JP5035296B2 - Steel wire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a steel wire.

  The following technique is disclosed regarding the manufacturing method of a steel wire or a copper wire.

  Patent Document 1 states that “a foreign material such as rolling oil and lubricant adhering to a steel wire by wire drawing, rolling, etc. is heated to a temperature of 400 to 600 ° C. by a heating furnace such as a fluidized bed and incinerated, followed by quenching and tempering treatment. The technique regarding the surface cleaning heat treatment method of the steel wire used as the final product is disclosed.

  Patent Document 2 states that “at least, in the method for producing a precipitation-strengthened copper alloy trolley wire having a solution treatment step, a cold working step, and an aging heat treatment step, the lubricant used last in the cold working step is 140. A technique relating to a method for producing a precipitation-strengthened copper alloy trolley wire, which is a solid lubricant composed only of an organic component that decomposes at ˜700 ° C. is disclosed.

JP-A-9-87738 JP 2003-237427 A

  FIG. 1 is a flowchart showing an example of a conventional method of manufacturing a steel wire coil, FIG. 2 is a diagram showing a pickling process, and FIG. 3 is a diagram showing a continuous annealing process.

  As shown in FIG. 1, high-carbon chromium bearing steel or steel wire products used for cold forging are subjected to annealing on hot-rolled wire rods and removing oxide scale by pickling or shot blasting. Then, intermediate wire drawing is performed, the lubricant adhering to the intermediate wire drawing is removed by pickling, and the intermediate stage steel wire that has been work hardened by intermediate wire drawing is softened and annealed again, followed by pickling and lubricating coating treatment. After being applied, it is often manufactured by adjusting the dimensional accuracy and hardness to satisfy customer specifications by finish drawing.

  In the method of manufacturing a steel wire shown in FIG. 1, in addition to the need to perform wire drawing and annealing twice each, pickling is also performed three times, so that the process is complicated and the manufacturing cost increases. Has a point.

In any pickling, for example, as shown in FIG. 2, the pickling process is performed by immersing the steel wire coil 1 in the pickling tank 4 in a state where the steel wire coil 1 is suspended from the C hook 3. After the pickling treatment, for example, as shown in FIG. 3, the steel wire coil 1 is placed in a vertical position (how to place the coil so that the central axis of the coil is substantially vertical. The furnace 2 (a batch type annealing furnace may be used) is charged, preheated in the preheating chamber, and then annealed in the annealing chamber. At this time, the annealing in the annealing chamber is performed while controlling the ratio of the CO amount and the CO ₂ amount in the annealing furnace atmosphere in order to suppress the formation of a decarburized layer or a carburized layer on the surface of the steel wire.

Here, in the intermediate wire drawing, wire drawing is performed while applying a lubricant mainly composed of metal soap and slaked lime immediately before the die, and the surface of the steel wire coil 1 after the intermediate wire drawing is subjected to the above-described process. Lubricant adheres and remains. Attempting to anneal the steel wire coil 1 as it is (that is, the route (a) in FIG. 1), the metal soap in the lubricant burns to generate carbon-containing gas such as CO _2, so the atmosphere in the annealing chamber It becomes difficult to control the ratio of the amount of CO and the amount of CO ₂ therein. Further, when the lubricant remaining on the surface of the steel wire is excessive, the coefficient of friction between the rings becomes small, and coil collapse is likely to occur during annealing. In order to cope with this, a method of suppressing the collapse of the load by using the inner stem is conceivable, but the workability is deteriorated and the manufacturing cost such as the production and management of the stem itself is increased.

  In order to avoid this problem, it is necessary to pickle and remove the lubricant adhering to the steel wire surface before annealing the steel wire coil along the route (b) in FIG. However, in this method, the metal surface of the steel wire after pickling is exposed. For this reason, as shown in FIG. 3, when the steel wire coil 1 after pickling is placed vertically into the continuous annealing furnace 2, there is a problem that the steel wire is crimped by its own weight. Therefore, in order to prevent crimping of the steel wire during annealing, the steel wire after intermediate wire drawing is pickled and further coated with slaked lime on the surface (that is, the route (c) in FIG. 1) and then annealed. Had to do.

  In the above pickling process, soap debris contained in the lubricant is generated, and costs are required for waste acid treatment and the like. Moreover, since the use of an acid has a high management load in the work environment, there is an advantage that the manufacturing cost can be reduced if it can be omitted.

