quenched and tempered steel wire has a tempered martensite microstructure. For the oil quenched and tempered steel wire, the wire drawing process and the oil quenching and tempering process are prior to the zinc coating process, so that the final steel wire has a matte and rough surface, and this may lead to the fiber holding problems of the flexible card clothing, the fiber holding problems cause the worse performance of carding process. And if the oil quenched and tempered steel wire has a tensile strength higher than 2000MPa, it becomes relatively more brittle during the zinc coating process, so that the risk of wire breaking is increased, while the bending performance of the steel wire is merely acceptable.

[7] Chinese Standard YBT056/94 discloses a zinc coated oil quenched and tempered steel wire for carding. This Standard discloses the zinc coated oil quenched and tempered steel wire has a tensile strength of no more than 2060MPa for round steel wire or a tensile strength of no more than 2210MPa for shaped steel wire.

[8] There is still a demand to develop a steel wire with excellent performance for flexible carding clothing.

Disclosure of Invention

[9] The object of the invention is to provide an elongated steel wire with high performance for flexible carding clothing.

[10] Another object of the invention is to provide an elongated steel wire with high tensile strength and better bending performance.

[11 ] According to the aspect of the invention, an elongated steel wire is provided, the elongated steel wire comprises a steel filament and a zinc coating covering the steel filament, the elongated steel wire having a tensile strength of more than 2200MPa, and the elongated steel wire has a bending performance of at least 25 bending times.

[12] The invention provides an elongated steel wire with high tensile strength, high corrosion resistance and improved bending performance. This is beneficial for the lifetime of the flexible carding clothing.

[13] Preferably, the elongated steel wire has a bending performance of at least 30 bending times. More preferably, the elongated steel wire has a bending performance of 35 to 55 bending times.

[14] According to the invention, the elongated steel wire has a metal microstructure of drawn sorbite. This means the elongated steel wire is a cold drawn steel wire without oil quenching and tempering treatment. For the manufacturing of the elongated steel wire, the zinc electroplating process is in between the wire drawing steps, i.e. , the final drawing step which is for reaching the target tensile strength by a series of drawing dies is after the zinc electroplating process. The surface of the elongated steel wire is bright and smooth, and this reduces the fiber holding problems of the flexible card clothing. And during the zinc electroplating process, the tensile strength of the steel filament is not very high, and thereby the concentration of the residual stress is reduced, and the hydrogen embrittlement of steel filament is reduced, as a result the steel wire brittle problem is reduced, and the bending performance of the steel wire is improved.

[15] The “elongated” steel wire means the steel wire is fine and long. The elongated steel wire has a diameter of less than 1 ,5mm. Preferably, the elongated steel wire has a diameter of less than 0.5mm, and preferably no less than 0.15mm.

[16] The elongated steel wire is a single steel wire, and the “steel filament” according to the invention is a bare steel filament without any coating, i.e., steel substrate.

[17] Preferably, the elongated steel wire has a straightness of no more than 80mm/1 m. More preferably, the elongated steel wire has a straightness of no more than 70mm/1 m. Most preferably, the elongated steel wire has a straightness ranging from 5 to 60 mm/1 m. With the improved straightness, the needles made of the elongated steel wire are easy to be accurately embedded into the fabric foundation during the production of the flexible card clothing.

[18] Preferably, the elongated steel wire has a tensile strength of more than 2300MPa, and preferably no more than 3200Mpa, for example 2600- 3000MPa.

[19] The zinc coating of the elongated steel wire is a thin coating, and it has a thickness of no more than 10p.m. Preferably, the zinc coating of the elongated steel wire has a thickness of no more than 6pm.

[20] The elongated steel wire can be any type of the existing steel wire for flexible card clothing. The elongated steel wire has a cross-section showing round, biconvex, ovoid, triangle, egg-shaped, diamond or flat. [21 ] According to the invention, a method for making an elongated steel wire is provided. The method comprises the steps: a) providing an elongated steel wire comprising a steel filament and a zinc coating covering said steel filament, said elongated steel wire having a tensile strength of more than 2200Mpa; b) making said elongated steel wire being subjected to a heating treatment, said heat treatment including a first heating at a first predetermined temperature of 100 to 300 °C for 10 to 20 seconds with a first heating up speed of 1 to 3 seconds from an environment temperature to that first predetermined temperature, and a second heating at a second predetermined temperature of 250 to 400 °C for 30 to 40 seconds with a second heating up speed of 1 to 3 seconds from an environment temperature to that second predetermined temperature.

[22] Preferably, step a) comprises a sub step: a1 ) straightening said elongated steel wire by multiple straighteners including at least one spiral straightener.

[23] With the use of straighteners particular the spiral straightener, the elongated steel wire has better straightness.

[24] The heat treatment in step b) makes the bending performance of the elongated steel wire being improved, while the straightness of the elongated steel wire is maintained.

[25] An elongated steel wire is for the textile, such as the flexible card clothing.

Brief Description of Figures in the Drawings

[26] Figure 1 describes the measurement of the straightness of the steel wire.

