US3551216A

US3551216A - Method of producing a steel packing strip of high strength

Info

Publication number: US3551216A
Application number: US764955A
Authority: US
Inventors: Herbert Severing; Dieter Radtke; Hans-Wilhelm Grasshoff; Heinz Kress
Original assignee: HOESCH AG HAUPTVERWALTUNG
Current assignee: HOESCH AG HAUPTVERWALTUNG
Priority date: 1967-11-23
Filing date: 1968-10-03
Publication date: 1970-12-29
Anticipated expiration: 1987-12-29
Also published as: BE724160A; DE1608163B2; GB1228929A; SE346332B; DE1608163A1; FR1592721A

Description

3,551,216 METHOD OF PRODUCING A STEEL PACKING STRIP OF HIGH STRENGTH Herbert Severing, Hohenlimburg, Dieter Radtke, Letmathe, Hans-Wilhelm Grasshofi, Hagen, and Heinz Kress, Holzen, Germany, assignors to Hoesch Aktiengesellschaft Hauptverwaltung, Dortmund, Germany No Drawing. Filed Oct. 3, 1968, Ser. No. 764,955 Claims priority, application Germany, Nov. 23, 1967, 1,608,163 Int. Cl. C21d N26 US. Cl. 148-12 5 Claims ABSTRACT OF THE DISCLOSURE A steel packing strip with a tensile strength of around 95 to 125 kp./mm. an elongation 6 of 10 to 17% and a yield point ratio of 0.86 to 0.98 is produced from a hot rolled steel strip of a composition of about 0.35 to 0.80% C., 0.15 to 0.50% Si, possibly as much as 0.045% of P and S, 0.4% to 2% Mn and/r Ni, and the balance substantially all iron of sorbitic or intermediate stage structure after hot rolling to the desired thickness of about 0.30 to 1.30 mm. is cold rolled and is finally subjected to a continuous brief recovery annealing with the beginning of recrystallation at a temperature between about 500 and 680 C., Mn and/or Ni content decreasing with increase in the content of carbon.

BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to a process for producing a steel packing strip of high strength with a tensile strength of about 95 to 125 kp./mm. an elongation 6 of to 17% and a yield point ratio of 0.86 to 0.98.

(2) The prior art It is known to produce packing strip with a tensile strength of less than 96 kp./mm. by the relaxation and recovery annealing of cold rolled strip of a steel of the type of DIM 1624, as well as undeoxidized, half-deoxidized or completely deoxidized structural steel with additives corresponding to-DIN 17100 with the desired tensile strength value. The relaxation and recovery annealing can be carried out in continuous, pot or cupola annealing ovens. The high strength packing strip with a tensile strength of more than 95 kp./mm. is produced in a known way through a continuous or intermittent heating in two heat treatments from a steel with a composition of about 0.20 to 0.40% C., 0.15 to 0.50%, Si, 1.0 to 1.5 Mn and, times, as much as 0.35% P and S.

A disadvantage of packing strips with a tensile strength of less than 95 kp./mm. is that they require a quite large cross section and for the same reason also substantial weight, in order to have adequate packing characteristics. A further disadvantage in the production of packing strips with a tensile strength of more than 95 kp./mm. is that two heat treatments are required, so that a yield point of only 0.75 to 0.85 is obtained.

SUMMARY OF THE DISCLOSURE The purpose of the present invention is to overcome these disadvantages in the known processes for the production of packing strips and to produce a packing strip which has a tensile strength of around 95 to 125 kp./ mmP, an elongation 6 of 10 to 17% and a yield point ratio of 0.86 to 0.98, which can be carried out in a simple manner with only one heat treatment.

"United States Patent 0 3,55 1 ,Z l 6 Patented Dec. 29, 1970 "ice This is achieved according to the invention by starting with a hot rolled strip with a composition of about 0.35 to 0.80% C.

0.15 to 0.50% Si possibly 0.045% P and S 0.40 to 2.0% Mn and/or NiC balance substantially all iron of sorbitic or intermediate stage structure after the hot rolling to the desired thickness of around 0.30 to 1.30 mm. is cold rolled and finally subjected to a continuous brief recovery annealing with the beginning of recrystallization at temperatures of 500 to 68 C. In order to obtain the desired mechanical characteristics, advantageously the carbon content of the steel strip used is varied inversely with that of the manganese and/or nickel content. Because the carbon content influences strongly the Working in hot and cold rolling, it is advantageous for the production of packing strip according to the invention to use a steel strip With a carbon content of 0.40% and manganese or nickel of 1.5 to 2%. If a steel strip with a higher carbon content than 0.40% is used, then according to the invention the manganese and/or nickel content is correspondingly reduced. A further advantageous embodiment of the process according to the invention is to wind up the steel strip after the hot rolling at a reeling temperature of between 500 and 620 C.

The advantages achieved according to the process of the invention are especially that, for the production of a high yield point ratio of about 0.86 to 0.98 with a simultaneous elongation of 10 to 17% and a tensile strength of 95 kp./mm. only one heat treatment for a very short time and at a reduced temperature is necessary, and, in contrast to a packing strip with a tensile strength of less than 95 kp./mm. and an elongation of 6 to 10%, the new packing strip can be more highly loaded, so as to save weight.

to the invention.

A steel strip with a composition of 0.47% C. 0.018% P 0.21% Si 0.014% S 1.43% Mn balance iron is hot rolled to 1.50 mm. and is reeled at a temperature of about 560 to 580 C., so that for the subsequent cold rolling a sorbitic starting structure is obtained. Without difiiculty (such as production of cracks in the edges of the strip) this hot strip is cold rolled to 0.5 or 0.8 mm. and finally in an annealing oven is subjected in the presence of a neutral protective gas at a temperature of 600 C. for two minutes to a recovery annealing (with a beginning of recrystallization). After this annealing treatment a finished packing strip with a full mechanical characteristic is measured:

Yield Tensile point strength Yield 0' 1B Elongation ratio, kp./mm. kpJmm. 6 percent o'S/a'B Band thickness, mm:

gation 6 of 10 to 17%, and yield point ratio of 0.86 to 0.98, in which:

a hot rolled steel strip with a composition:

0.35 to 0.80% C 0.15 to 0.50% Si 0.40 to 2.0% of a metal selected from the group consisting of Mn and Ni balance essentially all iron with a tensile strength of about 95 to 125 kp./mm. elonrolling to a thickness of about 0.30 to 1.50 mm. is cold rolled and thereafter subjected to a continuous brief recovery annealing with a beginning of recrystallization at temperature between 500 to 680 C., the content of said metal being substantially inversely proportional to the carbon content.

2. Process according to claim 1 in which said composition includes not more than 0.045% P and S.

3. Process according to claim 1 wherein the steel strip after the hot rolling and before the cold rolling is reeled at a reel temperature of about 500 to 620 C.

4. Process according to claim 1 in which recovery annealing is carried out in an oven.

5. Process according to claim 1 wherein the recovery annealing is carried out in the presence of an inert protective gas.

References Cited UNITED STATES PATENTS 2,814,578 11/1957 White 148l2 3,264,144 8/1966 Frazier et a1. 14812 3,311,512 3/1967 Mohri et a1. 14812.1 3,421,951 1/1969 Shelton 148--12.1

L. DEWAYNE RUTLEDGE, Primary Examiner W. W. STALLARD, Assistant Examiner US. Cl. X.R. 148-12.1