Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • 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
  • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
  • C21D3/02—Extraction of non-metals
  • C21D3/04—Decarburising
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing

Definitions

• ABSTRACT OF THE DISCLOSURE A deep drawing rimmed steel sheet and method of manufacture wherein the sheet consists of up to .02% carbon, 0.20-O.60% manganese, 0.0030.050% selenium, the balance iron and incidental impurities and wherein the sheet is produced by subjecting a rimmed steel sheet containing 0.020.l0% carbon along With the requisite manganese and selenium to hot and cold rolling to produce the sheet and thereafter decarburizing to reduce the carbon content to less than 0.02%.
• the present invention relates to a cold rolled steel sheet which has superior deep drawing qualities, excellent nonaging properties, and which is not subject to surface imperfections by fabrication and to a method for producmg same.
• aluminum killed steels adapted for both deep drawability and non-aging have been extensively employed for use in automobile body sheet, various kinds of machine parts, electrical appliances, home appliances, furniture, etc.
• the aluminum killed steels are inferior to rimmed ones in the yield of ingots as well as in surface finish and their production costs are high.
• the conventional rimmed steels are of low cost and of good appearance but rimmed steels have not been utilized in the past for the above purposes because of their rather poor deep drawing as well as non-aging properties.
• This invention contemplates to overcome the above disadvantages of rimmed steels, the principal object of this invention being to provide an improved rimmed steel sheet and a method of producing the same which is free from surface defects, of high yield as well as of low cost, and with excellent deep drawing as well as nonaging properties.
• This invention is directed specifically to a deep drawing rimmed steel sheet having a composition consisting of up to 0.02% carbon, 0.20-0.60% manganese, 0.003- 0.050% selenium, the balance iron and incidental impurities, the physical properties of which are:
• this steel may contain 0.010-0.040% phosplfatorus, the purpose for which will be described hereina er.
• a method for producing this improved cold rolled steel sheet first comprises adding 0.0030.050% selenium to a molten steel containing 0.020.l0% carbon and 0.20- 0.60% manganese to produce a rimmed steel of the above specified composition.
• phosphorus is also to be added both selenium and phosphorus are incorporated in the molten steel containing 0.020.10% carbon, 0.20- 0.60% manganese, and less than 0.010% phosphorus to produce a rimmed steel containing 0.0030.050% selenium and 0.010-0.040% phosphorus.
• this steel is subjected to a series of hot and cold rolling procedures and then to a decarburizing anneal at a temperature of 600800 C. to reduce the carbon content to less than 0.02%.
• the above decarburizing anneal tends to develop the growth of extraordinary crystal grains, and a steel sheet having a coarse crystal grain will tend to produce surface defects when subjected to press Work.
• the crystal grain size number should be in the range of 8.0-l0.0 as specified by the A.S.T.M.
• the carbon content of the steel ingot produced in the steel making step is required to be in the range of 0.020.10% to obtain the desired final product quality. If the carbon content of the steel is lower than the lower limit of the above range, the oxygen content thereof increases so much that the steel quality is deteriorated by the presence of non-metallic inclusions. If the carbon content is higher than the up er limit an uneconomical extended period of time is required for carrying out a decarburizing anneal described hereafter.
• Manganese may be included in an amount of 0.20- 0.60%, which is a normal amount for conventional rimmed steel, Further, as pointed out above, phosphorus may be incorporated in the steel along with the selenium but where there is a phosphorus addition the molten steel should be fully dephosphorized to less than 0.010% phosphorus in the steel making step. Where a phosphorus addition is made the final steel product should contain between 0.010 and 0.040% of this element.
• the above content of phosphorus is effective not only for the development of the (111) crystal grain aggregate structure in the steel sheet, but also to inhibit the decrease of tensile strength. Further it imparts a superior deep drawing quality to the steel sheet.
