JPH0557334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low-temperature heat treatment apparatus for wire coils, that is, a baking apparatus.

(Prior Art) Generally, high-strength steels and the like that are highly susceptible to cracking have a problem of delayed fracture. This is a phenomenon in which diffusible hydrogen in steel concentrates in stress concentration areas and is destroyed due to hydrogen embrittlement. As a countermeasure to this problem, a low-temperature heat treatment called baking treatment is performed to release the diffusible hydrogen in the steel. For example, high-tensile bolts are baked at 150-200°C in a special heat treatment furnace after forming to prevent delayed fracture. As described above, for final products, a technique for preventing delayed fracture by baking treatment after processing has been established.

For example, Utility Model Application No. 56-122002, Utility Model Application No. 56-122002,
Publication No. 122003 describes a hot air generator as a heat generation source. The purpose of this is to divide air into one or two directions via a fan built into the jet heater, and use it to prevent overheating of the combustion tube and the front half of the housing, or to use it as secondary air for combustion. It is something.

(Problem to be solved by the invention) However, despite the problem of delayed fracture in the wire coils that are the raw materials for these final products, there is no technology to uniformly and efficiently heat-treat the wire coils at low temperatures. , no baking process was performed. If the baking temperature is too high compared to the target temperature, the strength of the steel material will decrease, and if it is too low, diffusible hydrogen will be difficult to release, so although the target temperature varies depending on the steel type, in any case is also limited to a relatively narrow range. Therefore, conventional continuous heat treatment furnaces are not suitable for two reasons: several hours are required to uniformly heat-treat a tightly wound wire coil at low temperatures, and the amount of wire produced through hot rolling is large. Using a batch heat treatment furnace or a batch heat treatment furnace would require an enormous amount of equipment, making it impractical. Therefore, there has been a desire for an inexpensive and simple device that can uniformly and low-temperately heat-treat a large amount of wire coils at once.

(Means for Solving the Problem) The present invention comprises a cover with a hot air blowing port that collectively surrounds a plurality of wire rod coils piled up in a yard, and a hot air generator that supplies hot air from the hot air blowing hole into the surrounding area of the cover. This is a wire rod coil yard baking device characterized by the following configuration. Arranging the hot air inlet in the axial direction of the piled wire coils,
It is preferable to provide an outer cylinder near the hot air outlet of the hot air generator through a spacer so that outside air can be sucked in.

(Function) The wire coil is surrounded by a cover and hot air is blown in from the hot air inlet provided in the cover, so that the heat (hot air) supplied to heat and hold the wire coil is radiated directly into the atmosphere. In order to prevent this and to evenly heat the piled wire coils, we create positive pressure inside the cover to prevent cold air from entering.
This is to keep the ambient temperature around the coil constant. Here, the cover may be one that directly surrounds the coil or may be one that surrounds the coil at a certain distance.

The amount of hot air blown (the amount of heat input) is preferably 4,500 to 5,000 kcal/Th per ton of coil, considering that the temperature rise of the wire coil is controlled by convective heat transfer.

If the hot air inlet is placed in the axial direction of the piled wire coils, hot air will be supplied to the inner cylinder of the wire coils on the lower side of the piled coils and to the space created between the dirt floor and the wire coils, making it appear as if hot air were flowing inside a duct. In this way, the hot air easily reaches even the wire coil located farthest from the heat source. The hot air blowing speed v at this time may be set to v/1≧0.5 (m/s, m), where the distance to the target arrival position of the hot air is 1. Further, it is preferable to install a plurality of hot air blowing ports in order to uniformize the atmospheric temperature inside the cover.

Further, the hot air inlet is preferably installed at the lower part in order to effectively utilize the hot air draft, and the hot air outlet is also preferably installed at the lower part where the blown hot air is not short-circuited to the outlet.

When hot air is blown from both sides of the cover in the axial direction of the wire coil, the target position is the center of the cover in the axial direction of the wire coil. At this time, the hot air currents inside the cover collide in the space near the center of the cover, increasing the pressure in the space, and the hot air is forcibly discharged in the radial direction of the wire coil, so that the entire coil is uniformly heated. In addition, when blowing hot air only from one side of the cover, the end wire coil on the opposite side of the hot air inlet is at the target position, and the space here is slightly narrowed to suppress the hot air from blowing through and reduce the pressure in the space. By forcing hot air to flow in the radial direction of the wire coil, the atmospheric temperature inside the cover is kept uniform, and the wire coil can be heated evenly.

As an energy saving measure, it is also possible to use the discharged hot air as combustion air or as circulating gas to the heat generator, and this is done by providing a duct from inside the cover to the heat generator.

Further, it is also possible to make the cover surrounding the wire coils variable as appropriate by dividing the cover into sizes corresponding to the amount of wire coils.

Furthermore, the device of the present invention is not only capable of baking wire coils placed on the dirt floor of a yard, but also has a fixed structure with a cover that can be opened by sliding it back and forth, and a crane or carrier etc. It is also possible to insert a wire coil into the container, surround it, and bake it.

