JPH0488124A - Heating method for steel pipe of walking beam furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field This invention mainly relates to a heat treatment method for seamless steel pipes.
The present invention relates to a method for heating steel pipes that prevents transportation troubles by suppressing bending of steel pipes in a walking beam furnace, thereby stabilizing operations and improving quality.

Conventional technology Heat treatments performed to improve the strength, toughness, and corrosion resistance of steel pipes include normalization, QT (quench and temper), etc. Heat treatment furnaces can be roughly divided into two types: barrel type and walking type. There is.

The barrel type has a structure in which the charging, inside the furnace, and extraction conveyors are arranged in a straight line, and inside the furnace, the steel pipes are heated by multiple burners arranged in parallel on the furnace body.

On the other hand, the walking type heats the steel pipe while being transported by a walking beam through a furnace that is controlled at a predetermined temperature.
It is widely used because it has high temperature control accuracy and is easy to automate.

As is well known, in a walking beam type furnace, the hearth is divided into a moving beam and a fixed beam, and the moving beam repeatedly moves in a rectangular motion of ascending, descending, and retreating using pneumatic pressure, electric power, or a combination thereof. However, the walking beam furnace used for heat treatment of steel pipes has a furnace body (1
A charging zone (C-1) consisting of a skew roller conveyor (2) and an extraction zone (C-3) consisting of a skew roller conveyor (3) are provided at both ends of the fixed beam (
Heating zone (C-) consisting of B-1) and movable beam (B-2)
2) is provided.

It is. (4) indicates a charging roller conveyor, and (5) indicates an extraction roller conveyor.

That is, in the walking beam furnace for steel pipe heat treatment, the steel pipe is charged in the direction of the steel pipe (P) using the charging roller conveyor (4), and the skinny roller conveyor (2) of the furnace charging zone (C-1) is charged.
) and then placed on the steel pipe (P
) is heated while moving it forward in the lateral direction, and the extraction zone (
When placed on the skew roller conveyor (3) of C-3), the roller is rotated to advance in the tube axis direction and extracted by the extraction roller conveyor (5).

Problems to be Solved by the Invention In a walking beam type furnace used for heat treatment of seamless steel pipes, etc., as described above, the direction in which the steel pipes are conveyed by the charging conveyor is perpendicular to the direction in which they are transported by the walking beam. Therefore, during charging, the steel pipe (P) is placed in the charging zone (
It will temporarily stand still (for about 1 to 2 seconds) on the skew roller conveyor (2) of C-1).

However, while it is stationary, only the upper surface of the steel pipe (P) is heated, so it bends significantly due to the temperature difference with the lower surface, and may not ride on the movable beam (B-2), or may not ride on the beam. The skew roller conveyor (
2) Problems such as falling back upwards occur, which not only prevents smooth transportation by the walking beam, but also
In some cases, the bending remained even at the product stage, causing quality problems.

In view of these conventional circumstances, this invention seeks to propose a heating method for steel pipes that prevents bending of steel pipes in a walking beam type furnace and allows smooth transfer of the heating zone in the furnace without transportation troubles. It is.

Means for Solving the Problems The present invention is a means for preventing bending of steel pipes when they are introduced into a furnace, by eliminating the temperature difference between the upper and lower surfaces of the steel pipes while restraining the steel pipes in the furnace entry zone. This method uses a T-king beam to convey the material, and the gist of this method is to place a vertically movable upper skew roller driven by a cylinder above the charging belt skew roller conveyor in a walking beam furnace. Immediately after charging the steel pipe to be heated into the walking beam furnace, the skew roller conveyor is driven to rotate the steel pipe in forward and reverse directions while the steel pipe is pressed and restrained by the upper skew roller. This method heats the steel pipe uniformly to a predetermined temperature and then moves it forward with a walking beam.

Function: When a coated heated steel pipe is introduced into the furnace, the vertically movable upper skew roller, which is disposed opposite to the skinny roller conveyor in the furnace entrance zone, is lowered according to the size of the steel pipe, and the interval between the upper and lower skew rollers is adjusted. By setting the temperature appropriately, the heated steel pipe charged into the furnace is restrained as it is charged, and the temperature of the heated steel pipe is raised while the skew roller conveyor is rotated in the forward and reverse directions while being restrained. Therefore, there is no temperature difference between the upper and lower surfaces of the heated steel pipe on the skew roller conveyor in the furnace entrance zone, and no bending occurs due to the temperature difference.

