JPH0416246B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing stainless steel fibers, particularly stainless steel long fibers having a diameter of 20 μm or less. (Prior art and its problems) When producing stainless steel fibers, especially long fibers with extremely fine cross-sectional areas such as diameters of 20 μm or less, the conventional method is to bundle multiple thin stainless steel wires and cold-draw them ( (Focused wire drawing method) was used. This focused wire drawing method is more efficient than the cold drawing method for single wires because multiple wires are subjected to area reduction processing at the same time. It is necessary to perform annealing heat treatment several times, and in particular, when obtaining fibers of 20 μm or less, it is necessary to repeat the convergence process many times, resulting in lower overall productivity and higher manufacturing costs. . As a countermeasure to this problem, a method has been developed to manufacture stainless steel fibers by combining area reduction processing with hot rolling.A typical method is to hot extrude a billet with a stainless steel interior and a carbon steel exterior. - There is a method of rolling and drawing a composite wire, inserting a large number of these composite wires into a steel pipe to make a billet, and subjecting it to hot extrusion and cold wire drawing after rolling. Since this method can achieve a large reduction in area during the hot rolling process, it has the advantage of greatly simplifying the process compared to the cold converging wire drawing method. However, this method uses a steel pipe with a carbon content of 0.01 to 0.02 wt% as an internal separator to prevent stainless steel from adhering to each other during hot area reduction processing, which reduces the cost of the separator and the carbon content. There is a problem in terms of reducing the content, and when the composite wire obtained by hot processing after insertion is assembled and hot processed again, the exterior separator is a regular steel pipe with a carbon content of 0.1 to 0.4 wt%. Since the carbon from the separator is used and hot-worked again during the manufacturing process, it is unavoidable that the carbon in the separator diffuses into the stainless steel, which causes the fibers in the outer layer of the tow to undergo significant carburization and become brittle. In addition, wire breakage (fuzzing) and strength reduction occur due to a decrease in corrosion resistance, and tows with uniform properties cannot be obtained in the same cross section, resulting in a decrease in yield. For these reasons, the conventional methods have not been able to efficiently and inexpensively produce high-quality stainless steel fibers that are virtually free from the adverse effects of carburization. (Means for Solving the Problems) The present invention attempts to solve the above-mentioned problems in the production of conventional stainless steel long fibers, and its purpose is to take advantage of the advantages of combined hot rolling. At the same time, it reliably prevents the embrittlement and strength reduction of stainless steel caused by hot rolling, and has properties such as good strength without fraying, and in particular, almost uniform and good quality in all parts of the same cross section of the tow. The purpose of the present invention is to provide a method for inexpensively mass producing stainless steel fibers having the following properties. In order to achieve the above object, the present inventors conducted repeated research and experiments and found appropriate conditions for obtaining stainless steel long fibers using hot rolling in combination. First, as a measure to prevent carburization from separators, it is insufficient to simply specify the carbon content of interior materials; it is extremely important to control the carbon content of exterior materials. Even if the interior material is made of ultra-low carbon steel, if the exterior material has a large amount of carbon, carbon may be transferred indirectly from the exterior material to the stainless steel through the interior material during hot rolling of the bundled wire. This is because it spreads. Therefore, it is necessary to suppress the carbon content of the sheathing material to a value lower than that of the stainless steel wire. The next condition is the interior material, and the carbon content is 0.01wt.
