CA1052670A - Process and apparatus for improving the quality of steel sections - Google Patents
Process and apparatus for improving the quality of steel sectionsInfo
- Publication number
- CA1052670A CA1052670A CA237,123A CA237123A CA1052670A CA 1052670 A CA1052670 A CA 1052670A CA 237123 A CA237123 A CA 237123A CA 1052670 A CA1052670 A CA 1052670A
- Authority
- CA
- Canada
- Prior art keywords
- section
- container
- tempered
- strip
- zone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
-
- 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
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Drying Of Solid Materials (AREA)
Abstract
ABSTRACT
At the outlet of the finishing stand of a rolling mill, only the outer layer of a flat face of a steel section is subjected to surface quenching by a cooling fluid in a cooling zone. The cooling fluid is a suspension of a liquid (e.g. water) in a gas (e.g. air).
The cooling conditions are adjusted so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite and carbides in the unquenced parts of the section.
At the outlet of the finishing stand of a rolling mill, only the outer layer of a flat face of a steel section is subjected to surface quenching by a cooling fluid in a cooling zone. The cooling fluid is a suspension of a liquid (e.g. water) in a gas (e.g. air).
The cooling conditions are adjusted so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite and carbides in the unquenced parts of the section.
Description
` lOS;~670 The present inventio~ relates to a process for impro~ing the qualit~ of steel sections. ~he term "section~" should be u~derstood as includ~ng, according to the present in~ention, I-beams, channels, a~gle irons, Tees, plate~, laxge ~heets, flat bars, and sheet~, ~nd generally any rolled se¢tion ha~ing at lea~t one flat face.
~he pro¢es~ ac¢ording to the i~ention may be applied to ~illed steels or semiskilled ~teel~ or r~ming steel~.
~e m~in qualitie~ required b~ the users in steel se¢tion~ are, among others, a~ high as possible ultimate ten~ile ~tre~s, limit Or ela~ticity, and impact strength ~ ~or the grade o~ steel u~ed, a~ well as satis~actory `~ weldability, fatigue ~trength, ~nd ductility for the intended use o~ the steel section.
~o impro~e weldabilit~ and du¢tility of a steel it i~ necessary to decrease it6 carbo~ and manganese eontent, which i~ turn results in a decrease in ~t~ ten~ile strength.
~-~ Io remedy th~s incon~enience, the steel ma~ be sub~eGted to a ~u~table cooling process, preferably dire¢tly applied - at the outlet o~ the roll~ng mill, wh~¢h permits eertain ~; eharacteri tics of the seetion to be impro~ed to some e~tent~
8hould 8UC~ a cooling prooess result ~n an impro~ement :~ : .
deemed insufficient a~ far as properties of the seetions '~J ~re co~cerned, one may resort to other proeesses to ; co~plement the mere cooling action. ~mong such processe~, ~ re~erence should be made particularly to that which compri~es :~ ' :,. . . .
. ' - : ' - ` ~
... .. .. . . ... ..
~o5~670 adding dispersoid elements (Nb, V) to refine the steel grain and to cause hardening of ferrite by precipitation of such elements. ~his procedure is surely effective but has the inconvenience of a cost which increases in proportion as one aims at a higher limit of elasticity;
it is also the more expensive the larger the dimensions of the sections.
What is desired is a process which permits the above-mentioned inco~veniences to be avoided without increasing to an unacceptable extent the carbon and manganese contents in the steel of the sections concerned which would otherwise result in detrimental effects on their weldability and impact strength at low temperature.
,! ~he present invention provides a process for improving the quality of a steel sectio~ having at least one flat face, the process comprising at the outlet of the finishing stand of a section rolling mill, subjecting only the outer layer of a flat face of the section to surface quenching by means of a cooling fluid in a cooling zone, the cooling fluid being a suspension of a liquid in a gas, and adausting the conditions of the said cooling so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite '~'`'!, ~ ~ 25 and carbides in the unquenced parts of the section.
Depending upon the operating conditions for carrying ` out the process, the surface layer due to the section , i .
~he pro¢es~ ac¢ording to the i~ention may be applied to ~illed steels or semiskilled ~teel~ or r~ming steel~.
~e m~in qualitie~ required b~ the users in steel se¢tion~ are, among others, a~ high as possible ultimate ten~ile ~tre~s, limit Or ela~ticity, and impact strength ~ ~or the grade o~ steel u~ed, a~ well as satis~actory `~ weldability, fatigue ~trength, ~nd ductility for the intended use o~ the steel section.
~o impro~e weldabilit~ and du¢tility of a steel it i~ necessary to decrease it6 carbo~ and manganese eontent, which i~ turn results in a decrease in ~t~ ten~ile strength.
~-~ Io remedy th~s incon~enience, the steel ma~ be sub~eGted to a ~u~table cooling process, preferably dire¢tly applied - at the outlet o~ the roll~ng mill, wh~¢h permits eertain ~; eharacteri tics of the seetion to be impro~ed to some e~tent~
8hould 8UC~ a cooling prooess result ~n an impro~ement :~ : .
deemed insufficient a~ far as properties of the seetions '~J ~re co~cerned, one may resort to other proeesses to ; co~plement the mere cooling action. ~mong such processe~, ~ re~erence should be made particularly to that which compri~es :~ ' :,. . . .
. ' - : ' - ` ~
... .. .. . . ... ..
~o5~670 adding dispersoid elements (Nb, V) to refine the steel grain and to cause hardening of ferrite by precipitation of such elements. ~his procedure is surely effective but has the inconvenience of a cost which increases in proportion as one aims at a higher limit of elasticity;
it is also the more expensive the larger the dimensions of the sections.
What is desired is a process which permits the above-mentioned inco~veniences to be avoided without increasing to an unacceptable extent the carbon and manganese contents in the steel of the sections concerned which would otherwise result in detrimental effects on their weldability and impact strength at low temperature.
,! ~he present invention provides a process for improving the quality of a steel sectio~ having at least one flat face, the process comprising at the outlet of the finishing stand of a section rolling mill, subjecting only the outer layer of a flat face of the section to surface quenching by means of a cooling fluid in a cooling zone, the cooling fluid being a suspension of a liquid in a gas, and adausting the conditions of the said cooling so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite '~'`'!, ~ ~ 25 and carbides in the unquenced parts of the section.
Depending upon the operating conditions for carrying ` out the process, the surface layer due to the section , i .
- 2 -.
, '`
, ~4 , - 105'~ 7 quenching comprises tempered martensite or bainite.
The cooling fluid preferably comprises water (an aqueous suspension or solution of mineral salts and/or surfactants, for example) in the form of a mist (a suspension of a liquid in a gas, such as air or steam).
~he cooling fluid may be projected at supersonic speed.
From the practical point of view, a section can be cooled to the desired extent by suitably choosing the ~3 cooling apparatuses and by suitably adjusting the length ''! 10 and the relative position of such apparatuses, such as , cooling sprayers.
~he process according to the invention permits sections of a special type to be obtained, such sections -having at least one flat face whose outer layer comprises tempered bainite and/or tempered martensite and the other parts consist of ferrite and carbides.
According to an advantageous modification of the process of the invention, it is possible, during the ;, surface quenching operation, to control the temperature increase of the product by maintaining the heat exchange between the fluid and the product in substantially optimum conditions. ~his modification is oharacterised . ~
in that the intense surface cooling operation of the ; product is performed in at least two steps separated by . ~,, f ,.,.~i ~ - 3 --'~
"' :
. -105'~7 a stage duri~g wh~ch temperature homogeniz~tio~ t~ke~
place a~ least at the ~kin o~ the product.
According to such modification, the product i3 inten~ely cooled i~ several suaces~ive stage~ o~ ~hort duration ~eparated by periods of temperat~re homogenization for the product skin, at least the 1A~ cooliQg ~tage en~uring the martensitic and~or bainitic ~uenching o~
the rolled product.
~ccording to A WaY of carrying out the pxocess o~
the in~ention, one determine~ the number and the c~nditio~s ror carrying out the ~arious cooling a~d te~per~ture homogenizatio~ stage~ for the produet to ensure optimum ; remo~al of heat from the product. According to this wa~
o~ ¢arryi~g out the process, the optimum ¢o~di~ions for removins heat are determined by mean, of a diagram indicating the ~ariat-lon of the heat flow as a functio~
of the temperature at the ~urfa¢e of the processed product.
