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
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0273—Final recrystallisation annealing
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
  • C21D1/20—Isothermal quenching, e.g. bainitic hardening
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching

Definitions

• the present invention relates to a process for the annealing of cold worked steel sheet and strip and is more particularly concerned with a process for the production of plate having a hardness of at least 65 R30T units.
• Steel sheet and strip is produced for the tinplate industry in a number of grades having different ranges of hardness and these grades of material are known in the British and American tinplate industries as Temper 1, Temper 2, etc. up to Temper 6, the latter material being the hardest and having a hardness of 65 to 70 R301 units in the as annealed condition (RBOT units are Rockwell hardness numbers using the superficial Rockwell tester with a 30 kg. load).
• -t is an object of the present invention to provide a process whereby annealed steel sheet and strip having a hardness of at least 65 RSOT units can be obtained from ordinary grade, that is non-rephosporised, blackplate steel.
• a process for the production of annealed steel sheet and strip which comprises heating cold worked steel sheet or strip which contains from 0.07 to 0.14% carbon md less than 0.02% phosphorus to a temperature of from 740 to 850 C., rapidly quenching the steel from this temperature to a temperature of from 150 to 250 C., and over-aging the steel within the latter temperature range whereby a stable product having a hardness of at least 65 R301" units is obtained.
• the final hardness of the product after over-aging depends on the carbon content of the steel, the annealing temperature and, to a lesser extent, the quenching rate; thus in order to obtain the specified minimum hardness, it is necessary to employ a steel having a carbon content at the upper end of the specified range if an annealing temperature at the lower end of the specified range is used, or vice versa. More particularly, if an annealing temperature of from 740 to 770 C. (the "ice latter temperature being the Curie transition point for steel which is substantially independent of the carbon content) is used, the steel should contain from 0.12 to 0.14% carbon in order to obtain or exceed the specified minimum hardness. If annealing temperatures above the Curie point, that is from 770 to 850 C., are used, the specified minimum hardness can be obtained or exceeded with steels containing from 0.07 to 0.12% carbon.
• the final product will have a hardness greater than that of Temper 6 plate (which has a hardness of -70 R30T units), such a degree of hardness corresponding to that of so-called double-reduced tinplate.
• Double-reduced tinplate is produced by cold rolling tinplate after tinning so as to double its superficial area; owing to the increase in superficial area this product is much cheaper than conventional tinplate and although it has poorer properties than conventional tinplate, in respect, for example, of ductility, corrosion resistance, and uniformity of mechanical properties in the transverse and longitudinal directions with respect to the direction of rolling, the reduction in gauge is compensated by the considerable increase in hardness and stillness and the product can be used where the service conditions are not very severe.
• the present invention therefore provides a method of obtaining the necessary hardness in thin tinplate of this type (of 40 to 60 pounds substance, that is 0.0044 to 0.0066 inch thickness) by heat treatment rather than by cold rolling. Such a prodnot obtained by the present process has the advantages of greater ductility and less directionality over the product obtained by cold double reduction.
• the hardness of the product after over-aging also depends to some extent on the quenching rate. Quenching may be effected into water or into a mol en metal bath, for example a bath consisting of a 50% mixture of lead and bismuth.
• a mol en metal bath for example a bath consisting of a 50% mixture of lead and bismuth.
• the faster quenching rates obtainable by water quenching enable a somewhat harder product to be obtained than when a molten metal quenching medium is used.
• Temper 6 mechanical properties (hardness 65- R301 units) can be obtained with steels containing from 0.08 to 0.14% carbon by quenching from the Curie point, 770 (2., into water, but at the lower cooling rates associated with liquid metal quenching, the range of carbon contents which give Temper 6 hardness values using the same annealing temperature is narrowed to 0.12 to 0.14% carbon.
• the steel sheet or strip is preferably heated rapidly to the annealin temperature, for example in less than 10 seconds, and is quenched immediately or after only a short holding time, i.e., less than 5 seconds. After quenching, the steel is over-aged at a temperature of from to 250 C.
• Over-aging is preferably carried out, in the case of strip treatment, by coiling the strip as it leaves the quenching bath and holding the coil in a thermally insulated container for the required time. The period requ red for over-aging depends on the overaging temperature, a longer time being required at lower temperatures and vice versa; in the middle of the temperature range specified, i.e., 200 C., over-aging is normally complete in /2 hour.
• overaging temperature lower over-aging temperatures within the above range giving slightly heart er products higher temperatures within the range.
• Over-aging can be carried out in air without any appreciable oxidation taking place at ten peratures below 200 C.; if over-aging is carried out at higher temperatures it is preferable to surround the steel with a non-oxidising atmosphere.