(Example) FIG. 1 shows an example of the present invention. A plurality of wire rod coils 1 piled up in a yard are surrounded by a heat-resistant cover 2, a hot air generator 4 is set in a hot air blowing port 3 provided in the cover 2, hot air is blown into the cover 2, and the wire rod coils 1 are surrounded by a heat-resistant cover 2. Heat and retain. FIG. 2 is a cross-sectional view in the axial direction of the coils, and the wire coils 1 at room temperature are arranged in a line, and in this embodiment, the kerosene combustion gas discharge flow rate of the hot air generator 4 is attached to both sides of the cover in the axial direction of the coils. Using the ejector effect, outside air is sucked in and diluted, and the hot air is blown into the cover 2 at a temperature of approximately 160°C, where it is heated and held.

Usually, for yard baking, an easy-to-operate and inexpensive hot air generator such as a jet heater is used as a hot air generator. However, the temperature of the hot air at the outlet of the heater varies depending on its combustion capacity, and is often too high for the desired baking temperature, so that it cannot be used as is. Therefore, as shown in FIG. 4, in order to lower the temperature of the primary hot air 11 blown out from the jet nozzle 8 of the hot air generator 4, a necessary number of spacers 9 are inserted into the outer shell 14 near the jet nozzle 8 to reduce the temperature of the primary hot air 11. 10 is installed, outside air is sucked from the outside air suction port 13 using the jet flow of the primary hot air 11, and the primary hot air 11 is
The secondary hot air 12 is diluted and the temperature is lowered, and the secondary hot air 12 is supplied into the cover 2. Note that the outer cylinder 10 may be made slidable to adjust the amount of outside air sucked.

75 coils were placed on the concrete dirt floor of the yard via a wooden stand 7, and on top of that were 60 coils and a total of 135 coils (total weight approximately 140 tons) piled up in two tiers of PC steel wire coils. As shown in FIGS. 1 and 2, it was completely surrounded by a heat-resistant sheet cover 2. Next, the hot air generators 4 shown in FIG. 4 are placed in the hot air inlets 3 provided at both ends of the coil axis of the cover 2, and then the hot air generators 4 are operated one after another to blow secondary hot air into the cover. Approximately after the start of operation
Baking was completed in 390 minutes. At this time, the fuel (kerosene) consumption was 550, the outer surface temperature of cover 2 was about 55℃, and the thermal efficiency of the baking device was about 42℃.
It was %.

The wire coil temperature at that time is shown in Fig. 2, A, B,
Measurements were taken at points a to f in FIG. 1 using the coil located on line C. The temperature distribution of each coil is as shown in Figure 3, the target temperature of the PC steel wire is 80 to 120℃ (heating time
390 minutes). In addition, 5 of a to f
The point that showed the highest temperature value among the points was point e on the lo line, and on the contrary, the point that showed the lowest temperature value was point f on the ha line.

In this way, the target baking temperature could be satisfied by performing low-temperature heat treatment using the baking apparatus of the present invention.

The gas to be blown is generally fuel combustion gas, but inert gas such as N ₂ gas or reducing gas can also be used.

Furthermore, although a jet heater is used as the hot air generator in this embodiment, hot air generated from other heating equipment can also be used.

(Effects of the Invention) As explained above, the present invention is a yard baking apparatus for wire rod coils that can heat-treat a large amount at one time compared to conventional continuous heat treatment furnaces or batch-type heat treatment furnaces, and reduces the equipment cost and operation. It is inexpensive and anyone can easily make it anywhere as long as they have a large space. Furthermore, baking with this device completely eliminates troubles caused by hydrogen embrittlement of the wire coil.

[Brief explanation of drawings]

Fig. 1 is a diagram of an embodiment of the present invention as viewed from the coil radial direction, Fig. 2 is a sectional view similarly seen from the coil axis direction, and Fig. 3 is a wire coil baked using the embodiment of the present invention. A diagram showing the temperature history of
FIG. 4 is a diagram showing an example of a hot air generator used in the apparatus of the present invention. 1... Wire coil, 2... Cover, 3... Hot air inlet, 4... Hot air generator, 5... Inner cylinder, 6...
Space created between the earthen floor and the wire coil, 7... lint stand, 8... spout, 9... spacer, 10...
Outer cylinder, 11...Primary hot air, 12...Secondary hot air, 1
3...Outside air suction port, 14...Outer enclosure.

Claims (1)

[Scope of Claims] The present invention is characterized by being composed of a cover with a hot air blowing port that collectively surrounds a plurality of wire coils piled up in one yard, and a hot air generator that supplies hot air from the hot air blowing hole into the surrounding area of the cover. Yard baking equipment for wire rod coils. 2. The wire coil yard baking apparatus according to claim 1, wherein the hot air inlet is arranged in the axial direction of the piled wire coils. 3. The wire rod coil yard baking apparatus according to claim 1, further comprising an outer cylinder provided in the vicinity of the hot air outlet of the hot air generator to allow outside air to be sucked through a spacer.