JPS5852427A - Quenching method of metallic pipe - Google Patents

Abstract

PURPOSE:To quench a metallic pipe at a uniform cooling speed, by blowing jet water into a metallic pipe of a high temperature from its one end, executing its cooling, also controlling and jetting jet water over the full length from the outside surface, and correcting uneven distribution of cooling of the inside surface. CONSTITUTION:A metallic pipe to be quenched 1 of a high temperature is placed horizontally on a supporting roll group 2 and is rotated. From a nozzle group 3 placed linearly in the upper direction of the metallic pipe 1, laminar flow cooling water is dropped onto the top line of the metallic pipe 1, the outside surface is cooled, also a jet flow is blown into the metallic pipe 1 toward the other end B from its one end T, and the inside surface is cooled. As for the inside surface cooling, its cooling distribution becomes uneven because a temperature rises as the jet water approaches the other end B of the discharge side. In order to correct this unevenness, a header 4 of said nozzle group 3 is divided into plural pieces, and one of such 3 methods as the quantity of jet water is increased as it approaches the end B side, by controlling the outside surface cooling, the action that its cooling start time is quickened, or its cooling end time is delayed is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for quenching metal pipes such as steel pipes.
This method provides a method for uniformly and quickly cooling the entire metal tube during quenching under conditions including quenching.

When hardening a metal tube, blowing a high-speed jet of water from one end is effective in obtaining a high cooling capacity with a relatively small amount of water used. For example, the flow velocity of the inner jet is 6 blades/. So, it has a heat transfer coefficient of 8000 k=d/,/hr″C (surface temperature 600°C, water temperature 30°C),
In external immersion water cooling, if the surface temperature and water temperature are the same, and the water temperature rise after quenching is immersed in a volume of water that does not pose a problem, the increase in water temperature after quenching is only about 1000kj/m"hr"C, so the cooling rate is high. It can be seen that in the case of cooling that requires a large amount of water, the cooling by the inner surface jet is the main one, and the outer surface cooling is secondary.

However, in a relatively long metal tube, as the inner surface jet moves through the tube, the water temperature increases and the pressure decreases, so the cooling capacity becomes smaller at the discharge end. For example, when we conducted an experiment on a long steel pipe with a small diameter and thick wall, we observed a phenomenon in which the water temperature rose as the discharge end became a two-phase flow of steam and water. That is, depending on the conditions, the cooling capacity on the discharge end side may be considerably lower than that on the blow end side. Such non-uniform cooling in the longitudinal direction of the metal tube leads to non-uniformity in the material.

In addition, in recent years, from the perspective of energy conservation, direct quenching of steel pipes using the heat retained after rolling has been trending toward, but in this case, in addition to normal quenching, that is, continuing quenching cooling to near room temperature, Cooling is stopped at a suitable low temperature range of 18 points or less during quenching (interrupted Q
There are some people who do ``uench''.

As explained in, for example, Japanese Patent Application No. 55-111627, this cooling stop is intended to prevent burn-out due to hydrogen defects caused by direct quenching and to save energy for tempering heating in the subsequent step. However, when internal jet cooling is used for relatively long steel pipes, the cooling capacity in the longitudinal direction is uneven, and the temperature distribution in the length direction of the steel pipe at every moment after the start of quenching is not uniform. Stop (1n
terruptedQuench), the temperature at the time of cooling stop is not uniform, which is inconsistent with the original purpose.

In this way, internal jet cooling is indispensable for quenching, which requires a high cooling rate, and is an excellent cooling method as it generates a large amount of heat. There are drawbacks that make a difference.

The present invention is based on gold I! In the quenching method in which a jet of water is passed from one end of the tube to the inner surface, the uneven distribution of the inner surface cooling capacity that is inevitably formed in the longitudinal direction of the metal 1'I as described above is canceled out, and a uniform cooling rate is achieved. and/or provide a method for quenching a metal tube that can provide a uniform cooling stop temperature.

Particularly, the metal tube quenching method according to the present invention involves blowing a jet of water into the metal tube from one end thereof, and cooling the outer surface of the raw tube by colliding with the jet of water jetted from a nozzle over almost its entire length. The quenching method is characterized in that the longitudinal outer surface cooling of the gold Is tube is controlled by at least one of the following controls.

Where is the discharge end of the inner jet water? Medium: Increase the amount of water jetted.

(11) The timing of starting cooling (starting lit radiation) is postponed.

(lltl Delay the end of cooling a (injection end) time O Appropriate flow rate distribution in the length direction of the metal tube in the cooling PC on the outer surface and/or appropriate cooling start time and/or end time at each position in the longitudinal direction , without any active cooling from the outside surface, or with cooling from the outside surface under the same conditions at each position in the length direction, cooling is performed by blowing jet water into the inside surface, and the length when cooling is stopped. 2. Understand the temperature distribution in the direction, etc.
It can be easily determined by the experiment described in ~3.

The nozzle for cooling the outer surface is not particularly limited and may be spray, mist, laminar 70-, etc., but in order to efficiently cool the metal tube with a small amount of water, it is necessary to keep the outer surface of the metal pipe cool even after the jet collides with it. Laminar 70- is preferred along which a laminar water film is formed.

