JPS6345451B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an apparatus for cooling, quenching and tempering steel rods and wires by supplying cooling water while passing them through a tubular passage.

(Conventional technology) In direct surface hardening of steel bars and wires, following hot rolling, the surface layer of the bar and wire is heated with Ar ₃ by water jet cooling.
Rapid cooling from above the transformation temperature to below the martensitic transformation temperature. In other words, the relationship between the heat transfer coefficient αs on the surface of the rod and wire and the heat transfer coefficient αi in the inner radial direction of the rod and wire is αs>αi
Cool it so that The time from the final rolling until the start of quenching needs to be as short as possible in order to prevent coarsening of the austenite crystal grain size, so the rod or wire rod is cooled as soon as it enters the quenching device. Therefore, the quenching start position is always the same regardless of the size. On the other hand, the quenching end position is determined by the time it takes for the desired depth from the surface of the rod or wire to become below the martensitic transformation temperature, and therefore varies depending on the size.

Therefore, the amount of water drained at the end of quenching varies depending on the size, making the process complicated and difficult. Further, the rod and wire rod which has been drained after quenching is conveyed in the atmosphere between a water cooling device and a winding machine, and the surface layer portion is reheated by heat conduction from the high temperature center portion.

On the other hand, to improve weldability and ductility, the content of C and Mn must be reduced.
Furthermore, since the inclusion of alloying elements increases the cost of the material, it must be kept to the minimum necessary. The quenching time, that is, the quenching time for alloy steels with such compositions must be shortened.

The water cooling device used for cooling rods and wires as described above consists of a plurality of cooling units (cooling boxes) arranged in tandem. Each cooling unit has an annular shape and is provided with a forward direct injection nozzle or a reverse direct injection nozzle with respect to the conveyance direction of the rod or wire rod, from which cooling water is injected directly at high pressure onto the rod or wire rod.
Further, the above-mentioned draining device is arranged in the middle of the cooling unit row.

As a device for uniformly cooling the outer periphery of rods and wires, a continuous cooling jacket is disclosed in Japanese Utility Model Publication No. 19122/1983. In this device, the rod or wire is passed through a tubular passage, and cooling water is supplied from a nozzle in a direction of contact with the inner circumferential surface of the passage to form a swirling flow to cool the rod or wire.

(Problems to be Solved by the Invention) In the conventional cooling device described above, cooling water is directly injected onto the wire rod, and the tubular passage is filled with the cooling water to cool the wire rod. As a result, the following problems arose.

(1) Requires a large amount of cooling water.

(2) It is not easy to drain water after the rods and wires leave the cooling device.

(3) Due to insufficient drainage, the recuperation temperature varies widely.

(4) The transportation resistance of the rods and wires in the cooling device is large.

(Means for Solving the Problems) In the steel rod and wire cooling device of the present invention, a plurality of cooling units to which cooling water is supplied from nozzles to a tubular passage are arranged in tandem following a finishing rolling mill. . The nozzles of the cooling unit row arranged on the upstream side, where the surface temperature of the rod and wire rod is high, are direct injection nozzles toward the surface of the rod and wire rod, and the nozzles of the cooling unit row of the remaining downstream side, where the surface temperature is lower, are arranged around the inside of the passage. It consists of a swirling flow nozzle oriented tangentially to the surface.

It is desirable that the nozzles from the surface of the rod or wire rod to the cooling unit at least two stages upstream of the cooling unit where rapid cooling ends when the desired depth reaches a predetermined temperature or lower (for example, the martensitic transformation temperature) be direct injection nozzles. The nozzles in the remaining cooling unit rows are swirl flow nozzles. When the surface temperature of the rod or wire rod is below about 600°C, the nozzle of the cooling unit uses a swirl flow nozzle. The number of stages of direct injection nozzle cooling units to be used is determined by the diameter of the wire rod. Note that the diameter of the rods and wires processed by the cooling device of the present invention is 19 to 120 mm.

