US3615923A

US3615923A - Method for processing of strip metal in a continuous manner to remove undesired curvature

Info

Publication number: US3615923A
Application number: US833211*A
Authority: US
Inventors: Thomas J Rum
Original assignee: Gillette Co LLC
Current assignee: Gillette Co LLC
Priority date: 1969-01-31
Filing date: 1969-01-31
Publication date: 1971-10-26
Anticipated expiration: 1988-10-26

Abstract

Razor blade strip steel 0.2 inch wide and 0.0015 inch thick is transferred at a 30 foot per minute rate sequentially through a hardening furnace, an air-cooled tubular transition zone, a quench unit, a freeze unit, a tempering furnace, and a continuous inspection station to a takeup reel. The vertical position of the quench unit relative to the transition zone is adjustable so that a differential stress may be applied to the steel strip to prevent or minimize a dish condition in the processed strip.

Description

United States Patent Inventor Thomas J. Rum

South Boston, Mass.

Appl. No. 833,211

Filed Jan. 31,1969

Patented Oct. 26, 1971 Assignee The Gillette Company Boston, Mass.

METHOD FOR PROCESSING OF STRIP METAL IN A CONTINUOUS MANNER TO REMOVE UNDESIRED CURVATURE 6 Claims, 5 Drawing Figs.

US. Cl 148/131, 148/128,148/153 Int. Cl C2ld 1/18 Field of Search 148/131,

[56] References Cited UNITED STATES PATENTS 3,148,093 9/1964 Williams et a1. 148/131 Primary Examiner-Richard 0. Dean Attorney-Willis M. Ertman ABSTRACT: Razor blade strip steel 0.2 inch wide and 0.0015 inch thick is transferred at a 30 foot per minute rate sequentially through a hardening furnace, an air-cooled tubular transition zone, a quench unit, a freeze unit, a tempering furnace, and a continuous inspection station to a takeup reel. The vertical position of the quench unit relative to the transition zone is adjustable so that a differential stress may be applied to the steel strip to prevent or minimize a dish condition in the processed strip.

METHOD FOR PROCESSING OF STRIP METAL IN A CONTINUOUS MANNER TO REMOVE UNDESIRED CURVATURE This application is a division of my copending patent application Ser. No. 586,880, filed Oct. 14, 1966, now U.S. Pat. No. 3,466,022.

This invention relates to the processing of metal and more particularly to the processing of strip metal in a continuous operation in a manner to remove undesired curvature in the metal strip that extends transversely of its length.

In the processing of strip metal, of the type intended for use in razor blades, for example, a dish condition (curvature in the metal strip transversely of its length) may be produced during the process of the heat treatment of steel. Such a dish condition in the metal strip creates a particular problem related to the process of sharpening the edge of the strip to a shaving edge, as the dish condition efiectively offsets the edge of the metal strip to be sharpened relative to the supported body of the strip and the sharpening equipment so that an inferior sharpening process results.

The cause of such a dish condition in stainless steel strip is believed to result from an imbalance in the chemical composition and/or microstructure of the steel strip produced during the rolling process, specifically a difference in the amount of carbon and/or the size and distribution of carbides present at the two surfaces of the steel strip. During the best treatment process, a difference in the resulting carbon content of the austenite at the opposite surfaces of the strip results in a differential expansion (or contraction) of one surface of the strip relative to the other, and the resulting dish condition.

Accordingly, it is an object of the invention to provide novel and improved methods and apparatus for removing a dish condition from strip metal in a continuous processing operation.

In accordance with the invention, a dish condition is removed from a steel strip by subjecting the surfaces of the strip to a stress differential as austenite is being converted to martensite, the strip having passed through a hardening furnace but prior to the quenching of the strip during the hardening process. In the preferred embodiment of the invention, this stress differential condition is produced by bending the strip over a relatively sharp edge surface when the austenite to martensite conversion is still progressing.

In such continuous process, stainless steel strip, after passage through an austenitizing furnace in which it is subjected to a temperature of about 2,000 F. to form austenite has its temperature reduced at a controlled but relatively rapid rate to form martensite. When the temperature of the strip reaches approximately 320 F. (the martensite to austenite transformation still progressing) the strip is subjected to mechanical working if a dish condition is detected to exist. This mechanical working is imposed on the steel strip just prior to entry into a quench device and comprises subjecting the strip to an abrupt change in direction by bending it over a relatively sharp edge. In the preferred embodiment, a transition zone between the furnace and the quench unit is an aircooled tubular element that includes a guide structure of low thermal conductivity which guides both the edges and bottom surface of the strip. In the absence of dish, the horizontal strip support surface of the guide structure is aligned with the corresponding support surface of the quench unit. Where a dish condition is detected, the position of the quench unit relative to the guide surface in the transition zone is changed, preferably by lowering the quench unit, so that the strip is stressed as it passes over the edge of the guide structure at the end of the transition zone and also further stressed as the strip is again deflected through contact with the quench unit.

