CA1129312A - Reinforcing steel for concrete - Google Patents
Reinforcing steel for concreteInfo
- Publication number
- CA1129312A CA1129312A CA343,104A CA343104A CA1129312A CA 1129312 A CA1129312 A CA 1129312A CA 343104 A CA343104 A CA 343104A CA 1129312 A CA1129312 A CA 1129312A
- Authority
- CA
- Canada
- Prior art keywords
- steel
- reinforcing steel
- alloying elements
- cooling
- reinforcing
- 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
- 229910001294 Reinforcing steel Inorganic materials 0.000 title claims abstract description 45
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 48
- 239000010959 steel Substances 0.000 claims abstract description 48
- 238000001816 cooling Methods 0.000 claims abstract description 43
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 30
- 230000009466 transformation Effects 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 22
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 18
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 4
- 238000005275 alloying Methods 0.000 claims description 25
- 239000010410 layer Substances 0.000 claims description 19
- 239000010451 perlite Substances 0.000 claims description 19
- 235000019362 perlite Nutrition 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 17
- 238000002360 preparation method Methods 0.000 claims description 14
- 229910001566 austenite Inorganic materials 0.000 claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 10
- 239000002344 surface layer Substances 0.000 claims description 10
- 230000003014 reinforcing effect Effects 0.000 claims description 8
- 238000005096 rolling process Methods 0.000 claims description 7
- 238000010583 slow cooling Methods 0.000 claims description 3
- 238000003466 welding Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 230000015572 biosynthetic process Effects 0.000 description 11
- 229910000851 Alloy steel Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000000844 transformation Methods 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 230000002730 additional effect Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000003483 aging Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
-
- 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
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Steel (AREA)
- Reinforcement Elements For Buildings (AREA)
- Heat Treatment Of Articles (AREA)
- Laminated Bodies (AREA)
Abstract
REINFORCING STEEL FOR CONCRETE
ABSTRACT OF THE DISCLOSURE
The invention relates to weldable concrete reinforcing steel and a method of forming such steel. In this steel there is a central zone consisting of a perlite-ferrite mixture and a surface zone of annealed martensite. There is no intermediate layer or layers between the central zone and the surface zone. The steel is formed by a special cooling treatment in which transformation to bainite is avoided. The steel is advantageous because it is inexpensive to manufacture but is suitable for welding without loss of its advantageous characteristics.
The steel can also be manufactured into ribbed rods also without loss of advantageous characteristics.
ABSTRACT OF THE DISCLOSURE
The invention relates to weldable concrete reinforcing steel and a method of forming such steel. In this steel there is a central zone consisting of a perlite-ferrite mixture and a surface zone of annealed martensite. There is no intermediate layer or layers between the central zone and the surface zone. The steel is formed by a special cooling treatment in which transformation to bainite is avoided. The steel is advantageous because it is inexpensive to manufacture but is suitable for welding without loss of its advantageous characteristics.
The steel can also be manufactured into ribbed rods also without loss of advantageous characteristics.
Description
93~;Z
The invention relates to weldable concrete reinforcing steel having a carbon content of less than 0.25%. The invention also relates to a process for the formation of such a concrete reinforcing steel.
It is known to use steel with a chemical composition of 0.35 to 0.45~ carbon, up to 1.3~ manganese, 0.2 to 0.36 silicon and the usual impurities, as very hard concrete reinforcing steel. The formation of such steel is very inexpensive, since carbon, manganese and silicon are used as the principal hardening agents. ~owever, the shaping ability of this steel is relatively low, and in particular the weldability is low.
Concrete reinforcing steels are also known which have a lower carbon content (max 0.28%) and a silicon content of 0.5%, a manganese content of at most 1.6% and, in addition the usual impurities, a copper content of at least 0.2% (ASTM designation : A 440-74, page 336).
Such steel is however subjected to cold forming. A
particular disadvantage of this weldable reinforcing steel is thereby produced, in that it registers a reduc-tion of yield point or tensile strength after a short age-hardening at temperatures between room temperature and 800C. Such temperatures however are produced during welding as well as during warm bending of the reinforcing steel on the building site.
A reinforcing steel with desirable properties, which does not have these disadvantages, is described in DE-OS
24 26 920. By a special cooling procedure, reinforcing steel rods are prepared which consist of a more finely-grained micro-structure. At the periphery of the rods, the steel consists of strong tempered martensite-bainite, .*
`` llZ93~
and of ferrite-bainite to ~errite-perlite including b~ ite at the centre of the rods. Thereby the proportion of perlite with bainite~ expressed as a percentage, should be greater than the proportion of ferrite.
Such a steel exhibits the required welding proper-ties as well as sufficiently high tensile strength and sufficiently great yield point values. It has however come to light that the elongation at rupture of the known steel requires improvement. It tends to form cracks and therefore tends not to have an optimal fatigue performance.
The basis of the present invention is therefore to provide a steel having the desirable properties of known steel which however is less susceptible to cracking and which consequently has better values of breaking strain.
According to the invention there is provided weldable reinforcing steel having a carbon content of less than 0.25~, a yield point~ o 2 of at least 500 N/mm and a tensile strength of at least 550 N/mm , and which consists of a conc~entric central zone and surface layer, the central zone being formed from a pure perlite-ferrite mixture, in which the ferrite portion is between 20~ and 80~, and the central zone having no intermediate layer bordering the surface layer, the latter being formed from pure martensite.
The steel requires no additional treatment, e.g.
cold-forming, patenting (heat treatment for wire) or surface tempering and has a yield point ~ o 2 of at least 500N/mm and a tensile strength of at least 550 N/mm2.
The steel according to the invention is consequently characterized by a pure concentric two layer construction ~12931~:
in which both layers are completely free of bainite. The steel according to the invention shows good welding pro-perties and the mechanical properties required by DIN-Norm 4~8 as well as a substantially improved elongation at rupture, whereby it is substantially unsusceptible to crack formation and shows an improved fatigue performance.
In a preferred form the reinforcing steel in the central zone has ferrite and perlite in approximately equal proportions. It has been found that the reinforcing steel according to the invention is very well suited for ribbed reinforcing rods since both layers adapt themselves to the rib form so that the ribs have the same mechanical properties as unribbed rods.