In pra¢tice, i~ a first heavy ¢ooli~g stasef, th~f temperature at the surfa¢e of the rolled prod~ct i~ ~owered down to a ls~el slightly lower than the temperature corresponding to the maximum value of heat flow; cooling is stopped for a short Interval whi¢h results in a tempera~uxe in¢rease at the ~kin owing to the ef~e~t o~
heat being supplied from the ¢ore; a new cool~ng sta3e is ~tartèd whefn the temperature at the surfa~e attains a le~el ~lightly higher than the t6mpe~rature corresponding ~o the maximum ~lue o~ heat flow.
~he applica~ion of the ~arious succe~,si~ei stages, or ' . - 4 -.
:. .
.~ ' , .
lOS'~670 step~ then resultiQ~ in~mai~tainin$ the skin temperature within limits corresponding to heat exchange conditionR
close to the optimum OnO8-Owing to the optimum condition~ ensured by the . 5 process according to the ~e~tion, surface guenchiDg of the rolled product i8 performed with minimum consu~ption of water and/or by means Or a shorter i~stallation.
The proces~ ac¢ording to the invention may be easil~
, '`
, ~4 , - 105'~ 7 quenching comprises tempered martensite or bainite.
The cooling fluid preferably comprises water (an aqueous suspension or solution of mineral salts and/or surfactants, for example) in the form of a mist (a suspension of a liquid in a gas, such as air or steam).
~he cooling fluid may be projected at supersonic speed.
From the practical point of view, a section can be cooled to the desired extent by suitably choosing the ~3 cooling apparatuses and by suitably adjusting the length ''! 10 and the relative position of such apparatuses, such as , cooling sprayers.
~he process according to the invention permits sections of a special type to be obtained, such sections -having at least one flat face whose outer layer comprises tempered bainite and/or tempered martensite and the other parts consist of ferrite and carbides.
According to an advantageous modification of the process of the invention, it is possible, during the ;, surface quenching operation, to control the temperature increase of the product by maintaining the heat exchange between the fluid and the product in substantially optimum conditions. ~his modification is oharacterised . ~
in that the intense surface cooling operation of the ; product is performed in at least two steps separated by . ~,, f ,.,.~i ~ - 3 --'~
"' :
. -105'~7 a stage duri~g wh~ch temperature homogeniz~tio~ t~ke~
place a~ least at the ~kin o~ the product.
According to such modification, the product i3 inten~ely cooled i~ several suaces~ive stage~ o~ ~hort duration ~eparated by periods of temperat~re homogenization for the product skin, at least the 1A~ cooliQg ~tage en~uring the martensitic and~or bainitic ~uenching o~
the rolled product.
~ccording to A WaY of carrying out the pxocess o~
the in~ention, one determine~ the number and the c~nditio~s ror carrying out the ~arious cooling a~d te~per~ture homogenizatio~ stage~ for the produet to ensure optimum ; remo~al of heat from the product. According to this wa~
o~ ¢arryi~g out the process, the optimum ¢o~di~ions for removins heat are determined by mean, of a diagram indicating the ~ariat-lon of the heat flow as a functio~
of the temperature at the ~urfa¢e of the processed product.
In pra¢tice, i~ a first heavy ¢ooli~g stasef, th~f temperature at the surfa¢e of the rolled prod~ct i~ ~owered down to a ls~el slightly lower than the temperature corresponding to the maximum value of heat flow; cooling is stopped for a short Interval whi¢h results in a tempera~uxe in¢rease at the ~kin owing to the ef~e~t o~
heat being supplied from the ¢ore; a new cool~ng sta3e is ~tartèd whefn the temperature at the surfa~e attains a le~el ~lightly higher than the t6mpe~rature corresponding ~o the maximum ~lue o~ heat flow.
~he applica~ion of the ~arious succe~,si~ei stages, or ' . - 4 -.
:. .
.~ ' , .
lOS'~670 step~ then resultiQ~ in~mai~tainin$ the skin temperature within limits corresponding to heat exchange conditionR
close to the optimum OnO8-Owing to the optimum condition~ ensured by the . 5 process according to the ~e~tion, surface guenchiDg of the rolled product i8 performed with minimum consu~ption of water and/or by means Or a shorter i~stallation.
The proces~ ac¢ording to the invention may be easil~
3 a~d.adva~t~geou~ly employed ~or the manufa¢ture of rails for railways. In such an appiication, at the outlet o~
. the f~n;shing sta~d of a rail rolling mill, the upper part o~ the rail flange is sub~e¢ted to surfa¢e quen¢hing by ~, meaus of a suitable cooling fluid, and the conditions of the said ¢ool~g are ad~ustea 80 t.hat, at the outlet of 1g the zone of cool~ng by the fluid, the unquenched part of the flange is at.a suffi¢ie~t temperature to permit, while ~ the rail is on the ¢ooler, the ~uenched surfa¢e layer consisting then o~ martens~te or bainite to be tempered .~ and the austenite to be transformed into rerrite and ~1 , . .
~ ~ 20 aarbide~ in the said un~uenched part.
~`.1 1~ ~he pre~ent i~vention also relate~ to a stsel ,1. . .
section ha~ing a ¢omposite structure obtained b~ mea~s Or .3 the above-described process.
. AB me~tioned above, it is well know thab one ob~ain~
section3 whose propertie~ ha~e been impro~ed substantially ow~ng to grain re~ining obtained through suitable heat '~ treatments or b~ adding e1ements ~uch as niobium, ~or e~a~ple. A steol s~ctio~ having such fine gra~n combines ,. .
,. ! ' ' , ~.
.';
., .
105'~670 a ~ood ductility with a ~atis~actory limit Or elasti¢ity.
In view o~ the process according to the in~e~tion when applied to such section~, a steel i8 obtained whose most complex structure gives a section both m~chanical characteristics co~siderably improved with respe¢t to those of the above-mentioned ~ections a~d, the mecha~i¢al characteristics being equal, a particularly economic character, this economy beiug due ~or ex~mple to the fact that such ¢haracteristics are obtained with lower alloy-element co~tent~, or b~ usin~ a ~iemikilled steel rather than a killed one.
~he steel section accordi~g to the present invention has a stru¢ture, in a cro~-section take~ in a plane normal to it3 a~i~, having at least two zones sub~tanti~lly parallel to the ~urface o~ the flat element ~orming the -~ ~e¢tio~, one of these zones comprising untempered bainite aDd u~te~pered ferrite-pearlite.
~i Ihe section ac¢ording to the invention may ¢omprise i an intermediate zone between the said t~o zones, the intermediate zone substantially consi~ting of untempered bai~ite.
According to an advantaBeous modification Or the ~ ~tru¢ture of the above-defi~ed section, the zone comprising -1 tempered marten~ite a~d untempered bainit~ i~ also covered, ; on t~e ~ide thereof oppo~ite to the zone comprisin~
~-~ untempered bainits and ferrite-pearlite, by a zone mainly co~8i8ting 0~ pure tempered marten~ite.
Accord~ng to ano~her ad~antageou~ modi$icatio~ o$
,:', - , i~
. . ~, .
~........................................................................... ..
105;~670 such ~tructure, the zo~e compri~ing untemp~red bainite and ferrite-pearlite i8 ad~acent to a layer mainly consisting of untempered ferrite-pe~rlite, on ths side thereof opposite to the zone com~rising untempered bainite and tempered mart~n~ite~
Of course, according to the present in~ention, when cooling is applied to the two faces o$ a flat product or a sectiQn eompris~ng ~lat part~, it ~hould be under-stood that the coD~iguration of th- various zone~ for~;ng the structure of the flat se¢tion generally follows the configuration Or the product or the se¢tion itself.
~he invention will be described further, by way ~, of exa~ple only, with reference to the accompanying ;~i drawing6, in which:-Figure 1 i~ a cros~-~e¢tion through part of a flat ~ecticn;
Figure 2 i8 a side ele~ation of apparatus for ~ooling i, a beam;
Figure 3 is a cro~s-section of the apparatus of Figure 2;
Figuro 4 is a side elevation of apparatus for , cooling a flat product;
Figure 5 is a side ele~ation Or part or a similar apparatus for cooling a ~lat product; and Figure~ 6 to 8 photomicrograph~ of steel sections.