Mode(s) for Carrying Out the Invention

[27] The manufacturing of the elongated steel wire can be made from a wire rod.

[28] The wire rod is firstly cleaned by mechanical descaling and I or by chemical pickling in a H2SO4 or HCI solution in order to remove the oxides present on the surface. The wire rod is then rinsed in water and is dried. The dried wire rod is then subjected to a first series of dry drawing operations in order to reduce the diameter until a first intermediate diameter. [29] At this first intermediate diameter d1 , e.g., at about 2.30 to 3.50 mm, the dry drawn steel filament is subjected to a first intermediate heat treatment, called patenting. Patenting means first austenitizing until a temperature of about 1000 °C followed by a transformation phase from austenite to pearlite at a temperature of about 580 to 650°C. The steel filament is then ready for further mechanical deformation.

[30] Thereafter the steel filament is further drawn from the first intermediate diameter d1 until a second intermediate diameter d2 in a second number of diameter reduction steps. The second diameter d2 typically ranges from 1.0 mm to 2.00 mm.

[31 ] If the total reduction in the first and second dry drawing step is not too big a direct drawing operation can be done from wire rod till diameter d2.

[32] At this second intermediate diameter d2, the steel filament is subjected to a second patenting treatment, i.e. , austenitizing again at a temperature of about 900 to 1000 °C and thereafter quenching at a temperature of 500 to 600 °C to allow for transformation to sorbite.

[33] The steel filament is then galvanized, as thus a zinc coating is applied on the steel filament with a thickness of no more than 10pm, or even no more than 6p.m.

[34] The zinc coated steel filament is subject to the final drawing step for the final diameter d3 and final tensile strength. The final diameter d3 is typically less than 1 .50 mm, or even less than 0.50mm. The final tensile strength is more than 2200MPa, or even more than 2300MPa. Thus, an elongated steel wire is obtained, and it has a metal microstructure of drawn sorbite. The steel filament is carbon steel filament. The carbon content of the steel filament is preferably higher than 0.20% by weight, more preferably ranging from 0.50% to 1 .2%, most preferably ranging from 0.6% to 1 .1 %. The higher the carbon content, the higher the tensile strength. Besides the carbon content, the steel filament comprises one or more other elements, for example, silicon, preferably ranging from 0.10 % to 2.5 %, more preferably ranging from 0.15 to 1 .60 %; manganese, preferably ranging from 0.10 % to 2.0 %, more preferably ranging from 0.50 to 0.90 %; chromium, preferably ranging from 0.0 % to 2.0 %, more preferably ranging from 0.10 % to 1.50 %; vanadium, preferably ranging from 0.0 % to 2.0 %, more preferably ranging from 0.05 % to 0.60 %; tungsten, preferably ranging from 0.0 % to 1.5 %, more preferably ranging from 0.1 % to 0.70 %. The rest is iron and unavailable impurities. Besides the above elements, the other common elements known in the art can also be included in the steel composition. The above contents are calculated by weight. Optionally, the elongated steel wire is drawn and rolled with a nonround shape, e.g., flat, diamond, biconvex, triangle, ovoid, egg-shape and etc., and the non-round steel wire has an equivalent diameter less than 1 .50 mm, or even less than 0.5mm, in such as case, the equivalent diameter of the non-round steel wire is deemed as the diameter of the elongated steel wire. The elongated steel wire is straightened by multiple straighteners, for example a spiral straightener and the multiple common straighteners, as a result, the straightness of the steel filament is improved.

[35] The elongated steel wire is then subjected to a heat treatment for improving the bending performance, including a first heating at a first predetermined temperature of 100 to 300 °C for 10 to 20 seconds with a first heating up speed of 1 to 3 seconds from an environment temperature, i.e. , no more than 45°C for example -10°C to 45°C to that first predetermined temperature, and a second heating at a second predetermined temperature of 250 to 400 °C for 30 to 40 seconds with a second heating up speed of 1 to 3 seconds from an environment temperature, i.e., no more than 45 °C for example -10°C to 45°C, to that second predetermined temperature. The heating up speed can’t be very high, otherwise the zinc coating may be damaged. The specific heat treatment makes the bending performance of the steel filament being improved. The first heating and the second heating are two separate heating processes. The straightness of the elongated steel wire is maintained.

[36] Table 1 summarizes the comparison data.

[37] Table 1

[38] It is clear that the invention steel wire has better bending performance and the straightness. [39] The Bending performance is measured according to Chinese Standard

GB/T238 - 2002. The tensile strength is measured according to GBT228.1 -2021.

[40] Figure 1 illustrates the principle for measuring the straightness of steel wire: firstly, take about 1.1 meter length steel wire; secondly, fix one end A of the steel wire, let the steel wire fall naturally, set the base point C at a vertical distance of 1 m from the end A; thirdly, measure the horizontal distance from C to the steel wire, this horizontal distance is the straightness of the steel wire expressed in mm/1 m. Make sure the another end B of steel wire being fixed during the measurement.