Description

Technical Field

[1] The invention relates to a straight stainless steel wire and its manufacturing method. The invention also relates to a flexible card clothing comprising the needles made of the straight stainless steel wire.

Background Art

[2] In the production of textiles, a carding process is for arranging the fibres in a uniform state, i.e. uniform density and uniform thickness, and removing impurities. This can be done by means of flexible card clothing.

[3] Flexible card clothing, i.e. flexible fillet, comprise small needles which are set into resilient and multi-ply fabric foundation. The small needles are made of steel wires bent into a U 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. The steel wires for the flexible card clothing are usually very hard.

[4] The steel wire for making a flexible card clothing is required to have a certain 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 can’t provide the sufficient strength for carding, and this may cause the failure of the needles during the carding process.

[5] Therefore, a steel wire with good corrosion resistance is desired for making the flexible card clothing.

[6] WO0231239 discloses a flexible card clothing, wherein the carding needles are formed from a metal wire, especially stainless steel wire. The stainless steel wire provides a strong performance on corrosion resistance. However, there are some problems in practice, such as the needles are easy to be bent during the carding process so that the lifetime of the flexible card clothing is very short, or the needles are not possible to be embedded into the fabric foundation or the needles are embedded out of the desired position. Disclosure of Invention

[7] The primary object of the invention is to solve the problem of the prior arts.

[8] Another object of the invention is to provide a straight stainless steel wire with high tensile strength for flexible card clothing.

[9] A third object of the invention is to provide a method for making the invention stainless steel wire.

[10] According to one object of the invention a stainless steel wire is provided, the stainless steel wire has a tensile strength of more than 1950MPa, and the stainless steel wire has an arc height of less than 60mm/m. The unit of arc height “mm/m” means the arc height is measured with a gauge length of 1m.

[11] The invention improves both the straightness and the tensile strength of the stainless steel wire. With the improved straightness, the needles made of the invention stainless steel wire are easy to be accurately embedded into the fabric foundation during the production of the flexible card clothing. With the higher tensile strength, the needles will not bend during the carding process, and thereby the lifetime of the flexible card clothing is improved. The invention realizes a straight stainless steel wire with high tensile strength.

[12] Preferably, the stainless steel wire has an arc height of less than 40mm/m. More preferably, the stainless steel wire has an arc height ranging from 2 to 30 mm/m. The lower the arc height value, the better the straightness of the stainless steel wire.

[13] Preferably, the stainless steel wire has a high tensile strength of more than 2000MPa. More preferably, the stainless steel wire has tensile strength of more than 2100MPa. Even the stainless steel wire has a tensile strength up to 3200MPa.

[14] According to the present invention, the stainless steel wire has a yield ratio, i.e. the ratio of yield strength to tensile strength, of more than 80%, and this improves the flexibility of the needles made of stainless steel wire and thereby reduces or even prevents the bending of the needles during the carding.

[15] The stainless steel wire is a circular wire or a shaped wire, i.e. the stainless steel wire has a circular cross-section or a shaped cross-section such as triangular, flat or quadrangular cross-section. The stainless steel wire has a diameter of less than 1 mm for circular stainless steel wire or an equivalent diameter of less than 1mm for shaped stainless steel wire.

[16] The present invention is relating to the stainless steel wire. The stainless steel wire has a chromium of at least 12% in weight.

[17] The stainless steel wire is an austenitic stainless steel wire, a martensitic stainless steel wire, a duplex stainless steel wire or a precipitation hardening stainless steel wire. The austenitic stainless steel wire comprises carbon of 0.01 %-0.15%, manganese of 7.5%-10%, chromium of 17%-19%, nickel of 4%-6%, molybdenum of 0.01 %-0.9%, aluminium of

0.1%-0.48% and nitrogen of 0.01%-0.39%. Alternatively, the austenitic stainless steel wire comprises carbon of 0.01 %-0.15%, manganese of 0.5%-2.0%, chromium of 16%-19%, nickel of 6%-9.5%, molybdenum of 0.01 %-0.8%, aluminium of 0.1%-0.48% and nitrogen of 0.01%-0.39%. As another embodiment, the austenitic stainless steel wire comprises carbon of 0.01%-0.08%, manganese of 0.7%-2.0%, chromium of 17%-19%, nickel of 8%-10%, molybdenum of 0.01%-0.8%, aluminium of 0.1%-0.48% and nitrogen of 0.01%-0.39%. The precipitation hardening stainless steel wire comprises carbon of 0.05%-0.10%, manganese of 0.1 %-1.5%, chromium of 14%-18%, nickel of 3%-8.5%, molybdenum of 0.01 %-0.8%, aluminium of 0.7%-1.5% and nitrogen of 0.01 %-0.39%. The martensitic stainless steel wire comprises carbon lower than 0.15%, manganese lower than 1.0%, chromium of 12.0-14.0%, nickel lower than 1.0% and molybdenum lower than 0.3%. The duplex stainless steel wire comprises carbon lower than 0.03%, manganese lower than 2%, chromium of 21 %-24.5%, nickel of 1.0%-6.5%, molybdenum of 0.05%-3.5%, and nitrogen of 0.08%-0.26%. The above amounts of the ingredient content are the percentage in weight. The rest ingredients are the normal ingredients with the normal level for an austenitic stainless steel wire, a martensitic stainless steel wire, a duplex stainless steel wire or a precipitation hardening stainless steel wire.