Furthermore, if the proportion of the surface layer advantageously forms 20%, preferably 33%, of the cross sectional surface area of the rod.
The steel according to the invention has the addi-tional advantage that it is quite inexpensive and can be formed quickly on a wire rolling mill. The process according to the invention for the formation of the inventive reinforcing steel is characterized by the following process steps:
a) The reinforcing steel is prepared on a wire rolling mill b) after the preparation step the rolled stock is subjected to an intensive, preferably multi-stage cooling c) by the cooling, the surface of the rolled stock is cooled below the martensite initiating temperature d) the cooling proceeds with such an intensity that an equalization temperature between the centre and the surface is achieved before a transformation to bainite, ferrite or perlite commences and that the equalization temperature lies in the temperature region in which the earliest possible transformation of the austenite into ferrite and perlite can take place.
e) after the e~ualization temperature is achieved, the temperature is held approximately constant until the end of the perlite transformation and the rolled stock is then subjected to a slow cooling.
In a preferred embodiment the rolled stock is coiled i~nediately after t~e cooling step and cooled in the air in its coiled condition. Thereby the isothermal trans-formation strived for in the invention as well as the annealing of the martensite in the peripheral zone is achieved directly from the heat generated during rolling, i.e. without an additional step.
The process according to the invention makes possible a quick and dependable preparation of the inventive reinforcing steel, without great expenditure. In a surprisingly simple way, reinforcing steel is produced on a wire rolling mlll and so handled that the properties so long sought after can be achieved during the preparation without great expense.
In a preferred embodiment of the process of the invention, normal steel having a thickness of up to 13mm is used for the preparation of the reinforcing steel.
In normal steel, the sum of all the alloying elements (manganese, silicon, sulfur and the like) is below 1.7%.
This normal steel is especially inexpensive and is suitable for the preparation of a steel according to the invention of high quality using normal water cooling if the thickness of the reinforcing steel is below 13mm.
11~9;~1~
It is advantageous to use a normal steel with a di.ameter of > 13mm which is micro-alloyed with a proportion of micro-alloying elements up to 0.08%, in order to be able to achieve the cooling without too much expenditure.
Alternatively, for diameters between 13 and 25mm an alloy steel can be used. In such a steel the sum of the alloying elements is between l.7% and 3%. For diameters of more than 25rnm the alloy steel must be mixed with micro-alloying elements and indeed with a proportion of micro-alloying elements up to 0.03~.
These directions regarding the use of alloys depend upon the knowledge that the transformation of austenite to ferrite, perlite or bainite is postponed to a later time through the use of alloyed steel and/or micro-alloyed steel.
It appears that the process of the invention is economical if the first step of the cooling is terminated within 0.2 seconds~
Further explanation of the reinforcing steel and of the process according to the invention are given in the following description. Reference is made therein to the accompanying drawings, in which:
Figure l is a photograph of a cross-section of a known reinforcing steel according to DE-OS 24 26 920;
Figures 2a to 2d are photomicrographs at 500x magni-fication of the structure of the known reinforcing steel;
Figure 3, which appears on the same sheet of drawings as Figure l, is a photograph of the cross-section of a reinforcing steel according to the invention;
Figures 4a and 4b are photo-micrographs at 500x 9;~1Z
magnification of both structures of the reinforcing steel according to the invention;
Figure ~ is a diagram to explain the controlled coo:ling according to the process of the invention;
Figure 6 is a table to explain the cooling of steels of various diameters and their cooling behaviour;
Figure 7 is a time-temperature-transformation-graph of normal steel with a low carbon content; and Figure 3 is a time-temperatuare-transformation-graph of an alloy steel with a low carbon content.
Figures 1 and 2 are photographs of the reinforcing steels of DE-OS 24 26 920. It can clearly be seen from Figure 1 that the reinforcing steel has at least four concentric layers within its cross section. The outermost layer consists oE annealed martensite-bainite, the inner side of which is bordered by a bainitic intermediate layer. Then there follows a ring-like ferrite-bainite layer, while the centre consists essentially of ferrite and perlite.
These four stràta are shown in the micrographs of Figures 2a to 2d at 500 times magniEication. The finely striated outer layer of annealed martensite-bainite is clearly differentiated from the bainitic intermediate layer of Figure 2b. As can be seen from Figure 2c the bordering ferrite-bainite layer has a larger structure.
The structure of the central zone is shown in Figure 2d in which the dark flecks of perlite and the light flecks of ferrite can be seen.
Figures 3 and 4 are corresponding micrographs of a reinforcing steel of the invention. This steel is formed of only two layers. The outer layer consists of pure ~l~g3~Z
annealed martensite and borders directly onto a central layer which consists of a pure perlite-ferrite structure.
This is particularly clear from Figures 4a and 4b, in which Figure 4a shows the surface layer of annealed martensite and Figure 4b shows the sudden transformation of the annealed martensite structure into the clearly different ferrite-perlite structure. The micrographs of Figure 4 also have a magnification of 500 times.
The strictly two layer structure of the steels of the invention gives the pre~iously unexpected advantageous properties that were explained above.
The process for the preparation of the reinforcing steel of the invention is explained in further detail with reference to Fiyures 5 to 8. Figure 5 shows a diagram in which the cooling of a reinforcing steel is represented, which initially has a temperature of about 850C in the cooling operation and then undergoes a three step water cooling. The steel is immediately coiled after the termination of the cooling period and is further cooled in air in the form of a coil. The coiled rolled goods undergoes an isothermal transformation in the coil, whereby the ferrite in the central zone is transformed into ferrite and perlite and the martensite of the surface layer is annealed by the energy of transformation thus liberated. This is explained in further detail below.
Figure 5 shows in the left part the slow cooling of the rolled goods during the running through of the finished stage. The rolled goods are introduced into the cooling operation at t:h~ int of time identified as to and they remain approximately 0.15 seconds in the first cooling step. The third cooling step is of approximately 0.35 seconds duration.
