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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
• • 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
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/562—Details
  • C21D9/563—Rolls; Drums; Roll arrangements
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49544—Roller making

Definitions

• ABSTRACT Primary Examiner-Hyland Bizot Assistant ExaminerW. R. Satterfield Attorney, Agent, or Firm-Donald S. Ferito 5 7] ABSTRACT Generally, the method of the invention involves surface-conditioning new and used rebonded fused silica sleeved hearth rolls of a continuous silicon steel strip heat-treating furnace while the furnace is in production Operation.
• Method consists of scheduling the furnace, when new rolls are to be conditioned, to process silicon steel strip product requiring dry annealing in an atmosphere having a maximum dew point of 30F at a temperature the range of approximately 1,400 to 2,000F (preferably 1,500F) and processing such silicon steel strip through the furnace with the strip applying a Sustained force normal to the peripheral surfaces of the rolls for a period of 24 to 72 hours.
• used rolls are surface-conditioned to remove oxide roll-pickup by scheduling the processing of silicon strip product having rough surfaces through the furnace which requires a dry anneal in an atmosphere having a maximum dew point of 30F at a temperature ranging from 1,400 to 2,000F (preferably 1,500F) and processing such Strip through the furnace for approximately 16 hours.
• the present invention relates generally to the heat treating of steel strip and more particularly to a method of surface-conditioning rolls having sleeves thereon of rebonded fused silica especially suitable for use in continuous silicon steel strip heat-treating furnaces.
• Steel strip can be annealed in either coil form, commonly referred to as batch annealing or by passing the uncoiled strip through a continuous annealing furnace.
• the present invention addresses itself to the continuous annealing of steel strip.
• Continuous annealing furnaces are of two types, namely, vertical or horizontal. Vertical or horizontal refers to the strip alignment in the furnace during the heat treatment operation. The major affect on product quality in comparing the two types is the capability of the horizontal furnace to produce a stress-free strip product.
• a typical horizontal continuous heat-treating furnace roller hearth line consists of an entry section including coil-payoff reels, strip welder, horizontal looping equipment, electrolytic cleaning, scrubbing and drying units.
• the entry section is joined to a contiguous horizontal heat-treating section consisting of a gas-fired heating zone (72 feet long), and an electrically-heated holding zone (600 feet long), a controlled cooling zone (200 feet long), and a jet-cooling zone (90 feet long).
• the dimensions cited pertain to a typical unit now in operation. The dimensions are stated to illustrate 'the comparative lengths of the various elements of a typical horizontal continuous annealing furnace. These dimensions may vary as desired or necessary.
• the exit section of the furnace consists of a horizontal looping unit and tension reel.
• the strip is supported as it passes through the heat-treating, section of the furnace in catenary fashion by individually-motor-driven alloy steel rolls having sleeves of rebonded fused silica thereon.
• This type of roll is described and claimed in pending US patent application Ser. No. 172,947, now US. Pat. No. 3,75 1,195, which is assigned to the assignee of the present application.
• oxides of silicon and carbon are given off as gases (C0, C while the silicon oxide (SiO is retained on the strip surface.
• This silicon oxide is very much like a thin glass coating which is in a viscous state. Small portions of this oxide are sometimes picked up from the steel strip by the roll sleeve surfaces at various points on the periphery thereof. This spotty buildup on the roll sleeve surfaces causes a depression or dimple to form on strip subsequently passing over the roll surface. Such depressions or dimples are particularly objectionable on silicon steel strip since a major end use of this product is the forming of stator and rotor laminations of electrical equipment or devices.
• a specific number of laminations is required, for example, for building up the armature of an electric motor in order to attain certain desired electrical characteristics. Specifically, a fixed number of laminationsis required for each lineal inch of cross section of the armature in order to attain certain electrical characteristics. Therefore, distortions of the surface of silicon steel strip used for making these laminations cannot be tolerated.
• the susceptibility of silicon steel strip to surface deformation or marking is related to its silicon content.
• Low silicon steel strip one-half to 1% silicon content
• medium silicon steel strip (1 to 3% silicon content) has a lesser, but still objectionable, susceptibility to surface marking and deformation
• high silicon steel strip (above 3% silicon content) has the greatest resistance to surface marking or deformation by roll-pickup accretions on annealing furnace rolls.