Figure 1 show~ a portion of the cross-~ection Or one $ype of flat section which was quenched at its two faces.
~he ~ection has zones 1 and 1' mainly comprising pure :, .
1 , ~
.. ~ .
,. .. .
.,~,; ' :':
105'~670 tempered m~rten~ite, zones 2 and 2' compri~in~ tempered ; marten3ite and untempered bain;te, ~one~ 3 and 3' comprising untempered bainits and untempered ferrite-pearlite, a~d a zone 4 mainl~ comprising untempered ferrite-pearlite.
From a practical point of view, the desired aoolin~
Or the se¢tion is obtained by choosing the cooling de~ices and by suitably adjusting the length and the `relati~ position of these devices such a3 coolin~
spra~ers.
~he apparatus ~or processing sections ma~ comprise a container formin3 the reservoir for the cooling fluid a~d ha~ing fluid feeding means, a wall of the ¢ontainer being a perforated wall which has oririce~ arra~ged to atomiz0 the ¢ooling fluid onto ~he surra~e Or the section whi¢h i8 con~e~ed past the said perforated wall.
When the flat se¢tion such a~ a hot-rolled sheet has to be cooled at its two races, it is advantageous to combi~e two apparatusos according to the invention, the , ~ .
~ 20 atomized ~ets Or such element being opposite to each .. 1 .
other, and to displace the section through the tunnel thu~ formed.
, ~
.,, ` ~c~ording to a constructi~e embodiment Or the -~ - apparatus of the in~ention, ~he perforated wall has, 2~ trans~ersely to the direction of mo~ement Or the product, q a dimeniion at least equ~l to the width of the part to ~ bo treated.
. . ..
~1 Whe~, aGco~ding to the inventio~, step b~ step j -- ~ --! ' `
105'~670 quenchlng i8 planned for a given section, use is m~de o~ an installation of the type described aboYe but having at lea3t two coolin~ apparatuses arranged in series a~d separat0d by a re-heating zone for the product skin.
Particularly in such a case, the cooling apparatuses ; used ad~antageou~ly have a high hea~ transfer coe~ficient, such apparatu~es preferably having means for ad~usting the cooling fluid flow.
In a particular embodiment of the in~tallation according to su¢h modification, at least ona of the re-heating zones o~ the se¢tion skin has a de~ice such as a hood to ds¢rsase the heat removal rate.
In another embodiment of the in~tallation, at least on~ of the cooli~g zone~ ~or the se¢tion skin has : 15 de~i¢e arranged to heat the product.
~he a¢comp~nying drawi~gs show an apparatu~ arranged to aool a beam (~igures 2 and ~) and a flat product whil~
beine rolled (~igures 4 and 5).
~igure 2 shows a se¢tion 11 'Gre~ beam) while being rolled in the direction of the arrow 12. A carriage 14 is arried on the upper flange 13 of ~he beam 11 through roller~ 15.
~ he carriage 14 is maintained in position by an ''~! abutmen~ (not shown) and the ¢arrying rollers 15 rotate ~i 25 ~hile ~he beam 11 i8 displaced. ~he carriage 14 ha~
¢ooling ~luid containers 6 supplisd with ¢ooling fluid , ;, ~ia conduits 17. ~he position of the contain~rs 16 i8 ad~ustad with re~pect to the beam 11 b~ ~ean~ of screwq 18 _ 9 _ :~
~.
105;~670 and hand whee; 19. The co~ection between the ~crew 18 and the containers 1'6 i8 not shown, for simplicity of the ~rawi~gs.
A similar apparatu~, i.e. a container 112, i~
-locatod u~der the lowor flan~e 110 of the section 11, while the inner part 111 of the ~langes i8 u~der la~eral ~ets, on the two sides, by means of suitable sprayers 113 and 114 (~ee Figure 3~ which spray air and water.
According to the ~vention, apparatuses different from th~s cooling fluid orifices outside the co~tainer~ 16 or 112 may be employed ~uch as in the form of a transverse ~lot or a pattern of small diameter oririces.
The exa~ple given below pormits the gual~ty improvement or the sections obtai~ed by carr~ng out the process of the i~ven~ion to be appr~sciated. he section i exam~ned i~ a Gre~ beam DIN 40 of an aluminium ~nd ~ilicon killed ~teel containing 0.165% C and 1.~2h Mn. This beam leave~ thes rolling mill rough-rolled at 8 temperature o~
j 800C to 850C a~d has the follow~ng characteristics ;~ 20 without applying the proce-~s Or the i~ention:
- limit Or olasticit~ 38 ~gf/mm2 ultimate tensile ~tress 55 kgf/mm2 - impact ~trs~gth 5 ~gr m/cm2 at -20C
~he ~ame beam lea~ mg the rolling mill in the same temperature co~ditions ha~ the followi~g characteristics 7 after applicatio~ of the proce~s of the invention (~ntense ~urface-cooling) for 10 se¢ond~.
. ~ I ~
: ' ~ . .
.
, ., ;, , . .
105'~S,70 - limit of elasticity 45 kgf/mm2 - ult~mate tensile stres~ 60 ksf/mm2 -`
- impact strength 9.0 kgf m/cm2 at -~0C.
~he~e characteristics were obtained by means o~ a coolin~ apparatus operating in the following operating ¢ondition~:
- rolling speed 1 m/~
- cooling time 10 8 - length Or the cooling sprayer 10 m - water enclosure~ (containers 16 and 112) formed or elements of 100 mm in the rolling direetio~.
Distanee with respect to the seetio~: ~ to 6 mm !~ , Water pressure : 1 to 3 kg/cm2 Water flow : 15 to 50 m3/h -sprayers: eonvergent - diverge~t -diameter of the neck : one mm ~ -air pressure : 4 kg/¢m2 '''`'~! -a~r flow : 1.5 to 2.5 Nm3/h . ~ ,, 20 -water pressure : 3 to 4 kg/em' -water flow : 5 el/mi~
-di~tanee with respe¢t to th~ web o~ the se¢tion: 100 mm - -distance b~tween sprayers: 100 mm . -temperàtures: at the ~n~et: below the Ae~ point -~1 25 at the outlet: from 600C to 700C
.~:: (betwesn 10 and 20 seeonds after lsaving the`¢ooling sprayers).
. ~ , ~ he photomi¢rographs of Figures 6 and 7 show ~arious :~, ~.~` ' ' .
~05'~670 ~tructures of a fla~ge of a be~m DIN 40 treated in accordance with the ~n~ention: Figure 6 shows the skin structure of ~uch a flangs ~tempered martensite and/or baLnite~; Figure 7 ~hows the ~tructure at 7.5 mm from the skin of the external face of suGh glange (ferr~te ~
carbide ~tructure). Fi~ure 8 sho~s the structure of the same flange not being treated a¢cording to the invention.
~he structure comprises ferrite~ and carbides with coarser grains sin¢e the cooli4g speed is ~lower.
With~n the ~cope o~ the above de~cr~bdd apparatu~e~, in order to considsrably increase the cooling powsr o~ the u~ed fluids, it i~ advantageou~ to apply them in a lami~ar configuration. Such apparatu~, for cxample using water, comprises at lea~t one b~f~le portion whose configuration causes the cooling liquid su¢cessively to cha~ge direction several time~, the total length of the baffle and the dime~ions Or the fluid passage being ~uch that the ~low 3 of the coolin~ liquid throughout the apparatus is .~ .
-~ laminar.
In a con~tru¢tional embodiment of the invention, more rpecificall~ adapted to th~ treatment o~ flat ~eGtions such as she~ts, a ~eries of ~prayers of the abo~e-des¢ribed type with their outlet ~lits ro~ the cooling liquid par~llel to each other is arranged ., ,~ .
- 25 substa~tially in the ~ame plane.
~^ In a particular modification of such apparatu~
, ~ according to ~he invention, the straight length preceding :~J, the outlet lit comprise~ an element ~uch as a corrugated . . r ~ - ~2 -. . ~
.:, .