(Function) In the upstream cooling unit, a large amount of cooling water is supplied from the nozzle to the tubular passage so that the cooling water directly impinges on the surface of the rod and wire. The cooling water stagnates over a wide area on the surface of the rod and wire, and comes into direct contact with the surface of the rod and wire to prevent the formation of a vapor film. As a result, the heat transfer coefficient between the surface of the wire rod and the cooling water becomes high, and the wire rod is cooled with high cooling capacity.

In the cooling unit on the downstream side, the cooling water injected from the nozzle moves together with the rod and wire toward the outlet side of the cooling section while swirling around the circumferential surface of the rod and wire. During this time,
The cooling water cools the wire rod while swirling along the surface of the wire rod. If the surface temperature of the rod or wire rod falls below approximately 600°C, nucleate boiling heat transfer occurs and the heat transfer coefficient becomes extremely large. Therefore, cooling by immersion swirling flow can also achieve sufficient rapid cooling. In addition, the injected cooling water does not collide with the surface of the wire rod in a dotted manner, but swirls around the surface of the wire rod and wraps it, so that the wire rod is cooled uniformly. The cooling water sprayed from the nozzle is annular,
Since the center is hollow, the cooling water concentrates on the surface of the wire rod, and the transport resistance of the wire rod, especially at the tip of the wire rod, is small. When the wire rod leaves the cooling unit, the layer of cooling water accompanying the wire rod is separated from the surface of the wire rod by centrifugal force, and the cooling water easily flows out. In other words, even if the quenching end position changes depending on the size, since it is the area where the swirl flow nozzle is used,
Water is drained at the same time as cooling, and heat is immediately restored.

(Example) FIG. 1 shows an outline of a cooling device of the present invention. As shown in the drawings, a cooling device 3 and a winding machine 21 are disposed following the finishing mill 1.

The cooling device 3 is divided into a quenching zone 4 and a quenching and recuperation zone 5, and is composed of a plurality of cooling units 23 and 31 arranged in a row. Cooling unit 23 on the upstream side of the rapid cooling zone 4
is equipped with an annular direct injection nozzle, and the cooling units 31 in the fifth and subsequent stages are each equipped with a swirl flow nozzle. The rods and wires M running through the cooling units 23 and 31 are cooled by being supplied with cooling water from the surroundings by nozzles.

A draining device 11 is disposed approximately in the center of the cooling units 23 and 31 rows, that is, between the quenching zone 4 and the quenching and recuperation zone 5. The draining device 11 consists of a cooling water reverse injection device 12 and an air blowing device 13 adjacent to the outlet side thereof. The wire rod M that has been cooled in the quenching zone 4 and entered the draining device 11 is first subjected to a cooling water reverse injection device 12 in which the cooling water adhering to the rod or wire M is blown off by reverse injection of cooling water. Next, air blowing device 1
In step 3, the remaining adhering water is blown off with high pressure air and the surface of the rod wire is dried.

In addition, the outlet side of the draining device 11 and the winding machine 21
A quenching end temperature detector 15 and a recuperation temperature detector 17 are respectively disposed on the entry side of the quenching end temperature detector 15 and the recuperation temperature detector 17. Based on the measurement results of these temperature detectors 15 and 17, the amount of cooling water supplied by each cooling unit 23 and 31 is adjusted to cool the wire rod M at a required cooling rate.

FIG. 2 shows details of the cooling unit 23 with the annular direct injection nozzle. As shown in the drawing, the cooling unit 23 consists of an injection section 24 and a cooling section 29. In the injection part 23, a direct injection nozzle 26 made of an annular slit is formed inside a casing 25. Direct injection nozzle 26
is inclined so as to fall down to the upstream side, and is facing the wire rod M. An area near the outer periphery of the casing 25 serves as a reservoir for cooling water to be injected, and is connected to a water supply port 27 .

The cooling unit 29 has a cylindrical shape, extends horizontally from the casing 25, and has a tip open to the atmosphere.

The cooling water injected from the direct injection nozzle 23 is
The passage 30 of the cooling section 29 is filled with the cooling water, and the wire rod M is cooled while being immersed in the cooling water.

