RU2165809C1 - Method for making steel sheet for enamelling - Google Patents

Abstract

FIELD: manufacture of rolled pieces, namely, low carbon steel strips for enamelling. SUBSTANCE: method comprises steps of hot rolling at predetermined temperature values, cold rolling and skin pass rolling of coiled strips with predetermined reduction values. At rolling steel containing carbon no more than 0.05%, aluminium no more than 0.05% and nickel, (0.05-0.08)%, temperature of hot rolling termination is set equal to 760-800 C, temperature of coiling, 680-700 C. At cold rolling total reduction value is no less than 65% and at skin pass rolling total reduction value is in range 0.4-0.6%. Reduction value at skin pass rolling is increased in above mentioned range at rolling steel with increased carbon content. EFFECT: optimization of deformation modes of steel containing carbon and aluminium. 1 ex

Description

 The present invention relates to rolling production and can be used in the manufacture of sheet steel for subsequent enameling.

 Cold-rolled steel sheet intended for metallic and non-metallic coatings (including enameling) is obtained from hot-rolled strips rolled on continuous mills. Timely technology for hot and cold rolling of sheet steel is described in sufficient detail, for example, in the reference book edited by V.I. Zyuzin and A.V. Tretyakov "Technology of rolling production", Prince. 2, M., "Metallurgy", 1991, p. 556-569 and s. 640-664. Very important parameters that determine the properties of the finished product are: during hot rolling - the temperature of the end of rolling and winding, during cold rolling - the degree of total compression, and if the strips are trained (usually after annealing) - the amount of compression.

 The steels used for enameling are low-carbon and usually with a limitation of the content of individual elements (for example, aluminum and nickel); this is done to increase the so-called hydrogen embrittlement index (PVO), the reduction of which leads to a decrease in the "porosity" of steel, to a deterioration of the coating strength and a common defect during enameling - the appearance of "fish scales" on finished products, since to increase the enamel resistance Coatings The metal surface should contain micropores that promote adhesion of the coating.

A known method of producing sheet steel for enameling with a content of C ≤ 0.001% and Al ≤ 0.01%, which is rolled with a final temperature t _to ≥ 780 ^o C and wound into a roll at t _c = 450-800 ^o C, and cold rolling with a total deformation ε _Σ ≥ 50% (see Japanese. Application N 2236254, class C 22 C 38/00, B 22 D 11/00, publ. 09/19/90). There is also a known method of producing a steel sheet for enameling with a content of C ≤ 0.005% from a continuously cast strip of 1-6 mm thickness, subjected to cold rolling and annealing, i.e., without hot rolling (see Japanese application N 63-100132, class C 21 D 9/46, C 22 C 38/00, publ. 02.05.88).

 The disadvantage of these methods is their inapplicability for the production of a thin (0.8-1.5 mm thick) sheet of steel with a carbon content of up to 0.05% (i.e. more than in the above sources), which does not give a defect when enameling " fish scales. "

 The closest analogue to the claimed object is a method of manufacturing a cold-rolled steel sheet for enameling according to US Pat. GDR N 292392, class B 21 B 3/02, C 22 C 38/04, publ. 08/01/91

This method includes hot rolling of converter steel with a content of C ≤ 0.01%, Al ≤ 0.01% and Ni ≤ 0.05%, its cold rolling and training and is characterized by the fact that after hot rolling, the strips are rewound at t _with ≥ 720 ^o C, cold rolling is carried out with ε _Σ = 60 ... 72%, and training with ε = 3% (mainly ε = 1.2%) and in rolls with a given roughness R _a ≥ 4.5 μm, which eliminates the etching operation before enameling.

 The described technology is unsuitable (see below) for the production of cold-rolled sheet for defect-free enameling from steel with a higher content of carbon, aluminum and nickel.

 The technical task of the invention is to increase the yield in the manufacture of enameled products from low carbon steel containing aluminum and nickel.