The details of the present invention will be explained below based on examples.

Figure 1 shows the cooling rate distribution and mid-cooling stop observed in a quenching method in which a relatively long, thin-diameter, thick-walled steel pipe is immersed in a water tank and a jet is blown into the inner surface from one end of the steel pipe. This is the temperature distribution seen in . However, the details of the quenching conditions are as shown below.

Steel pipe 17)? Chair: 114X&6X290001+w
a Flow velocity of inner jet: 61/red.

II Inlet side water m: 30℃ Cooling start temperature: 900℃ Cooling stop time: 10 seconds after inner injection In the case shown in Figure 1, the water temperature rises as the inner jet water advances inside the pipe, and the outlet side water temperature Water temperatures of over 100°C were measured for several seconds. In other words, it is presumed that the water temperature rose to such an extent that the flow became a two-phase flow of steam and water on the discharge end side, and that there was a sudden pressure drop at the r section. For this reason, it is thought that the cooling capacity deteriorated on the discharge end side, the cooling rate was slow, and the temperature after cooling was stopped midway was high. However, in immersion cooling in a water tank, it is difficult to compensate for the non-uniformity of the inner jet from the outer surface.

The present invention corrects the temperature non-uniformity caused by the inner jet flow, and an embodiment thereof is shown in FIGS.
(shown on a reduced scale with respect to the figure). In this embodiment, the outer surface of the steel pipe is cooled by water jetted from a nozzle, and the hardening is controlled to be uniform over the entire length of the steel pipe.

That is, in Fig. 2, the steel pipe to be hardened 1 is
Place it almost horizontally on top of the screen and rotate it.

Then, the laminar 70-cooling water is dripped from the water injection nozzle group 6 arranged linearly above the fI41rF to the top line of the steel pipe, thereby rotationally cooling the outer surface of the steel pipe. On the other hand, the inner surface of the steel pipe is cooled by blowing a jet stream from one end (blowing end side T) of the steel pipe and discharging it from the other end (discharge end side B). The steel pipe is rotated during cooling and is moved in the longitudinal direction by means such as a feed roller (not shown) to move the collision point of the laminar flow. In this example, the water injection nozzle was a circular tube nozzle with an inner diameter of δ and φ, and the nozzle pitch was 40 m.

The circular pipe nozzle is connected to a header 4 having a length of 3 m in the pipe axis direction to supply water. By dividing the header 4 in this way, it is possible to control the flow rate, injection start timing, and injection stop timing for each header individually or in units of multiple units, making it easy to prevent misfire EiA. It is now possible to implement

By the way, as shown in Fig. 1, an uneven temperature distribution is formed in the tube axis direction due to the inner jet flow, but this embodiment uses an outer surface cooling method to reduce this temperature deviation and equalize the temperature. This is done using the following three methods.

(a) Change the flow rate of external cooling water in the longitudinal direction.

(b) Changing the start time of external cooling in the longitudinal direction (c)
Change the timing of stopping external cooling in the longitudinal direction.

Targeting a quenching stop temperature of 250°C, the results of each method (a) to (c) above are shown in the implementation table at that time.
As is clear from No. 1, both methods are effective and the temperature distribution in the longitudinal direction is good.

As described above, in the method for quenching metal tubes according to the present invention, the amount of heat absorbed by the cold gas on the outer surface is increased at the discharge end of the inner jet flow, so that the temperature non-uniformity associated with the inner jet flow is corrected, and the temperature in the longitudinal direction of the metal tube is corrected. temperature becomes uniform, and the drawbacks of conventional quenching methods are largely eliminated and improved. For this reason, the cooling of long steel pipes is stopped (lnte
ruptured quench) is now possible, reducing hydrogen defects associated with direct quenching and saving energy in the tempering process.

In addition, in order not only to have a uniform temperature in the longitudinal direction after the completion of the quenching operation, but also to make the average cooling rate of the thick wall of the pipe uniform in the longitudinal direction, it is necessary to adjust the flow rate of the external cooling water in the longitudinal direction. It is also desirable to have this, and it is also relatively easy to control.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram of cooling mid-stop, Figures 2 and 3 v! J
Fig. 1 is a front explanatory view and a side explanatory view of a method for quenching a metal tube according to an embodiment of the present invention; 1...Steel pipe to be hardened, 2...Support p-ru details, 3...
Nozzle I%/group, 4...Header. Agent: Masaru Sato, Patent Attorney Figure 1 of 2015 (1 cup of acid) (medium fire) (large fire) Figure 2 of the emblem of the Tojiku square

Claims (1)

[Claims] A quenching method in which a jet of water is blown into a metal tube from one end thereof, and the outer surface of the limb is cooled by collision of the jet of water jetted from a nozzle over almost the entire length of the metal tube. A method for quenching a metal tube, characterized in that longitudinal outer surface cooling is controlled by at least one of the following: The discharge end side of the inner jet water (1) increases the amount of water jetted. (11) The cooling start (injection start) timing is postponed. GiD delays the end of cooling (end of injection).