;, . ,.; ~, .
105;~67C~
element, arra~ged in the direction o~ the liquid flow to better ensure a laminar flow o~ the ~et. Such an element 18 is indicated in Figure 2 of ths draw mgs.
Figure 4 shows a modification of the apparatus accordi~g to the invention, particul~rly auitable for ensuring quick and controlled cooling of flat rolled products at the outlet of the finishing roller~. -~ccord~ng to this embodiment, the apparatus comprise~
in succes~ion:
(a) a cooling water case, possibl~ with a double wall, (b) ~ d~ying air case, (c) agai~ a cooling ca~e of the type referred to under (a) or the like, and one or more cooling water ca~e~ of the double-wall type but arxa~ged to be lecated be~we~n two ~uccessive roller~ at a standard distance from o~e ~nother.
~he cooling case 21 of the tgpe referred to u~der ~a) and illuslrated in Figure 4 is assoc~ated with a certain number of transport rollers 22, 23, lower rollers de~igned to carry and to ¢o~vey a strip or sheet 24 to be cooled, the sheet being displaced in the direction o~ the arrow 25.
he cooling case 21 comprises two ~uccessive part~, the fir~t Or whi¢h i8 an lnlet container 26 having a roof ; downwardly inclined in the d~rection Or movement of the ;~ 25 ~heet, ~wo Bide wall8 27 a~d 28 located at the ends of the rollars 22 a~d 23, a lower wall 29 located below the sheet 24 and leavi~g little space between itsslf and the rollers 22 and 23, wbile being slightl~ inclined downwards .; .
., .
. .
lns;~670 ~n the direction indicated b~ the arrow 25. ~he second of the succ~si~e parts of the ca~o 21 comprise~ a container 210 lower in height tha~ the inlet of the container 26 a~d haa a sub3tantiall~ horizontal roof 211, while the bottom wall 212 i9 located at a short distance from the two ~d~ace~t rollers 23 a~d 213 and i8 ~lightlyincli~ed in a d~ection opposite to that indicated by the arrow 25.
~he cooling case 21 has a de~ice 214 located at the upper part of the inlet of the roo~ of the contai~er 26 -; 10 and arr~nged to e~e¢t one or more water ~ets in~ids the ~- container in the direction of the roller 80 as to ~mpinge upon its upper zone 215. A pair of rollor~ 21~ and 217 ~ i8 advantageously located before the container 26, the roller -i 216 being a caxr~ins roller and bei~g located at the usual ;' 15 le~el under the sheet 24, the second roller 17 beingdispla¢ed ~pwards to ¢orrectly guide the sheet 24 towards the i~let of khe ¢ontainer 26, independently of the surface ir.regularities of the ~heet even at its end. The excess of water is discharged from this container past , 20 the roller 23.
: The ¢ooling case ~ust de~cribed has the following . , .
:; advantage~:
. . . ~ .
~, ` 1. ~he water ejected by the device 214 i~ guided along the rolled ~heet 24 owing to the limited space .3 25 between the roof 211 of the container and the sheet 24.
-~ 2. Pos~ibility of a¢ceptin~ without di~ficulty sheets - ha~ing sur~ace irregularitie~.
3. Po~sibili~y o~ actin~ on the water distributio~
; - 14 -. . - .
.: ' '` .
lOS'~670 depe~ding ~n the width of the sheet b~ selecting one or ~ore water jets.
. the f~n;shing sta~d of a rail rolling mill, the upper part o~ the rail flange is sub~e¢ted to surfa¢e quen¢hing by ~, meaus of a suitable cooling fluid, and the conditions of the said ¢ool~g are ad~ustea 80 t.hat, at the outlet of 1g the zone of cool~ng by the fluid, the unquenched part of the flange is at.a suffi¢ie~t temperature to permit, while ~ the rail is on the ¢ooler, the ~uenched surfa¢e layer consisting then o~ martens~te or bainite to be tempered .~ and the austenite to be transformed into rerrite and ~1 , . .
~ ~ 20 aarbide~ in the said un~uenched part.
~`.1 1~ ~he pre~ent i~vention also relate~ to a stsel ,1. . .
section ha~ing a ¢omposite structure obtained b~ mea~s Or .3 the above-described process.
. AB me~tioned above, it is well know thab one ob~ain~
section3 whose propertie~ ha~e been impro~ed substantially ow~ng to grain re~ining obtained through suitable heat '~ treatments or b~ adding e1ements ~uch as niobium, ~or e~a~ple. A steol s~ctio~ having such fine gra~n combines ,. .
,. ! ' ' , ~.
.';
., .
105'~670 a ~ood ductility with a ~atis~actory limit Or elasti¢ity.
In view o~ the process according to the in~e~tion when applied to such section~, a steel i8 obtained whose most complex structure gives a section both m~chanical characteristics co~siderably improved with respe¢t to those of the above-mentioned ~ections a~d, the mecha~i¢al characteristics being equal, a particularly economic character, this economy beiug due ~or ex~mple to the fact that such ¢haracteristics are obtained with lower alloy-element co~tent~, or b~ usin~ a ~iemikilled steel rather than a killed one.
~he steel section accordi~g to the present invention has a stru¢ture, in a cro~-section take~ in a plane normal to it3 a~i~, having at least two zones sub~tanti~lly parallel to the ~urface o~ the flat element ~orming the -~ ~e¢tio~, one of these zones comprising untempered bainite aDd u~te~pered ferrite-pearlite.
~i Ihe section ac¢ording to the invention may ¢omprise i an intermediate zone between the said t~o zones, the intermediate zone substantially consi~ting of untempered bai~ite.
According to an advantaBeous modification Or the ~ ~tru¢ture of the above-defi~ed section, the zone comprising -1 tempered marten~ite a~d untempered bainit~ i~ also covered, ; on t~e ~ide thereof oppo~ite to the zone comprisin~
~-~ untempered bainits and ferrite-pearlite, by a zone mainly co~8i8ting 0~ pure tempered marten~ite.
Accord~ng to ano~her ad~antageou~ modi$icatio~ o$
,:', - , i~
. . ~, .
~........................................................................... ..
105;~670 such ~tructure, the zo~e compri~ing untemp~red bainite and ferrite-pearlite i8 ad~acent to a layer mainly consisting of untempered ferrite-pe~rlite, on ths side thereof opposite to the zone com~rising untempered bainite and tempered mart~n~ite~
Of course, according to the present in~ention, when cooling is applied to the two faces o$ a flat product or a sectiQn eompris~ng ~lat part~, it ~hould be under-stood that the coD~iguration of th- various zone~ for~;ng the structure of the flat se¢tion generally follows the configuration Or the product or the se¢tion itself.
~he invention will be described further, by way ~, of exa~ple only, with reference to the accompanying ;~i drawing6, in which:-Figure 1 i~ a cros~-~e¢tion through part of a flat ~ecticn;
Figure 2 i8 a side ele~ation of apparatus for ~ooling i, a beam;
Figure 3 is a cro~s-section of the apparatus of Figure 2;
Figuro 4 is a side elevation of apparatus for , cooling a flat product;
Figure 5 is a side ele~ation Or part or a similar apparatus for cooling a ~lat product; and Figure~ 6 to 8 photomicrograph~ of steel sections.
Figure 1 show~ a portion of the cross-~ection Or one $ype of flat section which was quenched at its two faces.
~he ~ection has zones 1 and 1' mainly comprising pure :, .
1 , ~
.. ~ .
,. .. .
.,~,; ' :':
105'~670 tempered m~rten~ite, zones 2 and 2' compri~in~ tempered ; marten3ite and untempered bain;te, ~one~ 3 and 3' comprising untempered bainits and untempered ferrite-pearlite, a~d a zone 4 mainl~ comprising untempered ferrite-pearlite.
From a practical point of view, the desired aoolin~
Or the se¢tion is obtained by choosing the cooling de~ices and by suitably adjusting the length and the `relati~ position of these devices such a3 coolin~
spra~ers.