This processing of strip steel in this manner enables reduction of the dish condition to within a process limit of 0.0007 inch over a strip width of 0.193 inch and to a corresponding limit for strip of different width. In a process line where a dish sensor is employed, the position of the quench unit relative to the transition zone may be controlled automatically to produce hardened steel razor blade strip that is substantially flat.

Other objects, features and advantages of the invention will be seen as the following description of a particular embodiment thereof progresses, in conjunction with the drawings in which:

FIG. 1 is a block diagram of a steel-strip-hardening process line as used in the practice of the invention;

FIG. 2 is a diagrammatic perspective view of the transition between the transition zone and the quench unit;

FIG. 3 is an end view of the quench unit and its support arrangement is used in the practice of the invention;

FIG. 4 is a side view of the apparatus shown in FIG. 3; and

FIG. 5 is a sectional view of the quench unit taken along the line 5-5 of Fig. 4.

A processing line for treating stainless steel strip in a hardening and tempering operation to provide a strip of suitable metallurgical characteristics capable of having formed thereon a durable, high-quality shaving edge is shown diagrammatically in FIG. I. That processing line includes a supply reel 12 from which the strip 10 is taken for transfer sequentially through a hardening furnace 14, an air-cooled transition (fourth) zone I6, a quench unit 18, a freeze unit 20, a tempering furnace 22, and a continuous inspection station 24 to a takeup reel 26. The s trip 10 processed in this line is in the order of 0.2 inch wide and 0.00l5 inch thick. The steel employed in the preferred embodiment has the following composition range:

Carbon (LN-0.44% Chromium l3.0l4.0% Manganese Gib-0.50%

Silicon (XXI-0.50% Molybdenum I.l5-l.35%

the balance being essentially iron.

In the processing operation, the strip 10 is advanced at a constant rate of about 30 feet per minute and is heated to a temperature of approximately 2,000 F. in furnace I4. At the output of the furnace, the steel is subjected to an air-cooled environment so that its temperature is about 320 F. at the end of tubular zone 16. This fourth zone tube may vary in length, a 16 inch length being satisfactory in this system such that the austenite to martensite conversion begins in this unit and is still in progress at the exit end of tube 16. The strip is then further cooled by passage through a water-cooled quench block assembly 18 and then a freeze cooling unit 20 which is operated at approximately F. The steel is then passed through tempering furnace 22, which is maintained at approximately 500 F., and then through inspection station 24 where the quality of the processed steel in inspected. The heat treated steel is then wound on takeup reel 26.

The vertical position of the quench unit relative to the output of the fourth zone is adjustable as indicated in Figs. 3 and 4. That assembly includes a table 50 on which a quench block structure 52 is supported. As indicated in Fig. 5, that quench block structure includes a body 54 which defines a passage 56 to which are connected inlet and outlet tubes 58 for the flow of cooling water through the body. Supported on the body is a series of lower quench plates 60 held in place by clamp elements 62, and a corresponding series of upper quench plates 64. These quench plates in the this particular embodiment are manufactured of carbide (Carboloy grade 907 and each quench plate includes a central ridge 66 which contacts the upper surface of the steel strip 10 (not shown in Fig. 5) as it moves over the series of lower plates 60. The ends of the quench plate ridges 66 are radiused in the order of 0.025 inch and provide a smooth transitional surface at the entry of the strip to the quench unit. At the forward end of the quench block base 54 there is mounted an upstanding bracket 70 that receives an adjustment screw 72 and has a stop member 74 secured to its end. A lock nut 76 cooperates with bracket 70 to lock screw 72 in position so that the stop member 74 may hold the series of upper quench plates in the desired position relative to the body 54.

The quench block unit is coupled to table 50 by

side plate elements

80, 82 which are secured to the sides of the base 54 of the quench block by means of screws 84. Projecting laterally from the platform 50 are two arms 85, each having an upstanding bracket 86 which receives an adjustment screw 88 that is coupled respectively to the

blocks

80 and 82 through a universal joint structure 90. By movement of the screws 88, the lateral position of the quench block assembly on the platform 50 may be adjusted. A stop structure 92 is provided at the rear end of platform 50 which limits the backward movement of the quench block assembly.

Platform 50 is secured by pin 100 to an upstanding bracket member 102 which in turn is pivotally secured to intermediate member 104 by transverse pin 106. Member 104 includes an arm 108 that projects laterally from it which receives an adjusting screw 110. This adjusting screw, at its upper end, engages platform 50 and when moved pivots that platform 50 about the axis defined by pin 100 in a level adjustment operation. At the rear end of intermediate member 104 is still another adjusting screw 112 the upper end which is secured to the rear end of platform 50 by block 114 so that rotation of screw 112 produces rotation of platform 50 about the axis defined by pin 106.

intermediate member 104 is supported on a base structure 120 by adjustment screw 122 and is guided by rods 124, 126. Adjustment screw 122 is received in threaded relation by base 120 and is secured to intermediate member 104 so that rotation of screw 122 produces vertical movement of platform 50 (via intermediate member 104). (While these adjustments and particularly adjustment screw 122 are indicated as manually operable be obvious appropriate adjustment drives such as servomotors may be utilized which respond to signals supplied over line 134 from inspection unit 24 [FiG. 1].) Base 120 is secured on rails 130 by bracket members 132.