%, carburization is likely to occur due to the action of carbon solid solution energy during the hot rolling process. Therefore, it is suitable that the carbon content of the interior material is extremely small, such as 0.008wt% or less, and with this carbon content, the carbon solid solution capacity of the interior material is large even in hot rolling of bundled wire rods as described above. Therefore, it is possible to reliably prevent carbon from diffusing into stainless steel. Furthermore, it is appropriate that the interior material be used in the form of a strip rather than a tube (sheath), and that the starting material be a material coated in combination with stainless steel that has been expanded to the state of a wire. In addition to reducing costs by using thin steel plates as separators, which can easily be made to have extremely low carbon and are cheaper than small-diameter steel pipes, this method also reduces carburization through multiple hot rolling steps. This is to avoid it as much as possible. For example, if a billet of stainless steel and a tube of ultra-low carbon steel are used as starting materials, hot working, including hot extrusion, will be performed at least four times, and carbon content regulations must be met. Since there are limits to this, there is a great risk of carburization occurring. However, the feature of the present invention is that a stainless steel wire material is coated with an ultra-low carbon steel strip with a carbon content of 0.008wt% or less to obtain a composite wire material, and a large number of the composite wire materials are coated with a stainless steel wire material. Insert into a low or extremely low carbon steel pipe with a carbon content lower than that of the wire material, hot-roll it, then repeat cold wire drawing and annealing to make the wire thinner, and chemically remove both of the above carbon steels. It is in. (Example) Examples of the present invention will be described below based on the accompanying drawings. Figures 1 to 3 show the manufacturing method of stainless steel fibers according to the present invention in the order of steps, with a diameter of 20 μm.
In order to obtain the following stainless steel long fibers, the present invention first uses stainless steel wire material 1 and a C content as starting materials.
An ultra-low carbon steel strip 2 of 0.008 wt% or less is used, and the stainless steel wire material 1 is continuously coated with the ultra-low carbon steel strip 2. The stainless steel wire material 1 generally has an outer diameter of 3 because it is suitable for hot rolling, reduces the number of times it is rolled, and is easy to insert into the sheath in the convergence process.
A value of about mm or less is appropriate. The material is SUS316,
SUS316L, SUS304L, etc. are used, but it is more preferable to use a steel type in which Ti and Nb are added alone or both. This is because the embrittlement and corrosion resistance of stainless steel due to carburization phenomenon is caused by the Cr in stainless steel and carburized carbon precipitating as Cr carbide, but by adding Ti and Nb, These elements have a strong affinity for carbon and preferentially form carbides, eliminating the generation of Cr carbide due to carburization, and combining with the amount of C in the interior and exterior materials to more reliably produce high-quality stainless steel fibers. It is. One feature of the present invention is that the ultra-low carbon steel strip 2 is used as the interior material, and its C content is 0.008 wt% or less. This material can withstand hot rolling temperatures of 1100℃ or higher and is easy to remove by chemical dissolution.It also works with the exterior material to reliably prevent carburization when hot rolled into bundled wire material in the subsequent process. This is because, in order to achieve this, it is necessary to have at least the carbon content at the above value. Furthermore, since it has excellent workability such as malleability, it can be easily brought into close contact with the stainless steel wire material 1 even in the cold to the point of interfacial bonding, and it is also cheaper and more easily available than steel pipes. By coating this steel strip with linear stainless steel, the number of hot rolling operations can be reduced, thereby ensuring an improvement in the area reduction rate and at the same time preventing the intervention of carburization. . The stainless steel wire material 1 can be coated with the ultra-low carbon steel strip 2 in one continuous step using a single-head wire drawing machine, a die, or the like. Figures 2 and 3 I to H illustrate this process. The ultra-low carbon steel strip 2 is first continuously bent as shown in Figure 3 A, and at the same time a stainless steel wire is attached to the center. A shaped material 1 is fed. Next, as shown in FIG.