  Patent Document 1 does not specifically disclose what kind of lubricant is used. In addition, this technology does not heat the final steel wire after it has been made into the dimensions and shape required for the final product of oil tempered steel wire for springs, but continuously heats the steel wire in the state of the steel wire coil. It is preheated and hardened and tempered while running, and it does not heat treat the coiled steel wire. Even if this technique is applied to a steel wire coil after intermediate wire drawing, there is a possibility that crimping may occur between the steel wires of the steel wire coil annealed in a vertically placed state.

  The technique of patent document 2 decomposes | disassembles a solid lubricant simultaneously when carrying out the aging heat treatment at 350-550 degreeC not the steel wire but the trolley wire of a copper alloy. Unlike aging heat treatment of copper alloy at 350 to 550 ° C, annealing of steel wire at 600 to 800 ° C causes a phenomenon of decarburization or carburization, so the steel wire with a solid lubricant attached can be used as it is in a soft annealing furnace. Cannot be charged.

  The present invention solves such a problem, and is performed between the steel wires and the pickling for removing the wire drawing lubricant that has been performed between the intermediate wire drawing and the soft annealing. An object of the present invention is to provide a method of manufacturing a steel wire that can omit the application of slaked lime to prevent crimping and is less likely to cause collapse of the steel wire coil.

  In order to solve the above-mentioned problems, the inventors of the present invention, in order to stabilize the atmosphere in the annealing furnace, pickle a substance that generates a carbon-containing gas in a temperature range of 800 ° C. or less as a wire drawing lubricant. Based on the basic policy of drawing using a lubricant that can be removed by other methods, we conducted intensive research.

  As described above, when the wire drawing lubricant is completely removed, crimping occurs between the rings of the steel wire coil, but when the remaining amount of the wire drawing lubricant is excessive, load collapse occurs during annealing. . For this reason, when selecting a wire drawing lubricant, it has sufficient lubricity during wire drawing, but during annealing, the steel wire coil is in a thin film state to prevent crimping between the rings of the steel wire coil. It is necessary for the material to remain on the surface and to lose its lubricating action in order to prevent collapse of the load.

  As the wire drawing lubricant, the present inventors (1) stably maintain high lubricity at the wire drawing temperature, but (2) most of the wire is thermally decomposed in the preheating step (pre-annealing step). (3) At the start of annealing, a small amount of lubricant remains on the surface of the steel wire, but during annealing, a material that hardly generates carbon-containing gas is used. (4) Preheating conditions suitable for such a lubricant It was decided to adopt.

  In order to further investigate the thermal decomposition performance of the lubricant at the wire drawing temperature, the preheating temperature, and the annealing temperature, the inventors focused on the mass reduction rate of the lubricant obtained from the following formula (A), and further As a result of the investigation, the conventionally used lubricant (Kyoeisha Chemical Co., Ltd./Koshin S550) has a good mass reduction rate of 1% at 200 ° C., but the mass reduction rate at 400 ° C. is about 20% and is annealed. The mass reduction rate at 600 ° C. is also as low as about 31%. As a result, it is expected that a large amount of carbon-containing gas is generated in the annealing furnace.

The mass reduction rate R _m (%) is the following based on the change in mass when heated at a heating rate of 10 ° C./min from room temperature to T ° C. in the atmosphere using a thermogravimetric measuring device (TGA). (A).
R _m = (M ₀ −M _T ) / M ₀ × 100 (%) (A)
However, the meaning of each symbol in the formula (A) is as follows.
M _T : mass at temperature T (mg)
M ₀ : mass (mg) before heating (room temperature)

  The present inventors arranged various lubricants on the market from the viewpoint of mass reduction rate at 200 ° C., 400 ° C. and 600 ° C., and found a lubricant for wire drawing suitable for the production of steel wire coils. Completed the invention.

  The present invention is “a steel wire drawn using a lubricant having a mass reduction rate of 75% or more at 400 ° C. and 97% or less at 600 ° C. when heated at a heating rate of 10 ° C./min in the atmosphere. And a steel wire coil obtained by winding up the steel wire is charged into a continuous annealing furnace in a vertically placed state, followed by preheating in an oxidizing atmosphere in a temperature range of 400 to 600 ° C. The gist of the method is a method of manufacturing a steel wire, which includes a step of annealing in a temperature range of 600 to 800 ° C. ”.