The rolled goods are divided into concentric rings in Figure 5 for the illustration of the temperature development over the cross-section o the wire. The outer surface is identified as 1 and the middle point is identified as 4. The ring identified as 2 extends about half a diameter and the ring identified as 3 has a diameter that corresponds to a quarter of the diameter of the wire diameter. The ring identified as la has a radius of about 9/11 of the radius (R) of the rolled goods and it approximately identifies the boundary between the martensite layer and the central zone.
The temperature changes of the rings during the cooling can be seen from the curves of Fig. 5 identified by corresponding numerals 1, la, 2, 3 and 4. The outer ring is cooled below the martensite producing temperature Ms so that an outer layer of martensite forms between rings 1 and la. Since the central region is naturally noL
so rapidly cooled, the martensite layer between rings 1 and la is further heated up by the heat present in the central zone, whereby on the one hand the martensite is annealed and on the other hand an equalization tempera-ture TA is reached. The achievement of the equalization temperature is equivalent to the fact that the rolled goods have an equal temperature over the whole of the cross section after the cooling. This temperature is now maintained until the transformation of the austenite to ferrite and perlite is complete. Then a continued cooling may take place.
The equali~ation temperature TA is so chosen that during the isothermal transformation the bainite region 9~,z is not entered. Moreover, it desirably lies in a region in which the earliest possible transformation of the austenite into ferrite can take place. This assures that the transformation of austenite into ferrite and perlite takes place in the shortest possible time and that it does not degenerate to a very lengthy process.
It is clear from Fig. 5, that according to the in~ention the formation of bainite is prevented in that the equalization temperature is achieved before a trans-formation to ferrite can take place, and beyond that thetransformation ensues isothermally so that during the cooling the bainite region is not entered.
The transformation curves chosen in Figure 5 cor-respond to the usual time-temperature-transformation-graphs wherein the ferrite formation region is represented by F, the perlite formation region is represented by P, the bainite formation region is indicated by B and the martensite formation temperature is represented by Ms.
Austenite which is cooled below the martensite formation temperature is transformed immediately to martensite.
The table of Figure 6 shows, in a worked example, the possible arrangement oE the cooling for various steel diameters from 5.5 to 30mm. In this example, a normal alloy steel in which the sum of the alloying elements does not exceed a proportion of 1.7%, is cooled from an initial temperature of 850C.
From this it is clear tl~at the first cooling step lasts no longer than 0.2 seconds. While a single cooling step is sufficient for a diameter of 5.5mm, up to eight cooling steps can be considered for greater diameters.
The total cooling is therefore complete at the latest ~1~9~
~ `~
after three seconds. In the next column, the time required to reach the equalization temperature is given.
In this column the rein~orcing steels are divided into three groups 1, II and III according to diameter. The first group includes the diameters from 5.5 to 13mm, the second group from 13 to 25mm and the third group from 25 to 30mm.
The equalization temperature for the first group is reached within two seconds. The equalization temperature for the second group is reached within 10 seconds, and in the third group within 14 seconds. These associations have an important meaning for the a2plicability of the water cooling, which is explained in more detail below.
In the further columns of Figure 6, the temperatures of the central zone at the end of each cooling step are given Eor the various diameters. By "central zone", here we mean the diameter r=o. Furthermore, the equalization temperature achieved is given for each wire diameter.
The reason for~the above-mentioned division into three diameter groups is clear from Figures 7 and 8. Figure 7 shows the time-temperature-transformation-diagram for a low carbon (c _ 0.25%) normal steel. The earliest possible transformation from austenite to ferrite is possible in about two seconds at a temperature of about 500C. Corresponding to the teaching of the present invention, the equalization temperature should be adjusted to this point. From this it appears that normal steel up to a diameter of 13mm can be treated by the water cooling characterized in Figure 6. The equalization temperature lies somewhat above 500C.
In comparison to this, Figure 8 shows the ~" 11:Z~93~z time-temperature-transformation-graph of a low carbon stee] in which the sum of the alloying elements lies between 1.7% and 3%. From this it is clear that the earliest possible transformation of austenite to ferrite is Eirst possible after an order of magnitude of 10 seconds. Further, it is to be noticed that the required equalization temperature is substantially higher, since the earliest possible transformation to ferrite takes place at about 700C. By the addition of alloying elements the time of the earliest possible transfor-mation of austenite to ferrite can be protracted, so that more time is available to reach the equalization temperature.
A similar effect, namely the displacement of the time point of the earliest possible transformation of austenite to ferrite to a later time, can be achieved by the addition o~ micro-alloying elements, e.g. niobium, vanadium or molybdenum. In contrast to the use of alloy steel (Figure 8), the transformation curve of Fig~re 7 is entirely displaced by about a unit of ten to the right, without otherwise chan~ing the position or form of the transformation curve. Therefore the addition of micro-alloying element~, in contrast to the addition of other alloying elements, does not change the equalization temperature.
; For the water cooling indicated in Figure 6 it is necesarily, for the preparation of reinforcing steel with diameters - 13mm, either to use an alloy steel (having a sum total of alloying elements between 1.7% and 3%) or a micro-alloyed steel (containing vanadium, niobium or molybdenum up to 0.8%).
L129~12 At a diameter of > 25mm in an alloy steel the sum of the alloying elements should be more than 3%. This is not in general recommended, so that for these diameters addi-tional micro-alloying or micro-alloying alone is provided.
Instead of the alteration of the alloy proportion of the steel, a more intensive cooling can be effected, so that the equalization temperature is reached more quickly. Such a cooling is however very uneconomical.
From the graphs of Figure 7 and 8 it can be inferred that the ratio of ferrite to perlite in the central zone can be influenced by the choice of the equalization temperature.
In the actual example described above, the cooling of the rolled goods is commenced from an initial tempera-ture 850C. Other temperatures are conceivable, but the initial temperature must be high enough that the austenite remains stable and low enough that the cooling of the rolled goods within the required time is possible. This means that, particularly for small diameters, a higher initial temperature of the rolled goods can be tolerated.
All together the temperature of 850C has proved to be particularly suitable for this purpose.
