JPH02104442A - Horizontal continuous casting method for metal pipe - Google Patents

Abstract

PURPOSE:To prevent excess pushing-out force of molten metal to a product by setting the molten metal charging quantity into a holding furnace, which a pouring hole into a mold is set to the standard level so as to come to smaller than the value corresponding to yield load of a cast pipe at the temp. just after drawing from the mold. CONSTITUTION:The yield strength in the part having low strength at high temp. just after drawing from the mold device 13, is obtd. Further, the molten metal charging quantity before starting drawing or at the time of supplying the molten metal is controlled so as to come to smaller than the value corresponding to the yield load. By this method, it can be prevented to come to the excess static pressure of the molten metal acting to the pouring hole 12. That is, it is prevented to come to excess pushing-out force of the molten metal to the product and in this result, it is prevented that the cast pipe 14 is bent to low strength side or the buckling is developed or this is produced accompanied with uneven thickness.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for horizontal continuous casting of metal tubes.

[Prior art] Regarding the horizontal continuous casting method of metal tubes, Japanese Patent Application Laid-open No.
As described in Japanese Patent No. 4255, a molding device is disposed at the pouring port of a molten metal holding furnace, the molten metal is cooled in this molding device to form a cast tube, and this casting tube is drawn and cast by a drawing device.

By the way, in the horizontal continuous casting method for metal tubes as described above, it is necessary to manufacture the product metal tubes without bending or buckling and with uniform wall thickness.

[Problem 8 to be solved by the invention] However, when casting a metal tube, since the core is inside the molten metal cast in the #I# type, the cooling rate differs in the vertical and horizontal directions of the casting tube, and the mold There are localized areas of low strength in the hot cast pipe that has just been pulled out from the pipe. For this reason, the molten metal loading 1 (molten metal weight or molten metal head height) in the holding furnace with the mold spout as a reference level is excessive, and the hydrostatic pressure acting on the casting spout is greater than the yield load of the casting tube. If this happens, the cast pipe will bend to the side with lower strength, causing buckling or uneven thickness. This is noticeable in thin-walled metal tubes, and also in casting methods where drawing and stopping are repeated intermittently.

Note that Japanese Patent Publication No. 81-44588 proposes a method in which the wall of the holding furnace facing the mold is tilted to equalize the flow of molten metal and suppress fluctuations in molten metal pressure during replenishment of molten metal. This method does not take into consideration the increase in hydrostatic pressure when replenishing molten metal, and
Although Publication No. 553 proposes a method for detecting the amount of remaining metal in a holding furnace, which is useful for managing the operation of multiple furnaces by a small number of people, this method also detects the molten metal head height due to changes in the amount of molten metal in the furnace. In other words, these conventional techniques do not consider the effect that changes in the thickness have on the extrusion force for pipe production.
Moreover, it is related to the manufacture of products that are uniformly cooled.
There is no suggestion of the above-mentioned problems specific to metal pipes.

The present invention is applicable to continuous horizontal casting of cast pipes.

The purpose is to manufacture cast pipes with uniform wall thickness without bending or buckling.

[Means for Solving the Problems] The present invention as set forth in claim 1 is characterized in that a molten metal contained in a molten metal holding furnace is solidified into a tubular shape in a molding device to form a cast pipe, and this cast pipe is horizontally drawn by a drawing device. In the horizontal continuous casting method for metal pipes that are drawn at The amount of molten metal charged into the furnace is set to be smaller than the value corresponding to the yield load.

The present invention according to claim 2 is characterized in that the molten metal loading amount is 7.
The molten metal head height is set to be smaller than the critical molten metal head height that balances the yield load.

According to a third aspect of the present invention, the molten metal loading amount is managed by the molten metal weight, and the molten metal weight is set to be smaller than the yield load.