2 is reduced in diameter while being shifted in phase in the radial direction, and then the steel strip ends 21 and 22 are wound around the stainless steel wire material 1 in such a manner that they overlap each other as shown in FIG. 3D. This completely prevents stainless steel from adhering to each other during hot rolling. In the method of converging and winding a large number of stainless steel wire materials, it is impossible to avoid fusion of the stainless steel members. Note that, if necessary, pressure may be applied so that the cross section becomes a perfect circle as shown in FIG. 3E, and this step facilitates processing in subsequent steps. Moreover, when the ultra-low carbon steel strip 2 is thin, double coating may be performed. Through the above steps, a composite wire material 3 is obtained, in which the interior is made of stainless steel and the outer layer is made of ultra-low carbon steel with a stable C content of 0.008 wt% or less. This composite wire material 3 is appropriately wound into a coil shape using a winder, or is loaded into a straightening/cutting machine as it is, and is cut into a predetermined length (for example, 3 to 5 m). A large number of composite wire members 3' cut to a specified length are then inserted into a steel pipe 8 as an exterior material and hot rolled. In this process, the present invention provides steel pipes for exterior use.
A feature is that a low to extremely low carbon steel pipe with a lower carbon concentration than the stainless steel wire material 1 is used. Conventional stainless steel fiber manufacturing methods that combine hot rolling have only considered carburizing the interior material into stainless steel, but in reality, the process of hot rolling with the bundled composite wire material and the subsequent annealing process Carburization occurs, and this accounts for a fairly large proportion. This is because the exterior steel pipe is welded to the interior material of the outer layer during hot rolling, and the carbon contained in the exterior steel pipe is transferred to the interior material and diffused, which increases the amount of carbon in the interior material, resulting in an interfacial bonding condition. As a result, the fibers that make up the outer layer of the tow are carburized, causing breakage and significant strength loss due to embrittlement and deterioration of corrosion resistance, and the overall strength of the tow. The chemical composition has a considerably increased carbon content compared to the starting point. According to the present invention, since the carbon content of the exterior steel pipe 8 is lower than that of the stainless steel wire material 1, the absolute concentration of carbon that diffuses into the interior material during hot rolling of the bundled composite wire material or during post-process annealing treatment is small. and,
The interior material is coated on the stainless steel wire material 1 during cold rolling, so it is kept in a normal state with a carbon content of 0.008wt% or less, and in the hot rolling process, the outer diameter of the starting material is already small. Therefore, the conditions are relatively easy. Therefore, the carburization from the exterior steel pipe 8 to the interior material is extremely slight, and even if carburization occurs, the carbon concentration of the interior material is still significantly lower than that of the stainless steel wire material 1. Therefore, carburization of the fibers due to hot rolling or annealing treatment is extremely reduced in both the center and outer layers. There are no special conditions for hot rolling, and after inserting the composite wire material 3' into the exterior steel pipe 8, it is sufficient to perform appropriate overlay welding on the end face or weld a dummy material and pass it until it reaches a predetermined diameter. The hot-rolled bundled composite body 9 is then subjected to cold wire drawing and annealing treatment to thin the wire to the desired diameter, and the interior and exterior materials of the obtained fine wire 10 are dissolved and removed using a chemical agent in a known manner. The target diameter is 20 μm.
The following stainless steel long fiber tow 11 is obtained. In addition, in the above-mentioned hot rolling and cold wire drawing, the C content of the interior material and the exterior material are in a similar relationship, and the physical properties such as malleability are similar and good, so there is no undue restraint effect, and stainless steel has the side effect of being uniformly distracted. Next, details of the present invention will be described. Example 1 Stainless steel wire material of SUS316 with an outer diameter of 2.0 mmφ (C: 0.017%, Si: 0.61%, Mn: 1.64%, P:
0.031%, S: 0.005%, Cr: 17.53%, Ni:
A decarburized steel strip (C: 0.003%, Mo: 2.09%) with a thickness of 0.4 mm and a width of 11 mm was used as the interior material.
Mn: 0.3%, Si: 0.21%, P: 0.011%, S:
0.012%) and was coated continuously using a single-head wire drawing machine to create a composite wire material with an outer diameter of 2.9 mmφ. This was straightened and cut to a standard length of 3m, and then used as an exterior material for an ultra-low carbon steel tube with an outer diameter of 114mmφ, a wall thickness of 8mm, and a length of 3m (C: 0.013%, M: 0.4
%, Si: 0.22%, P: 0.010%, Si: 0.015%)
A hot-rolled specimen was produced by inserting 914 pieces into the specimen. Next, this is rolled on a hot rolling line to reduce the outer diameter.
