JPH0361325A - Hot rolling method for hard-to-work material - 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] The present invention relates to a method for warm rolling difficult-to-process materials.

[Conventional technology and issues to be solved]

Electrical steel sheets with a high amount of (Si + AQ) are extremely fragile and have poor impact properties. For this reason, conventionally, 1.6 to 2
．． To roll a 6m hot-rolled plate to 0.50nrn or less,
Reversal rolling is performed in which the cooling rate is kept small and the processing heat during rolling is used to carry out warm rolling, or the two-cold rolling and two-annealing method is used in which rolling is carried out with a small cold rolling rate in each cold rolling. Therefore, it is considered difficult to roll in one pass using a 4-5 stand tandem mill.

However, among the above methods, the reverse rolling method has low efficiency, and there are major problems in productivity, such as poor yield due to waste of top and bottom parts. In addition, the large number of manufacturing steps and complexity of the 2-cold pressure 2-incineration method is not desirable as a rolling method aimed at mass production. There are also some drawbacks such as this.

The present invention was made in view of such conventional problems, and provides a method that can efficiently roll difficult-to-process materials even on a tandem line without using reverse rolling or two-cold-pressing and two-annealing methods. This is what I am trying to do.

[Means to solve the problem]

Therefore, in the present invention, when hot rolling a difficult-to-process material specialized for electrical steel sheets, the material to be rolled is formed into a coil, heated at a low temperature, and then warm rolled at 70 to 200°C using a cold rolling machine. is its characteristic.

In addition, in such rolling, by connecting dummy materials to the leading and trailing ends of the rolled material prior to low-temperature heating, cooling of the inner and outer peripheral parts of the coil of the base material until rolling after heating is properly prevented. be able to.

The present invention will be explained in detail below.

The present invention is based on the premise that a difficult-to-process material such as an electrical steel sheet containing 23.0 wt% (Si + Al1) is rolled in one pass using a tandem mill for cold rolling, and a specific Heat to temperature.

To roll a material that is difficult to machine, it is necessary to heat the material to a temperature above the transition temperature at which it transitions from ductile fracture to brittle fracture.

This temperature has extremely poor workability (Si+An)≧3Id
t% electrical steel sheet is approximately 70°C, and if the original plate temperature is above this temperature, a 4-5 stand tandem mill will process 1.
0.5+n in one pass for a steel plate with a thickness of about 6 to 2.6 mm
It is possible to roll the sheet to a thickness of less than m. On the other hand, when the material temperature exceeds 200°C, a problem of oxidation of the material occurs, and therefore the upper limit of the material temperature is 200°C.

Methods for heating the rolled material by forming it into a coil include ■Tight coil annealing method (single or multi-type);
■Open coil annealing method, or ■So-called unifloor annealing method can be used.

When heating is performed using the open coil annealing method described in (2) above, it can be performed in combination with hot-rolled sheet annealing performed for the purpose of improving the hot-rolled texture.

In this case, the coil is extracted from the furnace during cooling (over 70'C) and rolled.

Further, it is preferable to heat the coil in a non-oxidizing or weakly reducing atmosphere.

In addition, even if the coil is heated to a temperature of 700°C or higher, if it comes into contact with the outside air or comes into direct contact with a crane hanging tool or reel, the inner and outer circumferential parts of the coil will heat up to 700°C in a short time while waiting for rolling.
There is a risk that the temperature will drop to below .degree. C., and in order to prevent this, it is preferable to connect dummy materials to the front and rear ends of the coil in advance. This dummy material appropriately prevents the temperature of the inner and outer circumferences of the coil (base material) from decreasing after heating and before rolling.

As the dummy material, a general thin plate with a low transition temperature can be used. Further, it is preferable that the dummy material has a thickness of about 10 turns at each of the inner and outer circumferential parts of the coil, and therefore, it is preferable that the length is usually about 50 m.

〔Example〕

A dummy material of 50 m each was connected to the top and bottom parts of a 2 m thick 3%5i-1% AQ hot rolled electrical steel plate using a laser welder, and after pickling, single annealing was performed at 250°C.
Annealing was performed for 20 hours, and extraction was performed at 150°C. Then, within 8 hours thereafter, it was rolled in one pass to 0.50 mm using a 4-stand tandem mill and a 5-stand tandem mill. The plate temperature during this rolling was approximately 80 to 100°C, and the plate could be easily rolled to the above-mentioned thickness without plate breakage or plate edge cracking.

〔Effect of the invention〕

According to the present invention described above, difficult-to-process materials such as electrical steel sheets can be efficiently rolled even on a tandem line without using complicated and inefficient methods such as reverse rolling or two-cold pressure two-annealing method. I can do it.

Claims (2)

[Claims] (1) When hot rolling difficult-to-process materials such as electrical steel sheets, the material to be rolled is formed into a coil, heated at a low temperature, and warm-rolled at 70 to 200°C using a cold rolling machine. Warm rolling method of material. (2) A method for warm rolling a difficult-to-work material according to claim (1), characterized in that, prior to low-temperature heating, dummy members are connected to the leading and trailing ends of the material to be rolled.