# US 5,706,689 A · Single-piece self-guiding high mill plug > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,689 A - Document ID: US5706689A - Status: Granted - Kind: A - Application number: 08/818,290 - Filed: 1997-03-14 - Granted: 1998-01-13 - Earliest claimed: 1995-03-09 - Assignees: Victor W. Nery - Inventors: Victor William Nery - Web page: https://patentgrep.com/patent/US5706689A ## CPC - B21B 25/00: Mandrels for metal tube rolling mills, e.g. mandrels of the types used in the methods covered by group B21B17/00; Accessories or auxiliary means therefor {; Construction of, or alloys for, mandrels or plugs} - B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04) ## Abstract A single-piece self-guiding, high integrity high mill plug for producing seamless tubular steel products in rolling mills is provided. The high mill plug is produced from a single a casting having a substantially bullet shape with an opening at each end and a passage therebetween to allow gases which develop during the casting process to escape. By designing the high mill plug to be produced from a single casting with no dead-end cores, the latent surface defects associated with the prior multi-piece casting designs are substantially avoided and the casting used to produce the single-piece self-guiding high mill plug has a very high integrity. The single-piece self-guiding high mill plug substantially improves rolling mill operations for producing seamless tubular steel products by eliminating both time and labor expenses associated with disassembling and reassembling the worn work plug sections as required by the prior art multi-piece high mill plug designs. ## Claims ### Claim 1 A single-piece self-guiding high mill plug, wherein said high mill plug has a front end, a back end, and a surface, said high mill plug comprising: a. a conical shaped entry zone extending aft from a front end of said high mill plug, said conical shaped entry zone comprising a wall having an outer surface, an inner surface and an essentially uniform thickness between the inner and outer surface of said wall for a major portion of said entry zone; b. a cylindrical shaped work zone extending forward from a back end of said high mill plug, said work zone having a bar cap receiver configured to receive a bar cap for centering said high mill plug in a workpiece and comprising a wall having an outer surface and an inner surface; and c. a passage extending longitudinally therethrough, said passage connecting a nose cone aperture at the front end of said high mill plug with said bar cap receiver aperture at the back end of said high mill plug; wherein the inner surfaces of said entry zone and said work zone define the passage and wherein the wall of said cylindrical work zone zone has a thickness which is substantially greater than the thickness of the wall of said entry zone. ### Claim 2 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is formed as a unitary casting. ### Claim 3 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is heat treated for stress-relieving said high mill plug to minimize residual stresses and to produce the desired physical properties for said high mill plug. ### Claim 4 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is heat treated for annealing said high mill plug to soften said high mill plug and to produce the desired physical properties for said high mill plug. ### Claim 5 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is heat treated for gas carburizing said high mill plug to produce a hard surface on said high mill plug. ### Claim 6 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is heat treated for controlling furnace atmospheres and surface carbon content to produce a carbon deposition on said high mill plug. ### Claim 7 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein the surface of said high mill plug is descaled and cleaned to produce the desired surface for said high mill plug. ### Claim 8 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein the surface of said high mill plug is machined to produce the desired surface finish and the desired shape for said high mill plug. ### Claim 9 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said high mill plug is made of a steel alloy having about 15% to about 25% chromium by weight, having about 2% to about 10% nickel by weight, and having about 1.0% to about 1.5% carbon by weight. ### Claim 10 (depends on 1) The single-piece self-guiding high mill plug of claim 1, wherein said bar cap receiver defines a conical shaped opening centrally disposed about a longitudinal centerline through said passage. ### Claim 11 A single-piece self-guiding high mill plug for producing a seamless tubular steel product from a steel shell, and wherein said high mill plug has a passage between a front end and a back end along a longitudinal centerline axis, said high mill plug comprising: a. a primary lead-in zone located aft of the front end, said primary lead-in zone having a nose cone defining a first aperture connected to one end of the passage, said primary lead-in zone defining a first outer geometry that increases in diameter in correspondence with the distance aft of the front end along the centerline axis, said primary lead-in zone being configured for receiving and guiding the steel shell and having a wall with an outer surface, an inner surface, and an essentially uniform thickness between said inner and outer surface for a major portion of said primary lead-in zone; b. a transition zone located immediately aft of said primary lead-in zone, said transition zone defining a second outer geometry that increases in diameter in correspondence with the distance aft of the front end along the centerline axis, said transition zone being configured for guiding the steel shell; c. a secondary lead-in zone located immediately aft of said transition zone, said secondary lead-in zone defining a third outer geometry that increases in diameter in correspondence with the distance aft of the front end along the centerline axis, said secondary lead-in zone being configured for guiding the steel shell; and d. a work zone located immediately aft of said secondary lead-in zone, said work zone having a plug base at the back end and a bar cap receiver configured to receive a a bar cap for centering the bar cap in the steel shell, wherein said bar cap receiver is defined through said plug base and connects with the other end of the passage, said work zone defining (i) a work surface located immediately aft of said secondary transition zone, said work surface defining a fourth outer geometry with a uniform outer diameter in correspondence with the distance aft of the front end along the centerline axis, said work surface being configured for working the steel shell, (ii) and a standoff surface located aft of said work surface, said standoff surface having a fifth outer geometry that decreases in diameter in correspondence with the distance aft of the front end along the centerline axis, said work zone further having an inner surface and a wall between said inner surface and said work surface; wherein the steel shell is worked in said work zone to decrease the cross sectional wall area of the steel shell and to thereby elongate the steel shell to produce the seamless tubular steel product; wherein the wall of said work zone has a thickness that is substantially greater than the thickness of the wall of said primary lead-in zone. ### Claim 12 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is formed as a unitary casting. ### Claim 13 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is heat treated for stress-relieving said high mill plug to minimize residual stresses and to produce the desired physical properties for said high mill plug. ### Claim 14 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is heat treated for annealing said high mill plug to soften said high mill plug and to produce the desired physical properties for said high mill plug. ### Claim 15 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is heat treated for gas carburizing said high mill plug to produce a hard surface on said high mill plug. ### Claim 16 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is heat treated for controlling furnace atmospheres and surface carbon content to produce a carbon deposition on said high mill plug. ### Claim 17 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein the surface of said high mill plug is descaled and cleaned to produce the desired surface for said high mill plug. ### Claim 18 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein the surface of said high mill plug is machined to produce the desired surface finish and the desired shape for said high mill plug. ### Claim 19 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug is made of a steel alloy having about 15% to about 25% chromium by weight, having about 2% to about 10% nickel by weight, and having about 1.0% to about 1.5% carbon by weight. ### Claim 20 (depends on 11) The single-piece self-guiding high mill plug of claim 11, wherein said high mill plug defines a cross sectional wall area which increases along said secondary lead-in zone.