~he apparatus ~or processing sections ma~ comprise a container formin3 the reservoir for the cooling fluid a~d ha~ing fluid feeding means, a wall of the ¢ontainer being a perforated wall which has oririce~ arra~ged to atomiz0 the ¢ooling fluid onto ~he surra~e Or the section whi¢h i8 con~e~ed past the said perforated wall.
When the flat se¢tion such a~ a hot-rolled sheet has to be cooled at its two races, it is advantageous to combi~e two apparatusos according to the invention, the , ~ .
~ 20 atomized ~ets Or such element being opposite to each .. 1 .
other, and to displace the section through the tunnel thu~ formed.
, ~
.,, ` ~c~ording to a constructi~e embodiment Or the -~ - apparatus of the in~ention, ~he perforated wall has, 2~ trans~ersely to the direction of mo~ement Or the product, q a dimeniion at least equ~l to the width of the part to ~ bo treated.
. . ..
~1 Whe~, aGco~ding to the inventio~, step b~ step j -- ~ --! ' `
105'~670 quenchlng i8 planned for a given section, use is m~de o~ an installation of the type described aboYe but having at lea3t two coolin~ apparatuses arranged in series a~d separat0d by a re-heating zone for the product skin.
Particularly in such a case, the cooling apparatuses ; used ad~antageou~ly have a high hea~ transfer coe~ficient, such apparatu~es preferably having means for ad~usting the cooling fluid flow.
In a particular embodiment of the in~tallation according to su¢h modification, at least ona of the re-heating zones o~ the se¢tion skin has a de~ice such as a hood to ds¢rsase the heat removal rate.
In another embodiment of the in~tallation, at least on~ of the cooli~g zone~ ~or the se¢tion skin has : 15 de~i¢e arranged to heat the product.
~he a¢comp~nying drawi~gs show an apparatu~ arranged to aool a beam (~igures 2 and ~) and a flat product whil~
beine rolled (~igures 4 and 5).
~igure 2 shows a se¢tion 11 'Gre~ beam) while being rolled in the direction of the arrow 12. A carriage 14 is arried on the upper flange 13 of ~he beam 11 through roller~ 15.
~ he carriage 14 is maintained in position by an ''~! abutmen~ (not shown) and the ¢arrying rollers 15 rotate ~i 25 ~hile ~he beam 11 i8 displaced. ~he carriage 14 ha~
¢ooling ~luid containers 6 supplisd with ¢ooling fluid , ;, ~ia conduits 17. ~he position of the contain~rs 16 i8 ad~ustad with re~pect to the beam 11 b~ ~ean~ of screwq 18 _ 9 _ :~
~.
105;~670 and hand whee; 19. The co~ection between the ~crew 18 and the containers 1'6 i8 not shown, for simplicity of the ~rawi~gs.
A similar apparatu~, i.e. a container 112, i~
-locatod u~der the lowor flan~e 110 of the section 11, while the inner part 111 of the ~langes i8 u~der la~eral ~ets, on the two sides, by means of suitable sprayers 113 and 114 (~ee Figure 3~ which spray air and water.
According to the ~vention, apparatuses different from th~s cooling fluid orifices outside the co~tainer~ 16 or 112 may be employed ~uch as in the form of a transverse ~lot or a pattern of small diameter oririces.
The exa~ple given below pormits the gual~ty improvement or the sections obtai~ed by carr~ng out the process of the i~ven~ion to be appr~sciated. he section i exam~ned i~ a Gre~ beam DIN 40 of an aluminium ~nd ~ilicon killed ~teel containing 0.165% C and 1.~2h Mn. This beam leave~ thes rolling mill rough-rolled at 8 temperature o~
j 800C to 850C a~d has the follow~ng characteristics ;~ 20 without applying the proce-~s Or the i~ention:
- limit Or olasticit~ 38 ~gf/mm2 ultimate tensile ~tress 55 kgf/mm2 - impact ~trs~gth 5 ~gr m/cm2 at -20C
~he ~ame beam lea~ mg the rolling mill in the same temperature co~ditions ha~ the followi~g characteristics 7 after applicatio~ of the proce~s of the invention (~ntense ~urface-cooling) for 10 se¢ond~.
. ~ I ~
: ' ~ . .
.
, ., ;, , . .
105'~S,70 - limit of elasticity 45 kgf/mm2 - ult~mate tensile stres~ 60 ksf/mm2 -`
- impact strength 9.0 kgf m/cm2 at -~0C.
~he~e characteristics were obtained by means o~ a coolin~ apparatus operating in the following operating ¢ondition~:
- rolling speed 1 m/~
- cooling time 10 8 - length Or the cooling sprayer 10 m - water enclosure~ (containers 16 and 112) formed or elements of 100 mm in the rolling direetio~.
Distanee with respect to the seetio~: ~ to 6 mm !~ , Water pressure : 1 to 3 kg/cm2 Water flow : 15 to 50 m3/h -sprayers: eonvergent - diverge~t -diameter of the neck : one mm ~ -air pressure : 4 kg/¢m2 '''`'~! -a~r flow : 1.5 to 2.5 Nm3/h . ~ ,, 20 -water pressure : 3 to 4 kg/em' -water flow : 5 el/mi~
-di~tanee with respe¢t to th~ web o~ the se¢tion: 100 mm - -distance b~tween sprayers: 100 mm . -temperàtures: at the ~n~et: below the Ae~ point -~1 25 at the outlet: from 600C to 700C
.~:: (betwesn 10 and 20 seeonds after lsaving the`¢ooling sprayers).
. ~ , ~ he photomi¢rographs of Figures 6 and 7 show ~arious :~, ~.~` ' ' .
~05'~670 ~tructures of a fla~ge of a be~m DIN 40 treated in accordance with the ~n~ention: Figure 6 shows the skin structure of ~uch a flangs ~tempered martensite and/or baLnite~; Figure 7 ~hows the ~tructure at 7.5 mm from the skin of the external face of suGh glange (ferr~te ~
carbide ~tructure). Fi~ure 8 sho~s the structure of the same flange not being treated a¢cording to the invention.
~he structure comprises ferrite~ and carbides with coarser grains sin¢e the cooli4g speed is ~lower.
With~n the ~cope o~ the above de~cr~bdd apparatu~e~, in order to considsrably increase the cooling powsr o~ the u~ed fluids, it i~ advantageou~ to apply them in a lami~ar configuration. Such apparatu~, for cxample using water, comprises at lea~t one b~f~le portion whose configuration causes the cooling liquid su¢cessively to cha~ge direction several time~, the total length of the baffle and the dime~ions Or the fluid passage being ~uch that the ~low 3 of the coolin~ liquid throughout the apparatus is .~ .
-~ laminar.
In a con~tru¢tional embodiment of the invention, more rpecificall~ adapted to th~ treatment o~ flat ~eGtions such as she~ts, a ~eries of ~prayers of the abo~e-des¢ribed type with their outlet ~lits ro~ the cooling liquid par~llel to each other is arranged ., ,~ .
- 25 substa~tially in the ~ame plane.
~^ In a particular modification of such apparatu~
, ~ according to ~he invention, the straight length preceding :~J, the outlet lit comprise~ an element ~uch as a corrugated . . r ~ - ~2 -. . ~
.:, .
;, . ,.; ~, .
105;~67C~
element, arra~ged in the direction o~ the liquid flow to better ensure a laminar flow o~ the ~et. Such an element 18 is indicated in Figure 2 of ths draw mgs.
Figure 4 shows a modification of the apparatus accordi~g to the invention, particul~rly auitable for ensuring quick and controlled cooling of flat rolled products at the outlet of the finishing roller~. -~ccord~ng to this embodiment, the apparatus comprise~
in succes~ion:
(a) a cooling water case, possibl~ with a double wall, (b) ~ d~ying air case, (c) agai~ a cooling ca~e of the type referred to under (a) or the like, and one or more cooling water ca~e~ of the double-wall type but arxa~ged to be lecated be~we~n two ~uccessive roller~ at a standard distance from o~e ~nother.
