Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment

Definitions

• the present invention is to provide an economical method for producing steel sheets or strips (herein after called sheets) for can-making, having satisfactory workability (can-making properties) similar or better than those of the can-making steel sheet (so-called twice cold rolled sheet abridged as 2 C R steel sheet) obtained by cold rolling annealed cold rolled sheet again and by metal coating the sheet, or those of the can-making steel sheet obtained by stress-relief annealing a cold rolled steel sheet.
• sheets steel sheets or strips
• the conventional two-step method for producing canmaking steel sheets includes steps of hot rollingacid picklingcold rolling-electrolytic degreasing-annealing-second cold rolling-electrolytic degreasing-plating, while the low temperature annealing method includes steps of hot rollingacid picklingcold rollingelectrolytic degreasing--stress-relief annealing-shape correcting (may be omitted)planting.
• complete annealing is conducted at a temperature higher than 600 C. in order to remove the work hardening effect of the cold rolled steel sheets or stress-relief annealing is conducted at a temperature between 400 and 600 C.
• the present invention is based on the above facts and has been completed as a result of extensive studies for obtaining good can-making properties by combination of steel composition and operational conditions of production steps without an annealing step.
• the gist of the present invention lies in the method for producing can-making steel sheets which is characterized in that a steel slab containing not more than 0.03% C, not more than 1.0% Mn, not more than 0.04% P, not more than 0.02% O with the balance being iron and unavoidable impurities is subjected to finishing rolling in a temperature range from its A transformation point to 750 C., coiled at a temperature not lower than 620 C.
• hot rolled steel sheet is acid pickled and cold rolled with a reduction rate not lower than More particularly, steel ingot or slab containing not more than 0.03% C, not more than 1.0% Mn, not more than 0.04% P, not more than 0.02% O with the balance being iron and unavoidable impurities is prepared by the conventional mold casting method or continuous casting method, and the slab which produced above method is heated to 1000 to 1300 C. in slab reheating furnace and hot rolled.
• the temperature when the sheet passes the final rolling rolls namely the finishing outlet temperature and the coiling temperature are important.
• the temperature at the hot rolling finishing outlet should be between the A transformation point of the steel and 750 C. and the coiling temperature should be not less than 620 C. for the reasons herein set forth.
• the hot rolled coil thus obtained is acid pickled and cold rolled at a reduction rate not less than 80% into cold rolled strip of 0.1 to 0.5 mm. thickness.
• This cold rolled strip is directly used as can-making cold rolled steel sheet, and no subsequent annealing for the purpose of stress relief is required.
• the carbon content is limited to not more than 0.03% for the following reason. It has been conventionally considered that when work strain remains in steel sheet, corrosion resistance is deteriorated, but it has been found by the present inventors that corrosion resistance is remarkably improved by lowering the carbon content to not more than 0.03%, preferably 0.018%, and that some carbon content is necessary for obtaining strength required by cans.
• Manganese is added to prevent lowering of hot workability of hot rolled sheet due to sulfur and to give the sheet required strength. However, the manganese content should be not more than 1.0%, but in an amount more than three times of the sulfur content.
• Phosphorus should be not more than 0.04% because it remarkably deteriorates corrosion resistance of the steel sheet.
• Oxygen is a harmful element, because it combines with manganese and silicon in the steel to form oxides, thus lowering cleanness of the steel and deteriorating can-making properties.
• Particularly high degree of cleanness of the steel is required when cold rolling of more than 80% reduction rate is done as in the present invention.
• the oxygen of the hot rolling does not exceed the A transformation point of the steel and the sheet is coiled at a temperature not lower than 620 C.
• the coiled steel strip is maintained at the temperature for substantial time so that the steel is subjected to recrystallization annealing by its own content is limited to not more than 0.02%.
• the 5 heat and the hot rolled structure is eliminated.
• the finish ng rolling temperature soft hot rolled steel sheet thus produced is subjected to and the corlmg temperature areimportant for obtaining cold rolling of more than 80% reduction according to excellent strength and workability for can-making, parthe present invention, tensile strength of the sheet as cold ticularly n case of cold rolled steel sheets which have rolled will be lower than about 70 kg./mm. and it is posbeen sub ected to strong cold reduction. The reason for sible to improve the productivity of cans without sacrifice defining the fin shmgrolhng temperature as between the of can-making properties.
• a transformation point and 750 is that this tempera-
• steel ture range is optimum for formation of complete equicontaining not more than 0.03% C, not more than 1.0% axed grains free from hot rolled structure, and the reason Mn, not more than 0.04% P, not more than 0.02% O for odefinlng coiling temperaturefis f lower than with the balance being iron and unavoidable impurities 62:0 C. that this temperature range is desirable for 0bis prepared in an ordinary steel making furnace such as 9 3 g L 3 of i sheet for can'makmg and a converter, an open hearth, and an electric furnace.
• Vac- IS eslra 6 mm e Pomt 0 ecolflomyfi uum degassing may be used to adjust the carbon and oxy-
• the advantage of the present invention is that satist t factory workability of the sheet for can-making can be gen con en d obtained only by the strong cold rolling of more than 80% Thus prePared molten.
• the can-making steel stocks produced by the EXAMPLE 1 conventional methods require annealing and workability of the sheet as cold rolled with heavy reduction is poor Steel having the composition shown in Table 2 was and it is impossible to work the sheet into cans directly.
• prepared in a converter and part of the molten steel was According to the present invention, excellent can-maksubjected to vacuum degassing to adjust the composition.
• No. l to No. 4 which are outside the composition of the present invention (No. 1 is outside the composition in respect of C and O, No. 2 in respect of C, No. 3 in respect of O, and No. 4 in respect of P) could not be worked into cans or had poor can-making feasibility even when they had some workability.
• No. 4 to No. 8 which are within the composition of the present invention were excellent both in can-making workability and can-making feasibility.
• EXAMPLE 2 Steel having the composition shown in Table 4 was hot rolled under the conditions shown in Table 4 and cold rolled with reduction rate of 87% into cold rolled sheets of 0.27 mm. thickness, and their mechanical properties, workability, can-making feasibility are shown in Table 5.
• a in Table 5 indicates the finishing outlet temperature not lower than the A transformation point, and B represents the finishing outlet temperature not higher than the A transformation point.
• the can-making feasibility of No. 3B which is within the composition of the present invention is poor due to the too low coiling temperature in spite of the finishing rolling temperature below the A transformation point.
• No. 4 due to its high carbon content, shows slightly lower can-making feasibility in spite of satisfactory hot rolling conditions.
• No. 1B and No. 2B which are within the scope of the present invention show remarkably excellent can-making feasibility in particular.
• a method for producing can-making steel sheet comprising subjecting a steel slab containing not more than 0.03% C, not more than 1.0% Mn, not more than 0.04% P, not more than 0.02% O, with the balance being iron and unavoidable impurities to finish hot rolling at a temerature between the A transformation point and 750 C., coiling the sheet at a temperature not lower than 620 C., and cold rolling thus obtained hot rolled sheet or strip after acid pickling with a reduction rate not lower than 80%.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=13821084

Family Applications (1)

Country Status (2)

Cited By (2)

Families Citing this family (2)

• 1972
  • 1972-08-24 JP JP8410072A patent/JPS539169B2/ja not_active Expired
• 1973
  • 1973-08-23 US US00391020A patent/US3843423A/en not_active Expired - Lifetime

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