The isothermal transformation of austenite to ferrite and perlite can be achieved by insertion into an oven after the cooling operation. It is indeed very advan-tageous to coil the uncut reinforcing steel coming from the wire rolling mill immediately after its emergence from the cooling operation. In the coil form the temperature of the reinforcing steel does not decrease as quickly, since the temperature is maintained by the liberation of transformation heat and in coil form a reduced heat loss `` 11~9~
to the air takes place. Furthermore, this method makes it possible to apply the cooling to the rapid Eormation process, which is known in connection with wire rolling mills but has not yet been used for the preparation of concrete reinforcing steel.
Under similar conditions, the elongation at rupture of a reinforcing steel prepared according to the teachings of DE-OS 24 26 920 amounted to 5.2%, whereas the reinforcing steel according to the invention amounted to 10.1%. This gives an improvement with respect to crack formation stability and creep resistance.
Under favourable conditions, the elongation at rupture for the reinforcing steel according to the invention can be increased even more. The average elongation at rupture can then, for example, be between 13.9% and 17.4%, whereby the value required by DIN 488/sheet l can be considerably exceeded.
The invention has been described in detail above, but should not be considered limited to such details. The modifications that can be made by a person skilled in this art after reading the above description fall within the scope of the invention as defined by the following claims.
The invention relates to weldable concrete reinforcing steel having a carbon content of less than 0.25%. The invention also relates to a process for the formation of such a concrete reinforcing steel.
It is known to use steel with a chemical composition of 0.35 to 0.45~ carbon, up to 1.3~ manganese, 0.2 to 0.36 silicon and the usual impurities, as very hard concrete reinforcing steel. The formation of such steel is very inexpensive, since carbon, manganese and silicon are used as the principal hardening agents. ~owever, the shaping ability of this steel is relatively low, and in particular the weldability is low.
Concrete reinforcing steels are also known which have a lower carbon content (max 0.28%) and a silicon content of 0.5%, a manganese content of at most 1.6% and, in addition the usual impurities, a copper content of at least 0.2% (ASTM designation : A 440-74, page 336).
Such steel is however subjected to cold forming. A
particular disadvantage of this weldable reinforcing steel is thereby produced, in that it registers a reduc-tion of yield point or tensile strength after a short age-hardening at temperatures between room temperature and 800C. Such temperatures however are produced during welding as well as during warm bending of the reinforcing steel on the building site.
A reinforcing steel with desirable properties, which does not have these disadvantages, is described in DE-OS
24 26 920. By a special cooling procedure, reinforcing steel rods are prepared which consist of a more finely-grained micro-structure. At the periphery of the rods, the steel consists of strong tempered martensite-bainite, .*
`` llZ93~
and of ferrite-bainite to ~errite-perlite including b~ ite at the centre of the rods. Thereby the proportion of perlite with bainite~ expressed as a percentage, should be greater than the proportion of ferrite.
Such a steel exhibits the required welding proper-ties as well as sufficiently high tensile strength and sufficiently great yield point values. It has however come to light that the elongation at rupture of the known steel requires improvement. It tends to form cracks and therefore tends not to have an optimal fatigue performance.
The basis of the present invention is therefore to provide a steel having the desirable properties of known steel which however is less susceptible to cracking and which consequently has better values of breaking strain.
According to the invention there is provided weldable reinforcing steel having a carbon content of less than 0.25~, a yield point~ o 2 of at least 500 N/mm and a tensile strength of at least 550 N/mm , and which consists of a conc~entric central zone and surface layer, the central zone being formed from a pure perlite-ferrite mixture, in which the ferrite portion is between 20~ and 80~, and the central zone having no intermediate layer bordering the surface layer, the latter being formed from pure martensite.
The steel requires no additional treatment, e.g.
cold-forming, patenting (heat treatment for wire) or surface tempering and has a yield point ~ o 2 of at least 500N/mm and a tensile strength of at least 550 N/mm2.
The steel according to the invention is consequently characterized by a pure concentric two layer construction ~12931~:
in which both layers are completely free of bainite. The steel according to the invention shows good welding pro-perties and the mechanical properties required by DIN-Norm 4~8 as well as a substantially improved elongation at rupture, whereby it is substantially unsusceptible to crack formation and shows an improved fatigue performance.
In a preferred form the reinforcing steel in the central zone has ferrite and perlite in approximately equal proportions. It has been found that the reinforcing steel according to the invention is very well suited for ribbed reinforcing rods since both layers adapt themselves to the rib form so that the ribs have the same mechanical properties as unribbed rods.
Furthermore, if the proportion of the surface layer advantageously forms 20%, preferably 33%, of the cross sectional surface area of the rod.
The steel according to the invention has the addi-tional advantage that it is quite inexpensive and can be formed quickly on a wire rolling mill. The process according to the invention for the formation of the inventive reinforcing steel is characterized by the following process steps:
a) The reinforcing steel is prepared on a wire rolling mill b) after the preparation step the rolled stock is subjected to an intensive, preferably multi-stage cooling c) by the cooling, the surface of the rolled stock is cooled below the martensite initiating temperature d) the cooling proceeds with such an intensity that an equalization temperature between the centre and the surface is achieved before a transformation to bainite, ferrite or perlite commences and that the equalization temperature lies in the temperature region in which the earliest possible transformation of the austenite into ferrite and perlite can take place.
e) after the e~ualization temperature is achieved, the temperature is held approximately constant until the end of the perlite transformation and the rolled stock is then subjected to a slow cooling.
In a preferred embodiment the rolled stock is coiled i~nediately after t~e cooling step and cooled in the air in its coiled condition. Thereby the isothermal trans-formation strived for in the invention as well as the annealing of the martensite in the peripheral zone is achieved directly from the heat generated during rolling, i.e. without an additional step.
The process according to the invention makes possible a quick and dependable preparation of the inventive reinforcing steel, without great expenditure. In a surprisingly simple way, reinforcing steel is produced on a wire rolling mlll and so handled that the properties so long sought after can be achieved during the preparation without great expense.
In a preferred embodiment of the process of the invention, normal steel having a thickness of up to 13mm is used for the preparation of the reinforcing steel.
