ACTIVATOR MIXTURE FOR INCREASING THE STRENGTH OF IRON ALLOYS

Abstract: An activator mixture for improving utilizable strength steels which consists essentially Ca and/or Na 16 to 30 %; Si 13 to 30 %; V and/or Mo 2 to 28 %, Nb and/or Ta 2 to 14 %, Al and/or Ba 1 to 15 %; B and/or Be 0,1 to 3,0 %, C 1 to 5 %; Fe 5 to 20 % and N 1 to 10 %.

Description: ACTIVATOR MIXTURE FCR INCREASING Tl-E STRENGTH CF IRON ALLOYS The invention relates to an activator mixture, consisting of a pluraty of components which improves πretal lurgic quality of al loy systems on iron basis and increases considerably the strength thereof, when used in course of steel production or wel¬ ding as a pulverized inset of filler wires. Increased requirements to be met by steels, as basic materials, in compliance with functional up-to-dateness and points of view of general energy and material savings, are directed to increased value in use and not to quantity. This increase in value of use has been directed to the increase of the corrplexicity. Accordingly, value of use of steels has been determined mostly - in dependence of final destination - by the metal lurgic quality, stress-tolerance of permanent deformation, e br itt lement, stress limit of fatigue, weldability and resistance to wear. Out of the characteristics forming the value of use of steels one of the most important features is the stress without permanent deformat ion. The value of the highest stress to be used without deformation represents a characteristic feature of steels, which determines the the loadabi I ity and weight of the structures or structural elements made thereof in the majority of cases but influences them fundamentally in all cases. Another important feature forming value of use of steels is the plasticity. In general with steels increase in strength is accompanied by a decreased plasticity. Development of presently used steels is determined by the up-to-dateness of processing technology in compliance with development of the general technical level. Nevertheless, increased utilization of strength range of pure iron has not been properly emphasized in industrial alloy systems in order to increase loadability and reduce weight. Presently used steels - with the exception of some functional parameters required by special technologies - do not serve for rreeting the endeavours of application technics directed to modernization, material and energy savings. Quick reduction of general energy and material reserves and thus ever increasing costs require necessarily that for producing or using any article of use or means a minirruri of material, steel and energy should be applied. Different rrethods are known for improving a single propert of a steel by al loying or by heat treatment, in accordance with the intended final use. With industrially produced steels, as a result of lattice faults, dislocations resulting from the different form, size and orientation of the single crystals, permanent deformation is induced by a stress, which is 1000- times lower, than theoretical lattice force. In this way, every hindurance which hinders motion of disloca- tions in steel, increases strength of the steels. Such are e.g. elements located in the lattice dissolved by substitution or in- terstition, dislocations, grain limits, twin crystals, alien phases, generations, all being independent strengthening mechanisms in itselves. Practice confirmed the fact, in so far as presently used methods for increasing steel strength - as they activate but one or two strengthening rrechani sms and mainly thermically - can plasticity characteristics and with a restrict¬ ed result in respect of strength increasing. The oject of the present invention is to provide an activator mixture a rretal lurgical way for strengthening steels in, under the additive effect of which strength of steels can be increased by keeping simultaneously plasticity on the proper level and im~ povement of metal lurgic quality can be simultaneously achieved, thus utilizuing theoretical lattice force for loadability, in systems of industrial appl icaton. According to the invention the composition of the mixture used in a quantity oif 5 to 17 kg/t in course of steel production or as a pulverized inset of filler wires