[18] According to another object of the invention, a method for making a stainless steel wire is provided, and the method comprises the following steps: a) drawing the stainless steel wire until a predetermined diameter and tensile strength; b) straightening the stainless steel wire by the straightener; c) heating the stainless steel wire at a predetermined temperature of 450 to 1200 °C for 20 to 30 seconds with a heating up speed of 5 to 10 seconds from room temperature to said predetermined temperature; d) taking up the stainless steel wire.

[19] Preferably, in step c) the predetermined temperature is 650-1200°C. The higher predetermined temperature for heating will be beneficial for achieving a lower arc height of stainless steel wire within the short heating time.

[20] The temperature for heating the stainless steel wire can be adjusted depending on the composition of the stainless steel wire to optimize the effect. [21] A use of the invention stainless steel wire is for the flexible card clothing or other existing applications of a stainless steel wire.

Mode(s) for Carrying Out the Invention

[22] Prepare an austenitic stainless steel wire rod.

[23] The stainless steel wire rod is firstly cleaned by mechanical descaling and / or by chemical pickling in a nitric acid solution in order to remove the oxides presenting on the surface. A salt coating is then applied on the stainless steel wire rod as a soap carrier. The stainless steel wire rod is then rinsed in water and is dried. The dried stainless steel wire rod is then subjected to a first series of drawing operations in order to reduce the diameter until a first intermediate diameter.

[24] At this first intermediate diameter, the drawn stainless steel wire is subjected to a first intermediate heat treatment. The stainless steel wire is then ready for further mechanical deformation.

[25] Thereafter the stainless steel wire is further drawn from the first intermediate diameter until a second intermediate diameter in a second number of diameter reduction steps. At this second intermediate diameter, the stainless steel wire is subjected to a second heat treatment. [26] Thereafter the stainless steel wire is further drawn from the second intermediate diameter until a final diameter in a third number of diameter reduction steps. The final diameter is less than 1 mm. More than the circular stainless steel wire, the stainless steel wire can also be a non circular shape made by rolling and drawing or by profile drawing, e.g. flat, rectangle, double convex, triangle, egg-shape or rhombus. The non circular wire, i.e. the shaped wire, has an equivalent diameter of less than 1 mm. The stainless steel wire with a final diameter has a tensile strength of more than 1950MPa.

[27] Then the stainless steel wire is subjected to a straightening process by the straightener to have a straight stainless steel wire. The straightener could be the existing straightener for straightening the wire in the field. And then the stainless steel wire is heated at a predetermined temperature of 450 to 1200°C for 20 to 30 seconds with a heating up speed of 5 to 10 seconds from room temperature, i.e.0-35°C, to the predetermined temperature. The heating can be done by a heating furnace. The heating up speed reduces the impact from heating to the tensile strength of the stainless steel wire while maintaining the straightness of the stainless steel wire, as thus, this heating up speed contributes to consolidate the tensile strength of the stainless steel wire after drawing and the straightness after straightening. Even though the stainless steel wire is finally wound on a spool and rewound for further processing such as processing a flexible card clothing, the straightness of the stainless steel wire is substantially not impacted or eliminated. If the heating up speed is too quick, the arc height of final stainless steel wire will be increased; and if the heating up speed is too slow, the tensile strength of the final stainless steel wire will be decreased. In addition, if heating time is too long, i.e., more than 30 seconds, the tensile strength of the final stainless steel wire will be decreased.

[28] Finally, a stainless steel wire is taken up on a spool or a coil with a length more than several thousand meters or even more than ten thousand meters.

[29] The stainless steel wire has a tensile strength of more than 1950MPa and an arc height of less than 60 mm/m. [30] The invention provides a measurement of the arc height of the stainless steel wire. The principle of the measurement of the arc height of the stainless steel wire is the same as the principle of the arc height measurement method of steel cord as described in GB/T 33159-2016, while there are two parameters of the measurement of the arc height of the stainless steel wire different from the arc height measurement method of steel cord as described in GB/T 33159-2016: first, the length between the two pins of the stainless steel wire arc height measurement device is 1000mm, and this is the gauge length, and as thus the arc height value is recorded with a unit of “mm/m” for easy understanding; second, the length of the stainless steel wire sample is 1200mm.

[31] Table 1 summarizes the comparison data.

[32] Table 1 [33] “Processing ability” means if the needles made of the stainless steel wire can be embedded into the fabric foundation in the desired position, i.e. accurate embedding. Accurate embedding is deemed as “OK”, otherwise is “NOK”.

[34] “Flexible card clothing lifetime” means the effective carding time of a flexible card clothing. The effective carding time of at least 2880 hours is deemed as “OK”, otherwise is “NOK”.

[35] From the table 1 , it is clear that the invention stainless steel wire with high tensile strength and improved straightness has better performance on the processing ability and the flexible card clothing’s lifetime.