  According to the present invention, sufficient lubrication performance is exhibited at the time of wire drawing, generation of carbon-containing gas is prevented at the time of annealing, and neither crimping nor collapse of the steel wire coil occurs. Moreover, since the pickling process and the slaked lime application process which were conventionally performed between the wire drawing process and the annealing process can be omitted, the manufacturing cost can be greatly reduced. In particular, since the pickling process that requires considerable care in handling can be omitted, the working environment can be greatly improved.

Flow diagram showing an example of a conventional method of manufacturing a steel wire coil Diagram showing pickling process It is a figure which shows a continuous annealing process. Flow diagram illustrating a method of manufacturing a steel wire coil according to the present invention It shows a temporal change of the measured value of CO ₂ concentration in the annealing chamber when the steel wire coil according to Comparative Example 2 Following the steel wire coil according to Comparative Example 1 was charged into a continuous annealing furnace It shows a temporal change of the measured value of CO ₂ concentration in the annealing chamber when the steel wire coil according to the present invention Example 1 Following the steel wire coil according to Comparative Example 1 was charged into a continuous annealing furnace

  The method of manufacturing a steel wire coil according to the present invention includes a step of drawing a steel wire by using a lubricant, and a continuous annealing of the steel wire coil obtained by winding the steel wire in a vertically placed state. It includes a step of charging in a furnace and performing preheating in a preheating chamber in a temperature range of 400 to 600 ° C., followed by annealing in an annealing chamber in a temperature range of 600 to 800 ° C.

  FIG. 4 is a flow diagram illustrating a method for manufacturing a steel wire coil according to the present invention. As shown in FIG. 4, in the method for manufacturing a steel wire coil according to the present invention, for example, the wire material after hot rolling is annealed (this annealing may be omitted), and pickling or shot. After removing the oxide scale by blasting, intermediate wire drawing is performed, the steel wire coil is preheated, the intermediate stage steel wire work hardened by intermediate wire drawing is softened and annealed again, and then pickling Lubricant coating is applied and finish drawing is adjusted to dimensional accuracy and hardness that satisfy customer specifications.

  Since the above-mentioned problems occur in the annealing after the intermediate wire drawing, the following description will mainly describe the intermediate wire drawing and the subsequent annealing. However, the present invention is applicable to any process in which annealing is performed after the wire drawing. The manufacturing method of a steel wire coil is applicable. Further, preheating and softening annealing can be carried out continuously using, for example, an annealing furnace shown in FIG. 3. In this case, a door, a purge chamber, and a purge chamber are provided between the preheating chamber and the annealing chamber. It is preferable to use a door provided with an independent atmosphere in each compartment.

  The preheating atmosphere needs to be an oxidizing atmosphere in order to thermally decompose the wire drawing lubricant, but an air atmosphere is desirable because there is no need to control the amount of gas.

Preheating is performed in a temperature range of 400 to 600 ° C. When the preheating temperature is less than 400 ° C., the wire drawing lubricant cannot be sufficiently pyrolyzed, and in the subsequent annealing, a large amount of carbon-containing gas is generated, and the amount of CO and CO _{2 in} the atmosphere of the annealing chamber Makes the control of the ratio difficult. On the other hand, if the preheating temperature exceeds 600 ° C., the thermal decomposition of the wire drawing lubricant proceeds too much, and the residual amount of lubricant on the surface of the steel wire decreases, and crimping occurs between the rings of the steel wire coil during subsequent annealing. To do. Further, if the preheating temperature exceeds 600 ° C., a decarburized layer may be formed on the surface of the steel wire due to the preheating oxidizing atmosphere. Accordingly, the preheating is performed in the temperature range of 400 to 600 ° C.

  The preheating time is not particularly limited, but it is preferably 3 to 30 minutes. If it is less than 3 minutes, the temperature of the coil will not increase sufficiently. On the other hand, if it exceeds 30 minutes, decarburization may occur at the maximum temperature (600 ° C.).

  Annealing is performed in a temperature range of 600 to 800 ° C. If it is less than 600 degreeC, a steel wire cannot fully be softened. On the other hand, if the annealing temperature becomes too high, only the fuel cost becomes high, and even if it exceeds 800 ° C., there is no particular effect. Therefore, the annealing is performed in the temperature range of 600 to 800 ° C.