~he cooling case 21 of the tgpe referred to u~der ~a) and illuslrated in Figure 4 is assoc~ated with a certain number of transport rollers 22, 23, lower rollers de~igned to carry and to ¢o~vey a strip or sheet 24 to be cooled, the sheet being displaced in the direction o~ the arrow 25.
he cooling case 21 comprises two ~uccessive part~, the fir~t Or whi¢h i8 an lnlet container 26 having a roof ; downwardly inclined in the d~rection Or movement of the ;~ 25 ~heet, ~wo Bide wall8 27 a~d 28 located at the ends of the rollars 22 a~d 23, a lower wall 29 located below the sheet 24 and leavi~g little space between itsslf and the rollers 22 and 23, wbile being slightl~ inclined downwards .; .
., .
. .
lns;~670 ~n the direction indicated b~ the arrow 25. ~he second of the succ~si~e parts of the ca~o 21 comprise~ a container 210 lower in height tha~ the inlet of the container 26 a~d haa a sub3tantiall~ horizontal roof 211, while the bottom wall 212 i9 located at a short distance from the two ~d~ace~t rollers 23 a~d 213 and i8 ~lightlyincli~ed in a d~ection opposite to that indicated by the arrow 25.
~he cooling case 21 has a de~ice 214 located at the upper part of the inlet of the roo~ of the contai~er 26 -; 10 and arr~nged to e~e¢t one or more water ~ets in~ids the ~- container in the direction of the roller 80 as to ~mpinge upon its upper zone 215. A pair of rollor~ 21~ and 217 ~ i8 advantageously located before the container 26, the roller -i 216 being a caxr~ins roller and bei~g located at the usual ;' 15 le~el under the sheet 24, the second roller 17 beingdispla¢ed ~pwards to ¢orrectly guide the sheet 24 towards the i~let of khe ¢ontainer 26, independently of the surface ir.regularities of the ~heet even at its end. The excess of water is discharged from this container past , 20 the roller 23.
: The ¢ooling case ~ust de~cribed has the following . , .
:; advantage~:
. . . ~ .
~, ` 1. ~he water ejected by the device 214 i~ guided along the rolled ~heet 24 owing to the limited space .3 25 between the roof 211 of the container and the sheet 24.
-~ 2. Pos~ibility of a¢ceptin~ without di~ficulty sheets - ha~ing sur~ace irregularitie~.
3. Po~sibili~y o~ actin~ on the water distributio~
; - 14 -. . - .
.: ' '` .
lOS'~670 depe~ding ~n the width of the sheet b~ selecting one or ~ore water jets.
4. Possibility of di~placing the 3heet by directing ; the water ~ets onto the sheet at the zone where it rests on the roller 23. The sheet is thuæ urged into the container 210. In practice, the water flow to ~uch co~tainer is high (of the order of 1000 m3/h) under relati~ely low pre~sure (about 1 kg/cm2). With these ; data, heat transfer coefficients of the order of 0.1 cal/cm2.~ C are frequently attai~ed.
~ he dr~ing air case referred to under (b) and indicated as 218 in Figure 4 is sssociated with at least two rollers 2~ and 219 carrying the ~heet Z4 while it moves through the ca~e 218. ~he height Or the pas~age cross-section of this case is ~ufficient to allow the shest togo through, ao¢ount being taken of the fact that the sheet may haYe surface irregularities which might result in rela~iTely large dimensions.
The roof of the case 218 has a number o~ orifica~ 220 through which a large amount of dry gas su¢h a~ air can be blown under low pre3sure 80 as to form an air cu~on ~ between the wall and the sheet and to define a barrier a~ for the water covering the sheet a~ the outlet of the , ¢ontsiner 210. This operation has the ad~antage that the subsequent cooling step can thus be carried out on a dry ~heet, which considerably increases its efficiency.
~ he cooling water case 221 of double-wall type such dicated i~ Figure 5, has ~n priaciple the Rame general ~ - 15 _ ; ` , 105'~70 configuration as the case 21, except that it~ upper part 222 and its lower part 223 following the roller 22~ are both doubled by a wall 225 and 226 having orifices 227 through which water i8 e~ected agaI~st the ~heet, these orifices being fed with water ~ia conduits 228 and 229. Thi8 arrangement pormit~ a better distribution of the water on the sheet and a pra¢tically symmetrieal cooling thereof to be obtained.
According to the in~e~tion, in the ¢ase where not much room is a~ailable for locating the abo~e de~cribed apparatuses, it i~ ad~a~tageously pos3ible to use a 8u¢ce~sion of ¢ooling apparatuses of the double-wall ease tgpe, for exa~ple arranged from abo~e do~wards between the carrying ~ollers arranged at standard distance from ea¢h other. Each of these apparatuses comprises a double-wall contaiQer within which the ~heet to be cooled is displaced. Such co~tainer~ have two openi~gs, an upper ope~ing and a lower opening, for feeding a cooling liguid inside the container the inner wall8 0~ whi¢h ~ 20 have orifices arranged to e~ect liquid onto the two '.'-! face~ of the sheet-Thi~ de~ice, particularly adapted to the troatm~nt of a m~al sheet while being rolled and hea~ily ¢ooled, eomprises, arra~ged one after the other, at least:
. :! 25 (a) a case (callea the inlet ca~e) comprising means for ,.q l water-cool^ng the sheet.
-i (b) a case (called an air drying case) comprisi~g meanQ
for remoYi~g from the sheet the water applied to it . i ~ ~ .
' ' .
. . :
1(~5'~670 while going throu~h the inlet case.
According to an intere~ting modification of thi~
apparatus, it further ¢omprises at least one double-wall container arranged to water cool the ~heet at the outlet of the dryin~ ca~e, and a member arranged to dry the sheet at the outlet of the double-wall container.
The inlet case ad~antageou~ly co~prises a container havin~ two distinct parts, the fir~t of which, on ~he inlet side of the sheet, has a height decreasin~ down to ri~ht abo~e the upper generatrix of a rcller, the upper part Or this roller being located inside the said f caRe, owing to the presence of a~ opening formed in thebottom wall of the said ¢a~e, th0 roof of the second part being sub~ta~tially horizontal with respect to the plane t~ken a~ a referen¢e plane for the shest goin~ through the ca~e, the botto~ wall~ Or the two parts of the case, one being arranged before said roller and the other a~ter it, are slightly in¢lined towards said roller 1 . without touching it; moreo~er, on the inlet side of the ., 20 #heet, the ¢a~e has a devi¢e arranged to o~ect water : onto th~ upper part of the shoet substantially in the dire¢tion of th~ zone where the said shcet, a~sumed to .; be pl~ne, ¢o~tacts the said roller, the roller ¢arrging ~ the ~heet and con~e~ing it towards the outlet of said ., ~ .i : 25 case.
. ,-, The dr~ing ~a~e ¢omprise~, according to a preferred smbodime~t, a co~tainer which iB ope~ at its ends to permit the pas8ag8 therethrough of the sheet to be treated, .
- . - 1? -. , , :; ,`, ' ~' `
the roof of the said con~ainer being ~ubstantially parallel to the plane o~ the sheet and bei~g double-walled, the outer wall having an orifice for connectio~
to a pres~urized air supplying in~tallation, the inner wall havin~ a ~umber of orifiae~ along most of it~
length arranged to permit air to be blown o~to the sheet, the bottom wall of Qaid container having at l~a~t one recess arranged to allow the upper part o* a sheet ~ carrying and conveying rollers to be introduced into : 10 the container.
~he double-wall container for feeding water adva~tageously comprises an elongated case in the diraction :J ' of moveme~t of ths sheet, the case being open at its two ends ~nd compri~ing two di~tinct parts, the first of which, o~ the inlet side, has a height de¢rea~iDg approximatoly to right above the upper generatrix of a roller, the upper part of this roller being located inside 3aid ¢ase owing to ths presence of an opening formed in the bottom wall of ~aid case, the roof of ~he second part being substantially horiæontal ~ith re~pect to the plane taken ;, . as a refersnce plane for the sheet pas~ing throu~h the oase, in that the bottom walls of two parts of the case, one o~ w~i¢h is loca~éd before ~aid roller a~d the other after it, are slightly i~clined towards s~d roller without ¢o~tacting it, the roof~ of sa~d two parts as well a~ the bottom wall of ~h~ second part ha~ing a double-wall the outer element of which ha~.an opening .il for the connection to a water 8uppl~ device, whereas the ., ll - 18 -, ~
.
