JPS6167723A - Direct heat treating and device of middle and high carbon steel wire rod - Google Patents

Abstract

PURPOSE:To transform uniformly austenite to pearlite by cooling the closed ring pitch under the specified condition after a heat rolled wire rod of middle and high carbon is coiled like a non-concentric ring and induced in a heat treating tank for controlled cooling. CONSTITUTION:A wire rod immediately after heat rolling is made into a non- concentric ring wire rod 4 in a loop player 3 and is loaded in a cooling medium 8 of a heat treating tank 7 through conveyers 5, 6. The cooling medium 8 uses about 60-100 deg.C hot water which is produced by mixing cooled water and hot water of a cooling water tank 32 and a hot water storage tank 33, and most of austenite are transformed almost uniformly into a fine pearlite structure by controlled cooling throughout the full length of a wire rod 4. Thereafter, a ring pitch of the non-concentric ring wire rod 4 is reduced to about 1/10 by the fall difference and speed difference between an upper oblique conveyer 11 and transferring out conveyer 12, held in a heat holding tank 13 while 60-300sec and the residual austenite is transformed to pearlite to send a collector 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for direct heat treatment of high carbon steel wire immediately after hot rolling.

[17f Final Technique (17) Medium-high carbon steel wire manufactured by rolling a steel billet in one heat 1;:j 4
．． In order to improve cold pressability and increase tensile strength,
Usually, before wire drawing, ll14A is puttyed/chipped to form a fine pearlite 111 weave.

The lead patenting method is the most dangerous method known.
The wire is heated to 850°C or higher to 1-450-[i50'
This is a method of processing using a cooling strip '1' in which the wire H is continuously immersed in a molten lead bath of C, and the workability and mechanical t4+ ability of the wire H formed by this method are good.

In addition, the so-called air patenting method, in which the wire is heated at a low temperature and then subjected to controlled cooling by blowing cold air onto it, is also widely used as a simple method.

However, these methods are able to
++ Since heating is performed, additional equipment and personnel are required for heating and the work, which inevitably results in high costs.

In view of this, a direct patenting method was developed in which hot-rolled high-temperature wire rods are directly controlled and cooled to produce wire rods with properties equivalent to those of the patented wire rods described in -1-. Since the 2-l-culm can be omitted and the cost of the process can be reduced, this method is also widely used.

There are various methods for this direct control cooling method, but among them, the method of cooling the rolled wire rod in 1ill water of a constant 7Qe has been evaluated as ij'f+ because of the simplicity of the equipment and the low cost of operation. ing. Unlike the case of cold water, when hot water is used for cooling, a film of water is uniformly formed on the surface of the high 1 FIA wire, resulting in the so-called film boiling phenomenon.
If direct contact between the preparation and hot water is avoided, the cooling rate is moderated, and the cooling rate is 1 m, a cooling rate suitable for direct patenting treatment can be obtained, and a wire rod with a fine pearlite structure can be obtained.

[Problems to be solved] By the way, wire rods that have not been subjected to the above treatment are subjected to electromagnetic stirring treatment to prevent center segregation during the continuous casting stage of manufacturing. However, some billets may include billets with micro-segregation.

Since the hardening rate of this micro-segregation area is extremely large, a normal controlled cooling treatment may produce a martensitic structure and result in a product with no deformation.

In addition, even for billets that do not have micro-segregation areas such as those connected to -ni, the cooling rate varies widely due to equipment and work problems, and localized overcooling causes martheno→noi I structure. Sometimes it gives rise to

[Means for solving the problem] Figure 1 shows a CCT curve (continuous cooling transformation diagram) of a high carbon steel and its segregated portion.

In the figure, PΔ indicates the austenite→pearlite start curve, and P+ indicates the austenite→pearlite finish curve.