  Although there is no restriction | limiting in particular in annealing time, It is preferable to carry out in 600-1800 minutes. If it is less than 600 minutes, the steel wire may not be sufficiently softened. If the annealing time is too long, only the fuel cost is increased.

The wire drawing lubricant is a mass reduction rate when heated at a heating rate of 10 ° C./min from room temperature to T ° C. in the atmosphere using a thermogravimetric measuring device (TGA), that is, from the following formula (A). The required mass reduction rate R _m (%) is required to be 75% or more at 400 ° C. and 97% or less at 600 ° C.
R _m = (M ₀ −M _T ) / M ₀ × 100 (%) (A)
However, the meaning of each symbol in the formula (A) is as follows.
M _T : mass at temperature T (mg)
M ₀ : mass (mg) before heating (room temperature)

  The mass reduction rate at 200 ° C. is preferably 10% or less. If it exceeds 10%, the lubricating effect is reduced by frictional heat during wire drawing, seizure with the die is likely to occur, and the amount of lubricant consumed increases.

Here, when the mass reduction rate at 400 ° C. of the wire drawing lubricant is less than 75%, the residual amount of the lubricant in the preheating step is excessive, and a large amount of carbon-containing gas is generated in the subsequent annealing step, It will disturb the annealing atmosphere. Therefore, most of the lubricant can be removed by performing preheating in a temperature range of 400 to 600 ° C. using a wire drawing lubricant having a mass reduction rate of 75% or more at 400 ° C. Therefore, the control of the ratio between the CO amount and the CO ₂ amount in the atmosphere of the subsequent annealing chamber is not hindered.

  When the mass reduction rate at 600 ° C. of the wire drawing lubricant exceeds 97%, the amount of lubricant remaining on the surface of the steel wire at the start of annealing decreases, and crimping is performed between the rings of the steel wire coil in the subsequent annealing process. Will occur. Accordingly, as the wire drawing lubricant, one having a mass reduction rate by heating of 75% or more at 400 ° C. and 97% or less at 600 ° C. is used.

  In order to confirm the effect of the present invention, a wax-based lubricant (Kyoeisha Chemical Co., Ltd./Kashin U-100) as a lubricant of the present invention example, and a soap + slaked lime mixed lubricant (Kyoeisha Chemical Co., Ltd./Koshin S550) as a lubricant of a comparative example. And prepared. The mass reduction rate due to heating of the lubricant of the present invention in the atmosphere (temperature increase rate: 10 ° C./min) is 2% at 200 ° C., 80% at 400 ° C., and 96% at 600 ° C. On the other hand, the mass reduction rate due to heating of the lubricant of the comparative example in the atmosphere (temperature increase rate: 10 ° C./min) is 1% at 200 ° C., 20% at 400 ° C., and 31% at 600 ° C.

  Subsequently, the 17.0 mmφ SCr435H wire coil was drawn using the above wax-based lubricant (Kyoeisha Chemical Co., Ltd./Kashin U-100) to produce a plurality of 14.2 mmφ steel wire coils. 1 steel wire coil.

  Similarly, a wire coil of 17.0 mmφ SCr435H was drawn using the above-mentioned soap + slaked lime mixed lubricant (Kyoeisha Chemical Co., Ltd./Koshin S550) to produce a plurality of 14.2 mmφ steel wire coils. A wire coil was used. A part of the steel wire coil according to the comparative example was immersed in 11% by mass of sulfuric acid for 5 minutes, and then applied with slaked lime to prevent crimping between the steel wires during the subsequent annealing, and Comparative Example 1 (with pickling) ) Steel wire coil. The balance of the steel wire coil according to the comparative example was the steel wire coil of Comparative Example 2 (without pickling).

  First, the steel wire coil of Comparative Example 1 (with pickling) was continuously charged into a continuous annealing furnace, and then the steel wire coil of Comparative Example 2 (without pickling) was continuously loaded into a continuous annealing furnace. Then, preheating in the preheating chamber and annealing in the annealing chamber were performed. Next, the steel wire coil of Comparative Example 1 (with pickling) was continuously charged into a continuous annealing furnace, and then the steel wire coil of Invention Example 1 was continuously charged into a continuous annealing furnace. In the same manner, preheating in the preheating chamber and annealing in the annealing chamber were performed. These results are shown in FIG. 5 and FIG.

