JPH0531595A - Production of granular substance packed pipe - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents internal swelling of the tube during the cold rolling of the tube filled with powder and granules, thus achieving good diameter reduction rolling and wire drawing up to the product size. Let [Structure] A metal strip is continuously formed into a tubular body by a forming roll while being fed in the longitudinal direction, and powder particles are supplied from the opening of the tubular body in the middle of this forming, and the opening edges of the tubular body facing each other are opposed. In a method of butt-welding the surfaces and continuously manufacturing a powder-filled tube by cold-rolling and wire-drawing the tube obtained by welding, in the cold rolling step, the powder-filled rate Until at least 100%, the rolling speed of each rolling stand is set so that the tensile ratio is 5 to 40%, and rolling is performed while applying tension to the pipe. As a result, the inner surface of the tube is not stretched during cold rolling, and cracking and disconnection do not occur when the tube is reduced in size to the product size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder / granule-filled tube in which carbon steel, stainless steel, copper alloy, aluminum alloy or other metal tube is filled with the powder / granular material.

The term "powder / granulate" as used herein means a powder such as a flux for welding, an oxide superconducting material, an additive for molten steel or the like, a particle or a mixture of the powder and the particle. INDUSTRIAL APPLICABILITY The present invention is used for manufacturing a flux-cored wire for welding, a wire containing an oxide superconducting material, and other powder-filled tubes.

[0003]

2. Description of the Related Art A flux-cored seamless wire for welding is one of the powder and granular material filling pipes. Generally, as a technique for manufacturing a flux-cored wire for welding in which a joint portion in the wire length direction is welded, a metal strip is continuously molded from a U cross section to an O cross section to form a tubular body, and a metal powder is used in this forming process. A flux containing a desired component such as a deoxidizer or deoxidizer is supplied from the opening of the tubular body into the tubular body, and then filled, and then the opposite opening edge surfaces of the tubular body are butt-welded, followed by cold rolling to reduce the pipe diameter. There is known a method for producing a flux-cored wire for welding by carrying out wire drawing.

As the butt welding, low frequency welding, high frequency induction welding or high frequency resistance welding is widely used. In all of these welding methods, when the metal strip is formed into a substantially O-shaped tubular body, the low-frequency current and high-frequency current heat the edge surfaces of the opening to the melting temperature, and the opposite edge surfaces are paired with a pair of squeeze rolls. Weld by pressure welding.

Then, in the step of cold rolling the welded pipe having the flux filled therein, the outer diameter of the pipe is sequentially reduced by a two-roll or three-roll hole type roll row incorporated in a continuous multi-stage rolling stand. Scale to a desired diameter. Conventionally, cold rolling for reducing the pipe diameter has been carried out by so-called tensionless rolling in which the roll peripheral speed is made to match the exit pipe speed.

[0006]

However, in the conventional cold rolling described above, disconnection or cracking frequently occurs in the process of reducing the diameter of the pipe and reducing the diameter of the pipe. The cause is that the inner surface of the tube becomes free when the diameter is reduced, and the deformation of the outer tube of the tube becomes unstable, resulting in the formation of the inner surface of the tube. That is, when the diameter is reduced, uneven thickness increase occurs on the inner surface side of the pipe jacket, and angular expansion occurs on the pipe inner surface side corresponding to the seam portion of the rolling roll contacting the pipe outer surface.
When the diameter of the tube having the inner surface is reduced, a crack is generated from the recess of the angle when the diameter becomes small to some extent, which grows to cause the tube to be cracked or even disconnected.

As a measure against this, conventionally, the outer diameter reduction rate is 5%.
By limiting to the following, occurrence of inner surface angular tension is suppressed. However, rolling with such a low outer diameter reduction rate is not economical because the number of rolling stands increases. In the case of producing only a tube by hot rolling, there is also known a method of rolling at a maximum outside diameter reduction rate of 7% using a stretch reducer as a measure against the above-mentioned inner surface angular tension, but this method fills the tube with flux. This method cannot be applied to the production of welding flux-cored wires because the flux is altered by high heat.

In view of this, the present invention is a method for producing a powder-filled tube which does not cause internal surface angulation which causes wire breakage and cracks even when cold rolling with a high outer diameter reduction rate of about 10%. Is to provide.