In normal controlled cooling, the wire is cooled along the PQR. In addition, if pearlite transformation begins when P∆ passes, or if it reaches the dotted line CD without passing P∆, the metamorphosis continues to progress, and then it is cooled as it is and overcharged to the Ms point.
At this point, martensitic metamorphosis begins ÷ martensitic transformation],
When the fabric is rapidly cooled without interacting with the PA, it begins to undergo martensitic transformation and ends up as a martensitic fII weave.

While the carbon steel wire is homogeneous, a heat treatment time of 30 seconds is sufficient for patenting, but in the micro-segregation area, C, M
n is 1.2 to 2.0 times larger, and the hardenability is high, and in this case, several minutes are required for transformation.

Also, as I have already touched on, forced cooling, even if homogeneous,
Air-water cooling and hot water cooling, both of which rely on cooling in a layered non-concentric ring state, have large variations in cooling rate, resulting in local supercooling and martensitic transformation.

In the present invention, the untransformed residual austenite structure caused by such abnormal cooling or center segregation of the material is completely transformed into pearlite, and if martensitic transformation has already occurred locally, it is sufficiently sintered. This is an attempt to reduce the degree of harmfulness by adding a carbonization treatment.

When a medium to high carbon steel wire rod is immersed in hot water and subjected to direct patenting treatment, the wire material will have a hardness of 450 to 63 when it passes through the austenite → barley curve.
0°C, and the segregated portion in the medium-high carbon steel wire still remains as an untransformed retained austenite structure, but immediately after leaving the 2-layer region shown in Fig. 1, the temperature ranges from 450°C to
The transformation area for untransformed retained austenite X texture with high content of C, Mn, etc. in the 1111 segregation area (in the figure, the dotted line pL,
If the PQS preparation is followed by a path of 1.5 to 11 weaves can also be sufficiently roasted and the degree of damage can be reduced.

1111, 450°C is below this level, the austenite structure that is transforming into pearlite will not transform into the barley 1 structure, but will remain as austenite 1. Ba,
The obtained kA +111 becomes softer lA, l
It is Iz.

The time required for the transformation of the untransformed retained austenite structure into pearlite is 60 to 300 seconds, and the present invention provides the method of converting the untransformed retained austenite structure into pearlite immediately after normal controlled cooling of the medium-high carbon steel wire.
The wire rod No. 111 is maintained at a constant tNa of 450 to 30'C in the 11 degree range for 60 to 300 seconds to completely transform the structure into pearlite (austenite due to excessive cooling),
Gives a sufficient charring effect to areas where martensitic structures are already occurring! It is based on a continuous direct heat treatment method that allows for continuous heat treatment. The time limit of 1itlGo seconds required for the transformation of the untransformed retained austenite to pearlite is:
The time limit below which austenite remains is 300 seconds.
This means that it is unnecessary, and that if it were to be processed further than this, the equipment would be large and uneconomical.

Furthermore, the present invention provides direct heat treatment as described above. l! To put it simply, the ring pitch of the non-concentric ring-shaped wire H that is continuously carried out immediately downstream of a normal controlled cooling area is changed from that of the previous controlled cooling area. A heat retention tank is provided surrounding the discharge conveyor with a density of approximately l/10, and the densely layered non-concentric ring-shaped wires are heated at 450 to 630℃ while passing through the heat retention tank.
It is configured so that it can be held for 300 seconds and slowly cooled.

FIG. 2 shows an example of an apparatus for implementing the present invention.

In the figure, 1 is a hot-rolled medium-high carbon steel wire H supplied into four pieces, 2 is a pinch roller that grips the wire 1, and a loop layer 3 winds the wire 1 into a circular shape.

5 is a horizontal conveyor, and 6 is a downwardly inclined chain conveyor connected to the horizontal conveyor 5, the lower end of which is in the heat treatment tank 7. Connected to the downward inclined chain conveyor 6,
A chain conveyor 9 is provided in the heat treatment instant heat treatment tank 7, and a -14 direction inclined chain conveyor 9 is provided in a cascade pattern sequentially connected to this chain conveyor 9, and finally a 1-right inclined chain conveyor 9 is provided. A conveyor 11 is provided, and the -
The right inclined chain conveyor 11 is connected to the discharge conveyor 12.