[Function] According to the present invention, the yield load of the high temperature and low strength portion immediately after being pulled out from the mold is determined. Furthermore, since the amount of molten metal loaded (molten metal head height or molten metal amount) before the start of drawing or when replenishing the molten metal is controlled to be smaller than the value corresponding to the above-mentioned yield load, the amount of molten metal acting on the pouring hole is It is possible to prevent hydrostatic pressure from becoming excessive.

In other words, the product extrusion force of the molten metal is prevented from becoming excessive! As a result, it is possible to prevent the cast tube from bending or buckling toward the side with lower strength, or from being manufactured with uneven thickness.

[Example] FIG. 1 is a control system diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view showing the mold device, and FIG. 3 is an end view showing the mold device.

i! ! ! As shown in FIG. 1, the continuous casting apparatus 10 inserts a mold into a pouring port 12 formed at the lower side of a molten metal holding furnace 11. It
fi13 is attached and installed. The continuous casting device 10 cools the molten metal using a mold device 13 to form a casting tube 14, which is horizontally drawn and cast.

The continuous casting apparatus IO is additionally equipped with a molten metal supply device 10A, and is capable of supplying an appropriate amount of molten metal to the molten metal holding furnace 11 at the appropriate time.

The continuous casting device 10 is configured to cast a casting tube 1 at the exit side of the mold device 13.
4 and a drawing roller device 16 for drawing out the cast pipe 14. The pulling roller device 16 consists of a pinch roller 17 and a press roller 18. In addition, the pulling roller device 16
is a hydraulic motor 16 driven by a hydraulic pump 16A.
B, and this hydraulic motor 16B operates a pinch roller.
17 to apply a pulling force to the cast tube 14 as a result.

As shown in FIGS. 2 and 3, the mold assembly N13 is composed of a mold 19 made of graphite and a core 20 also made of graphite.

The mold 19 has a hollow shape and includes a core holding inner diameter part 21 at the end on the molten metal inflow side, and a tube outer surface forming inner diameter part 22 around the mold center axis extending substantially over the entire length excluding the core holding inner diameter part 21.

The core 20 is inserted into the mold 19, and the flange portion 2 is fitted into the core holding inner diameter portion 21 of the mold 19 at the end on the molten metal inflow side.
3, and a pipe inner molding outer diameter part 24 that is provided around the mold center axis over substantially the entire length excluding the flange part 23 and forming a pipe molding passage 25 between the pipe outer molding inner diameter part 22 of the mold 19. . The core 20 also includes molten metal injection passages 26 that communicate with the tube forming passage 25 at each of a plurality of positions (four positions in this embodiment) around the mold center axis in the flange portion 23 . Each molten metal injection passage 26 has a cross-sectional shape of an arc. It is preferable that the thickness g of the joint portion 27 sandwiched between adjacent molten metal injection passages 26 be as small as possible to ensure strength, and that the passage area of each molten metal injection passage 26 be made larger.

That is, in the mold assembly 2t13, the flange portion 23 of the core 20 is fitted and fixed to the core holding inner diameter portion 21 of the mold 19, and the molten metal injection passage 26 and the tube forming passage 25 are communicated in a straight manner. Reference numeral 28 in FIG. 2 is a fixing pin between the mold 19 and the core 20.

In addition, mold mounting g! 113 specifically, a copper water cooling jacket body 30 is fitted to the molten metal outflow side end of the M mold 19 via a copper liner 29, and an insert ring made of brick is fitted to the molten metal inflow side end of the mold 19. 31 and 32, and an iron plate 33 is fitted between the water cooling jacket body 30 and the insert ring 31. As a result, the molding device 13 includes a cooling part for forming and solidifying the water-cooled jacket body 30, a non-cooling part for the insert ring 31, and a non-cooling part for the insert ring 32, and a part for the holding furnace 11 for the insert ring 32. It is attached to the furnace wall ILB.

Further, the continuous casting apparatus 10 of this embodiment has a mold IA station 1.
In order to prevent the molten metal flowing into the core 3 from being overcooled, a thank-you slot 20A is provided at the end of the molten metal inflow side of the core 20, and the end of the mold device 13 is made to protrude into the furnace.