In normal steel, the sum of all the alloying elements (manganese, silicon, sulfur and the like) is below 1.7%.
This normal steel is especially inexpensive and is suitable for the preparation of a steel according to the invention of high quality using normal water cooling if the thickness of the reinforcing steel is below 13mm.
11~9;~1~
It is advantageous to use a normal steel with a di.ameter of > 13mm which is micro-alloyed with a proportion of micro-alloying elements up to 0.08%, in order to be able to achieve the cooling without too much expenditure.
Alternatively, for diameters between 13 and 25mm an alloy steel can be used. In such a steel the sum of the alloying elements is between l.7% and 3%. For diameters of more than 25rnm the alloy steel must be mixed with micro-alloying elements and indeed with a proportion of micro-alloying elements up to 0.03~.
These directions regarding the use of alloys depend upon the knowledge that the transformation of austenite to ferrite, perlite or bainite is postponed to a later time through the use of alloyed steel and/or micro-alloyed steel.
It appears that the process of the invention is economical if the first step of the cooling is terminated within 0.2 seconds~
Further explanation of the reinforcing steel and of the process according to the invention are given in the following description. Reference is made therein to the accompanying drawings, in which:
Figure l is a photograph of a cross-section of a known reinforcing steel according to DE-OS 24 26 920;
Figures 2a to 2d are photomicrographs at 500x magni-fication of the structure of the known reinforcing steel;
Figure 3, which appears on the same sheet of drawings as Figure l, is a photograph of the cross-section of a reinforcing steel according to the invention;
Figures 4a and 4b are photo-micrographs at 500x 9;~1Z
magnification of both structures of the reinforcing steel according to the invention;
Figure ~ is a diagram to explain the controlled coo:ling according to the process of the invention;
Figure 6 is a table to explain the cooling of steels of various diameters and their cooling behaviour;
Figure 7 is a time-temperature-transformation-graph of normal steel with a low carbon content; and Figure 3 is a time-temperatuare-transformation-graph of an alloy steel with a low carbon content.
Figures 1 and 2 are photographs of the reinforcing steels of DE-OS 24 26 920. It can clearly be seen from Figure 1 that the reinforcing steel has at least four concentric layers within its cross section. The outermost layer consists oE annealed martensite-bainite, the inner side of which is bordered by a bainitic intermediate layer. Then there follows a ring-like ferrite-bainite layer, while the centre consists essentially of ferrite and perlite.
These four stràta are shown in the micrographs of Figures 2a to 2d at 500 times magniEication. The finely striated outer layer of annealed martensite-bainite is clearly differentiated from the bainitic intermediate layer of Figure 2b. As can be seen from Figure 2c the bordering ferrite-bainite layer has a larger structure.
The structure of the central zone is shown in Figure 2d in which the dark flecks of perlite and the light flecks of ferrite can be seen.
Figures 3 and 4 are corresponding micrographs of a reinforcing steel of the invention. This steel is formed of only two layers. The outer layer consists of pure ~l~g3~Z
annealed martensite and borders directly onto a central layer which consists of a pure perlite-ferrite structure.
This is particularly clear from Figures 4a and 4b, in which Figure 4a shows the surface layer of annealed martensite and Figure 4b shows the sudden transformation of the annealed martensite structure into the clearly different ferrite-perlite structure. The micrographs of Figure 4 also have a magnification of 500 times.
The strictly two layer structure of the steels of the invention gives the pre~iously unexpected advantageous properties that were explained above.
The process for the preparation of the reinforcing steel of the invention is explained in further detail with reference to Fiyures 5 to 8. Figure 5 shows a diagram in which the cooling of a reinforcing steel is represented, which initially has a temperature of about 850C in the cooling operation and then undergoes a three step water cooling. The steel is immediately coiled after the termination of the cooling period and is further cooled in air in the form of a coil. The coiled rolled goods undergoes an isothermal transformation in the coil, whereby the ferrite in the central zone is transformed into ferrite and perlite and the martensite of the surface layer is annealed by the energy of transformation thus liberated. This is explained in further detail below.
Figure 5 shows in the left part the slow cooling of the rolled goods during the running through of the finished stage. The rolled goods are introduced into the cooling operation at t:h~ int of time identified as to and they remain approximately 0.15 seconds in the first cooling step. The third cooling step is of approximately 0.35 seconds duration.
The rolled goods are divided into concentric rings in Figure 5 for the illustration of the temperature development over the cross-section o the wire. The outer surface is identified as 1 and the middle point is identified as 4. The ring identified as 2 extends about half a diameter and the ring identified as 3 has a diameter that corresponds to a quarter of the diameter of the wire diameter. The ring identified as la has a radius of about 9/11 of the radius (R) of the rolled goods and it approximately identifies the boundary between the martensite layer and the central zone.
The temperature changes of the rings during the cooling can be seen from the curves of Fig. 5 identified by corresponding numerals 1, la, 2, 3 and 4. The outer ring is cooled below the martensite producing temperature Ms so that an outer layer of martensite forms between rings 1 and la. Since the central region is naturally noL
so rapidly cooled, the martensite layer between rings 1 and la is further heated up by the heat present in the central zone, whereby on the one hand the martensite is annealed and on the other hand an equalization tempera-ture TA is reached. The achievement of the equalization temperature is equivalent to the fact that the rolled goods have an equal temperature over the whole of the cross section after the cooling. This temperature is now maintained until the transformation of the austenite to ferrite and perlite is complete. Then a continued cooling may take place.
The equali~ation temperature TA is so chosen that during the isothermal transformation the bainite region 9~,z is not entered. Moreover, it desirably lies in a region in which the earliest possible transformation of the austenite into ferrite can take place. This assures that the transformation of austenite into ferrite and perlite takes place in the shortest possible time and that it does not degenerate to a very lengthy process.
It is clear from Fig. 5, that according to the in~ention the formation of bainite is prevented in that the equalization temperature is achieved before a trans-formation to ferrite can take place, and beyond that thetransformation ensues isothermally so that during the cooling the bainite region is not entered.
