Secondary Recrystallization Temperature Research Articles

The onset temperature of secondary recrystallization and the sharpness of Goss secondary recrystallization texture in the nitrided Fe–3%Si alloy

Primary recrystallized Fe–3%Si specimens were nitrided and annealed intermittently with a heating rate of 15°C/h in 100% N 2 atmosphere. The magnetic induction B 8 was measured after each annealing. The onset of secondary recrystallization was detected by the rapid rise of B 8. The maximum B 8 obtained was about 1.94 T when the onset temperature of the secondary recrystallization ( T cr) was around 1075°C. The same primary specimens were coated with MgO and annealed with the same heating rate in 5% H 2–N 2. The initial grain size and nitrogen content for the maximum B 8 were quite different in this annealing. The difference in the optimum grain size and nitrogen content for obtaining the highest B 8 in both annealing methods was explained by assuming that T cr determines the B 8 in both annealing methods.

Effects of sulfur on the primary and secondary recrystallization in 3% Si-Fe grain oriented electrical steels

In this study, where AIN particles for grain growth inhibition were formed during the heating stage of secondary recrystallization annealing by nitriding from N2-rich atmosphere, the effect of sulfur on the primary and secondary recrystallization in 3%Si-Fe was investigated. As the sulfur content decreases, the size of primary grains increases and the distribution of AlN precipitates becomes more uniform and finer, as a results, the secondary recrystallization is formed at higher temperature. Because of the increase in the secondary recrystallization temperature, the specimen with less sulfur shows better magnetic properties.

窒化したFe-3%Si合金のGoss集合組織形成に及ぼす二次再結晶温度の影響

Primary recrystallized Fe-3%Si specimens were nitrided and annealed with the heating rate of 15°C/h in 100% N2 atmosphere. With an increase in the heating temperature by 10°C, the heating was interrupted and the specimen was rapidly cooled and the magnetic induction B8 was measured and rapidly heated again to the heating temperature. Onset of secondary recrystallization was detected by the rapid rise of B8. B8 after secondary recrystallization was closely related with the onset temperature of secondary recrystallization (Tcr). The maximum B8 obtained was about 1.94 T when the Tcr was around 1075°C and the B8 decreased with increasing in the Tcr. The Tcr was closely related with the primary grain size and it was about 1075°C when the grain size was about 15 μm. The Tcr increased with increasing primary grain size and it was about 1100°C when the primary grain size was about 22 μm.The same primary specimens were coated with MgO and annealed with the same heating rate in 5%H2-N2. The maximum B8 obtained was almost the same as the above annealing condition; however, the primary grain size for obtaining the maximum B8 was different in this annealing. The difference in the optimum grain size for obtaining the maximum B8 in both annealing methods was explained on the assumption that the maximum B8 is obtained when the Tcr is about 1075°C in both annealing methods.

Recrystallization and Related Phenomena. Mechanism of Orientation Selectivity of Secondary Recrystallization in Fe-3%Si Alloy.

Selective growth behavior of {110} <001> grains has been studied utilizing the temperature gradient annealing method. As grains grow, the average deviation angle from the ideal {110} <001> orientation becomes smaller and orientation distribution changes corresponding to that of coincidence grains in the matrix. Secondary recrystallization temperature depends on the orientation of secondary recrystallized grain and sharper {110} <001> grains grow preferentially at lower temperatures. These phenomena are explained by modified Hillert's model of grain growth, which takes the grain boundary characteristics into account. Sharper {110} <001> grains, which have higher frequency of coincidence grains in the primary recrystallized matrix, suffer lower pinning force from the precipitates and thus grow preferentially at lower temperatures.

High temperature magnetization of 3.5% Si steel

Thermomagnetic curves of rapidly solidified ribbons of Fe-3.5 wt% Si prepared using the single wheel and double roller techniques are discussed in comparison with those of commercial grain oriented transformer sheet samples. It is concluded that the arrangement of defect clusters or silicon or impurity atoms, fixed at the temperature of secondary recrystallization, influence the distribution of magnetic moments at high temperature.

Influence of Secondary Recrystallization Temperature on Secondary Recrystallization Texture in Fe-3%Si Alloy

Influence of Secondary Recrystallization Temperature on Secondary Recrystallization Texture in Fe-3%Si Alloy

The role of special grain boundaries during the grain growth in Fe-3%Si

An experimental study of the role of coincidence site lattice (CSL) boundaries in the process of grain growth in grain oriented Fe-3%Si has provided important information about the development of texture. Specimens obtained after decarburization were annealed at temperatures both lower and higher than the temperature of secondary recrystallization. The textures of these specimens were analyzed and the frequency of CSL boundaries from all grains was calculated. In addition, the frequency of CSL boundaries with respect to the 110 〈001〉 grains was calculated for the investigated specimens. By comparing the distribution of CSL boundaries obtained for Goss grains and the distribution of CSL boundaries from all grains, it was possible to predict which CSL boundaries affect the Goss grain growth during secondary recrystallization. Our analysis indicates that Goss grains having a high amount of Σ5 CSL boundaries before the secondary recrystallization have a lower number of these boundaries during grain growth. Analysis of other types of grain boundaries indicate that development of the 110 〈001〉 texture in silicon steel is not influenced by the total number of CSL boundaries, but rather by the frequency of specific CSL boundaries such as the Σ5 CSL boundaries. In the investigated specimens, the Goss grains have a size advantage over other grains, which can be considered another important factor in the preferred growth of Goss grains.