Thus, the continuous casting apparatus MlO includes a control device 41, a temperature measuring device 42, a head measuring device 43, and an arithmetic device 44.
And display? 45.

The control device 41 controls the casting tube 14 according to ■drawing time (t e)
In order to repeat as one cycle the opening and stopping of pulling out by K and P at a constant pulling speed (Ve), and waiting time (tw) after pulling out, the pulling roller device 1
The hydraulic pump drive control unit 46 of No. 6 is controlled. The drawing speed of the cast tube 14 is fed back to the control device 41 via a drawing speed detector 47 connected to the output shaft of the hydraulic motor 16B.

The temperature measuring device W142 measures the temperature of the cast tube 14 immediately after being pulled out from the M-type device 113, and transfers the measurement result to the arithmetic device 44. Note that the temperature measuring device 42 measures the ambient temperature of the cast tube 14.

The temperature measurement results are 1, for example, 800°C on the F side of the tube, 700-800''C on both sides of the tube, and 850°C on the eT side. Because it contacts the inner surface, the temperature tends to be low.The upper surface of the tube falls under its own weight immediately after solidification inside the mold device 13 and separates from the inner surface of the mold, so cooling is delayed and the temperature tends to be high.

The head measuring device 43 is configured, for example, by a float system, and is connected to the molten metal at a height of -7 degrees H (the pouring port 1 of the #1g type device 13).
2 as a reference level) and transfers this measurement result to the arithmetic unit 44.

Arithmetic device 44 operates as follows.

(2) The calculation device 44 obtains the measurement results from the temperature measurement device 42 and calculates the yield load of the highest temperature portion in the circumferential direction of the cast pipe 14, and hence the lowest strength portion at that temperature.

(φNext, the calculating device 44 calculates the critical molten metal head height Hk (the head height with the pouring port 12 of the molding device 13 as the reference level) that balances the yield load obtained in the above ①,
This is displayed on the threshold value display section 45A of the display device 45.

(2) The arithmetic unit 44 also obtains the measurement results of the head measuring device 43 and displays the current molten metal head height H on the current value display section 45.
Display on B.

Therefore, when the operator of the continuous casting apparatus 10 supplies the molten metal to the holding furnace 11 using the molten metal supply device 10A, the current molten metal head height H is the critical molten metal head height) based on the above display on the display device 45. (Set so that it is smaller than k.

Here, the above setting work is performed by adjusting the amount of operation of the two molten metal supply devices 10A.

However, in implementing the present invention, 1, for example, the arithmetic device 44
The drive control unit of the molten metal supply device 10A to which the calculation result is transferred controls the amount of molten metal supplied from the molten metal supply device 10A, and as a result, the current molten metal head height H becomes smaller than the critical molten metal head height Hk. It may also be automatically controlled.

In addition, in implementing the present invention, the amount of molten metal loaded into the holding furnace is managed by the molten metal weight (the weight of the molten metal with the pouring port of the mold device as a reference level), and if this molten metal weight is smaller than the yield load mentioned above, It may be set so that

Next, the operation of the above embodiment will be explained.

According to the above embodiment, the yield strength of the high-temperature and low-strength portion immediately after being pulled out from the mold device 13 is determined. Furthermore, since the amount of molten metal loaded (molten metal head height or molten metal weight) before the start of drawing or at the time of molten metal replenishment is controlled to be smaller than the value corresponding to the yield load, the amount of molten metal acting on the pouring port 12 is controlled to be smaller than the value corresponding to the yield load. It is possible to prevent hydrostatic pressure from becoming excessive. That is, it is possible to prevent the product extrusion force of the molten metal from becoming excessive, and as a result, it is possible to prevent the casting tube 14 from bending or buckling toward the side with lower strength, or from being manufactured with uneven thickness.

That is, the relationship between the amount of molten metal loaded and the bending of the pipe is as follows.

