JPS6254170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for heat treatment of steel wire.

High carbon steel wire generally has a coarse pearlite structure consisting of cementite and ferrite when it is hot rolled, so wire breakage may occur during subsequent wire drawing, or products manufactured by wire drawing. However, the specified high strength and toughness cannot be achieved. For this reason, it is necessary to patent the steel wire. Patenting is a method in which a steel wire is heated to an austenite region, held for a predetermined period of time, and then subjected to controlled cooling to cause pearlite transformation under conditions close to isothermal transformation, thereby obtaining a fine pearlite structure. In addition, when manufacturing wire rope strands with a diameter of 2 mm or less as a product, it is not possible to obtain the product by a single wire drawing process from a thick wire, so the wire drawing process is divided into two stages, and the In some cases, a patenting treatment is performed as well as softening annealing.

Traditionally, heating in patenting was done using a kerosene furnace,
This is done using a heavy oil furnace, a gas furnace, etc., and one of the following three methods is used for cooling.

(a) Method of cooling by immersing in a molten lead bath.

(b) A method of cooling by immersing it in a fluidized bed of metal oxide particles.

(c) A method of cooling by natural cooling in the atmosphere.

The steel wire processed by the method (a) above has excellent wire drawability, strength, and toughness.
This method can be said to be the best in terms of product quality. However, the use of molten lead in the cooling bath creates a poor working environment, and there are also problems in that wastewater treatment is time-consuming because lead is diffused through the steel wire cooling water, dust, and the like. In addition, this method inevitably causes lead to adhere to the steel wire, and this adhered lead does not fall off during the subsequent wire drawing process, and it is difficult to completely remove it even by cleaning with hydrochloric acid, sulfuric acid, etc. Therefore, it becomes a big problem when plating steel wire.

Since the method (b) above uses metal oxide particles, it generates a lot of dust, creating a poor working environment.
In addition, incidental equipment such as a dust collection device and a flow device for metal oxide particles become large-scale, and the noise generated from these devices significantly impairs the working environment. Furthermore, maintenance of these devices requires a great deal of effort and expense.

The above method (c) poses no problems in terms of working environment and pollution, but has the disadvantage that the quality of the treated steel wire is inferior.

FIG. 6 is a diagram showing the relationship between cooling characteristics and pearlite transformation in each of the above methods, where curve 11 is a pearlite transformation start curve, curve 13 is a pearlite transformation end curve, 14 is a lead bath cooling curve, and 15 is an air cooling curve. , 16 respectively show rapid cooling curves by air. In the case of cooling with a lead bath, pearlite transformation occurs at a lead bath temperature of 17.
If the lead bath temperature is set at 500 to 600°C, a fine pearlite structure will be obtained, exhibiting excellent strength and toughness. On the other hand, in the case of air cooling 15, pearlite transformation occurs only at high temperatures, and therefore a fine pearlite structure cannot be obtained. On the other hand, in the case of rapid cooling 16 with air, the starting temperature of pearlite transformation is low, but it does not intersect the pearlite transformation completion curve.
Therefore, a portion of the hard and brittle martensitic structure remains. Note that pearlite transformation is an exothermic reaction, and as the pearlite transformation progresses, the temperature of the steel wire itself increases. This phenomenon is noticeable in the air cooling curves 15 and 16. In such a case, the pearlite transformation temperature becomes partially high, resulting in a mixed structure of fine and coarse structures, which is not good in terms of quality. Therefore, the most preferable cooling method is one that immediately removes the heat generated by the exothermic reaction while maintaining the temperature of the steel wire at around 500 to 600°C.

This invention was made to solve these conventional drawbacks, and provides a method for heat treating wire rods that does not cause problems in the working environment or pollution, and can produce products of excellent quality. . That is, in the patenting process of steel wire, the steel wire is heated to austenite and transferred in the length direction, while a heat source for heating a cooling roller in a cooling furnace and a cooling roller for cooling during overheating are used in advance. The steel wire is pressed almost continuously against a plurality of roller groups maintained at a pearlite transformation temperature by a gas blowing device, the roller group undergoes pearlite transformation at approximately the same temperature, and the steel wire that has undergone pearlite transformation is continuously pulled out from the rollers. This is what I did.

Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 shows the entire process, in which the steel wire 1 taken out from the bobbin 10 is heated in a heating furnace such as kerosene gas, electricity, etc.
The steel wire is heated to the austenitic region here, and the fully austenitized steel wire is guided by guide rollers 19 and fed into the cooling furnace 3, where the outer surface of the roller group 4 is maintained at the pearlite transformation temperature. is crimped. This cools at a predetermined rate and transforms into pearlite. The steel wire 1, which is crimped to the roller group 4 until the pearlite transformation is completed, then passes through a water cooling section 5, a pickling section 6, a water washing section 51, a coating section 7, a water washing section 52, and a drying section 8 to a winding bobbin 9. It is wound up. Pickling may be carried out with 20% hydrochloric acid at 40°C, coating may be carried out with zinc phosphate, and drying may be carried out with air at 200-300°C.