When the heated steel pipe reaches a uniform temperature, the upper skew roller is raised to release the steel pipe, and forward movement by the walking beam is started.

In this invention, the steel pipe to be heated is uniformly heated in a restrained state on the furnace entrance skew roller conveyor, and then transferred by a walking beam, so that the temperature difference on the furnace entrance skew roller conveyor causes This prevents bending and allows for smooth transfer by the walking beam within the furnace.

Note that the uniform heating temperature on the skew roller conveyor immediately after charging into the furnace is not particularly limited, but is 20
0 to 400°C is preferred. This is because the effect of preventing the steel pipe from bending is small at temperatures below 200°C, while the effect of preventing the steel pipe from bending is sufficient at about 400°C, and heating to a temperature higher than this is undesirable because it reduces the heat treatment efficiency.

Embodiment FIGS. 1 and 2 are schematic diagrams showing an apparatus according to an embodiment of the present invention. It is a side view which shows the state which restrains the heated steel pipe on the furnace entrance skew roller conveyor in an apparatus, (6) is an upper skew roller for steel pipe restraint.

The upper skinny roller (6) is installed opposite to the skew roller conveyor (2) located below it,
Its mounting means is that it is vertically movably suspended from a rod (8) of a cylinder (7) installed on the ceiling of the walking beam furnace via a roller support bracket (9). The rod (8) is attached to a guide tube (11) protruding from the furnace wall.
) is held so that it can move up and down.

The cylinders (7) of each upper skew roller are remotely synchronously driven.

Note that the uniform heating temperature of the steel pipe to be heated can be measured by, for example, installing a thermometer or the like on the furnace wall.

In the above device, when heating a steel pipe, the upper skew roller (6
) and the skew roller conveyor (2) are set in advance. In this state, when the steel pipe to be heated (P) is charged in the tube axis direction on the charging roller conveyor (1), the steel pipe to be heated (P) is transferred to the skew roller conveyor (2) in the charging zone as it is loaded into the furnace. and the upper skew roller (6).

When the charging of the heated steel pipe (P) is completed, the rotation drive system (1
0), the skew roller conveyor (2) is repeatedly rotated in the forward and reverse directions until the entire heated steel pipe reaches a uniform temperature.

When the entire heated steel pipe reaches a uniform temperature, the cylinder (7)
Raise the upper skew roller (6) to remove the heated steel pipe (
P) and drive the walking beam to start the transfer. When the steel pipe to be heated is placed on the skew roller conveyor (3) of the extraction zone, the upper skew roller (6) is lowered again to prepare for the next material charging.

As described in detail, according to the method of the present invention, the steel pipe to be heated is restrained until it reaches a uniform temperature from the moment it is charged into a walking beam furnace, so that bending of the steel pipe can be prevented, and walking Transport by the beam can be carried out smoothly without trouble, and there is no problem of deterioration in quality due to bending, which is particularly effective for heat treatment of seamless steel pipes.

[Brief explanation of drawings]

1 and 2 are schematic diagrams showing an embodiment of the present invention, in which FIG. 1 is a partially longitudinal front view of a walking beam furnace seen from the entrance direction, and FIG. 2 is a furnace in the same apparatus. FIG. 3 is a side view showing a state in which the heated steel pipes on the internal skew roller conveyor are restrained, and FIG. 3 is a schematic plan view showing a conventional walking beam type furnace to which the present invention is applied. 1... Furnace body 2. 3... Skew roller conveyor 6... Skew roller conveyor for restraining heated steel pipes 7.
...Cylinder 10...Rotary drive system P...Heated steel pipe

Claims (1)

[Claims] In a method of heating the steel pipe to be heated in a walking beam furnace, a vertically movable upper skew roller driven by a cylinder is disposed opposite to the charging zone skew roller conveyor in the walking beam furnace. Immediately after charging the steel pipe into the walking beam furnace, the skew roller conveyor is driven to rotate the heated steel pipe forward and backward while the steel pipe is pressed and restrained by the upper skew roller, so that the steel pipe is maintained at a uniform temperature at a predetermined temperature. A method for heating a steel pipe in a walking beam furnace, which is characterized in that the steel pipe is moved forward by a walking beam after being heated.