The internal cross-sectional area of the molten metal holding furnace is D + , the molten metal pressure is Pl,
If the pressure acting on the pipe (cross-sectional area D 2 ) is P2, then
According to Pascal's principle, D + P + =02 P
2, D+ PI > D2 In the case of P2, bending of the pipe etc. occurs m PI Since I corresponds to the yield strength of the pipe material at high temperature, (molten metal head pressure) < (
Pipe yield strength: Pipe cross-sectional area x yield strength) can prevent pipe deformation.

To explain with a specific example, the internal cross-sectional area of the molten metal holding furnace is 8
00mmX 800mm, pipe size 65A (outer diameter ?7I
111, inner diameter 87 mm), the cross-sectional area of the molten metal is 3800 cm2, and the cross-sectional area of the tube is 1l-3c2. Table 1 shows the strength measurements of cast iron materials at high temperatures.

Considering the deformation at the weakest point of the tube immediately after being pulled out from the mold, that is, at the maximum temperature of 900° C., the yield load (cross-sectional area x yield strength) of the tube is approximately 1800 kg.

Also, since the density of molten cast iron at this time is 8.9 g/c■3, the critical molten metal head height Hk that balances the pipe strength is 72
．． It will be 8cm.

Therefore, in this specific example, before starting to draw the cast pipe,
Alternatively, when supplying molten metal during molten metal replenishment, if the molten metal head height H in the holding furnace is kept smaller than 72.8 cm or the molten metal weight is kept smaller than about 1800 kg, it will bend.
A product cast iron pipe without buckling and uneven thickness can be obtained.

In the practice of the present invention, the height H of the molten metal head in the holding furnace may be measured using the drawing length measuring device 48 shown in FIG. 1 instead of the head measuring device 43 of the above embodiment. That is, the pull-out length measuring device 48 is connected to the mold bag 51.
Measure the length of the cast iron pipe 14 to be pulled out from the pipe 13,
This measurement result is transferred to the arithmetic unit 44. calculation bag fi4
4 obtains the measurement results of the drawing length measuring device 48, and determines the initial head of the molten metal initially loaded into the holding furnace 11, and the amount of molten metal drawn out as the cast iron pipe 14 from the holding furnace 11 as the operation progresses. Based on this, the current molten metal head H in the holding furnace 11 can be calculated.

[Effects of the Invention] As described above, according to the present invention, when a cast pipe is horizontally continuously cast, the cast pipe can be manufactured without bending or buckling and with a uniform wall thickness.

[Brief explanation of drawings]

FIG. 1 is a control system diagram showing one embodiment of the present invention. FIG. 2 is a sectional view showing the mold device, and FIG. 3 is an end view showing the mold device. lO... Continuous casting device, 12... Casting port. 13... Mold device. 14...Casting pipe, 42...Temperature measuring device, 43...Head measurement! / is placed, 44...Arithmetic unit, 45-...Display! lcM. 48... Pull-out length measuring device a. Agent: Patent attorney Osamu Shiokawa, Haruhata 1 Figure 2

Claims (3)

[Claims] (1) In the horizontal continuous casting method for metal tubes, the molten metal contained in the molten metal holding furnace is solidified into a tubular shape in a molding device to form a cast tube, and the cast tube is pulled out horizontally by a drawing device. Measure the temperature of the cast pipe immediately after the casting, calculate the yield load of the cast pipe at this temperature, and calculate the amount of molten metal to be loaded into the holding furnace with the casting inlet of the mold at the reference level from the value corresponding to the above yield load. A horizontal continuous casting method for metal tubes, characterized in that the metal tubes are set so as to be small. (2) Horizontal continuous casting of a metal tube according to claim 1, wherein the molten metal loading amount is managed by a molten metal head height, and the molten metal head height is set to be smaller than a critical molten metal head height that balances the yield load. Method. (3) The method for horizontal continuous casting of a metal tube according to claim 1, wherein the molten metal loading amount is managed by molten metal weight, and the molten metal weight is set to be smaller than the yield load.