[0009]

The method for manufacturing a powder-filled body filling tube of the present invention is such that a metal strip is continuously formed into a tubular body by a forming roll while being fed in the longitudinal direction of the metal strip, and a tubular body is formed during this forming. The powder and granules are supplied from the opening of the body, the opposite opening edge surfaces of the tubular body are butt-welded, and the pipe obtained by the welding is cold-rolled and wire-drawn to reduce the diameter of the powder-filled pipe. In the continuous manufacturing method, in the cold rolling step, the roll peripheral speed of each rolling stand is represented by the following equation (2) until the powder / granule filling rate represented by the following equation (1) reaches at least 100%. It is characterized in that the tensile ratio is set to be 5 to 40% and rolling is performed while applying tension to the pipe.

[0010]

[Equation 2]

[0011]

In general, in continuous rolling, the roll volume on the inlet side and the volume on the outlet side are the same, that is, (inlet side cross-sectional area) x (inlet tube speed) = (outlet side cross-sectional area). ) × (outlet pipe speed) holds.

In the conventional cold rolling immediately after welding in the manufacture of the powder-and-granule-filled pipe, so-called tensionless rolling is performed in which the roll peripheral velocity (= velocity at the bottom of the carver) is made to coincide with the stand outlet pipe velocity. .. However, according to this method,
Immediately after filling the granular material and welding the pipe opening, the granular material-filled tube is subjected to a diameter reduction rolling with a maximum outer diameter reduction rate of 10%, and then subjected to annealing (650 ° C x 5 hr) and further diameter reduction rolling. When continued, cracks or disconnections frequently occurred when the diameter decreased to some extent. Upon investigating the cause of this, an internal surface tension was generated in the pipe by roll rolling at the stage of diameter reduction rolling immediately after welding, and a crack was generated from the concave portion of the inner surface tension at the stage of diameter reduction rolling after annealing, It was confirmed that the cracks grow as the diameter of the pipe becomes smaller and develop into cracks and breaks in the pipe.

As a countermeasure against this, the present inventors have examined a method of applying a tension in the longitudinal direction of a pipe which is applied by a stretch reducer in hot rolling. As a result, the roll peripheral speed of each rolling stand is set to the above formula (2) until the filling ratio of the above formula (1) becomes at least 100% for the welded pipe filled with the powder and granules immediately after welding. If the cold rolling is performed while setting the tensile ratio of 5 to 40% and applying tensile force in the longitudinal direction to the tube, the occurrence of inner surface angular expansion is suppressed, and the diameter reduction rolling for the subsequent diameter reduction. It was found that cracking and disconnection did not occur during wire drawing, and that the product wire diameter could be smoothly reduced to 0.8 to 2.0 mmφ.

The powder / granule filling rate represented by the above equation (1) is the tube volume occupying rate (= tube cross-sectional area occupying rate) when the powder / granular elements are filled in the tube at the tap density. When the filling rate is 100%, the tube filled with the powder and granules necessary for obtaining the desired packing rate of the powder and granules is subjected to diameter reduction rolling to reduce the cross-sectional area in the tube and finally the powder and granules have a tap density. (DIN5319
At 4), the inside of the pipe is filled with the powder, and then the powder and granules inside the pipe are compacted.

When compaction of the powder and granules is started, the deformation behavior of the pipe jacket changes from that until then, and the powder and granule filling rate is 100.
It will show a different coat change than when it is less than%. Therefore, the range in which the application of tension in the longitudinal direction of the pipe is effective in preventing the non-uniform deformation of the pipe jacket that causes the inner surface swelling is judged to be up to this consolidation start point, and the filling rate of the granular material is at least 1.
It was decided to apply the above tension in the longitudinal direction of the tube until it reached 00%. The range of tension applied in the longitudinal direction of the pipe is a tensile ratio of 5
The reason for setting 40% is that if it is less than 5%, it is not effective in preventing uneven deformation of the jacket, and if it exceeds 40%, slip between the roll and the pipe becomes severe and stable rolling cannot be performed. Is.

[0016]

EXAMPLE An example of manufacturing a flux-cored wire for welding will be described with reference to the process block diagram shown in FIG.

The steel strip unwound from the reel is formed into a tubular body having a U-section to an O-section by a forming roll while being fed in the longitudinal direction thereof, and flux is supplied from the opening of the tubular body during the forming. The steel strip used is a carbon steel strip (JIS SPHC), width 62.9, wall thickness 2.2 mm, density 7.85 g / cm ³ , flux used is rutile flux, tap density 1.8 g / cm 3. ^{In 3} , the flux was supplied into the tubular body so that the filling rate was 12.0%.

Next, high-frequency induction welding is performed on the opposing opening edge surfaces of the tubular body filled with the flux. The welding conditions were a heat input of 85 to 95 kVA and a welding speed of 15 m / min. Immediately after welding, the pipe has an outer diameter of 21.7 mm and a wall thickness of 2.2 mm.
The flux filling rate is 34.1%.

