JP3025363B2 - Rolling method for copper and tin containing steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling steel containing copper and tin.

[0002]

2. Description of the Related Art In hot working of Cu-containing steel, Cu0.
Even at less than 3%, very slight surface flaws are observed. Cu
If it exceeds 0.3%, small cracks are formed, and Cu0.8
%, The cracks become remarkably large.
It is known that as the u content is increased, cracks increase further with an increase in the Cu content (influence of alloying elements on steel, page 378, Seibundo Shinkosha).

[0003] In addition, the problem of so-called tramp elements such as automobiles and household electric appliances scraps, particularly the environment (scrap disposal) of scraps having high Cu and Sn has been raised, and the dilution of scraps has been proposed for the regeneration of scraps containing Cu and Sn. (1990 Elliott Symposium Pr
receivedings 599).

Japanese Patent Application Laid-Open No. Sho 59-215275 discloses a method for welding overlay of aluminum bronze which prevents Cu from penetrating into the iron grain boundaries.
Disclosed is a method of performing underlay welding with 30% or more of Fe-Ni-based material and then using 7Ni-aluminum bronze as an overlaid first layer to prevent cracking due to Cu penetration.

[0005] Trump elements, particularly Cu and Sn, are difficult to remove in refining, and the Cu and Sn contents are controlled to below allowable levels in raw material management, or Cu, Sn is used in hot metal, type pig iron and the like.
A method of diluting with a raw material having a small Sn content is known.

On the other hand, it has been proposed to add a predetermined amount of Ni to Cu-containing and Sn-containing steel and fix Cu and Sn in the steel as an alloy of Ni-Cu-Sn to prevent generation of surface flaws. Ni is scarce in resources and expensive.

[0007]

SUMMARY OF THE INVENTION The present invention proposes a method for hot rolling a playing card element, particularly a steel containing Cu and Sn, which makes it possible to use a poor scrap containing Cu and Sn, which has been difficult to use in the past. is there.

[0008]

According to the present invention, Cu ≧ 0.3
%, When hot rolling a high-temperature steel material containing Sn ≧ 0.01%, copper that cools the surface layer of the material to be rolled to a temperature equal to or lower than a crack initiation temperature determined by the material of the material to be rolled immediately before the roll is engaged.
This is a method for rolling tin-containing steel. In addition, the present invention provides a copper- and tin-containing material that cools the material to be rolled by 0.5 to 3 mm from the surface of the material to be rolled immediately before biting by each roll in continuous multi-stage rolling, and further cools the material to be rolled before and after biting by the rolls of tandem rolling. This is a steel rolling method.

The present invention will be described below with reference to the drawings. FIG.
At the entrance of the rolls 10-1 and 10-2 of the hot rolling mill, water spray nozzles 11-1, 11-2 and 12-1,
12-2 is provided opposite to the upper and lower surfaces of the material 15 to be rolled. The material to be rolled 15 heated to, for example, 1200 ° C. in a heating furnace is bitten by the roll 10-1 and the water spray nozzle 11-
The upper and lower surfaces are cooled by 1, 11-2.

[0010] According to experiments, biting into a roll is 0.2-
It is preferable to cool the material to be rolled by water spray from 0.4 seconds to immediately before. That is, when the cooling zone length L is set, the time t seconds before being engaged with the roll is obtained by the equation (1). L = v · t (1) where v is the threading speed of the material to be rolled, and t is 0.2 to 0.4 seconds.

In the present invention, the material to be rolled is water-cooled to a temperature not higher than the crack initiation temperature. The crack initiation temperature is 900 to 950 ° C. or lower for ordinary scrap-based component steel, and the Cu (Sn-free) steel is 1050 ° C. or lower. Therefore, the crack initiation temperature is selected according to the composition of the material to be rolled. The cooling layer of the material to be rolled is 0.5 to 3 mm from the material surface, preferably 1 to 2 mm.

Therefore, according to the present invention, as shown in FIG. 2, the material to be rolled 15 having a surface temperature of 1200 ° C. is 0.2 mm.
Cooled by water spray from 0.4 seconds before to just before the roll bite, the surface is cooled to 0.3 to 3 mm, preferably 1 to 3 mm.
A Cu-Sn layer 14 having a thickness of about 2 mm is formed.

That is, Cu and Sn dissolved in the steel have a low melting point Cu-Sn alloy phase concentrated on the surface when the slab is heated.
Scale with 15. Scaled Cu-S
n does not diffuse into the early steel and does not cause cracking.

In the case of continuous multi-stage rolling, the roll 10-
When the rolled material is bitten into the roll 10-2 after the rolling by 1, the material is recuperated, and is again water-spray cooled. The cooling condition may be adjusted by adjusting the nozzle opening so as to obtain the same condition as when the roll 10-1 is engaged.

[0015] The Cu-Sn layer on the surface of the material to be rolled is rolled together with the material to be rolled. The target steel type of the present invention is a steel of Cu ≧ 0.3% and Sn ≧ 0.01%. This is because if the content is less than 0.3% Cu and less than 0.01% Sn, there is little risk of surface flaws and cracks occurring during hot working. When Ni is included, Ni ≦ Cu / 2 is satisfied. This is because Ni in the steel can promote the formation of a Ni-Cu-Sn alloy. The present invention is, of course, also effective for steel types to which Cu and Sn are positively added, such as weathering steel.

Although the present invention has been described with respect to the rolling by a continuous multi-roll, the same effect can be obtained by providing a water spray nozzle before and after the roll and performing cooling for a predetermined time before and after the roll is engaged in tandem rolling. Was confirmed.

[0017]

According to the present invention, it is possible to prevent the occurrence of flaws in the hot rolling of copper and tin-containing steel, so that a sound rolled product can be obtained even with steel containing tramp elements.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the present invention.

FIG. 2 is a chart of the operation of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B21B 3/00 B21B 1/02 B21B 45/00 C21D 8/00-8/02

Claims (3)

(57) [Claims] When hot rolling a high-temperature steel material containing Cu ≧ 0.3% and Sn ≧ 0.01%, the surface layer of the material to be rolled is cracked immediately before the roll is engaged by a crack determined by the material of the material to be rolled. A method for rolling copper and tin-containing steel, wherein the steel is cooled to a temperature lower than the generation temperature. 2. The method for rolling copper and tin-containing steel according to claim 1, wherein 0.5 to 3 mm is cooled from the surface of the material to be rolled immediately before the engagement of each roll in continuous multi-stage rolling. 3. The method for rolling copper- and tin-containing steel according to claim 1, wherein the material to be rolled is cooled before and after the tandem rolling roll bites.