  Preheating was performed at 550 ° C. for 10 minutes, and annealing was performed at 760 ° C. (maximum temperature) for 720 minutes.

5 and 6 show the results of measuring the CO ₂ concentration in the annealing chamber of each continuous annealing furnace. In these figures, the inlet side portion of the annealing chamber is divided into four zones (each zone contains three steel wire coils), and Z1, Z2, Z3, and Z4 from the inlet side of the annealing chamber are referred to as CO in each zone. _Two concentration measurements are shown. In addition, the measured values of each graph change while moving up and down like a wave. This is because the steel wire coil is moved by the opening and closing of the door provided between the preheating chamber and the annealing chamber. It is the fluctuation of the CO ₂ concentration when it is moved into the annealing chamber. That is, the fluctuation of the CO ₂ concentration when one steel wire coil moves into the annealing chamber corresponds to one wave.

As shown in FIG. 5, even when Comparative Example 1 with pickling is charged into an annealing furnace, the CO ₂ concentration in the annealing chamber of the annealing furnace is hardly changed, but Comparative Example 2 without pickling is used as an annealing furnace. It is understood that the CO ₂ concentration in the annealing chamber of the annealing furnace rises rapidly when it is inserted into the furnace, making it difficult to control the furnace atmosphere. On the other hand, as shown in FIG. 6, in Example 1 of the present invention, the CO ₂ concentration in the annealing chamber of the annealing furnace hardly changed.

  Subsequently, in order to confirm the load collapse prevention performance in the annealing furnace, the invention example 1 and the comparative examples 1 and 2 after the annealing were slid 5 times, the load: 3 kgf, the sliding with the Bowden test machine. The friction coefficient was measured under the conditions of length: 2 mm and steel ball size: 2φ. As a result, the respective friction coefficients μ were 0.38 for Invention Example 1, 0.30 for Comparative Example 1 (with pickling), and 0.20 for Comparative Example 2 (without pickling). Comparative Example 1 had a low coefficient of friction due to slaked lime applied to prevent crimping between steel wires after pickling, and Comparative Example 2 had the lowest coefficient of friction because a large amount of lubricant remained after annealing. On the other hand, in Example 1 of the present invention, the lubricant was thermally decomposed by preheating, and only a small amount of the lubricant remained after annealing, so that the friction coefficient was the highest. Therefore, according to this invention, it is excellent also in the load collapse prevention effect of a steel wire coil.

  Next, with respect to the invention example 1 and the comparative example 1, it was confirmed by visual observation whether or not the lower 30 turns in each coil after annealing were crimped. Further, in Comparative Example 1, the application of slaked lime after pickling was omitted as a steel wire coil of Comparative Example 3, and annealed in the same manner as Invention Example 1 and Comparative Example 1 in the above-described continuous annealing furnace, It was confirmed by visual observation whether or not the lower 30 turns of the coil after annealing were crimped. As a result, in Comparative Example 3, crimping was confirmed with 75% of the coils, but in the inventive example and Comparative Example 1, crimping was not confirmed in all the coils. Therefore, according to the present invention, it was also confirmed that excellent anti-crimping performance can be obtained without applying slaked lime that had to be applied when the drawing lubricant was removed by pickling.

  According to the present invention, sufficient lubrication performance is exhibited at the time of wire drawing, generation of carbon-containing gas is prevented at the time of annealing, and neither crimping nor collapse of the steel wire coil occurs. Moreover, since the pickling process and the slaked lime application process which were conventionally performed between the wire drawing process and the annealing process can be omitted, the manufacturing cost can be greatly reduced. In particular, since the pickling process that requires considerable care in handling can be omitted, the working environment can be greatly improved.

1. 1. Steel wire coil 2. Annealing furnace C hook4. Pickling tank

Claims (1)

  A step of obtaining a steel wire by drawing using a lubricant having a mass reduction rate of 75% or more at 400 ° C. and 97% or less at 600 ° C. when heated at a heating rate of 10 ° C./min in the air; The steel wire coil obtained by winding this steel wire was charged in a continuous annealing furnace in a vertically placed state, pre-heated in an oxidizing atmosphere in a temperature range of 400 to 600 ° C., and subsequently 600 to 800 ° C. The manufacturing method of the steel wire characterized by including the process of annealing in the temperature range.

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