As shown in FIG. 2, the roller group 4 consists of five rollers arranged in series, and the steel wire 1 is inserted into a groove on the outer circumferential surface of the roller, and the steel wire 1 is inserted into the upper right quarter of the first roller 41. circumference, the lower half circumference of the second roller 42, the third
, the lower half of the fourth roller 44 , and the upper left quarter of the fifth roller 45 . In this way, while being pressed against the outer peripheral surface of each roller and moving, heat is absorbed by the rollers and the material is cooled, thereby undergoing pearlite transformation. Then, the distance at which the steel wire 1 is pressed onto the roller so that it can be taken out from the roller after the pearlite transformation is completed is determined in relation to the moving speed of the steel wire 1. Also,
As shown in FIG. 3, a pair of rollers 46 and 47 are arranged close to each other in the direction of transport of the steel wire 1 in the cooling furnace 3, and the steel wire 1 fed into the furnace is moved between the rollers 46 and 47.
7 in the order of A→B→C→D→E→F→G→D→A and then taken out of the furnace. In this case, A→ at roller 47
The groove on the path B→C→D and the groove moving from G to D→A are two adjacent grooves. During this time, the inside of the furnace is heated by the heater 31, and the temperature inside the furnace is made uniform by the heat shield plate 32 and the stirrer 33. The roller 46 is connected to the steel wire 1 as shown in FIG.
an annular portion 61 formed with a groove 60 into which the
It consists of end plates 63 and 65 connected with bolts 64 via a heat insulating material 62 on both sides, and a rotating shaft 66 connected to the end plate 65. An air blowing pipe 68 is connected to the roller 46 through the rotating shaft 66. introduced, end plate 6
3 is formed with an air outlet 67, and furthermore, a thermocouple 69 is embedded in the annular portion 61. When the annular portion 61 reaches a predetermined temperature or higher due to the heat introduced from the steel wire 1, air is blown out from the air blowing pipe 68 to cool it down. In this way, the annular portion 61 of the roller 46 is maintained at a predetermined pearlite transformation temperature, and the steel wire 1 crimped thereto is maintained at a predetermined pearlite transformation temperature.
The steel wire 1 undergoes pearlite transformation by removing heat from the steel wire 1.

Note that the annular portion 61 may be formed of a material having better thermal conductivity than air, such as heat-resistant steel, ceramic, or carbon. Alternatively, the heater 31 may not be provided in the cooling furnace 3, but the heater may be embedded in the annular portion 61. It is also possible to create a non-oxidizing atmosphere in the cooling furnace 3. rollers 41 to 45,
47 may also have the same configuration as the roller 46 described above. Further, although only one steel wire 1 is shown in the drawing, a plurality of grooves may be formed in each roller so that a plurality of steel wires may be transferred and processed in parallel.

FIG. 5 is a comparison diagram of the properties of a steel wire treated according to the present invention and a steel wire treated by a conventional lead bath method, with lines 50 and 70 showing the elongation and tensile strength according to the present invention, and lines 60 and 80 showing the elongation and tensile strength according to the present invention. Elongation and tensile strength by conventional method are shown. In addition, 0.71% as the test material
A steel wire with a diameter of 1.5 mm and containing carbon, 0.60% Mn, and 0.23% Si was used. As is clear from this figure, the treatment method according to the present invention provides product characteristics equivalent to those obtained using a lead bath. And there is no problem of pollution or deterioration of the working environment as in lead baths, and the cooling zone can be shorter than in lead baths, and the speed of steel wire movement can be increased to improve processing speed. can.

As explained above, this invention cools the steel wire by pressing it onto the roller surface, and there is no problem of deterioration of the working environment or pollution, and the cooling rate can be controlled reliably. It is possible to obtain products of excellent quality.

[Brief explanation of the drawing]

FIG. 1 is an overall layout diagram of an apparatus for carrying out the present invention, FIG. 2 is a side explanatory view of a cooling roller, FIG. 3 is a side explanatory view showing another example of a cooling roller, and FIG.
The figure is a partial side sectional view taken along the - line in Figure 3;
FIG. 5 is a characteristic diagram of a steel wire treated according to the present invention, and FIG. 6 is a relationship diagram between a pearlite transformation curve and a cooling curve. 1... Steel wire, 2... Heating furnace, 3... Cooling furnace,
4,41~47... Laura.

Claims (1)

[Claims] 1. In the patenting process of steel wire, the steel wire is heated to austenite and transferred in the length direction, and pearlite is preliminarily used in a cooling furnace using a heat source that heats a cooling roller and a gas blowing device for cooling when overheated. A method for heat treatment of a steel wire, characterized in that the steel wire is substantially continuously pressed against a plurality of roller groups maintained at a transformation temperature, and the steel wire that has undergone pearlite transformation is continuously pulled out from the rollers.