Then, cold rolling (primary) was performed according to the rolling schedule shown in Table 1 by a rolling machine having a 3-roll type and an 8-stand structure.
Then, a flux-filled tube having a flux filling rate of 100% or more was obtained. The outer diameter of the pipe at this time is 10.7 mm. Table 1 shows rolling stand Nos. In the examples (Examples Nos. 1 to 5) when the tensile ratio was increased from 0% (Example No. 0) by 10%. Flux filling rate in each stand outlet of 1 to 8 alpha, tube average thickness t _m, shows a rolling roll peripheral velocity V _n. However, No. 1 in Table 1 Stand N
o. , D _m represents the tube outer diameter, and R represents the outer diameter reduction rate.

FIG. 2 is a diagram showing the relationship between the tube average outer diameter and the flux filling rate in Table 1 for each example. It can be seen from FIG. 2 that the flux filling rate gradually increases as the diameter decreases, and exceeds 100% in all the examples at a tube average outer diameter of 11.08 mm (outlet of stand No. 7). If the flux filling rate exceeds 100%, the flux in the tube becomes a consolidated state.

[0021]

[Table 1]

The tube having an outer diameter of 10.7 mm obtained by cold rolling (primary) was annealed and cooled, and then cold rolled (2) according to the rolling schedule shown in Table 2.
The following) was carried out. In this cold rolling (secondary), cold rolling was performed by repeating oval and round by a rolling machine having a three-roll type and a ten-stand structure, and the pipe outer diameter was reduced from 10.7 mm to 3.2 mm. Subsequently, after annealing / cooling, wire drawing was performed to reduce the wire diameter to a product size of 1.2 mm and wound.

[0023]

[Table 2]

The results of the cold rolling (secondary) in Table 2 are shown in Table 3.

[0025]

[Table 3]

As is apparent from Table 3, Example No. 0
At (tensile ratio 0%), the pipe was cracked and wire breakage occurred during the diameter reduction. This is because during the cold rolling (primary) shown in Table 1 immediately after welding, the inner surface of the pipe is squared, and the concave part of this square becomes a crack during the cold rolling (secondary) of this time and grows due to the diameter reduction. Then the pipe breaks, causing a wire break. In addition, No. At 5 (tensile ratio 50%), the tensile ratio in the primary cold rolling was too high, and slipping of the roll became severe, so that stable rolling could not be performed. On the other hand, No. In Nos. 1, 2, 3 and 4, the tensile ratio was in the proper range of 10 to 40%, and therefore a good rolled state was shown without cracking or disconnection.

[0027]

According to the present invention, in the process of cold rolling a welded tube filled with powdery or granular material, the roll peripheral speed of each rolling stand is controlled until the powdery or granular material filling rate becomes at least 100%. Rolling is performed while setting the tensile ratio to 5 to 40% and applying tension to the pipe. This reduces the outer diameter by 10
Even when cold rolling with a high outside diameter reduction rate of about%, the inner surface of the pipe does not have an angular tension. Therefore, when the welded pipe filled with the powder or granular material is reduced in diameter to the product wire diameter, no inconvenience such as cracking or disconnection occurs, and the diameter-reducing rolling and wire drawing can be favorably performed. Therefore, it is possible to improve the production efficiency in the continuous production of the powder / granule-filled pipe.

[Brief description of drawings]

FIG. 1 is a process block diagram of manufacturing a flux-cored wire for welding.

FIG. 2 is a diagram showing a relationship between a tube average outer diameter and a flux filling rate in cold rolling (primary).

Front Page Continuation (72) Iwao Yamada, Inventor Iwao Yamada, 3-5-4 Tsukiji, Chuo-ku, Tokyo Inside Nippon Steel Welding Industry Co., Ltd. (72) Haruji Hashimoto, 3-5-4 Tsukiji, Chuo-ku, Tokyo Inside the Iron Welding Industry Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A metal strip is continuously formed into a tubular body by a forming roll while being fed in the longitudinal direction of the metal strip, and powder particles are supplied from the opening of the tubular body during the forming. Butt-welding the opposite opening edge surfaces of the tubular body, in a method for continuously producing a powder-and-granule-filled tube by reducing the diameter of the tube obtained by welding by cold rolling and drawing, In the rolling process, the roll peripheral speed of each rolling stand is 5 to 40% as shown in the following formula (2) until the powdery or granular material filling ratio shown in the following formula (1) becomes at least 100%.
The method for producing a powder-and-particles-filled tube is characterized in that the tube is rolled while applying tension to the tube. [Equation 1]