A multi-stage cascade-shaped -1-right inclined chain conveyor 9. Each stage of the chain conveyor 9 is provided with a step, a speed difference, and a chain width difference, and a head is also provided between the 1-right inclined conveyor I■ and the carry-out conveyor 12. This makes it easy to move the non-concentric ring-shaped coil 4 from one conveyor to another and to transfer the non-concentric ring-shaped wire 4 in a high ring-pitch array on the discharge roller conveyor I2, which will be described later.

Covering the unloading roller conveyor 12, the second cross section A-A
It is configured as a heat retention tank +3 as shown in FIG. In the figure, the heat retention tank I3 is equipped with a heat retention cover and is formed so that it can be opened on one side by a lid I4,
It is equipped with a convection promoting fan 15 and a heating fan 16, and an unloading conveyor 12 passes through the lower part.

An unloading chain conveyor 17 is further provided connected to the unloading conveyor 12, and a concentrator 18 is connected to the unloading chain conveyor 17.
are provided in series.

On the other hand, in Fig. 2, 32 is a cold water tank, and 33 is a lA
1 is a water storage cypress, and 31 is a cooling tower. The cold water from the wet water storage tank 33 and the cold water tank 32 is mixed by the system pump P in the water conditioning cold water mixer 42, and is flowed into the heat treatment tank 7 from the end on the wire dipping side at a predetermined temperature, and the wire +1 draw-1 A hot water storage tank 33 is also accessed from the exposed end, a part of which is cooled by a cooling tower 31 and stored in a cold water cypress 32 .

Further, 39 is an oxidizing gas pipe for a plurality of nozzles 40 attached to the lower surface in the longitudinal direction of the heat treatment tank 7, and 41 is a bubble cutting device.

1. The refrigerant 8, which has been adjusted to a constant temperature of 60 to +00°C by the water-cooled water mixer 42, is heated to a heat-treated M17 wire.
Although it is discharged from the same direction as the front side of Dl, in this case, the flow velocity in the heat treatment tank 7 is set to be approximately the same speed as the moving speed of the wire rod 4. Further, by using the plurality of nozzles 40, oxidizing gas such as air can be blown into each position of the heat treatment tank 7. The oxidizing gas generated by the plurality of nozzles 40 is lK! This contributes to stabilizing and equalizing the cooling conditions of the wire rod 4 in a state where air and water are mixed together with water. At the same time, the partial injection of oxidizing scum from the nozzle 40 at a specific position is
It also has a turbulence effect.

The following part 1-1 is an explanation of the refrigerant supply section, but there are cases where only air is used as the refrigerant, and in such cases, the refrigerant supply section includes air nozzles for each of the blowers and heat treatment tanks. Ru.

Here, an example of implementing the present invention will be described using an oxidizing air-water multiphase fluid refrigerant in which one item of water is maintained at 60 to 100 degrees Celsius, and the air bubble content is 01 to 0.35.

The rolled medium-high carbon steel wire rod 1 at a temperature of 850° C. or higher is rolled down into a ring shape by a loop layer 3, and is transferred onto a horizontal conveyor 5 as a non-concentric ring-shaped wire rod 4 with a ring pitch of 30 to 200 n+TI. chain conveyor 6
2, the mixed fluid refrigerant transforms most of the austenite into a fine pearlite structure almost uniformly along the entire length.

Pull the refrigerant out at a predetermined 1n degree with a wire temperature of 450 to 630 degrees Celsius.
However, in this case, by utilizing the step and speed difference between the upwardly inclined chamber conveyor 11 and the discharge conveyor I2, the rings are transferred to the discharge roller conveyor +2 in a densely layered state with a ring pitch of 3 to 30 mm. . Is this /J? The ring pitch is approximately 171 degrees, which is the ring pitch during soaking. This state is shown in FIG.

