US3779817A

US3779817A - Method of producing quenched and tempered hollow steel structural members of polygonal cross section

Info

Publication number: US3779817A
Application number: US00291854A
Authority: US
Inventors: W Brunko
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1972-09-25
Filing date: 1972-09-25
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18
Also published as: FR2200360B1; DE2348152A1; CA986824A; IT996728B; FR2200360A1; GB1398062A; JPS49123963A

Abstract

Method of producing quenched and tempered hollow steel structural members of polygonal cross section includes the steps of hot rolling a hollow steel tube, austenitizing the tube, water quenching it, reheating the tube to a tempering temperature just below the lower critical transformation temperature, and rolling the tube to the desired polygonal cross section while holding the temperature of the member at the tempering temperature.

Description

United States Patent [191 Brunko Dec. 18, 1973 [54] METHOD OF PRODUCING QUENCHED 2,256,455 9/1941 Crawford l48/l2.4 AND TEMPERED HOLLOW STEEL 2,748,039 5/1956 Adams et al |48/I2.4

STRUCTURAL MEMBERS OF POLYGONAL CROSS SECTION [75] Inventor: Wade D. Brunko, Library, Pa. [73] Assignee: United States Steel Corporation,

Pittsburgh, Pa.

[22] Filed: Sept. 25, 1972 [21] Appl. No.: 291,854

[52] US. Cl. 148/12.4 [51] Int. Cl C21d 9/08 [58] Field of Search l48/l2.4

[56] References Cited UNITED STATES PATENTS 2,222,263 ll/l940 Nelson l48/l2.4

Primary ExaminerW. W. Stallard Att0rneyRalph H Dougherty [57] ABSTRACT Method of producing quenched and tempered hollow steel structural members of polygonal cross section includes the steps of hot rolling a hollow steel tube, austenitizing the tube, water quenching it, reheating the tube to a tempering temperature just below the lower critical transformation temperature, and rolling the tube to the desired polygonal cross section while holding the temperature of the member at the tempering temperature.

8 Claims, No Drawings 1 METHOD OF PRODUCING QUENCHED AND TEMPERED HOLLOW STEEL STRUCTURAL MEMBERS OF POLYGONAL CROSS SECTION within the tempering temperature range; and g. Allowing the resulting product to be air cooled. The chemical composition of the steel in the tube may be any steel which is suitable for the production of This invention relates to hollow steel structural tub- 5 q n h and tempered ubes. A Suitable composition ing, and more particularly t nch d d t d is a silicon-aluminum killed steel, having a composition structural steel tubing of polygonal cross section such bf about 020% Carbon, t-45% rhahgahese and 006% as square or rectangular. Tubular structural stccls pro- Vahadhlrh- This steel composition is martehsitic and cessed in this manner developed high yield strengths hibits g weldabihtyand high tensile strengths, together with high notch l0 Austehittzihg is accomplished at a temperature toughness at l tempetatures greater than the A temperature of the steel in the tube.

Heretofore, structural steel tubing of polygonal cross For t steels, this means a temperature greater than sections has been produced in one of two ways. In the 155001: but will usualty be r about 16000}? to about fi method, a Substantially round tube iS f d by 1750F. Preferably, the austenitization is carried out in hot rolling in a tube-mill, which tube is formed into the a gas'fired furhaee in ah excess air atmosphere r a desired cross sectional dimensions and shape by passsuffieteht time b assure uniform heating of the tubeing it through a squaring pass after the round tube has water qttehehmg ts aeeemphshed by Passing the tube been formed. The squaring or sizing operation is carthrough a sertes of p y quench rthgs to Provide 100% i d out at a temperature of from about llOOO to surface coverage of the tube circumference The tube 1500F. In the second method, the tube is hot rolled in is quenched to a temperature of about 1500b, but y a conventional manner, then reheated to about be quenched to y temperature below 2000K 1300F-.,- and passed through a sizing mill to form the The tempering temperature is j above the stress b i a polygonal crosslsootion H treatment of relieving temperature and just below the lower critical the finished shapes has resulted in distortion of the flat transformation temperature of the steel that is, l faces of the shapes beyond acceptable commercial limbelow the el temperature For most steels, pe g i Thus, the physical properties such as Strongth and will be carried out at a temperature between about toughness of these tubes are limited to those properties 1 1500b and 1225OF- The tube ls pe for a Perted which can be attributed to chemical composition alone. suffieteht to bring the tube to a uhttbrm tempering US Pat. No. 2,748,039 teaches a method of producing P r a quenched and tempered pipe of round cross Section The tube 15 rolled to the des red polygonal cross secwhich requires additional small reductions to be made such as a round'ebrhereft q rbuhdjeorhered after the quench and temper process to remove minor rectangle or y desired CI'OSS b Whlle distortions caused n within the tempering temperature range. This 18 nor- This invention is predicated upon my development of a e wtth a 512mg haylhg a number or stands a weldable waterquenched and tempered structural wtth sqbarrhg'bassestube of polygonal cross section to meet the demand for h shapes Pr y thrs rhethbd e free of higherstrength structural materials with superior notch ht a e high hbteh toughness, g ytetd strength toughness properties and ultimate Strength.