,., :.-105;~670 inner elemant has a ~eries Or orifice3 arra~ed to e~ect water onto the two face~ of the sheet.
~¢¢ording to another interestIng 6mbodiment o~
the double wall container, being designed to be arranged verti¢ally a~ove the spAce between two ~uc¢essively rolling rollers, the container ¢omprises a simple parallelepipedic case, with neither an inlet nor an outlet wall, in the direction of movement of the sheet, the roof and the bottom wall of the case bei~g double-walled, the outer wall~ thereof having an opening for the ¢on~ection to a water supply devi¢e, wherea~ the Inner walls haYe a serie~ of orifice~ arra~ged to psrmit ths e~e¢tion Or water onto the two fa¢e~ of the sheet.
~he member which i~ arra~ged to dry the sheet at the outlet of tbe double-wall container advantageou~ly comprises a du¢t the outlet se¢tion of whi¢h is in the form of a narrow horizontal slit Pnd its orientation i8 such bhat the plane air ~et ~rom it impinges the wetted ~heet at a very ~mall a~gle, ~o as to permit an ea~
adju tment o~ the water flow o~ the upper fa¢e of the ~ ~heet; the water e~ected against the lower ~a¢e of the ~heet being eliminated owing to t~e pre~sure exerted 'i Rgainst th~ face by the roller on whi¢h the sheet i8 :. ~
- di~placsd.
.
't ;`'"'~ , .
, .
.
,'''''`' J
, .
.
~ he dr~ing air case referred to under (b) and indicated as 218 in Figure 4 is sssociated with at least two rollers 2~ and 219 carrying the ~heet Z4 while it moves through the ca~e 218. ~he height Or the pas~age cross-section of this case is ~ufficient to allow the shest togo through, ao¢ount being taken of the fact that the sheet may haYe surface irregularities which might result in rela~iTely large dimensions.
The roof of the case 218 has a number o~ orifica~ 220 through which a large amount of dry gas su¢h a~ air can be blown under low pre3sure 80 as to form an air cu~on ~ between the wall and the sheet and to define a barrier a~ for the water covering the sheet a~ the outlet of the , ¢ontsiner 210. This operation has the ad~antage that the subsequent cooling step can thus be carried out on a dry ~heet, which considerably increases its efficiency.
~ he cooling water case 221 of double-wall type such dicated i~ Figure 5, has ~n priaciple the Rame general ~ - 15 _ ; ` , 105'~70 configuration as the case 21, except that it~ upper part 222 and its lower part 223 following the roller 22~ are both doubled by a wall 225 and 226 having orifices 227 through which water i8 e~ected agaI~st the ~heet, these orifices being fed with water ~ia conduits 228 and 229. Thi8 arrangement pormit~ a better distribution of the water on the sheet and a pra¢tically symmetrieal cooling thereof to be obtained.
According to the in~e~tion, in the ¢ase where not much room is a~ailable for locating the abo~e de~cribed apparatuses, it i~ ad~a~tageously pos3ible to use a 8u¢ce~sion of ¢ooling apparatuses of the double-wall ease tgpe, for exa~ple arranged from abo~e do~wards between the carrying ~ollers arranged at standard distance from ea¢h other. Each of these apparatuses comprises a double-wall contaiQer within which the ~heet to be cooled is displaced. Such co~tainer~ have two openi~gs, an upper ope~ing and a lower opening, for feeding a cooling liguid inside the container the inner wall8 0~ whi¢h ~ 20 have orifices arranged to e~ect liquid onto the two '.'-! face~ of the sheet-Thi~ de~ice, particularly adapted to the troatm~nt of a m~al sheet while being rolled and hea~ily ¢ooled, eomprises, arra~ged one after the other, at least:
. :! 25 (a) a case (callea the inlet ca~e) comprising means for ,.q l water-cool^ng the sheet.
-i (b) a case (called an air drying case) comprisi~g meanQ
for remoYi~g from the sheet the water applied to it . i ~ ~ .
' ' .
. . :
1(~5'~670 while going throu~h the inlet case.
According to an intere~ting modification of thi~
apparatus, it further ¢omprises at least one double-wall container arranged to water cool the ~heet at the outlet of the dryin~ ca~e, and a member arranged to dry the sheet at the outlet of the double-wall container.
The inlet case ad~antageou~ly co~prises a container havin~ two distinct parts, the fir~t of which, on ~he inlet side of the sheet, has a height decreasin~ down to ri~ht abo~e the upper generatrix of a rcller, the upper part Or this roller being located inside the said f caRe, owing to the presence of a~ opening formed in thebottom wall of the said ¢a~e, th0 roof of the second part being sub~ta~tially horizontal with respect to the plane t~ken a~ a referen¢e plane for the shest goin~ through the ca~e, the botto~ wall~ Or the two parts of the case, one being arranged before said roller and the other a~ter it, are slightly in¢lined towards said roller 1 . without touching it; moreo~er, on the inlet side of the ., 20 #heet, the ¢a~e has a devi¢e arranged to o~ect water : onto th~ upper part of the shoet substantially in the dire¢tion of th~ zone where the said shcet, a~sumed to .; be pl~ne, ¢o~tacts the said roller, the roller ¢arrging ~ the ~heet and con~e~ing it towards the outlet of said ., ~ .i : 25 case.
. ,-, The dr~ing ~a~e ¢omprise~, according to a preferred smbodime~t, a co~tainer which iB ope~ at its ends to permit the pas8ag8 therethrough of the sheet to be treated, .
- . - 1? -. , , :; ,`, ' ~' `
the roof of the said con~ainer being ~ubstantially parallel to the plane o~ the sheet and bei~g double-walled, the outer wall having an orifice for connectio~
to a pres~urized air supplying in~tallation, the inner wall havin~ a ~umber of orifiae~ along most of it~
length arranged to permit air to be blown o~to the sheet, the bottom wall of Qaid container having at l~a~t one recess arranged to allow the upper part o* a sheet ~ carrying and conveying rollers to be introduced into : 10 the container.
~he double-wall container for feeding water adva~tageously comprises an elongated case in the diraction :J ' of moveme~t of ths sheet, the case being open at its two ends ~nd compri~ing two di~tinct parts, the first of which, o~ the inlet side, has a height de¢rea~iDg approximatoly to right above the upper generatrix of a roller, the upper part of this roller being located inside 3aid ¢ase owing to ths presence of an opening formed in the bottom wall of ~aid case, the roof of ~he second part being substantially horiæontal ~ith re~pect to the plane taken ;, . as a refersnce plane for the sheet pas~ing throu~h the oase, in that the bottom walls of two parts of the case, one o~ w~i¢h is loca~éd before ~aid roller a~d the other after it, are slightly i~clined towards s~d roller without ¢o~tacting it, the roof~ of sa~d two parts as well a~ the bottom wall of ~h~ second part ha~ing a double-wall the outer element of which ha~.an opening .il for the connection to a water 8uppl~ device, whereas the ., ll - 18 -, ~
.
,., :.-105;~670 inner elemant has a ~eries Or orifice3 arra~ed to e~ect water onto the two face~ of the sheet.
~¢¢ording to another interestIng 6mbodiment o~
the double wall container, being designed to be arranged verti¢ally a~ove the spAce between two ~uc¢essively rolling rollers, the container ¢omprises a simple parallelepipedic case, with neither an inlet nor an outlet wall, in the direction of movement of the sheet, the roof and the bottom wall of the case bei~g double-walled, the outer wall~ thereof having an opening for the ¢on~ection to a water supply devi¢e, wherea~ the Inner walls haYe a serie~ of orifice~ arra~ged to psrmit ths e~e¢tion Or water onto the two fa¢e~ of the sheet.
~he member which i~ arra~ged to dry the sheet at the outlet of tbe double-wall container advantageou~ly comprises a du¢t the outlet se¢tion of whi¢h is in the form of a narrow horizontal slit Pnd its orientation i8 such bhat the plane air ~et ~rom it impinges the wetted ~heet at a very ~mall a~gle, ~o as to permit an ea~
adju tment o~ the water flow o~ the upper fa¢e of the ~ ~heet; the water e~ected against the lower ~a¢e of the ~heet being eliminated owing to t~e pre~sure exerted 'i Rgainst th~ face by the roller on whi¢h the sheet i8 :. ~
- di~placsd.