As explained above, the heat retention tank 13 is configured to cover the carry-out conveyor 12, and normally, the densely layered non-concentric ring-shaped wire rods 4 are heated to a temperature of 450 to 630°C.
KJ degree range, and depending on the relationship between the length of the heat holding tank 13 and the speed of the conveyor 12, the moving wire 4 is held in the heat holding tank 13 for 60 to 300 seconds, thereby removing residual austenite. Transforms light into pearlite and does not burn out the martensite that occurs several times. The wire rod 4 comes out of the heat retention tank 13 in a slowly cooled state and is bundled by a converging machine I8.

Note that the convection promoting fan 15 is used to make the lQ degree uniform in the heat holding tank 13 [1], and the heating source 16 is used when the temperature inside the cypress is insufficient.

In order to confirm the effect of the method of the present invention, steel type 5WRH82B
Homogeneous material and segregation-retaining material of wire rods rolled to 12.0φ were subjected to controlled cooling as shown in Table 1, and their tensile strength and structure were investigated with and without heat retention treatment.

Table 1 P, Pearly Day 11 Weave M, Martensitic Structure According to the present invention, which adds heat retention treatment, martensite formation in the skin area due to localized cooling, which often occurs during moderate boiling cooling, is prevented, and segregation is maintained. In the case of paulownia wood, it is possible to prevent band-like martensite in the center.

The present invention can be applied not only to the above-mentioned hot water controlled cooling and controlled cooling using a steam/water mixed fluid refrigerant, but also to the treatment of medium to high carbon steel wire rods by blast controlled cooling using air blowing.

On the other hand, the equipment can be used even if the material is homogeneous and has only segregation.
Depending on the treatment, it can also be applied to treated wires ( ) 1 that have a partially full-tensile 1!11 weave or 11 sheaves. It can also be widely used for processing II lines.

[Effect] In continuous casting mills, center segregation is unavoidable in the product, and for this reason, the micro-segregation part with extremely high hardenability that occurs in the wire H is also heated at 500 to 600°C at about 1I'L. Te60~3
In 00 seconds, pearlite transformation occurs and becomes a fine pearlite structure, which is different from the martensitic structure.Also, even in the case of homogeneous grains, cooling strips are not necessary! (Local martensis that often arises due to variations in the quality of martensitic marten) can also be heated to produce a homogeneous product with a structure similar to that of the normal part.

[Brief explanation of the drawing]