• the steel sheet with both added elements, phosphorus and selenium has a better deep drawability than a sheet added with selenium only as described hereinafter.
• a steel containing 0.020.10% carbon and O.200.60% manganese is produced by either converter, open hearth furnace or electric furnace and then either selenium or selenium and phosphorus are added to either ladle or mold to obtain a rimmed steel ingot. N0 deoxidizing treatment whatsoever is applied.
• the steel ingot thus produced is subjected to a series of conventional steps, such as, slabbing, hot rolling, pickling, and cold rolling. Then the cold rolled steel sheet is subjected to a decarburizing anneal to reduce the carbon content of the steel sheet to less than 0.02%, preferably less than 0.01%. With a considerable decrease of carbon the (111) crystal grain aggregate structure develops gradually whereby deep drawability and plastic anisotropy are improved.
• the type of anneal furnace is not particularly critical but an open coil type anneal is most desirable from the viewpoint of economy as well as product quality.
• An anneal temperature is preferred to be in the range of 600-800 C.
• the anneal temperature is too low, the time for decarburization will adversely efiect deep drawability. If it is too high an extraordinary growth of crystal grain will take place so that it will be diflicult to obtain a product of uniform quality.
• the anneal temperature is in the range of 650750 C. in order to obtain superior deep drawability with the crystal grain under control.
• the composition of the atmosphere gas for the anneal may be any of the known decarburizing compositions. Further a combination atmosphere may be utilized. Satisfactory atmospheres include ones consisting of hydrogen containing a small amount of water. Also the atmosphere may contain nitrogen which is desirable from an economic standpoint.
• ferrophosphorus and ferromanganese alloys were added to the molten steel which had been poured into the ladle whereby a steel of the following composition was produced:
• the molten steel was poured into an ingot mold while, at the same time, 670 g. metallic selenium was added and a 10 t. rimmed steel ingot was obtained.
• This steel ingot was heated in a soaking pit uniformly to about 1300 C. and then subjected to slabbing to produce a slab of mm. thickness.
• This slab was hot rolled in a hot strip mill to make a hot strip coil of 2.8 mm. in thickness.
• the hot coil was pickled and cold rolled in a cold strip mill to obtain a cold strip coil of 0.8 mm. in thickness.
• the cold strip coil was subjected to a decarburizing anneal.
• the cold strip coil was subjected to the decarburizing anneal for 20' hours at the temperature of 710 C. Lastly, the cold coil was subjected to a temperrolling with a slight (1.0%) reduction to produce a smooth surface thereon.
• Table I chemical analysis
• Table II physical properties
• Erichsen test is a cupping test, using a tool with a spherical end of 20 mm. diameter to deform the test specimen which is held between annular jaws of 27 mm. internal diameter.
• the test sheet which is 3% inches square, is first clamped between the jaws to measure the thickness; the jaws are then moved apart by 0.05 mm. and clamped in that position to allow metal to be drawn into the cup as the test progresses.
• the tool is pressed into the metal until a fracture appears in the cup, and the depth of the cup at fracture is taken as a measure of the ductility of the metal.
• R value shows whether deep drawability is good or not and can'be obtained by measuring the deformation of a tensile test specimen in the thickness direction and that of the same specimen in the width direction.
• the larger R value the smaller the deformation of sheet in the tensile deformation which shows greater drawability.
• N0. 1 refers to a known rimmed steel in which the crystal grain is very fine, but its C.C.V. is 38.48
• No. 2 refers to a commercial aluminum stabilized steel which has a good deep drawability for its fine crystal grain size, and in addition, a good aging property, but
• N0. 3 refers to a commercial rimmed steel which has been subjected to the decarbnrizing anneal and its deep drawability is more improved than that of No. 1 but its crystal grain is noticeably coarsened.