To solve this problem in a method including hot rolling with predetermined temperatures, cold rolling and training of rolled strips with predetermined reductions, when the content of carbon and aluminum in the steel is not more than 0.05% of each and 0.05-0.08% of nickel, the temperature of the end hot rolling is taken equal to 760-800 ^o C and the temperature of the winding is 680-700 ^o C, during cold rolling the total relative compression is done at least 65%, and during training - within 0.4-0.6%, and the degree of compression during training, increase within the specified limits with increasing content in s carbon hoist.

The essence of the proposed technical solution is to optimize the determining modes of hot and cold deformation of steel, which has a relatively large weight among the range of converter steels and is cheaper than steel with a very low content of carbon and aluminum. Thus the recommended modes (t _a, t _c and ε), as the experiments have shown give good results when using steels with a low content of C and Al, while the method chosen as the closest analogue, is unsuitable when the content of the box office over 0 , 01% carbon or aluminum.

An experimental verification of the proposed technology was carried out during hot rolling of 08ps converter steel of the above composition at mill 2000, during cold rolling at mill 2500 and during training at sheet rolling shop No. 5 of OJSC Magnitogorsk Iron and Steel Works. To this end, the rolling and training varied _to t, t _s and ε, fixing the yield and the presence of the defect "fish scales" enamelling steel with a thickness of 0.8-1.5 mm and the production of finished products.

The best results (yield of about 99%) were obtained when implementing the proposed method. Deviations from the above optimal parameters worsened the quality of the enameled metal. Thus _to increase t> 800 ^o C increased "raznoballnost" microstructure of the steel to deteriorate its formability, and at t _k <760 ^o C unacceptably increased load during rolling. A decrease in the winding temperature t _with <680 ^o C reduced air defense, i.e. the ability of steel to enamel deteriorated, and at t _c > 700 ^o C the plastic properties of the sheets decreased, which negatively affected their formability.

 The use of total reductions of less than 65% during cold rolling worsened the microstructure of steel and its ability to enamel (yield decreased). Exceeding the recommended value of the relative reduction during training after annealing the bales (more than 0.6%) increased the yield of the fish scale defect, and when the reduction was less than 0.4%, slippage of the rolls was observed, which sharply increased their wear and injured the surface of the strips. During training, it was noted that with an increase in the carbon content in steel, compression should be increased (within 0.4-0.6%).

 During the experiments, the manufacturing technology of sheet steel for enameling, chosen as the closest analogue, was also tested (see above). The use of this technology for steel with a carbon and aluminum content of more than 0.01%, and nickel over 0.05% yielded negative results: the yield decreased by almost 35%. Thus, the experiments confirmed the acceptability of the proposed method for solving the problem and its advantages over the known technology.

 According to the Central Laboratory of the plant, the implementation of the technical solution found in the production of enameled sheet steel allows us to increase the yield of suitable products from it by about 20% with a corresponding increase in profits from the sale of marketable products.

Concrete example
08ps low-carbon steel with a content of 0.03% carbon, 0.02% aluminum and 0.065% nickel is rolled on a continuous broadband hot rolling mill with a temperature of the end of the process t _to = 780 ^o C and with a winding temperature of the strips 690 ^o C.

The total relative compression of the strips during cold rolling to a final thickness of 1.2 mm is ε _Σ = 70%. After annealing in bell-type furnaces, the steel is trained with compression ε = 0.45% and then transferred to enameling.

Claims (1)

A method of manufacturing a steel sheet for enameling, including hot rolling with predetermined temperatures, cold rolling and training of rolled strips with predetermined reductions, characterized in that when the content of carbon and aluminum in the steel is not more than 0.05% of each and 0.05 to 0.08 % of nickel, the temperature of the end of hot rolling is taken equal to 760 - 800 ^o C and the temperature of the winding 680 - 700 ^o C, during cold rolling the total relative compression is not less than 65%, and when training within 0.4 - 0.6%, and the degree compression during training increase in the specified x range with increasing carbon content steel.