• the process according to the invention is particularly suitable for the continuous high speed production of Temper 6 strip for the tinplate industry. Gwing to the very short processing times of the steps which take place (Steel A was over-aged at 230 C. for /2 hour, instead of at 200 C.)
• the process can be operated continuously at high speed in plant which costs a fraction of that for the continuous high speed production of Temper 6 plate by present methods, and which occupies a fraction of the space required for the latter.
• EXAMPLE 1 Samples 4 /2 in. x 6 in. of cold worked steel sheet having different carbon contents were annealed under the conditions described in Example 1. After over-aging, the samples were temper rolled on a 6 in. mill with smooth rolls to 234-2344 extension and were then given a simulated lacquer stoving treatment by being maintained at Samples of cold worked steel sheet having different carbon contents were induction heated to the Curie point (770 C.) and quenched into a molten metal quenching bath consisting of 50% lead50% bismuth. Two heating cycles, namely heating to 770 C. in 5 seconds with 5 seconds hold (lstheating cycle) and to 770 C.
• Table 2 2nd heating 1st heating cycle cycle Carbon content, percent Quench to Quench to Quench to 200 C.
• EXAMPLE 4 stituents of the steels other than iron are given in Table equivalent to a heating time of 15 seconds and a holding 3 below: time of 5 seconds).
• Table 6 1 sec. heating to 770 C. 5 sec. heating to 770 C. 10 sec. heating to 770 0.
• R301 RI R301 R301 R301 R301 R301 R301 sheet were heated to 810 C. in a salt bath, quenched into The results obtained With the samples heated to the lead-50% bismuth baths maintained at 200 C., 250 C. and 350 C. reseectively and held in the baths for 30 minutes. In addition some of the samples were quenched into the baths at 350 C. and 250 C. and then hnrnediately transferred to other baths for holding at lower temperatures.
• EXAMPLE 8 Samples of steel sheet 0.010 to 0.013 inch thick containing 0.0 to 0.125% carbon were cold rolled to a nominal Table 5 Holding temperature 350 0. 250 0. 200 C.
• the cold reduced samples Were then heated to 810 C. by immersion for 4 seconds in a salt bath, quenched into a 50% lead-50% bismuth bath maintained at 150 C. and held at the latter temperature for 45 minutes. After this treatment, some of the samples were temper rolled to give a 2 /2% reduction and strain aged at 350 C. for 20 seconds.
• Table 7 An annealed (Qnenched As temper rolled and strain aged 1 The R301 values are converted R151 values (Wilson conversion chart).
• EXAMPLE 7 The hardnes of the treated samples containing 0.105% or more carbon is comparable to that of so-called doublereduced tinplate, that is tinplate of 40 to 60 pound su stance (corresponding to a thickness of 0.0044 to 0.0066 inch); but the ductility is greater and the directionality less, than that of double reduced tinplate (a typical example of the latter having Erichsen value of 3.0 mm. and
• Can peaking pressure values were, on average, 10% 33 il- I r t 2:: g i g a greater than the minimum requirement for beer cans and 8,, It g gig 0 to thp 12% greater than for cans made using a commercial rean en Y e w K phosphorised Ste e1 of the same gauge temper rolled 1m latter temperature range until a stable product having a 1 C7 3 J- der identical conditions.
• a process for the production of annealed steel sneet and 9 1/2/5 1/2 res angel p 20 and strip which comprises the steps of rapidly heating p cold worked steel sheet or strip which contains from 0.07 EXAMPLE 10 to 0.14% carbon and less than 0.02% phosphorus in less Cold reduced steel strip 5 inches Wide and containing than 10 W to tempjsrature of from 740 to 012% carbon 0.935% sulphur 001070 phosphorus and 850 C., holding the steel at said temperature for less than 043% manganesa was passed through a Continucus am 5 seconds, rapidly quenching the steel from said tempera nealing plant at approximately 150 feet/minute. In this l to a temperaiur?
• the strip wa heated to an annealing temperature m the Steel Wlth1n.the tamperamre range a of in approximately 3 seconds and than quenched period of about minutes until a stable product having m 0 O in a molten 50% 16ad 5O% bismuth bath a hardness of at least 65 R30T units is obtained.
• the strip was coiled as it came from the quench bath and 30 A accordmg to clalm Wherem 9 steel was maintained in the coil at 200 C. for 30 minutes. 15 quenched mm a 50% lead-50% blsmuth The strip was then temper rolled to 2 /2% extension A 9 Process, for the production of gnnealfid using shot blasted and smooth rolls and then electrolyticallsteel P, which omprises e steps of continuously 1y tinned (4 0L denosfl) and flow brightened on a cominw passing cold rolled steel strip which contains from 0.07 ous electrolytic tinning line.
• a process for the production of annealed steel sheet and strip which comprises the steps of heating cold worked steel sheet or strip which contains from 0.07 to 0.14% carbon and less than 0.02% phosphorus to a temperature of from 740 to 850 C., rapidly quenching the steel irom this temperature to a temperature of from 150 to 250 C., and then over-aging the steel within the latter temperature range until a stable product having a hardness of at least R30T units is obtained.

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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)

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Citations (1)

• 0
  • BE BE624419D patent/BE624419A/xx unknown
  • NL NL285173D patent/NL285173A/xx unknown
• 1961
  • 1961-11-07 GB GB39805/61A patent/GB956879A/en not_active Expired
• 1962
  • 1962-09-24 US US225831A patent/US3117897A/en not_active Expired - Lifetime
  • 1962-11-02 LU LU42631D patent/LU42631A1/xx unknown
  • 1962-11-05 DE DEB69505A patent/DE1242662B/de active Pending
  • 1962-11-07 AT AT876262A patent/AT242180B/de active

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