The transition zone structure 16 includes a cylindrical tube 136 which has disposed in it an insert 140 that has a channel of U-shaped configuration as indicated in FIG. 2 that extends the full length of the tube and which is secured in position by four locking screws located in the sides of the tube. The channel has two

sidewalls

144, 146 and a base wall 148. The end of base wall 148 is an abrupt straight line surface. This insert is a material of low thermal conductivity and a satisfactory material is Marinite an asbestos fiber material having an inorganic binder.

In operation, strip is passed through the processing line at a continuous and uniform rate of speed and is continually sensed for a dish condition by a suitable gauging element, a satisfactory gauging element being disclosed in the copending patent application Ser. No. 586,874, filed Oct. 14, 1966, now US. Pat. No. 3,465,571, and assigned to the same assignee as this application. Upon detection of a dish condition the quench block assembly is lowered relative to the guide surface 146 so that the strip steel 10 is forced over the sharp edge 150 at the output end of insert 140. The upper surface of the strip steel is similarly subjected to a transition of somewhat lesser magnitude by the first upper quench plate 64. This stressing of the strip is effective to remove the dish condition and result in a substantially flat steel strip, the edge of which is suitable for sharpening by high-volume mass production techniques to a durable, high-quality razor edge. in general, in the processing of this thin strip steel for commercially acceptable razor blades it is preferred that the orientation of the dish condition be of concave downward configuration. With such configuration, the steel strip is more uniformly guided by the insert in the transition zone and creation of stains (oxidation) on the finished strip is minimized.

Thus the steel strip during the hardening process, is subjected to mechanical working at a point in the process where the condition of the steel is such that it can be mechanically worked without adverse effect (such as marring) on its surface and yet the steel is in such condition that enables a dish condition to be removed through relatively minor manipulation of the steel prior to completion of the austenite to martensite transformatiom While a particular embodiment of the Invention has been shown and described, various modifications thereof will be ob vious to those skilled in the art and therefore it is not intended that the invention be limited to the disclosed embodiment or to details thereof and departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. A method of treating continuously moving steel strip for reducing transverse curvature of the strip comprising the steps of heating said strip to produce austenite, cooling said strip rapidly to convert the austenite to martensite, and during the conversion of austenite to martensite, subjecting the opposite surfaces of said strip to a differential stress by bending said strip over a relatively sharp edge disposed generally perpendicularly to the direction of strip movement to reduce transverse curvature of the c8 strip so that the strip produced by said method is substantiaily flat.

2. The method as claimed in claim I wherein said strip is subjected to said differential stress when said strip is at a temperature of about 320 F. and further including the step of passing said strip through quench means immediately after said bending step.

3. The method as claimed in claim 1 and further including the steps of inspecting the strip after it has cooled for transverse curvature and controlling the amount of differential stress to which said strip is subjected by varying the position of said relatively sharp edge as a function of said inspection.

4. The method as claimed in claim 1 wherein said strip is a razor blade steel strip in the the order of 0.0015 to 0.0039 inch in thickness, said strip is heated to a temperature in the order of 2,000 F and further including the step of passing said strip through quench means immediately after said bendin g step.

5. The method as claimed in claim 4 wherein said strip is subjected to said differential stress when said strip is at a temperature of about 320 F.

6. The method as claimed in claim 5 and further including the steps of inspecting the strip after it has cooled for transverse curvature and controlling the amount of differential stress to which said strip is subjected by varying the position of said relatively sharp edge as a function of said inspection.

Claims

2. The method as claimed in claim 1 wherein said strip is subjected to said differential stress when said strip is at a temperature of about 320* F. and further including the step of passing said strip through quench means immediately after said bending step.
3. The method as claimed in claim 1 and further including the steps of inspecting the strip after it has cooled for transverse curvature and controlling the amount of differential stress to which said strip is subjected by varying the position of said relatively sharp edge as a function of said inspection.
4. The method as claimed in claim 1 wherein said strip is a razor blade steel strip in the order of 0.0015 to 0.0039 inch in thickness, said strip is heated to a temperature in the order of 2,000* F., and further including the step of passing said strip through quench means immediately after said bending step.
5. The method as claimed in claim 4 wherein said strip is subjected to said differential stress when said strip is at a temperature of about 320* F.
6. The method as claimed in claim 5 and further including the steps of inspecting the strip after it has cooled for transverse curvature and controlling the amount of differential stress to which said strip is subjected by varying the position of said relatively sharp edge as a function of said inspection.