JP2962155B2 - Continuous cold rolling method for difficult-to-weld materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous cold rolling method for difficult-to-weld materials such as high silicon steel and high carbon steel.

[0002]

2. Description of the Related Art Generally, when a coiled hot-rolled steel sheet is continuously rolled by a cold tandem rolling mill, the ends of the steel sheets of different coils are flash butt-welded at the entry side of the pickling line or the cold tandem rolling mill. Then, continuous rolling is performed. However, in the case of a difficult-to-weld material such as a silicon steel sheet or a high carbon steel sheet, the welding strength cannot be sufficiently secured, and the welded portion is easily broken in cold rolling to which a load or tension is applied. In particular, a silicon steel sheet of (Si + Al) ≧ 1.0 wt% or C ≧ 0.
It is remarkably recognized in a 6 wt% high carbon steel sheet and the like.

In order to prevent the breakage of the welded portion, Japanese Unexamined Patent Publication (Kokai) No. Hei 3-60804 discloses that leader strips which can be easily flash butt welded to both ends of a coil of a difficult-to-weld material by laser welding or plasma welding in advance. A method has been proposed in which the leader strip and a leader strip similarly joined to a preceding coil or a succeeding coil are joined by flash butt welding at the entry side of a pickling line or a cold tandem rolling mill to perform continuous rolling.

[0004]

However, when the method described in Japanese Patent Application Laid-Open No. Hei 3-60804 was actually applied, it was found that a welded portion between a difficult-to-weld material and a leader strip during continuous cold rolling, especially a difficult-to-weld material Breakage often occurred at the weld when the rolling transition from the steel to the leader strip.

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of continuously cold rolling a difficult-to-weld material without breaking.

[0006]

The above object is achieved by (Si + A
l) Silicon steel sheet of ≧ 1.0 wt% or C ≧ 0.6 wt%
When continuous cold rolling is performed after joining a difficult-to-weld material made of any of high carbon steel sheets via a leader strip,
The flame welding material and the Li - Da - load 1k weld strip
Vickers measured in g - scan hardness Hw, Vickers hardness was measured under a load 1kg of the flame welding material - Hp the scan hardness, when the rolling dumping speed and Vm / min, formula {(Hw-Hp) / H
The problem is solved by a continuous cold rolling method for difficult-to-weld materials, characterized in that rolling is performed under conditions satisfying p｝ · V ≦ 10.

[0007]

The thickness of the welded portion where the above-mentioned fracture occurred was measured and found to be significantly thicker than that of the welded portion which could be rolled without fracture. Therefore, it is presumed that the cause of the fracture largely depends on the hardness of the welded portion.

Therefore, a hot rolled sheet of 3 wt% silicon steel with a different content of a strengthening element such as P is used as a difficult-to-weld material, and a hot rolled sheet of 0.04-0.16 wt% C steel is used as a leader strip. Various samples having welds having different hardnesses were prepared by changing the welding conditions and filler wires by laser welding, and were subjected to continuous cold rolling to investigate the presence or absence of breakage. Since the strain rate is considered to be related to the fracture, the rolling charging speed was changed in the range of 17 to 28 m / min.

FIG. 1 shows the results. As shown in the figure,
The Vickers hardness measured at a load of 1 kg of the welded portion is Hw,
The Vickers hardness of a difficult-to-weld material measured with a load of 1 kg is H
p, when the rolling charge speed is Vm / min, ｛(Hw
-Hp) / Hp｝ · V ≦ 10 indicates that continuous cold rolling can be performed without breaking the weld.

[0010]

[Embodiment] As a difficult-to-weld material, a reinforcing element such as P or Mn is used.
A 2.5 mm thick leader strip of 0.04 to 0.16 wt% C steel was laser-welded to both ends of a 2.3 mm thick hot rolled sheet of 3 wt% silicon steel having different contents by a recoil line. The hardness of the laser weld was varied by changing the composition of the filler wire, the carbon content of the leader strip, and the welding conditions. Φ0.9mm as filler wire
Kobe Steel MGS308, MG50T, MGS63B
Was used. As the welding conditions, the feed speed of the filler wire was 1-4 m / min, and the welding traverse speed was 5-8.
The laser output was kept constant at 5 kW while changing within a range of m / min. The width of the difficult-to-weld material and the leader strip are aligned by trimming in the pickling line, and 3 wt.
% Silicon steel to a thickness of 0.32 mm and a rolling charging speed of 17
Continuous cold rolling was performed in a range of ２８28 m / min. Then, the presence or absence of breakage of the weld was examined.

The results are shown in Table 1. Vickers hardness Hw measured at a load of 1 kg on the welded portion, Vickers hardness Hp measured at a load of 1 kg on the difficult-to-weld material, rolling charging speed V (m / m
in) is {(Hw−Hp) / Hp} · V ≦
It can be seen that the method of the present invention satisfying No. 10 does not cause fracture of the welded portion.

[0012]

[Table 1]

The leader strip is not particularly limited as long as it does not cause any problem in flash butt welding.
% Or more, the thickness of which is 80 to 120% of the thickness of the difficult-to-weld material
Is desirably within the range. In welding a difficult-to-weld material and a leader strip, it is actually desirable to change the hardness of the weld by changing the composition of the filler such as a filler wire rather than the welding conditions such as heat input and cooling rate. The use of a filler such as a filler wire also increases the reliability of the welding itself. Therefore, as a welding method, it is desirable to perform laser welding, plasma welding, arc welding or the like using a filler such as a filler wire.

[0014]

Since the present invention is configured as described above, a silicon steel sheet having (Si + Al) ≧ 1.0 wt% or
Can provide a method for continuously cold rolling a difficult-to-weld material made of any of high carbon steel sheets with C ≧ 0.6 wt% without breaking.

[Brief description of the drawings]

FIG. 1 is a diagram showing the presence or absence of breakage of a welded portion when {(Hw−Hp) / Hp} and V are changed.

Claims (1)

(57) [Claims] 1. Silicon steel with (Si + Al) ≧ 1.0 wt%
Sheet or high carbon steel sheet with C ≧ 0.6wt%
Flame welding material re that - Da - upon rolling between successive cold after joining through strip, the flame welding material and the Li - Da - Vickers measured under a load 1kg of welding of the strip - Hw a scan hardness, the Vickers measured with a load of 1 kg on difficult-to-weld materials
When the hardness is Hp and the rolling charging speed is Vm / min, rolling is performed under conditions that satisfy the formula {(Hw−Hp) / Hp} · V ≦ 10. Rolling method.