The transformation curves chosen in Figure 5 cor-respond to the usual time-temperature-transformation-graphs wherein the ferrite formation region is represented by F, the perlite formation region is represented by P, the bainite formation region is indicated by B and the martensite formation temperature is represented by Ms.
Austenite which is cooled below the martensite formation temperature is transformed immediately to martensite.
The table of Figure 6 shows, in a worked example, the possible arrangement oE the cooling for various steel diameters from 5.5 to 30mm. In this example, a normal alloy steel in which the sum of the alloying elements does not exceed a proportion of 1.7%, is cooled from an initial temperature of 850C.
From this it is clear tl~at the first cooling step lasts no longer than 0.2 seconds. While a single cooling step is sufficient for a diameter of 5.5mm, up to eight cooling steps can be considered for greater diameters.
The total cooling is therefore complete at the latest ~1~9~
~ `~
after three seconds. In the next column, the time required to reach the equalization temperature is given.
In this column the rein~orcing steels are divided into three groups 1, II and III according to diameter. The first group includes the diameters from 5.5 to 13mm, the second group from 13 to 25mm and the third group from 25 to 30mm.
The equalization temperature for the first group is reached within two seconds. The equalization temperature for the second group is reached within 10 seconds, and in the third group within 14 seconds. These associations have an important meaning for the a2plicability of the water cooling, which is explained in more detail below.
In the further columns of Figure 6, the temperatures of the central zone at the end of each cooling step are given Eor the various diameters. By "central zone", here we mean the diameter r=o. Furthermore, the equalization temperature achieved is given for each wire diameter.
The reason for~the above-mentioned division into three diameter groups is clear from Figures 7 and 8. Figure 7 shows the time-temperature-transformation-diagram for a low carbon (c _ 0.25%) normal steel. The earliest possible transformation from austenite to ferrite is possible in about two seconds at a temperature of about 500C. Corresponding to the teaching of the present invention, the equalization temperature should be adjusted to this point. From this it appears that normal steel up to a diameter of 13mm can be treated by the water cooling characterized in Figure 6. The equalization temperature lies somewhat above 500C.
In comparison to this, Figure 8 shows the ~" 11:Z~93~z time-temperature-transformation-graph of a low carbon stee] in which the sum of the alloying elements lies between 1.7% and 3%. From this it is clear that the earliest possible transformation of austenite to ferrite is Eirst possible after an order of magnitude of 10 seconds. Further, it is to be noticed that the required equalization temperature is substantially higher, since the earliest possible transformation to ferrite takes place at about 700C. By the addition of alloying elements the time of the earliest possible transfor-mation of austenite to ferrite can be protracted, so that more time is available to reach the equalization temperature.
A similar effect, namely the displacement of the time point of the earliest possible transformation of austenite to ferrite to a later time, can be achieved by the addition o~ micro-alloying elements, e.g. niobium, vanadium or molybdenum. In contrast to the use of alloy steel (Figure 8), the transformation curve of Fig~re 7 is entirely displaced by about a unit of ten to the right, without otherwise chan~ing the position or form of the transformation curve. Therefore the addition of micro-alloying element~, in contrast to the addition of other alloying elements, does not change the equalization temperature.
; For the water cooling indicated in Figure 6 it is necesarily, for the preparation of reinforcing steel with diameters - 13mm, either to use an alloy steel (having a sum total of alloying elements between 1.7% and 3%) or a micro-alloyed steel (containing vanadium, niobium or molybdenum up to 0.8%).
L129~12 At a diameter of > 25mm in an alloy steel the sum of the alloying elements should be more than 3%. This is not in general recommended, so that for these diameters addi-tional micro-alloying or micro-alloying alone is provided.
Instead of the alteration of the alloy proportion of the steel, a more intensive cooling can be effected, so that the equalization temperature is reached more quickly. Such a cooling is however very uneconomical.
From the graphs of Figure 7 and 8 it can be inferred that the ratio of ferrite to perlite in the central zone can be influenced by the choice of the equalization temperature.
In the actual example described above, the cooling of the rolled goods is commenced from an initial tempera-ture 850C. Other temperatures are conceivable, but the initial temperature must be high enough that the austenite remains stable and low enough that the cooling of the rolled goods within the required time is possible. This means that, particularly for small diameters, a higher initial temperature of the rolled goods can be tolerated.
All together the temperature of 850C has proved to be particularly suitable for this purpose.
The isothermal transformation of austenite to ferrite and perlite can be achieved by insertion into an oven after the cooling operation. It is indeed very advan-tageous to coil the uncut reinforcing steel coming from the wire rolling mill immediately after its emergence from the cooling operation. In the coil form the temperature of the reinforcing steel does not decrease as quickly, since the temperature is maintained by the liberation of transformation heat and in coil form a reduced heat loss `` 11~9~
to the air takes place. Furthermore, this method makes it possible to apply the cooling to the rapid Eormation process, which is known in connection with wire rolling mills but has not yet been used for the preparation of concrete reinforcing steel.
Under similar conditions, the elongation at rupture of a reinforcing steel prepared according to the teachings of DE-OS 24 26 920 amounted to 5.2%, whereas the reinforcing steel according to the invention amounted to 10.1%. This gives an improvement with respect to crack formation stability and creep resistance.
Under favourable conditions, the elongation at rupture for the reinforcing steel according to the invention can be increased even more. The average elongation at rupture can then, for example, be between 13.9% and 17.4%, whereby the value required by DIN 488/sheet l can be considerably exceeded.
The invention has been described in detail above, but should not be considered limited to such details. The modifications that can be made by a person skilled in this art after reading the above description fall within the scope of the invention as defined by the following claims.
Claims (15)
1. Weldable reinforcing steel having a carbon content of less than 0.25%, a yield point .betaØ2 of at least 500 N/mm and a tensile strength of at least 550 N/mm , and which consists of a concentric central zone and surface layer, the central zone being formed from a pure perlite-ferrite mixture, in which the ferrite portion is between 20% and 80%, and the central zone having no intermediate layer bordering the surface layer, the latter being formed from pure martensite.
2. Reinforcing steel according to claim 1, wherein the ferrite and perlite are contained in approximately equal amounts in the central zone.