FIG. 1 shows a continuous cooling transformation diagram of medium-high carbon steel wire +A for explaining the present invention. FIG. 2 shows an embodiment of the apparatus of the present invention. FIG. 3 is a sectional view of the heat retention tank. The 41st ring 1 is an explanatory diagram of the ring pitch difference of the wire rod 4 in the -1 one-sided inclined chain conveyor and the discharge roller conveyor. DESCRIPTION OF SYMBOLS 1... Cotton material, 2... Pinch roller, 3... Loop layer, 4... No. 1 concentric ring-shaped wire material, 5...
Horizontal conveyor, 6... Downward inclined chain conveyor, 7.
...Heat treatment tank, 8...Refrigerant, 9...Upward inclined chain conveyor, 11...-1 One side inclined chain conveyor, I
2... Carrying out roller conveyor, 13... Heat retention tank,
15... Convection promoting fan, 16... Add Q [117.
...Export chain conveyor, 18...Concentrator, 31...
・Cooling tower, 32...cold water tank, 33...l! lλ water storage tank, 39... Oxidizing gas piping, 40... Nozzle, 42
... Cold water hot water mixer. Procedure Amendment Book dated 1982/(item 1, 1 [A 11 Indication 1988 Patent Application No. 1.88838 2, Title of invention Direct heat treatment method and apparatus for medium and high carbon steel wire rods 3, Person making the amendment Representative President Kawa-1 Yu Tetsu Department 4th Elf', Person 6, Supplementary 1F S.J. Scope of Claims Column Detailed Description of the Invention Column 7 Contents of Amendment (1) Patent Claims (2) Page 15 of the specification, lines 3 to 5, “The device of the present invention
...Can be used widely. '' should be corrected to ``The apparatus of the present invention itself can be used for the heat treatment of stainless steel wire rods and general steel wire rods, as well as the treatment of medium and high carbon steel by this type of controlled cooling.'' 11+81 Claims (1) Conveyor 1. A wire rod immediately after hot rolling is processed into a non-concentric ring-shaped wire rod. While transferring the J1 concentric ring-shaped wire, controlled cooling in a refrigerant is carried out to transform most of the austenite into a fine pearlite structure almost uniformly over the entire length of the wire. ℃60
A method for direct heat treatment of medium-high carbon steel wire, characterized by holding the wire for ~300 seconds to transform residual austenite into pearlite. (2) Ring pitch of wire rod immediately after hot rolling is 30 to 200.
Formed as a concentric ring-shaped wire, after controlled cooling,
1j
Direct heat treatment method for 'il carbon steel wire H. (3) As the controlled cooling, hot water immersion ix' cooling, steam/water mixed fluid refrigerant 1Ω clean cooling, or blast cooling is used. , a direct heat treatment method for high carbon steel wire rods. (4) At least a loop layer for winding down the wire,
Said IJ! A water SL'con/a that transfers the shrine in a non-concentric ring shape, and a tilted che/co/baa that sends it to a heat treatment tank.
The processing JJll is equipped with a multi-stage cascade-like chain conveyor, a chain conveyor with one drawer per drawer, an unloading conveyor with a head and speed difference from the conveyor, and a heat holding tank covering the unloading conveyor. -) (processing equipment for steel wire rods, characterized by being equipped with a phantom t6 medium supply device. Claim 4. A heat treatment device for steel wire 4,1 of the war. (6) As a refrigerant supply device, l!1 adjusted by 1 degree.
411'AQ The straight 1i, 4il processing apparatus for steel wire H according to claim 4 or 5, characterized in that it is provided with an M water supply device and an oxidized 1'l waste supply device. ”

Claims (6)

[Claims] (1) While the wire rod immediately after hot rolling is transferred on a conveyor as a non-concentric ring-shaped wire rod, it is cooled in a controlled manner in a refrigerant so that the entire length of the wire rod is almost uniform, and most of the austenite is transformed into a fine pearlite structure. , the ring pitch of the non-concentric ring-shaped wire is made dense, and the temperature is 60-3 at 450-630°C.
1. A direct heat treatment method for medium-high carbon steel wire rod, characterized by holding the wire for 00 seconds to transform residual austenite into pearlite. (2) Ring pitch of wire rod immediately after hot rolling is 30 to 200.
Formed as a non-concentric ring-shaped wire of mm, after controlled cooling,
A direct heat treatment method for high carbon steel wire according to claim 1, characterized in that the ring pitch is 3 to 30 mm. (3) Direct cooling of the high carbon steel wire rod according to claim 1 or 2, characterized in that hot water immersion cooling, air/water mixed fluid refrigerant immersion cooling, or blast cooling is used as the controlled cooling. Heat treatment method. (4) At least a loop layer for winding down the wire,
a horizontal conveyor that transports the wire in a non-concentric ring shape;
It is equipped with a downwardly inclined chain conveyor for sending to a heat treatment tank, a multi-stage cascade chain conveyor and an upwardly inclined pull-out chain conveyor in the heat treatment tank, a carry-out conveyor having a head and a speed difference from the conveyor, and a heat holding tank covering the carry-out conveyor, A heat treatment apparatus for medium-high carbon steel wire, characterized by comprising a refrigerant supply device for the heat treatment tank. (5) A heat treatment apparatus for high carbon steel wire according to claim 4, characterized in that the heat holding tank is equipped with a convection promoting fan and a heating source. (6) A direct heat treatment device for high carbon steel wire rods as set forth in claim 4 or 5, characterized in that a temperature-controlled hot water supply device and an oxidizing gas supply device are provided as refrigerant supply devices. .