• the amount of roll-pickup and subsequent strip marking has been found to be related to annealing temperature and moisture content of the atmosphere in the continuous annealing furnace.
• a normal operating cycle to anneal silicon strip in a typical horizontal continuous annealing furnace would be in a range of 1 ,400 to 2,000lF with steam being introduced in the electrically-heated holding zone to decarburize the strip.
• a normal decarburization atmosphere would have a minimum F dew point.
• high silicon approximately 3% silicon content
• Such a fast oxide pickup occurs because of the surface condition of the sleeves of the newly manufactured or newly ground rolls.
• the roll sleeves not only have grinding marks resulting from the pre-service conditioning of the sleeve surface, but the nature of the rebonded fused silica surface is such that it is also somewhat porous. Therefore, if the fresh roll is initially exposed to conditions of high temperature and high dew point, the glutinous oxide produced on the silicon strip being heat treated is picked up in the sleeve pores and the imperfections resulting from pre-service surfaceconditioning. Although the amounts of oxide pickup are minute, the oxide penetrates the porous surfaces of the sleeves and then serve as a base for further cumulative pickup. The sleeved roll must, therefore, be initially conditioned to form a compact peripheral surface which will not readily permit oxide adherence.
• the method of our invention utilizes the normal catenary disposition of the strip between hearth rolls to an advantage.
• the weight of the strip while operating in the dry annealing atmosphere applies a sustained force normal to the peripheral surface of the roll which. results in a polished peripheral surface on the sleeved roll which is essentially free of pores which, if present, would later attract strip oxides.
• the annealing line will operate free of oxide pickup for at least fourteen days.
• This modified embodiment of the invention includes two alternatives depending upon the severity of oxide pickup on the rolls.
• the first alternative comprises scheduling the annealing furnace to anneal high silicon (3% or more silicon content, by weight) strip which has'been previously box annealed at high temperature.
• a coating of magnesium oxide is applied to the strip prior to box annealing to prevent spot welding of concentric wraps of the strip coil at the high temperature used during box annealing.
• the magnesium in this coating and the silicon in the strip combine to form a magnesium silicate on the strip surface. This magnesium silicate imparts an abrasive surface to the strip. Processing this type of silicon strip through the annealing furnace for approximately sixteen hours at a low temperature of approximately 1,500F and in a dry atmosphere (30F maximum dew point) will effectively remove oxide pickup from the hearth rolls with no detrimental effect on productivity.
• the furnace could be scheduled to process high silicon strip which has been given a rough temper mill finish during its previous processing.
• a method for surface-conditioning newly installed continuous silicon steel strip heat-treating-furnace rolls having sleeves of rebonded fused silica thereon during production operation of said furnace which comprises the step of processing production silicon steel strip through said furnace in a relativelydry atmosphere having a maximum dew point of approximately 30F at a temperature in the range of substantially l,400 to 2,000F for a period of approximately 24 to 72 hours with the weight of said silicon steel strip applying a sustained force normal to the peripheral surfaces of said rolls whereby a polished surface free of pores is produced on said furnace rolls.
• a method for removing roll-pickup fron continuous silicon steel strip heat-treating-furnace rolls having sleeves of rebonded fused silica thereon during production operation of said furnace which comprises the step of processing rough-surfaced silicon steel strip through said furnace in a relatively dry atmosphere having a maximum dew point of approximately 30F at a temperature in the range of substantially 1,400" to 2,000F for a period of approximately 16 hours with the weight of said silicon steel strip applying a sustained force normal to the peripheral surfaces of said rolls whereby a polished surface free of roll-pickup is produced on said furnace rolls.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Rolls And Other Rotary Bodies (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23155223

Family Applications (1)

Country Status (10)

Cited By (2)

Families Citing this family (1)

Citations (2)

• 1972
  • 1972-10-20 US US00299533A patent/US3789647A/en not_active Expired - Lifetime
• 1973
  • 1973-10-19 DE DE2352611A patent/DE2352611C2/de not_active Expired
  • 1973-10-19 IT IT30361/73A patent/IT998803B/it active
  • 1973-10-19 CA CA183,837A patent/CA992439A/en not_active Expired
  • 1973-10-19 JP JP48117035A patent/JPS5858408B2/ja not_active Expired
  • 1973-10-19 FR FR7337451A patent/FR2208982B1/fr not_active Expired
  • 1973-10-19 YU YU02735/73A patent/YU273573A/xx unknown
  • 1973-10-20 BG BG024804A patent/BG21376A3/xx unknown
  • 1973-10-20 RO RO7376388A patent/RO67729A/ro unknown
  • 1973-10-22 GB GB4907173A patent/GB1450957A/en not_active Expired

Patent Citations (2)

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