is as follows Ca and/or Na 16 to 30 % Si 13 to 30 % V and/or Mo 2 to 28 % Nb and/or Ta 2 to 25 % Zr and/or Ce 2 to 15 % Ti 2 to 14 % AI and/or Ba 1 to 15 % B and/or Be 0,3 to 3,0 % C 1 to 5 % Fe 5 to 20 % and N 1 to 10 %. Proportion and quantity of alloying components in accordance with the invention, as wel l as rrethod of aI loyage ensure optimal phy- sico-chemical and metal-phys ical conditions in course of steel production or welding conditions, when using a fil ler wire with pulverized inset, which - when becoming predominant in industrial al loy systems on iron basis - improve etal lurgical quality and simultaneously considerably increase strength but also keep plas- ticity properties on the proper level, at the same time increas¬ ing ratio of theoretical lattice force to be utilized for load bear ing. In course of steel production the mixture is alloyed with a maximal grain size of 8 mm, well mixed, packed in an easily treatable size into the ladle while discharging, utilizing the agitating effect of the liquid steel beam or by means of the ethode - widely used in practice - in course of which - after having finished discharge - the mixture is blown into the liquid steel. Wien producing fil ler wire with pulverized inset, the ac- tϊvator is charged in hte prescribed fraction and wel I mixed. Properties of the single alloying components and properly chosen proportion thereof in the alloy systems result in local physico- chemical, nuclear and kynetic conditions in course of alloyage, strengthening, heating and hot formation, as wel l as re-crystal¬ lization, which considerably increase the quantity of the ele¬ ments which can be utilized for increasing the strength and rele¬ vant efficiency. Out of the conrponents used in an expedient proportion seme form complex compounds in the steel with a melting point, which are producing partly crystal nuclei of active size already in the melt thus increasing crytal I iazat ion ability, simultaneously shortening time of solidification, partly on their effect primary grain size and possibility of enrichment are reduced, advanta¬ geous conditions of re-crystallization are considerably improved. Thereafter, the alloy proportion in accordance with the invention establish conditions in course of solidification and re-crystal- lization, which are considerably increasing dissolving activity of the single elements built-in by interstition and thus soluble quantity thereof, and so number of the pre-stressed lattices and extent of their stressed state. Pre-stressing of the lattices by interstition increases intensely number of produced dislocations, which are partly promoting, partly determining the formation of the segregations for hindering their displacement. Out of the components of the mixture some are forming complex rre¬ tal lie segregations of high shear-strength, which are partly in¬ creasing, partly stabi lizing the internal stress of the lattice of the basic material, when built-in into the lattice faults. In such a manner lattice faults produced nretal lurgical ly of increas¬ ed nurber promote formation of metal lic segregations determining their place and density of arrangement, thus considerably in¬ creasing efficiency of anchoring function of segregations, in the motion of dislocation beginning under the influence of loading. Some of the conrponents of the mixture, when deposited in the lat¬ tice faults on the grain boundaries, decrease diffusion velocity of the nretal atoms in their envirorment thus delaying the process of non-coherent segregations in this place. In such a manner en- richment of undesired segregations along the grain boundaries are hindered, their inhemogenity in the alloying elements wil l be prevented. In such a manner strength of homogeneous grain boundaries wi l l be considerably increased, premature cracking occuring as a result of loading can be delayed, stretching and contraction up to creeping-break increases, ducti lity of the al loy system, cold and hot mal leability and ductibil ity, fatigue limit and strength to be uti lized for loadability increase. Some of the components of the mixture produce inclusions of low specific weight, which are easily up into the slag, thus considerably reducing harmful inclusion content of steel. In addition, complex spherical inclusions are also formed, which are partly remaining in the steel and keep their original shape even in course of plastic deformation, partly they bind sulfur atoms on their surface, forming a sulfid coating, thus considerably re¬ ducing possibi lity of ironic sulfid formation; in this way more advantageous plasticity and anisotropic properties can be assured for the steel . Accordingly, the mixture according to the invention guarantees automatically improved metallurgical quality of given steels, complete function of strengthening mechanisms without thermic in¬ fluences and predominance thereof in an optimal proportion in compliance with the basic material, additive superposition of their combination, simultaneously increasing utilizable strenght of steels. The effect of the mixture according to the invention will be il¬ lustrated by means of the following examples. Table 1 contains the chemical composition of charges A-1, A-2 and A-2 treated with activator, and the basis charges B-1, B-2 and B-3 in weight-%. Table 1. Al B 1 B A 2 2 A 3 B 3 C 0,15 0,14 0,23 0,27 0,07 0,07 Mn 1,54 1,65 1,88 1,77 0,60 0,68 Si 0,52 0,42 0,72 0,45 0,47 0,64 P 0,013 0,021 0,009 0,019 0,009 0,008 S 0,006 0,013 0,009 0,021 0,018 0,021 Cr 0,32 0,27 0,50 0,23 11,32 11,43 Ni 0,10 0,07 0,21 0,07 0,08 0,07 Cu 0,09 0,23 0,12 0,21 0,13 0,07 Mo 0,10 0,08 0,16 0,06 0,07 0,02 Nb 0,09 0,04 0,11 - 0,043 - V 0,14 0,16 0,10 - 0,02 0,04 Zr 0,01 - 0,02 - 0,03 - Ti 0,02 0,03 0,02 0,01 0,03 0,64 Al 0,04 0,12 0,062 0,072 0,032 0,053 N 0,026 0,007 0,010 0,009 0,029 0,007 B 0,0024 - 0,0017 - 0,0020 - Ce 0,030 - 0,024 - 0,012 - Ca 0,0012 - 0,0006 - 0,00009 - Charges were prepared on a steel-manufactur ing equipment LHP+AOD with a volume of 50 tons; the composi ton and amount of the acti¬ vator mixture having been used for steel production is given in Table 2. Table 2. Ac Ca 21,14 12,96 19,29 Na - Si 20,50 17,34 27,57 V 10,69 7,51 1,67 Mo 7,63 12,01 5,86 Nb 6,87 8,26 3,60 Ta - Zr 3,05 4.50 7,53 Ce 2,29 1,80 1,00 Ti 3,05 3,00 5,02 Al 6,11 7.51 5,86 Ba - C 1 r __9 0,75 1,67 Fe 17,1 15,41 10,94 N 3,94 1,88 5,02 B 0,18 0,13 0,17 Be - After production sheets in a thickness of 12,5 rrm were fomned in course of traditional hot nretalworking. Mechanical properties of the sheets in a hot rol led state and tempered at three different temperatures are contained in Table 3, wherein these are compared with similar states of the basic charge. Taking the basic charge as 100 %, %-ual ratio of the charges produced with an activator are also s πrarized. Table 3. h o t r o l l e d A-1 841 147 720 149 600 259 20,7 B-1 572 100 483 100 231 100 21,0 A-2 1443 173 1130 151 994 258 15,9 B-2 832 100 750 100 384 100 14,6 A-3 1362 250 988 244 810 346 18,0 B-3 545 100 405 100 234 100 16,0 annealed x and air cooled A-1 854 158 749 184 758 303 20,1 B-1 540 100 407 100 250 100 21,3 A-2 1175 142 1113 149 1084 302 17,1 B-2 872 100 747 100 359 100 15,0 A-3 1338 257 1131 290 1038 447 20,6 B-3 520 100 390 100 232 100 20,0 Frr, = tensi le stress Rp 0 ' 2 = Yielc I point belonging to an elongation of 0, 2% RpO.2 = elastic I imiit A5 = alongation of a length (I) wherein I = 5x diameter of the specimen Λ% = difference with respect to the base value + = A 1 and B-, at 400 C° for 90 min A 2 and B 2 at 500 C° for 90 min A3 and B 3 at 600 C° for 90 min It should be noted that the activator mixture according to the invention may be applied for welding as well. The activator mix¬ ture can be in the form of a powder filled band electrode in this case.

Claims: C L A I M S 1. An activator mixture for improving utilizable strength steels characterized in that it consists essentially Ca and/or Na 16 to 30 %; Si 13 to 30 %; V and/or Mo 2 to 28 %, Nb and/or Ta 2 to 25 %; Zr and/or Ce 2 to 15 %; Ti 2 to 14 %, Al and/or Ba 1 to 15 %; B and/or Be 0,1 to 3,0 %, C 1 to 5 %; Fe 5 ° to 20 % and N 1 to 10 %. 2. A process for applying the activator mixture as claimed in claim 1, characterized in that the mixture is used in the final phase of the steel production, in a quantity of 5 to 17 5 kg/t steel.

Inventors: GIFLO HENRIK, GIFLO, HENRIK
Applicants: GIFLO HENRIK, GIFLO, HENRIK
Application year: 1986
Main classification: C22C35
IPC codes: C21C7, C22C33, C22C35