• No. 4 refers to the same steel as No. 3 but subjected to a lower anneal temperature, up to 680 C., so as to prevent the crystal grain size from coarsening but, owing to the insufficient anneal, inferior deep drawability results.
• Nos. 5-13 refer to the steel sheet of this invention. Nos.
• 6 and 7 refer to the rimmed steel sheet containing 0.0030.050% selenium subjected to the decarbnrizing anneal at the temperature of 710 C., in which the crystal grain size is sufficiently fine, and the deep drawability is rather good, its C.C.V. being about 37.
• No. 8 refers to an improved steel sheet subjected to the anneal temperature of 690 C. in which an appropriate crystal grain size is developed by the addition of 0.003% selenium.
• No. 9 refers to a steel sheet of this invention in which the anneal temperature of 740 C. which is somewhat high but coarsening of crystal grain is prevented by adding 0.028% which is relatively high. Nos.
• No. 10 refers to the rimmed steel containing 0.0100.040% phosphorus in addition to selenium and wherein the steel is subjected to a decarburizing anneal at the temperature of 710 C., in which the crystal grain is suitably fine, and its deep drawability is more improved than those of Nos. 5, 6 and 7 containing selenium only, and further, in which the decrease of tensile strength is inhibited.
• No. 13 refers to the steel sheet contaning 0.003% selenium and 0.018% phosphorus subjected to the anneal at a temperature of 690 C. in which an 8.6 A.S.T.M. crystal grain size is obtained due to the slight decrease of selenium content.
• Elongation (EL) and stretchability (EL) of the steel sheet in accordance with the present invention are the same or better than those of the aluminum killed steel.
• a method for producing a deep drawing steel sheet which comprises forming a rimmed steel ingot containing 0.020.l0% carbon, 0.200.60% manganese, and 0.0030.050% selenium, subjecting said rimmed steel ingot to hot and cold rolling to produce a thin steel sheet, and then decarburizing said sheet by anneal at a temperature of 600-800" C. to reduce the carbon content to less than 0.02%.
• decarburizing atmosphere is a mixture of hydrogen, nitrogen and steam.
• decarburizing anneal is effective at a temperature of between 650 and 750 C.
• a method for producing a deep drawing steel sheet which comprises providing a rimmed steel ingot containing 0.0030.050% selenium and 0.010.040% phosphorus by adding selenium and phosphorus to a molten rimmed steel containing 0.020.10% carbon, 0.20 0.60% managnese, and up to 0.010% phosphorus, subjecting said rimmed steel ingot to hot rolling and then to cold rolling to produce a thin steel sheet, and then decarburizing said sheet by an anneal at a temperature of 600-800 C. to reduce the carbon content to less than 0.02%.
• a method according to claim 9 wherein the anneal is of the open coil type.
• a method according to claim 8 wherein the decarburizing atmosphere is a mixture of hydrogen, nitrogen and steam.
• a method according to claim 8 wherein the decarburizing anneal is efiected at a temperature between 650 and 750 C.
• a deep drawing rimmed steel sheet consisting of up to 0.02% carbon, 0.200.60% manganese, 0.003- 0.050% selenium, the balance iron and incidental impurities, said steel sheet characterized by having an A.S.T.M. crystal grain size number of 8.010.0, a C.C.V. of less than 37.3 for 0.8 mm. thickness and containing predominantly a (111) crystal aggregate structure.
• a deep drawing rimmed steel sheet consisting of up to 0.02% carbon, 0.200.60% manganese, 0.003- 0.050% selenium, 0.010-0.040% phosphorus, the balance iron and incidental impurities, said steel sheet being characterized by having an A.S.T.M. crystal grain size number of 80-100, a C.C.V. of less than 37.3 for 0.8 mm. thickness and containing predominantly a (111) crystal aggregate structure.

Landscapes

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=11556650

Family Applications (1)

Country Status (7)

Cited By (4)

Families Citing this family (1)

Citations (5)

• 0
  • BE BE658771D patent/BE658771A/xx unknown
• 1965
  • 1965-01-18 SE SE614/65A patent/SE302471B/xx unknown
  • 1965-01-19 US US426667A patent/US3335036A/en not_active Expired - Lifetime
  • 1965-01-21 DE DE19651483253 patent/DE1483253B2/de active Pending
  • 1965-01-22 GB GB2916/65A patent/GB1094745A/en not_active Expired
  • 1965-01-25 LU LU47843A patent/LU47843A1/fr unknown
  • 1965-01-25 NL NL6500896A patent/NL6500896A/xx unknown

Patent Citations (5)

Also Published As

Similar Documents