3 and 4 show details of the cooling unit with said swirl nozzle. As shown in these drawings, the cooling unit 31 consists of an injection section 32 and a cooling section 39.

The injection section 32 includes an annular nozzle block 34 inside a casing 33. The nozzle block 34 is provided with eight swirl flow nozzles 35, each nozzle 35 opening tangentially to the inner peripheral surface of the nozzle block 34. A cooling water supply pipe 37 is connected to the casing 33 . A portion near the outer periphery of the casing 33 serves as a reservoir for cooling water to be injected. The wall thickness of the nozzle block 34 is desirably 3 mm or more in order to determine the jet direction.

The cooling unit 39 has a cylindrical shape, extends horizontally from the casing 33, and has a tip open to the atmosphere. The number of swirl flow nozzles 35 is generally 2 to 8, but if the passage 40 is narrow, a smaller number is sufficient. The swirling flow nozzle 35 may be slit-shaped or hole-shaped.

The inner diameter of the tubular passage 40 is D, and the diameter of the wire rod M is d.
Then, the appropriate thickness δ of the cooling water layer based on the state without rods and wires is δ≧(1.2 to 1.6)(D−d)/2. If δ(D-d)/2, the water amount density distribution in the circumferential direction becomes non-uniform. Also, δ>(D
-d)/2, the amount of cooling water increases and the conveyance resistance of the rod and wire increases. In addition, although d/D is generally 0.3 to 0.8, it is preferable to increase d/D in order to reduce the amount of water. Adjust the amount of cooling water supplied to control the swirling flow rate and the thickness of the water layer.

It is desirable that the cooling water supply pressure is 1.2Kg/cm ² abs or more. If the supply pressure is less than 1.2 Kg/cm ² abs, a constant and stable cooling water layer cannot be formed within the passage 40. As the distance from the nozzle 35 to the drainage section at the tip of the passage increases, the supply pressure needs to be increased.

A flow rate is adjusted by a throttle valve (not shown) provided in the cooling water supply pipe 37 to adjust the thickness. The cooling water moves toward the exit side of the cooling section 40 together with the cooling M while swirling around the circumferential surface of the rod and wire M. When the wire rod M exits the cooling section 40, the cooling water accompanying the wire rod M is separated from the surface of the wire rod M due to centrifugal force, and the cooling water flows out of the cooling section 40.

(Effects of the Invention) According to the present invention, since the cooling water is supplied so as to form a cooling water layer around the rod and wire on the downstream side where the surface temperature of the rod and wire decreases, only a small amount of cooling water is required. Further, it is easy to drain water after the rod and wire leaves the cooling device, water is drained sufficiently, and variation in recuperation temperature is small. Furthermore, the cooling transport resistance within the cooling device is small.

[Brief explanation of drawings]

1 is a schematic representation of a cooling device implementing the method of the invention, FIG. 2 is a sectional view of a cooling unit with direct injection nozzles, FIG. 3 is a sectional view of a cooling unit with swirl flow nozzles, and FIG. FIG. 4 is a sectional view taken along the - line in FIG. 3. 1... Finishing rolling mill, 3... Cooling device, 4... Rapid cooling zone, 5... Quenching and recuperation zone, 7...
...Cooling unit, 11...Drainer, 12...
Cooling water reverse injection device, 13...Air blowing device, 2
1... Winder, 23, 31... Cooling unit, 2
6,35...nozzle.

Claims (1)

[Claims] 1 In a cooling system in which a plurality of cooling units are arranged in tandem following a finishing rolling mill, in which cooling water is supplied from nozzles to a tubular passage, the nozzles of the cooling unit row arranged on the upstream side where the bar and wire surface temperature is high are A steel rod comprising a direct injection nozzle directed toward the surface of the wire rod, and a nozzle in the cooling unit row on the remaining downstream side, where the surface temperature is lowered, comprising a swirl flow nozzle directed tangentially to the inner circumferential surface of the passage. Wire cooling device.