3. Reinforcing steel according to claim 1, wherein the reinforcing steel is in the form of ribbed rods.
4. Reinforcing steel according to claim 1, claim 2 or claim 3 wherein the proportion of the surface layer forms at least 20% of the cross sectional surface area.
5. Reinforcing steel according to claim 1, claim 2 or claim 3 wherein at a diameter of ?13mm, the sum of all of the alloying elements is ?1.7%.
6. Reinforcing steel according to claim 1, claim 2 or claim 3 wherein the sum of all of the alloying elements at a diameter of >13mm is ?1.7% and wherein the steel contains a portion of micro-alloying elements up to 0.08%.
7. Reinforcing steel according to claim 1, claim 2 or claim 3 wherein, at a thickness between 13mm and 25mm, the sum of all the alloying elements lies between 1.7% and 3.0%.
8. Reinforcing steel according to claim 1, claim 2 or claim 3 wherein the sum of the alloying elements for a thickness of more than 25mm lies between 1.7% and 3.0% and wherein the steel contains micro-alloying elements up to 0.03%.
9. A process for the preparation of reinforcing steels characterized by the following process steps:
a) the reinforcing steel is prepared on a wire rolling mill;
b) after completion of the preparation step, the rolled goods are subjected to an intensive, cooling;
c) by the cooling the surface layer of the rolled goods is cooled below the martensite forming temperature;
d) the cooling is carried out with such an intensity that an equalization temperature between the central zone and surface layer is reached before a transformation to bainite, ferrite or perlite takes place, and that the equalization temperature lies approximately in the region in which the earliest possible transformation of austenite to ferrite and perlite takes place; and e) after reaching the equalization temperature, the temperature is held approximately constant until the end of the perlite transformation and the rolled goods are then subjected to slow cooling.
a) the reinforcing steel is prepared on a wire rolling mill;
b) after completion of the preparation step, the rolled goods are subjected to an intensive, cooling;
c) by the cooling the surface layer of the rolled goods is cooled below the martensite forming temperature;
d) the cooling is carried out with such an intensity that an equalization temperature between the central zone and surface layer is reached before a transformation to bainite, ferrite or perlite takes place, and that the equalization temperature lies approximately in the region in which the earliest possible transformation of austenite to ferrite and perlite takes place; and e) after reaching the equalization temperature, the temperature is held approximately constant until the end of the perlite transformation and the rolled goods are then subjected to slow cooling.
10. Process according to claim 9 wherein the rolled goods are coiled immediately after the termination of the cooling and then cooled in the coil form in air.
11. Process according to claim 9 or claim 10 wherein the first step of the cooling is finished within 0.2 seconds.
12. Process according to claim 9 or claim 10 wherein normal steel (in which the sum of all of the alloying elements is ?1.7%) is used for the preparation of reinforcing steels having a diameter of ?13mm.
13. Process according to claim 9 or claim 10 wherein normal steel having a porportion of micro-alloying elements up to 0.08% micro-alloyed therewith, is used for the preparation of reinforcing steels having a thickness of ?13mm.
14. Process according to claim 9 or claim 10 wherein alloyed steel (in which the sum of all of the alloying elements is between 1.7% and 3%) is used for the preparation of reinforcing steels having a thickness between 13 and 25mm.
15. Process according to claim 9 or claim 10 wherein alloyed steel having a proportion of micro-alloying elements of up to 0.03% micro-alloyed therewith, is used for the preparation of reinforcing steels having a thickness of more than 25mm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2900271.9-24 | 1979-01-05 | ||
| DE2900271A DE2900271C2 (en) | 1979-01-05 | 1979-01-05 | Weldable reinforcing steel and process for its manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129312A true CA1129312A (en) | 1982-08-10 |
Family
ID=6060073
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA343,104A Expired CA1129312A (en) | 1979-01-05 | 1980-01-04 | Reinforcing steel for concrete |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS55115949A (en) |
| AU (1) | AU534561B2 (en) |
| BE (1) | BE881003A (en) |
| CA (1) | CA1129312A (en) |
| DE (1) | DE2900271C2 (en) |
| ES (1) | ES8107320A1 (en) |
| FI (1) | FI69120C (en) |
| FR (1) | FR2445858A1 (en) |
| GB (1) | GB2047270B (en) |
| IT (1) | IT1164547B (en) |
| LU (1) | LU82058A1 (en) |
| NL (1) | NL8000059A (en) |
| SE (1) | SE451020B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6395109B1 (en) | 2000-02-15 | 2002-05-28 | Cargill, Incorporated | Bar product, cylinder rods, hydraulic cylinders, and method for manufacturing |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| LU85475A1 (en) * | 1984-07-23 | 1986-02-12 | Arbed | PROCESS FOR PRODUCING HARD STEEL MACHINE WIRE |
| DE3431008C2 (en) | 1984-08-23 | 1986-10-16 | Dyckerhoff & Widmann AG, 8000 München | Heat treatment of hot rolled bars or wires |
| DD231577B1 (en) * | 1984-12-17 | 1987-09-09 | Brandenburg Stahl Walzwerk | METHOD FOR INCREASING THE STRENGTH OF REINFORCING STEELS |
| DD234281B1 (en) * | 1984-12-21 | 1989-06-21 | Florin Stahl Walzwerk | METHOD FOR PRESSURE WATER TREATMENT OF ROLLING STEEL PRODUCTS |
| DD239805B1 (en) * | 1985-07-29 | 1988-06-22 | Thaelmann Schwermaschbau Veb | METHOD FOR PRODUCING A CONCRETE STEEL |