Accordingly, it is the principal object of this inven- To llustrate thepresent invention, two steels having tion to provide a method of producing quenched and 40 ehethleat ebrhpbsttlbhs as shown Table e tempered hollow Stool Structural members of polygonal melted in an electric furnace and rolled into 10 inch dlcross section having high yield strengths, and excellent emetet b rouhde h were Subsequently rolled notoh toughness and elongation propertios into 10 ea inch outside diameter seamless tubes, half of It is a further object of this invention to provide a each eerhbbsrttbh hafthg'three'elghths lrleh walls a method of producing dimensionally Correct holloW half having one-half inch walls. The lower vanadium Stool structural members content tubes were austenitized at l600F, and the The method-of the invention consistS higher vanadium tubes at l650F, in a walking beam H lli a ll Steel b i substantially furnace for 100 minutes per inch of wall thickness. This oval or circular cross section by any conventional was followed y P y quenching with q h water at tube rolling method; a temperature of about 92F. The one-half Inch wall b, A i i i h b tubes were quenched at a speed of 26 ft. per minute 0. Water quenching the tube to about 150F; and the three-eighths inch wall tubes at 36 ft. per mind. Reheating the tube to a temperature above the tubes were regrbuped and some were stress relieving temperature and below the Ac Pered at and m at l2 25F. All tempering temperature; .was for 72 minutes total furnace time, after which the Tampering th b i h tempering temperature round tubes were formed into square tubes at the temrange; pering temperature in a five-stand sizing mill having f. Rolling the tube to the desired polygonal cross secsquaring P The final tubes Were a d t air tion while holding the temperature of the tube e001- 0 w *7 TABL E l C Mn P S, Si Al V Cu Ni Cr M0 N2 night No. l .22 1.49 0.011 0.019 0.45 0.064 0.037 0.01 0.16 0.08 0.01 0.008 Ingot N0. 2 .22 1.51 .009 .019 .47 .067 .071 .01 .16 .03 .01

Table 2 shows the mechanical properties from two as-rolled tensile tests and tests from each tube quenched and tempered according to this process. From this data, it is clear that 75,000 psi minimum 4 above the stress relieving temperature and below the Ac temperature; e. tempering said tube at said tempering temperature; f. rolling said tube to the desired polygonal crossyield strength may be attained in all wall thicknesses to 5 section while within said tempering temperature one-half inch. range; and

TABLE 2 Longitudinal strip tensile Temper Yield Ultimate Elong.

Pipe N0. Austenilizing temperastrength strength in 2" Y|eld and end Composition Wall temperature ture (F.) (psi) (psi) tens|le lE-S 0.04 V 0.500" As-rollcd 68,490 98,480 32.0 0.70 2ES.. 74,070 103,790 28.5 .72 lA-N. 88,630 102,980 30.0 .86 1BS... 89,770 103,300 27.5 .87 lC-N.. 79,400 94,350 34.0 .84 1DS.. 80,300 95,460 35.0 .84 lE-N.. 86,090 100,680 33.0 .86 lG-S... 82,590 94,200 35.0 .88 ll-N 80,800 95,220 35.0 .85 2A-N. 98,070 111,420 30.0 .88 2BS..... 102,990 1 14,480 29.0 .90 2C-N. 91,420 104,790 31.0 .87 2DS.. 95.440 100,260 32.5 .95 2ES..... 90,670 106,680 31.0 v .85 2G-N. 84,590 101,200 33.5 .84 21-S... 85,360 102,610 36.0 .83

b. austenitizing said tube at a temperature greater than the A temperature of the steel in said tube; c. water quenching said tube; d. reheating said tube to a tempering temperature V g. air cooling said tube.

2. A method according to claim 1 wherein said austenitizing temperature is above 1550F.

3. A method according to claim 2 wherein said austenitizing temperature is from about 1600F to about 1750F.

4. A method according to claim 1 wherein said tube is water quenched to a temperature below about 200F.

S. A method according to claim 4 wherein said tube is water quenched to a temperature of about F.

6. A method according to claim 1 wherein said tempering temperature is from about 1150F to about 1225F.

7. A method according to claim 1 wherein said polygonal cross-section is a round-cornered rectangle.

8. A method according to claim 1 wherein said polygonal cross-section is a round-cornered square.

Claims

2. A method according to claim 1 wherein said austenitizing temperature is above 1550*F.
3. A method according to claim 2 wherein said austenitizing temperature is from about 1600*F to about 1750*F.
4. A method according to claim 1 wherein said tube is water quenched to a temperature below about 200*F.
5. A method according to claim 4 wherein said tube is water quenched to a temperature of about 150*F.
6. A method according to claim 1 wherein said tempering temperature is from about 1150*F to about 1225*F.
7. A method according to claim 1 wherein said polygonal cross-section is a round-cornered rectangle.
8. A method according to claim 1 wherein said polygonal cross-section is a round-cornered square.