A wire rod of 1050 m containing many fine stainless steel wires of 5.5 mmφ was obtained. The outer diameter of the stainless steel thin wires included in this wire material is approximately 108μ, and ultra-low carbon steel is interposed between each thin wire. This wire rod was cold drawn to an outer diameter of 2.0 mmφ, then annealed at 950°C, and then made into a thin wire with an outer diameter of 0.41 mmφ using a cold wire drawing machine. A fiber bundle (tow) consisting of 914 8μ stainless steel fibers was obtained by dissolving and removing the fibers. The fibers in the center and outer layers of this tow were taken out separately and subjected to carbon analysis. Table 1 shows the results.

[Table] As is clear from Table 1, the fibers of the present invention are less carburized, so the carbon content is 0.03% or less even in the outer layer, which satisfies the component specifications of SUS316L. The tow was made of high-quality stainless steel fibers with no fiber breaks in the outer layer and uniform strength in the same cross section. For comparison, the interior material was the same as above, and the exterior material was a low carbon ordinary steel pipe with a carbon content of 0.11%.
When stainless steel fibers were produced under the same conditions, there were many breaks in the outer layer of the tow, and the strength was greatly reduced. The carbon content of the fiber is as shown in Table 1 Comparative Method 1, and the carbon content of the outer layer fiber is 0.13%.
It can be seen that carburization from the exterior material is significant. Furthermore, for comparison, the carbon content is 0.08% as an interior material.
Stainless steel fibers were manufactured under the same conditions using steel strips and low carbon steel pipes with a carbon content of 0.11% as the exterior material. In this case, there were many disconnections throughout all the fibers in the outer layer and center of the tow, making it difficult to take out the tow as a continuous fiber bundle. The amount of carbon in the fiber is the first
This is shown as Comparative Method 2 in the table, and it can be seen that all the fibers were significantly carburized. Example 2 SUS347, which is Nb (niobium) added steel, was used as the stainless steel wire material. The component is C: 0.02
%, Si: 0.41%, Mn: 1.72%, P: 0.025%,
S: 0.003%, Ni: 9.86%, Cr: 18.88%,
Nb: 0.56%. A stainless steel fiber tow was produced from the stainless steel wire material in the same process as in Example 1. This tow also had no fiber breaks and was excellent in appearance and quality. (Effects) According to the present invention as described above, it is possible to improve the area reduction rate, which is an advantage of hot rolling, and at the same time eliminate the deterioration of quality and properties due to the carburization phenomenon, which is a problem, and thereby prevent wire breakage. This provides the excellent effect of easily and inexpensively producing high-quality stainless steel long fibers with uniform strength.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing the stainless steel fiber manufacturing process according to the present invention, FIG. 2 is a perspective view showing the composite linear material manufacturing process according to the present invention, and FIG. It is a sectional view showing a state change. 1... Stainless steel wire material, 2... Ultra-low carbon steel strip, 3... Composite wire material, 8... Exterior steel pipe.

Claims (1)

[Claims] 1. In order to obtain stainless steel long fibers, a stainless steel wire material is coated with an ultra-low carbon steel strip having a carbon content of 0.008wt% or less to obtain a composite wire material, and a large number of this composite wire material is The wire is inserted into a carbon steel tube with a lower carbon content than the stainless steel wire material, hot rolled, and then cold drawn and annealed repeatedly to make the wire thinner, and both carbon steels are chemically removed. A method for producing stainless steel fiber. 2. The method for producing stainless steel fibers according to claim 1, wherein a material to which Ti and Nb, or both, are added is used as the stainless steel wire material.