| CA1265421A (en) * | 1985-10-31 | 1990-02-06 | Norio Anzawa | Method and apparatus for cooling rolled steels |
| FR2684691B1 (en) * | 1991-12-04 | 1995-06-09 | Unimetall Sa | PROCESS FOR THE CONTINUOUS MANUFACTURE OF A THREADED STEEL WIRE, PARTICULARLY A WIRE FOR REINFORCING CONCRETE. |
| DE19962801A1 (en) | 1999-12-23 | 2001-06-28 | Sms Demag Ag | Process for heat treating wire |
| IT1391760B1 (en) * | 2008-11-11 | 2012-01-27 | Danieli Off Mecc | THERMAL TREATMENT PROCESS OF LAMINATES |
| KR101787287B1 (en) * | 2016-10-21 | 2017-10-19 | 현대제철 주식회사 | High strength steel deformed bar and method of manufacturing the same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE790867A (en) * | 1972-10-31 | 1973-02-15 | Centre Rech Metallurgique | PROCESS FOR IMPROVING THE QUALITY OF LAMINATED PRODUCTS, SUCH AS ROUND OR CONCRETE BARS, MACHINE WIRE, ETC .... |
| NL170159C (en) * | 1973-06-04 | 1982-10-01 | Estel Hoogovens Bv | METHOD FOR MANUFACTURING WELDABLE LOW CARBON STEEL MATERIAL BY CONTROLLED COOLING |
| AT368774B (en) * | 1973-09-11 | 1982-11-10 | Salzgitter Peine Stahlwerke | STEEL WIRE AND METHOD FOR THE PRODUCTION THEREOF |
| DD106661A1 (en) * | 1973-09-24 | 1974-06-20 | ||
| IT1090143B (en) * | 1975-01-29 | 1985-06-18 | Centre Rech Metallurgique | PROCESS FOR MANUFACTURING LAMINATED STEEL PRODUCTS |
-
1979
- 1979-01-05 DE DE2900271A patent/DE2900271C2/en not_active Expired
- 1979-12-21 IT IT28312/79A patent/IT1164547B/en active
- 1979-12-27 JP JP17389279A patent/JPS55115949A/en active Pending
- 1979-12-28 FI FI794092A patent/FI69120C/en not_active IP Right Cessation
-
1980
- 1980-01-02 AU AU54287/80A patent/AU534561B2/en not_active Ceased
- 1980-01-03 FR FR8000255A patent/FR2445858A1/en active Granted
- 1980-01-04 LU LU82058A patent/LU82058A1/en unknown
- 1980-01-04 NL NL8000059A patent/NL8000059A/en not_active Application Discontinuation
- 1980-01-04 BE BE0/198857A patent/BE881003A/en not_active IP Right Cessation
- 1980-01-04 SE SE8000069A patent/SE451020B/en not_active IP Right Cessation
- 1980-01-04 ES ES487449A patent/ES8107320A1/en not_active Expired
- 1980-01-04 CA CA343,104A patent/CA1129312A/en not_active Expired
- 1980-01-07 GB GB8000407A patent/GB2047270B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6395109B1 (en) | 2000-02-15 | 2002-05-28 | Cargill, Incorporated | Bar product, cylinder rods, hydraulic cylinders, and method for manufacturing |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2900271C2 (en) | 1984-01-26 |
| BE881003A (en) | 1980-05-02 |
| GB2047270B (en) | 1982-12-15 |
| IT7928312A0 (en) | 1979-12-21 |
| NL8000059A (en) | 1980-07-08 |
| FI794092A (en) | 1980-07-06 |
| FI69120C (en) | 1987-05-05 |
| FR2445858B1 (en) | 1984-05-04 |
| GB2047270A (en) | 1980-11-26 |
| FI69120B (en) | 1985-08-30 |
| IT1164547B (en) | 1987-04-15 |
| ES487449A0 (en) | 1980-12-16 |
| AU534561B2 (en) | 1984-02-09 |
| LU82058A1 (en) | 1980-04-23 |
| ES8107320A1 (en) | 1980-12-16 |
| FR2445858A1 (en) | 1980-08-01 |
| JPS55115949A (en) | 1980-09-06 |
| AU5428780A (en) | 1980-07-10 |
| SE451020B (en) | 1987-08-24 |
| DE2900271A1 (en) | 1980-07-17 |
| SE8000069L (en) | 1980-07-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100661789B1 (en) | High carbon steel pipe excellent in cold formability and high frequency hardenability and method for producing the same | |
| US5458699A (en) | Steel wire for making high strength steel wire product and method for manufacturing thereof | |
| US20090020189A1 (en) | Steel wire material for spring and its producing method | |
| EP0429094A1 (en) | High strength low carbon steels, steel articles thereof and method for manufacturing the steels | |
| CA1129312A (en) | Reinforcing steel for concrete | |
| KR890002653B1 (en) | Process for producing steel wire or rods of high ductility and strength | |
| CA2502114C (en) | Cold-worked steels with packet-lath martensite/austenite microstructure | |
| JP2006506534A5 (en) | ||
| JPH10280088A (en) | Steel product for building structural use and its production | |
| SU1087078A3 (en) | Method for making section stock from low-alloy dispersion-solidifiyng steels | |
| JPH05105957A (en) | Production of heat resistant high strength bolt | |
| JPH0995735A (en) | Production of steel for reinforcing bar excellent in earthquake resistance | |
| JP2984889B2 (en) | High carbon steel wire or steel wire excellent in wire drawability and method for producing the same | |
| US5650027A (en) | High-carbon steel wire rod and wire excellent in drawability and methods of producing the same | |
| JP2546070B2 (en) | High-strength electric resistance welded steel pipe for vehicle door impact bar and manufacturing method thereof | |
| JP3018268B2 (en) | High carbon steel wire or steel wire excellent in wire drawability and method for producing the same | |
| JPH0759738B2 (en) | Ultra-high-strength PC steel wire or steel bar excellent in uniform elongation and method for producing the same | |
| US5658402A (en) | High-carbon steel wire rod and wire excellent in drawability and methods of producing the same | |
| UA80009C2 (en) | Process for production of high-test, high-plastic alloyed carbonaceous steel | |
| JPS6144122B2 (en) | ||
| JPH0995734A (en) | Production of steel for reinforcing bar excellent in earthquake resistance | |
| JP3487957B2 (en) | Wire with excellent wire drawing processability | |
| KR20000025991A (en) | High strength wire rod having an excellent wire drawing property and method for manufacturing the same | |
| JP2984888B2 (en) | High carbon steel wire or steel wire excellent in wire drawability and method for producing the same | |
| JPS5913024A (en) | Manufacture of directly spheroidized steel material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |