Showing papers on "Bainite published in 1987"
TL;DR: In this paper, an excellent combination of elongation over 30% and high strength about 100kgf/mm2 is achieved in processing of a 0.4C-1.8Mn steel by intercritical annealing, rapid cooling into bainite transformation temperature to soak several minutes.
Abstract: An excellent combination of elongation over 30% and high strength about 100kgf/mm2 is achieved in processing of a 0.4C-1.5Si-0.8Mn steel by intercritical annealing, rapid cooling into bainite transformation temperature to soak several minutes. This combination is caused by transformation induced plasticity of retained austenite. Sufficient amount of stable austenite is a requisite for the good ductility. For the rapid cooling after annealing, the soaking temperature for the best combination of strength and ductility is immediately above Ac1. On the other hand, a delay before rapid cooling provides good properties if the soaking temperature is near Ac3 and the subsequent cooling is performed at a lower rate before pearlite transformation; in this case the critical cooling rate is reduced. These phenomena are discussed in terms of the growth of ferrite and the diffusion of alloying elements inclusive of Mn during slow cooling.
349 citations
TL;DR: In this article, a modified heat treatment has been suggested whereby lower temperature plane-strain fracture toughness (KIC) of 4340 ultrahigh strength steel is dramatically improved in developed strength and Charpy impact energy levels.
Abstract: A modified heat treatment has been suggested whereby lower temperature plane-strain fracture toughness (KIC) of 4340 ultrahigh strength steel is dramatically improved in developed strength and Charpy impact energy levels. The modified heat-treated 4340 steel (MHT-4340 steel) consists of a mixed structure of martensite and about 25 vol pct lower bainite which appears in acicular form and partitions prior austenite grains. This is produced through isothermal transformation at 593 K for a short time followed by an oil quench (after austenitizing at 1133 K and subsequent interrupted quenching in a lead bath at 823 K). The mechanical properties obtained at room temperature (293 K) and 193 K have been compared with those achieved using various heat treatments. Significant conclusions are as follows: the MHT-4340 steel compared to the 1133 K directly oil-quenched 4340 steel increased theKIC values by 15 to 20 MPa • m1/2 at increased strength and Charpy impact energy levels regardless of the test temperature examined. At 193 K,KIC values of the MHT-4340 steel were not less than those of the 1473 K directly oil-quenched 4340 steel, in whichKIC values are significantly enhanced at markedly increased strength, ductility, and Charpy impact energy levels. The MHT-4340 steels compared to austempered 4340 steels at 593 K, which have excellent Charpy impact properties, showed superiorKIC values at significant increased strength levels irrespective of test temperatures. The lower temperature improvement inKIC can be attributed to not only the crack-arrest effect by acicular lower bainite but also to the stress-relief effect by the lower bainite just ahead of the current crack.
51 citations
TL;DR: In this article, the authors conducted fatigue tests under plastic strain control with dual-phase steels having martensite contents of 19 and 50 vol.% and found that specimens with 19 vol.%.
38 citations
36 citations
TL;DR: In this paper, the effect of thermo-mechanical treatment on the mechanical properties of Cu bearing age hardenable steels was examined, and it was revealed that the improvement of mechanical properties was partly attributed to the retardation of recrystallization in hot working due to Cu addition over 1% and the suppression of e-Cu precipitation during cooling due to rapid cooling.
Abstract: The effect of thermo-mechanical treatment on the mechanical properties of Cu bearing age hardenable steels was examined. Accelerated cooling and direct quenching after controlled rolling enhanced to produce the microstructure dominant of low carbon bainite which caused the improvement of strength and toughness. Addition of Cu over 1% was effective in both e-Cu precipitation strengthening and microstructural control through its effect on hardenability. Studies were focussed on the specific effects of Cu in thermo-mechanical process. It was revealed that the improvement of mechanical properties was partly attributed to the retardation of recrystallization in hot working due to Cu addition over 1% and the suppression of e-Cu precipitation during cooling due to rapid cooling.
32 citations
TL;DR: In this article, a review of existing HVEM studies of Widmanstatten ferrite/austenite interface migration is presented, particularly as they relate to the question of the Widmanstein ferrite growth.
25 citations
TL;DR: In this paper, the microstructure of 3CR12 steel has been studied as a function of heat treatment and the kinetics of both the decomposition of austenite and the reaustenization reactions have been investigated using a series of isothermal anneals.
Abstract: To optimize the properties of the new corrosion resisting steel 3CR12 the microstructure has been studied as a function heat treatment. The kinetics of both the decomposition of austenite and the reaustenization reactions have been investigated using a series of isothermal anneals. The steel has a dual phase ferrite–austenite structure between 800 and 1350°C and the amount of austenite is maximum at about 1050°C. At this temperature a higher nickel version of the alloy is fully austenite. On cooling to ambient temperature, the austenite transforms to a lath-type martensite. Heat treatments at temperatures up to 800°C cause the slow tempering of the martensite, the recovery and recrystallization of original ferrite regions, and the nucleation and growth of newly formed ferrite. The growth of ferrite requires the concomitant precipitation of carbides and nitride particles from the austenite or martensite and these particles mark the stepwise movement of the interface. In contrast the reaustenization...
25 citations
TL;DR: The continuous cooling transformation diagram for low-carbon low-alloy steel containing 0.05% C, 1.99% Mn, 0.31% Mo and 0.06% Nb was constructed by dilatometry and metallography.
Abstract: The continuous cooling transformation diagram for low-carbon low-alloy steel containing 0.05% C, 1.99% Mn, 0.31% Mo and 0.06% Nb was constructed by dilatometry and metallography. The intermediate transformation between martensite and polygonal ferrite involves two typical stages: the formation of ferrite matrix and the formation of microphases. Four intermediate transformation products obtained from various cooling rates and designated B1, B2, A1 and A2, were studied. The B1 and B2 structures are composed of pockets of parallel ferrite laths and interlath microphases, which are films of retained austenite in B, and are fragments of retained austenite or martensite or martensite-retained austenite (M-A) constituents in B2. The B1 structure is further characterized by the appearance of martensite particles inside the ferrite laths. The A1 structure is comprised of the randomly arranged ferrite groups. Each group contains several short ferrite laths in the same crystallographic orientation and granular M-A constituents or martensite located at the rim of ferrite laths or groups. The A2 structure is morphologically analogous to Widmanstatten ferrite. The formation mechanisms of these products are also discussed.
25 citations
TL;DR: In this article, the erosion behavior of AISI 4140 steel under various heat treatment conditions was investigated, and a variety of microstructures, such as the primary and tempered martensites, varying proportions of martensite and bainite, cementite spheroids embedded in a ferrite matrix and ferrite and pearlite were obtained.
24 citations
TL;DR: In this paper, the critical cooling rates for the transformation to martensite of 90 and 50% of the Austenite present were determined as functions of the carbon content of the austenite.
Abstract: Microstructure maps were constructed for a C–Mn steel and microalloyed steels of the same base composition, after intercritical annealing to produce 23 and 50% of austenite. The critical cooling rates for the transformation to martensite of 90 and 50% of the austenite present were thus determined as functions of the carbon content of the austenite. At the 90% martensite level, the hardenability of the austenite was very similar to that of fully austenitized steel of the same composition, and varied identically with carbon content. At the 50% martensite level, the hardenability of the austenite was considerably greater than that of fully austenitized steel of the same composition. The presence of niobium and vanadium had no effect on the martensitic hardenability of the austenites: by forming carbides they simply altered the carbon content of the austenite at a fixed volume fraction of austenite. It is proposed that the martensitic hardenability of austenite of dual-phase steel depends on the size ...
23 citations
TL;DR: In this paper, a mathematical model of hot deformation resistance in austenite ferrite two phase region has been developed and successfully applied to roll force prediction in a production plate mill.
Abstract: Flow stress of a Si-Mn steel in ferrite plus metastable austenite region and austenite plus ferrite two phase region has been examined by single-stage and multi-stage tension tests. Flow stress of “ferrite” (92% ferrite plus 8 metastable austenite) has been found to be expressed by an equation similar to that applicable to austenite. Strain hardening exponent is smaller in “ferrite” than in austenite region, while strain rate exponent is larger in “ferrite” region. The hot deformation resistance in austenite ferrite two phase region can be approximated by the law of mixture for the hot deformation resistance of austenite and “ferrite”. By adding a term expressing release of strain concurrent with phase transformation to the conventional formula describing static restoration process in austenite, the kinetic of static restoration in austenite-ferrite two phase region can be formulated as a simple mathematical equation. On the basis of experimental results a mathematical model of hot deformation resistance in austenite ferrite two phase region has been developed and successfully applied to roll force prediction in a production plate mill.
TL;DR: In this article, microstructures of hot work tool steels, AISI H13, H10, HIO, and H19 tempered after quenching at various cooling rates are studied for improvements of the toughness of these steels.
Abstract: Microstructures of hot work tool steels, AISI H13, HIO, and H19 tempered after quenching at various cooling rates are studied for improvements of the toughness of these steels. It is found that the development of upper bainite with decreasing rate of quenching is accompanied by the following microstructural changes.1) Increase in the width and length of bainite grains and the effective grain size2) Preferential precipitation of carbides along prior austenitegrain boundaries3) Dispersion of fine carbides in matrixThese microstructural changes lead to reduction of the toughness in all the steels; deterioration occurs in H10 and H19 at a higher cooling rate than in H13. The toughness value reduces in the order of H13, H10, and H19, in good correlation with increasing order of the density of frne carbides in matrix and the fraction of retained carbides.
TL;DR: In this article, microstructural features have been examined for 3.5NiCrMoV steam turbine rotor steel, in the as-quenched state and tempered at 500 °C.
Abstract: The microstructural features have been examined for 3.5NiCrMoV steam turbine rotor steel, in the as‐quenched state and tempered at 500 °C. Quenching produces lath martensite, with bands of retained austenite at the lath boundaries and, to a lesser extent, at prior austenite grain‐boundaries. Autotempering occurs during the quench, resulting in loss of tetragonality of the martensite and extensive carbide precipitation in the matrix and to a lesser degree at prior austenite grain boundaries, but not at lath boundaries. Tempering at 500 °C leaves the lath structure largely intact, but causes retained austenite to transform to bands of ferrite and cementite. This transformation does not correlate with the reduction in stress corrosion crack velocity which occurs on tempering. The strength of 3.5NiCrMoV steel in the as‐quenched and 500 °C tempered conditions is most probably due to the combination of carbide precipitation strengthening and substructure strengthening. Copyright
TL;DR: A review of relevant welding literature as well as ongoing research at the University of Illinois at Chicago indicate the important influences of manganese and oxygen on the weld metal microstructure of low carbon steel welds as discussed by the authors.
Abstract: A review of relevant welding literature as well as ongoing research at the University of Illinois at Chicago indicate the important influences of manganese and oxygen on the weld metal microstructure of low carbon steel welds. These microstructures are composed of several distinct ferrite morphologies, bainite, and other microconstituents. Both manganese and oxygen affect the transformation behavior of the weld metal as it cools from the austenitic range. A high oxygen content, in the form of oxide inclusions, shifts the transformation curve to the left by increasing the number of effective nucleation sites for high temperature transformation products (proeutectoid and side-plate ferrite). Manganese, on the other hand, shifts the transformation curve to the right, thereby increasing the weld metal hardenability and promoting the formation of lower temperature transformation products (acicular ferrite, bainite). Welds with a high proportion of acicular ferrite possess superior fracture toughness because the short, interlocking needles resist crack propagation.
TL;DR: In the hydrogenated state, failure was almost entirely intergranular along prior austenite grain boundaries and cracking of martensitic laths as discussed by the authors, and the fracture surface of the ferrite-pearlite and ferrite bainite specimens consisted of small cleavage regions surrounding nonmetallic (oxide) inclusions.
Abstract: Hydrogen embrittlement (HE) tests were carried out on a carbon-manganese pipeline steel having a low sulphur content (<0.01%). It was shown that the susceptibility to HE increased as the microstructures changed from ferrite-pearlite to martensite. In the hydrogenated state the fracture surface of the ferrite-pearlite and ferrite-bainite specimens consisted of small cleavage regions surrounding non-metallic (oxide) inclusions; these were called rosettes and were a characteristic feature of the embrittled state. In hydrogenated martensitic specimens, failure was almost entirely intergranular along prior austenite grain boundaries and cracking of martensitic laths. In the martensitic specimens a relationship between inverse time to failure and prior austenite grain size was established.
Patent•
19 May 1987
TL;DR: In this article, a steel slab consisting of 0.01W0.20% C, ≤ 0.6% Si, 0.5W2.2%, 0.001W 0.1% Al, ≤0.006% N, and the balance Fe with inevitable impurities is heated to 900W1,200°C.
Abstract: PURPOSE: To manufacture a steel combining low yielding ratio with high tensile strength, by hot-rolling a steel having a specific composition containing Mn and Al under specific conditions, by air-cooling the hot-rolled plate until a temp. where proper amounts of ferrite are precipitated is reached, and by successively applying quench-and-temper treatment to the above. CONSTITUTION: A steel slab consisting of, by weight, 0.01W0.20% C, ≤0.6% Si, 0.5W2.2% Mn, 0.001W0.1% Al, ≤0.006% N, and the balance Fe with inevitable impurities is heated to 900W1,200°C. Subsequently, rolling is applied so that cumulative draft at ≤900°C and finishing temp. are regulated to ≥30% and Ar 3 +80°CWAr 3 -20°C, respectively, and austenite grains are refined. Successively, air cooling is applied until a temp. of Ar 3 -20°CWAr 3 -100°C is reached, followed by cooling down to ≤300°C at ≥2°C/sec cooling rate. Then, tempering treatment is applied at a temp. of the Ac 1 point or above to form the structure into ferrite=bainite=martensite. Moreover, Ni, Mo, Cu, Cr, V, Nb, Ti, B, Ca, and REM are incorporated by specific amounts or below to the above steel composition, if necessary. COPYRIGHT: (C)1988,JPO&Japio
TL;DR: In this article, the mechanical deformation of granular bainite in a normalized high strength, low alloy steel (18CD4 steel) was evaluated by comparing with the dual-phase microstructures containing, 100, 65 and 45 vol.% martensite particles.
TL;DR: In this article, the structure-property relationships of two HY-100 steel weldments prepared by submerged arc (SAW) and gas metal arc (GMAW) welding processes using identical heat input (2.2 kJ mm-1) have been studied.
Abstract: Structure-property relationships of two HY-100 steel weldments prepared by submerged arc (SAW) and gas metal arc (GMAW) welding processes using identical heat input (2.2 kJ mm-1) have been studied. It has been found that submerged arc welded (SAW) HY-100 steel weldments have a lower weld toughness than welds produced by the gas metal arc welding (GMAW) process. Optical, scanning, and transmission electron microscopy were used in conjunction with microhardness traverses to characterize and compare the various microconstituents that are present in the last weld pass of both weldments. TEM examination revealed the presence of coarse upper bainite, B-II bainite, and carbides in a highly dislocated ferrite matrix as well as in ferrite laths in the SAW weldment, while the GMAW weldment exhibited a typical fine low carbon lath martensite, autotempered martensite, and mixed B-II and B-III bainites which occasionally contained small regions of twinned martensite. The measured cooling rate in the SAW was found to be about 40 pct slower than that in GMAW. It was also found in the SAW that the weld metal inclusion number density was about 25 pct greater than that in GMAW. Micro-hardness traverses exhibited significantly lower hardness (about 50 HV) in the SAW weldment compared with GMAW, but the tempered weld metal microhardness in both the weldments was measured about the same, at 250 HV. The ductile-to-brittle transition temperature (DBTT) of both weldments was determined by Charpy impact test. Based on an average energy criterion, the DBTT of the SAW weldment was 323 K (50 °C) higher than that of the GMAW weldment. This difference in fracture resistance is due to the different weld metal microstructures. The different microstructures most probably result from differences in cooling rate subsequent to welding; however, the SAW weld also has a higher inclusion number density which could promote a higher transformation temperature for the austenite.
Patent•
21 Sep 1987
TL;DR: In this paper, a high-tensile cold-rolled steel sheet has been produced by hot rolling a billet having a specific compsn. to form a hot rolled sheet having the structure mainly composed of bainite, then subjecting the steel sheet to continuous annealing under specific conditions to form the ferrite/martensite structure contg. a prescribed ratio of residual austenite.
Abstract: PURPOSE:To produce a high-tensile cold rolled steel sheet having an excellent fatigue characteristic and bulging property by hot rolling a billet having a specific compsn. to form a hot rolled sheet having the structure mainly composed of bainite, then subjecting the steel sheet to continuous annealing under specific conditions to form the ferrite/martensite structure contg. a prescribed ratio of residual austenite. CONSTITUTION:The billet contg., by weight, 0.10-0.25% C, 0.20-2.0% Si, 1.0-2.5% Mn, =40% draft to the final sheet thickness and is then annealed continuously. The steel sheet is subjected to recrystallization heating in the austenite/ferrite region where the content of the austenite decreases to =10 deg.C/sec average cooling rate, and held at 250-450 deg.C. The high-tensile cold rolled steel sheet having the composite structure contg. >=30% ferrite, >=40% residual austenite and the balance martensite is thus produced.
Patent•
21 Jul 1987
TL;DR: In this paper, the authors proposed a hot rolling of a steel which has a composition containing, as principal components, 0.01-0.07%, by weight, C, Si, Mn, and 0.5-2.0% Mn, further containing one or more kinds among <=0.060% Nb, <= 0.10% V, and >=0.050% Ti, and having the balance Fe with inevitable impurities is completed at Ar3 or above point.
Abstract: PURPOSE:To manufacture a steel for electric resistance welded tube combining toughness at low temp. with high strength without adding alloying elements, by subjecting a steel in which respective contents of C, Si, Mn, etc., are specified to hot rolling at a specific temp. and also controlling cooling velocity and winding temp. CONSTITUTION:The hot rolling of a steel which has a composition containing, as principal components, 0.01-0.07%, by weight, C, <=0.5% Si, and 0.5-2.0% Mn, further containing one or more kinds among <=0.060% Nb, <=0.10% V, and <=0.050% Ti, and having the balance Fe with inevitable impurities is completed at Ar3 or above point. Subsequently, cooling is applied to the hot-rolled plate from a temp. of the Ar3 point or above at <=20 deg.C/sec cooling rate to form fine bainite and island martensite, followed by winding at <=250 deg.C. By using this steel, the high-strength seam welded tube excellent in toughness at low temp. can be manufactured while obviating the necessity of heat treatment over the whole tube.
TL;DR: In this article, a 1Cr-Mo-V turbine rotor steel forging, heat treated to obtain a bainite-20% ferrite microstructure, has been investigated for low cycle fatigue behavior at room temperature and 535°C.
TL;DR: In this paper, the formation of isothermal martensite from retained austenite in an AISI 52100 ball bearing steel was investigated, and X-ray diffraction showed that during the isothermal transformation, the ratio of lattice constantsc/a decreases.
Abstract: The formation of isothermal martensite from the retained austenite in an AISI 52100 ball bearing steel was investigated. Optical microscopy reveals that there are mainly two types of isothermal martensite formation: the growth of the athermal martensite and the nucleation and growth of new martensite in the retained austenite. X-ray diffraction shows that during the isothermal transformation, the ratio of lattice constantsc/a decreases, and TEM verifies the precipitation of Fe, Cr)3C in martensite. The kinetics of the isothermal transformation in the quenched steel also shows “C” shape characteristic. At the first stage of the isothermal formation, recovery of the athermal martensite occurs with an activation energy of 91.8 kJ mol-1, implying that the diffusion of carbon in athermal martensite results in the precipitation of carbide and the relaxation of the strain energy at the martensite/matrix boundary. In the second stage, the activation energy for the isothermal formation is 130 kJ mol-1; that may be the energy required for the rearrangement of the configuration of dislocations, forming preferred sites for nucleation.
Patent•
09 Jul 1987
TL;DR: In this paper, the head of a rail is cooled to a temperature not lower than the A 3 transformation point at a rate lower than critical quenching rate so that the head acquires a fine perlitic structure.
Abstract: Starting from a temperature at or above the A 3 transformation point of the steel of the rail, the head of the rail is cooled to a temperature not lower than the Ms point at a rate lower than the critical quenching rate so that the head acquires a fine perlitic structure. Simultaneously the web is superficially cooled to the Ms point or below, at a rate greater than the head, so as to obtain a surface layer of martensite and/or bainite, and the surface cooling is controlled so that, at the end of controlled cooling, internal portions of the web not transformed to martensite and/or bainite retain sufficient heat to temper the surface layer during subsequent cooling to ambient temperature. At the same time the flange of the rail is cooled at a rate ensuring straightness of the rail.
TL;DR: In addition to the 18R1-type martensite, 12R, 6R, and 2H martensites were found in quenched Cu-Zn-Al alloys using this technique.
Abstract: Electron diffraction technique for identifying structure types of martensite in beta-Hume-Rothery alloys is described. It includes determination of the stacking sequence of the martensite of the basal planes, differentiation of the long-range ordering in martensite inherited from its parent phase (A2 type disordered; B2 type ordered; and D03, or Heusler, type ordered), and distinguishing between normal-type and modified-type martensite. In addition to the 18R1-type martensite, 12R, 6R, and 2H martensites were found in quenched Cu-Zn-Al alloys using this technique.
Patent•
21 Jul 1987
TL;DR: In this article, a low-carbon steel with a specific composition was used to construct a reinforcing steel bar having a bainite + ferrite structure and excellent in toughness at low temp.
Abstract: PURPOSE:To manufacture a reinforcing steel bar having a bainite + ferrite structure and excellent in toughness at low temp. and corrosion resistance, by finish-rolling a low-carbon steel with a specific composition while specifying working interval, cumulative draft, and temp., respectively, and also by controlling cooling. CONSTITUTION:A steel stock which has a composition consisting of, by weight, 0.02-0.10% C, =30%, and 700-650 deg.C. Subsequently, the surface of the steel stock is cooled, without delay, at 30-150 deg.C/sec cooling rate, by which the reinforcing steel bar having a bainite + ferrite structure of which a bainite structure comprises >=20% can be obtained.
Patent•
06 Feb 1987
TL;DR: In this paper, a steel slab consisting of martensite, bainite, ferrite and retained austenite is hot rolled at the Ar 2 transformation temp. under specified conditions and by successively carrying out heating, slow cooling an rapid cooling to form the specified composite structure.
Abstract: PURPOSE: To manufacture a high ductility and high strength steel sheet having superior spot weldability and a composite structure by not rolling coiling a steel slab having a specified compsn. under specified conditions and by successively carrying out heating, slow cooling an rapid cooling to form the specified composite structure. CONSTITUTION: A steel slab consisting of, by weight, 0.12W0.25% C, 1.5W3.0% Si, 1.1W2.0% Mn, <0.005% S, 0.02W0.50% sol, Al and the balance Fe with inevitable impurities is hot rolled at the Ar 2 transformation temp. or above coiled at <650°C. Continuous annealing is then carried out by heating, holding at ≥800°C in the austenite+ferrite two-phase for ≥4min and cooling followed by holding at 350W450°C for 1W5min. The cooling is carried out by slow cooling from the holding temp. to 600W800°C at ≤30°C/sec cooling rate and rapid cooling to 350W450°C at ≥30°C/sec cooling rate of form a composite structure consisting of martensite, bainite, ferrite and retained austenite. COPYRIGHT: (C)1988,JPO&Japio
TL;DR: In this article, the effect of ferrite content on the creep of a 12Cr-2Mo-0.08C, ferritemartensite, heatresisting steel was investigated.
Abstract: The effect of ferrite content on the creep of a 12Cr-2Mo-0.08C, ferritemartensite, heatresisting steel was investigated. Creep tests were performed at 550, 600, and 650 °C for up to 10,000 hours on four steels containing, respectively, 51, 38, 23, and 12 pct ferrite. The variation in ferrite content was obtained through nickel additions of 0.6, 1.3, and 2.0 pct. Rupture time, minimum creep rate, elongation, and reduction in area are reported. The effect of ferrite content was found to be small but significant. At short rupture times, increasing ferrite content reduces creep strength. At long exposure times, however, increasing ferrite content increases creep strength. This effect is explained by the precipitation of Laves phase, Fe2Mo, and possibly Cr2N, in the ferrite during testing. This precipitation progressively strengthens the ferrite relative to martensite. In addition, martensite is continually weakening because of the coarsening of M23C6, the only precipitate found in the martensite. Nickel at the 2.0 pct level radically decreased creep resistance in these steels by accelerating aging of the precipitate structure in martensite.
TL;DR: In this paper, a steel of 0.05%C, 1.99%Mn, 0.31%Mo and 0.06%Nb was studied and it was found that the microphases in a bainitic structure contain retained austenite, twinned martensite, dislocated martensites, and a mixed martinsite-retained Austenite constituent.
Patent•
23 Jun 1987
TL;DR: In this paper, a composite treatment composed of carburization and austempering treatments to cast steel product, then applying compressive stress to surface part is presented. But the composite treatment is applied to surface of cast steel goods by shot peening or roll working, etc.
Abstract: PURPOSE:To manufacture cast steel goods having superior fatigue strength and toughness, by applying composite treatment composed of carburization and austempering treatments to cast steel product, then applying compressive stress to surface part CONSTITUTION:Cast steel goods having compsn contg 02-08% C, 20-45% Si, <08% Mn, <005% P, <005% S, <10% Mo, <20% Ni, <10% Cr is subjected to composite treatment in which it is heated and carburization treated under existence of carburizing material, and austemper treated by lowering temp to 200-450 degC and holding for a fixed time By the treatment, inner part is made to bainite structure while leaving a large quantity of residual austenite structure at surface part Next, compressive stress is applied to surface of cast steel goods by shot peening or roll working, etc, to cause transformation induced by working of residual austenite structure at surface to martensite structure High strength and toughness cast steel goods comparable with forged steel is obtd
Patent•
18 Sep 1987
TL;DR: In this article, the authors present a process for manufacturing tension steels suitable for threading or similar, according to which steels having a C content of between 0.30 and 0.80 % by weight are subjected, by means of cooling after hot rolling provided by the rolling heat on the output side of the finishing stand, to a surface hardening operation in such a way that the material is immediately and completely transformed into martensite in an edge region, whereas the heat content remaining in the central region causes, during subsequent cooling, the tempering of the martensitic
Abstract: Process for manufacturing rolled steel products, for example tension steels suitable for threading or similar, according to which steels having a C content of between 0.50 and 0.80 % by weight, an Si content of between 0.20 and 0.60 % by weight, and a Mn content of between 0.30 and 0.80 % by weight are subjected, by means of cooling after hot rolling provided by the rolling heat on the output side of the finishing stand, to a surface hardening operation in such a way that the material is immediately and completely transformed into martensite in an edge region, whereas the heat content remaining in the central region causes, during subsequent cooling, the tempering of the martensitic edge region which does not go beyond the bainite region. The process is characterized in that after cooling, cold working is effected followed by tempering. The degree of elongation is preferably 0.5 to 1.5 %; tempering is preferably effected at a temperature between 350°C and 380°C and for a hold time of 5 to 60 seconds at maximum temperature. With this process it is possible to manufacture, in a simple and a profitable manner, rolled steel products, for example tension steels, which fully comply with the requirements of the building industry as regards deformability and mechanical characteristics.