JP3148041B2 - Method for producing Cu, Sn-containing steel material - 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 producing a Cu / Sn-containing steel material from a Cu / Sn-containing steel without causing surface defects when hot working.

[0002]

2. Description of the Related Art In hot working of Cu-containing steel, very slight surface flaws are observed even when the Cu content is less than 0.3%. When this becomes 0.3% or more, small cracks occur,
Further, when it reaches 0.8%, cracks become extremely large,
It is known that if the Cu content is further increased, the cracks further increase with the Cu content (“Effects of Alloying Elements on Steel”, page 378, Seibundo Shinkosha).

There are environmental problems (disposal) of bad scraps such as playing cards, especially automobiles, home appliances and cans having high Cu and Sn contents. It is known that Sn promotes surface flaws of Cu-containing steel, but it is difficult to remove both Cu and Sn by refining. Therefore, Cu, S
Dilution of scrap has been proposed for the regeneration of scrap containing n ("1990 Elliott S").
ymposium Proceedings "599
page).

[0004] Further, by adding a predetermined amount of Ni to the Cu-containing steel, it is possible to suppress the precipitation of the Cu melt on the steel surface during high-temperature oxidation, which causes flaws, and to prevent cracking.
However, Ni is scarce as a resource and leads to high costs.
When Sn is included in addition to u, the effect of preventing cracking is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to produce a hot-rolled steel material having good surface properties without adding Ni from a poor scrap containing Cu and Sn which has been difficult to use in the past. It is assumed that.

[0006]

Means for Solving the Problems The present inventors have proposed Cu, S
The following points have been found as a mechanism for generating surface flaws during hot working of n-containing steel. Due to the selective oxidation of Fe at high temperature, C on the steel surface
The u, Sn concentration relatively increases, and Cu, Sn in Fe
In order to exceed the solid solubility limit, the Cu and Sn melts
e. The Cu and Sn melts enter the grain boundaries at the same time as the processing, and surface defects occur. The grain boundary penetration of the Cu, Sn melt is caused by the fact that Cu contained in the Cu, Sn melt and steel (F
e) is small (liquid Cu-
(Steel contact angle: <2 deg.). The Cu: Sn ratio of the Cu and Sn melts is equal to the Cu: Sn ratio in steel, and is about 10: 1 in a normal scrap melting material.

Therefore, if a substance having a large interfacial energy with Fe can be contained in a Cu, Sn melt to increase the interfacial energy between the Cu, Sn melt and Fe,
The Cu and Sn melts do not enter the grain boundaries and can prevent surface flaws. An example of a substance having a large interfacial energy with Fe is Sn (contact angle between liquid Sn and steel = about 150 de).
g.), and Pb.

That is, the present invention has been completed based on the above findings, and has the following gist. 0.1 Cu
Weight% or more, or steel containing 0.1% by weight or more of Cu and 0.01% by weight or more of Sn,
This is a method for producing a Cu, Sn-containing steel material for the purpose of preventing hot cracking caused by Cu, Sn, characterized by rolling after spraying a substance having a large interfacial energy with e. In particular,
As a substance having a large interfacial energy with Fe, Sn, P
At least one of b may be sprayed.

[0009]

Hereinafter, the present invention will be described together with its operation. During continuous casting and during heating in a heating furnace before hot rolling, the selective oxidation of Fe causes Cu and Sn to concentrate on the steel surface layer and precipitate as a liquid between the scale and the steel. Usually, this Cu, Sn melt is F
Since the interfacial energy with e is small, it penetrates the grain boundaries and cracks occur.

Therefore, after the scale is formed and before hot working, a substance having a large interfacial energy with Fe is scattered on the steel surface to be contained in the Cu and Sn melt, and the interfacial energy between the Cu and Sn melt and the steel is reduced. Enlarge. Thereby, Cu, S
It inhibits the n melt from entering the grain boundaries and prevents cracking. Substances having a large interfacial energy with Fe include Sn and Pb,
Each powder may be sprayed, or a mixed powder thereof may be sprayed. The Cu concentration in the steel to be used in the present invention is usually 0.1% by weight or more which has an effect on hot cracking.

[0011]

EXAMPLE A steel containing Cu and Sn was heated in air at 1100 ° C. for 60 minutes to produce scale.
The amounts of the Cu and Sn melts were measured and subjected to hot rolling. Table 1 shows the state of occurrence of cracks when Pb or Sn powder or a mixed powder thereof was sprayed immediately before processing and when neither powder was sprayed. The state of cracking was evaluated by an index of ○: no cracking occurred, ×: cracking occurred. No cracking occurred in the example of the present invention. In the comparative example of No. 6, many cracks occurred on the surface. The Cu concentration is 0.05% by weight.
No. In the comparative example of No. 7, cracking did not occur even if Sn was not sprayed. The composition of the Cu and Sn-containing steel used was Fe and unavoidable impurities, with the balance being other than those described in Table 1.

[0012]

[Table 1]

[0013]

According to the present invention, it is possible to obtain a hot-rolled steel material having good surface properties without surface flaws from a poor scrap containing Cu and Sn without adding cost by adding Ni. Can be.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naoki Tokumitsu 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (56) References JP-A-6-297025 (JP, A) JP-A-6 JP-A-55-79827 (JP, A) JP-A-6-198304 (JP, A) JP-A-6-31302 (JP, A) JP-A-5-220504 (JP, A) JP-A-5-111701 (JP, A) JP-A-5-212429 (JP, A) JP-A-5-212428 (JP, A) JP-A 5-237509 (JP, A) 292949 (JP, A) JP-A-6-31393 (JP, A) JP-A-4-162943 (JP, A) JP-A-5-222447 (JP, A) JP-A-5-220505 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 45/00

Claims (2)

(57) [Claims] 1. A steel containing 0.1% by weight or more of Cu or a steel containing 0.1% by weight or more of Cu and 0.01% by weight or more of Sn has a large interfacial energy with Fe. Cu, characterized by rolling after spraying the material
A method for producing a Sn-containing steel material. 2. The method for producing a steel material containing Cu and Sn according to claim 1, wherein at least one of Sn and Pb is sprinkled as a substance having a large interfacial energy with Fe.