.
't ;`'"'~ , .
, .
.
,'''''`' J
, .
.
Claims (14)
1. A process for improving the quality of a steel section having at least one flat face, the process comprising at the outlet of the finishing stand of a section rolling mill, subjecting only the outer layer of a flat face of the section to surface quenching by means of a cooling fluid in a cooling zone, the cooling fluid being a suspension of a liquid in a gas, and adjusting the conditions of the said cooling so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite and carbides in the unquenched parts of the section.
2. A process as claimed in claim 1, in which the surface quenching of the section is carried out in at least two quenching steps separated by a non-quenching stage, at least the last quenching step ensuring the formation of martensite and/or bainite in the outer layer.
3. A process as claimed in claim 1, in which the liquid in suspension comprises water.
4. A process as claimed in claim 1, in which the liquid in suspension contains at least one mineral salt and/or at least one surfactant.
5. A process as claimed in claim 1, in which the gas in which the liquid is suspended is air or steam.
6. A process as claimed in claim 1, in which the cooling fluid is ejected onto the section at a super-sonic speed.
7 A process as claimed in claim 1, in which during surface quenching of the flat face, a heat transfer coefficient of substantially 0.1 cal/m2. .°C is attained.
8. A process as claimed in claim 1, in which the surface quenching is carried out by apparatus comprising a container forming a reservoir for the said liquid and being provided with means for supplying the said liquid, one wall of the container being perforated by orifices for atomizing the liquid and directing it towards the flat surface of the rolled section being displaced past the perforated wall, whereby a liquid-in-air suspension is formed in the space between the perforated wall and the said flat surface.
9. A process as claimed in claim 1, in which the steel section is constituted by a steel strip, and the strip is subjected to the said surface quenching by apparatus comprising, arranged one after the other:
(a) a first enclosure comprising means for atomizing water so as to form a water-in-air suspension for cooling the strip, and (b) an air-drying enclosure comprising means for removing from the strip water deposited on it while passing through the first enclosure.
(a) a first enclosure comprising means for atomizing water so as to form a water-in-air suspension for cooling the strip, and (b) an air-drying enclosure comprising means for removing from the strip water deposited on it while passing through the first enclosure.
10. A process as claimed in claim 9, in which the apparatus further comprises at least one double-walled container arranged to cool the strip by means of a water-in-air suspension at the outlet of the drying enclosure, and a member arranged to dry the strip at the outlet of the double-walled container.
11. A process as claimed in claim 9, in which the first enclosure comprises a container having two distinct portions, the first of which, on the inlet side of the strip has a height decreasing down to vertically above the upper generatrix of a roller, the upper part of this roller being located inside the container owing to the presence of an opening in its bottom wall, the roof of the second portion being substantially parallel to the plane taken as a reference plane for the sheet going through the container, the bottom walls of the two portions of the container, one being arranged before said roller and the other after it, being slightly inclined towards the said roller without touching it; on the inlet side of the strip, the container has a device arranged to atomize water and to direct the atomized water towards the upper part of the strip substantially in the direction of the zone where the strip, assumed to be plane, contacts the said roller, the roller carrying the strip and conveying it towards the outlet of the container.
12. A steel section whose structure, in a cross-section thereof taken in a plane normal to its axis, comprises at least two zones substantially parallel to the surface of a flat part of the section, one of these zones comprising non-tempered bainite and tempered martensite, the other comprising non-tempered bainite and non-tempered ferrite-pearlite and lying beneath the said one zone.
13. A steel section as claimed in claim 12, in which the zone comprising tempered martensite and non-tempered bainite is also covered, on the side opposite to the zone comprising non-tempered bainite and non-tempered ferrite-pearlite, by a zone substantially consisting of tempered martensite.
14. A steel section as claimed in claim 12, in which the zone comprising non-tempered bainite and non-tempered ferrite-pearlite, on the side opposite to the zone comprising non-tempered bainite and tempered martensite, is adjacent to a layer substantially consisting of non-tempered ferrite-pearlite.
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BE6044769A BE820750A (en) | 1974-10-04 | 1974-10-04 | Low carbon steel sections - quenched to produce a martensite-bainite hard surface layer |
| BE6044914A BE825138A (en) | 1975-02-03 | 1975-02-03 | STEEL PROFILE, COMPOSITE STRUCTURE |
| BE6044937A BE826200A (en) | 1975-02-28 | 1975-02-28 | COOLING DEVICE FOR LAMINATED STEEL PRODUCTS |
| BE6044939A BE826202A (en) | 1975-02-28 | 1975-02-28 | PROCESS FOR TREATING LAMINATED STEEL PRODUCTS |
| BE6044940A BE826203A (en) | 1975-02-28 | 1975-02-28 | DEVICE FOR TREATMENT OF FLAT ROLLED PRODUCTS |
| BE6044944A BE826456A (en) | 1975-03-07 | 1975-03-07 | PROCESS FOR THE TREATMENT OF RAILS |
| BE6044965A BE827175A (en) | 1975-03-25 | 1975-03-25 | DEVICE FOR QUICK COOLING OF FLAT METAL ROLLED PRODUCTS AT THE EXIT OF THE FINISHING TRAIN |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052670A true CA1052670A (en) | 1979-04-17 |
Family
ID=27560811
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,123A Expired CA1052670A (en) | 1974-10-04 | 1975-10-06 | Process and apparatus for improving the quality of steel sections |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1052670A (en) |
| FR (1) | FR2286879A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4203783A (en) * | 1977-09-19 | 1980-05-20 | Centre De Recherches Metallurgiques | Process for improving the quality of steel sections |
-
1975
- 1975-10-03 FR FR7531197A patent/FR2286879A1/en active Granted
- 1975-10-06 CA CA237,123A patent/CA1052670A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2286879B1 (en) | 1980-02-08 |
| FR2286879A1 (en) | 1976-04-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1193176A (en) | Method for the production of improved railway rails by accelerated colling in line with the production rolling mill | |
| EP2870268B2 (en) | Method and device for avoiding surface defects caused by zinc dust in a continuous strip galvanising process | |
| CN1075838C (en) | Primary cooling method in continuously annealing steel strip | |
| JP2721861B2 (en) | Direct quenching method for hot rolled steel wire | |
| US20100307646A1 (en) | Cooling system and cooling method of rolling steel | |
| EP0276457B1 (en) | A method for producing non-aging hot-dip galvanized steel strip | |
| EP0752479A1 (en) | Process for the interrupted quenching of a light alloy casting coming from a solution treating furnace | |
| EP0178799A2 (en) | Apparatus for cooling hot rolled steel rod | |
| DE2233057A1 (en) | QUENCHING MODULE | |
| CA1052670A (en) | Process and apparatus for improving the quality of steel sections | |
| JP2764167B2 (en) | Direct Patenting Apparatus and Method for Hot Rolled Ring Wire | |
| US6170284B1 (en) | Apparatus for the controlled cooling of hot-rolled sections, particularly beams, directly from the rolling heat | |
| GB2062692A (en) | Multi-purpose apparatus for treating hot rolled steel wire rod | |
| EP0181101B1 (en) | Apparatus and method for air cooling hot rolled steel rod | |
| EP0582180B1 (en) | Heat treatment process for wire rods | |
| US20210095367A1 (en) | Method and an arrangement for manufacturing a hot dip galvanized rolled high strength steel product | |
| JP3101980B2 (en) | Direct quenching method for hot rolled steel wire | |
| US4161800A (en) | Apparatus for improving the quality of steel sections | |
| JPH01313108A (en) | Method for uniform and rapid cooling of hot rolled wire stock | |
| US4417720A (en) | Continuous heat treatment plant for steel sheet | |
| DE2543750A1 (en) | Cooling and drying box for metal strip - to sharply cool the strip during rolling | |
| US3989231A (en) | Heat treatment of steel | |
| US2466870A (en) | Apparatus for heat-treating steel | |
| JPH08511064A (en) | Method and apparatus for continuous treatment of galvanized strip steel | |
| JP4242932B2 (en) | Primary cooling method in continuous annealing of steel strip |