Relationship between Recrystallization Kinetics and Rate of Creep Cavitation in Bubble Strengthened Tungsten

The kinetics of secondary recrystallization and high temperature creep fracture behaviour of bubble-strengthened (KSiAl-doped) tungsten wires have been investigated using emission electron microscopy and scanning electron microscopy. Two different doped wires were chosen that exhibited different creep properties, and their recrystallization and fracture behaviour were compared. In addition, creep and fracture behaviour of an undoped wire was also investigated. Under the applied creep conditions (T = 2900 K ; = 5 MPa), fracture of the samples was caused by grain boundary cavitation, due to the coarsening and growth of the bubbles in doped wires, and due to the growth of deformation-induced microcracks in the undoped material. The results suggested that, in the case of bubble-strengthened tungsten, the high temperature fracture behaviour of the wire can be predicted from its recrystallization kinetics.

Coincidence grain boundary and role of primary recrystallized grain growth on secondary recrystallization texture evolution in Fe3%Si alloy

Secondary recrystallization behavior in the presence of AlN in Fe3%Si alloy was investigated with special reference to the influence of primary recrystallized grain growth on secondary recrystallization texture. The more dominant grain growth was marked by the evolution of {110}<001> secondary recrystallized grains in the higher temperature range. In the case of smaller primary recrystallized grains, the {110}<227> secondary recrystallized grains were mainly evolved on annealing at the lower temperature range. The frequency of Σ9 coincidence boundaries in relation to the {110}<001> texture component was higher than that of Σ5 coincidence boundaries in relation to {110}<227> component. The mechanism of these evolutions of secondary recrystallization texture can be explained by the assumption that the Σ5 coincidence boundaries are more mobile than the Σ9 coincidence boundaries in the lower temperature range. The primary recrystallized grain growth is considered to have a role in determining what should be the secondary recrystallization temperature.

The effect of wire history on the coarsened substructure and secondary recrystallization of doped tungsten

This article reports a study of primary and secondary recrystallization in tungsten wire. Samples with two different processing histories were annealed in the electron emission microscope, and the recrystallization process was followed. The fibers produced by drawing were first observed to widen and break up into shorter lengths. As the temperature was raised, the secondary recrystallization occurred in a characteristic, stepwise motion, with the secondary grain moving from one position to the next and then remaining pinned at the new position, sometimes for the entire length of the test. It was found that the temperature at which secondary recrystallization occurred depended on the heating rate. If a slow heating rate was used, the temperature at which secondary recrystallization occurred would be higher. This result was interpreted to mean that the slower heating rate allowed more strain to be annealed out of the wire before secondary recrystallization occurred and thus lowered the driving force for this process. The secondary recrystallization temperature could not be correlated with the primary grain structure or differences in the potassium bubble distribution in the wire. The primary recrystallized grain structures of the two wires were also different, and this difference, too, was attributed to differences in the amount of stored energy in the wire at the start of the annealing. It was also shown that even though the bulk potassium content of the two wires was the same and the bubble distributions in the two wires were similar, the bubble distributions in the ingots were different.

Microstructure Development in Ti Bearing Interstitial Free Steel with Simulated Hot Rolling Practice.

The critical hot rolling condition which prevents abnormally large grains from forming in the microstructure was investigated in Interstitial Free (IF) steel, using thermomechanical simulation equipment. Abnormal grain structure was produced at finishing temperatures (FT) below 900°C, accompanied by coiling temperature (CT) above 700°C. The said critical FT and CT represent the dynamic transformation temperature (DTT) and the secondary recrystallization temperature (SRT), respectively. The unusually large size grain of >150 μm in diameter is attributed to the high driving force due to the extremely fine grains around itself. These grains are produced through the transformation from unrecrystallized austenite. The austenite recrystallization rate was drastically reduced through the drag effect of dissolved Ti atoms. Unlike typical low carbon steel, a strong retardation of ferrite grain growth due to TiC precipitates resulted in the elimination of the abnormal grain below SRT coiling. Precipitation hardening due to TiC as well as hot deformation hardening was recognized in IF steel. Excessively high hardness might be encountered, if the FT is <DTT and the CT is <SRT.

一回冷間圧延法一方向性電磁鋼板の二次再結晶に及ぼすSi含有量の影響

A study has been made on the effect of the Si concentration on the secondary recrystallization of the grain oriented electrical steel produced by the single stage cold rolling process by use of MnS and AlN as inhibitors.(1) In case of the Si increase from 3.0 to 3.3 mass%, the secondary recrystallization temperature is shifted to higher under constant heating rate. In case of the Si increase to 3.7 mass%, no secondary recrystallization occurs.(2) The phenomena mensioned above are supposed to owe to the less intensity of (110) oriented primary grains and the larger primary grain size and the less effective inhibitors in case of the increased Si concentration.

Effects of the amount of γ′ and oxide content on the secondary recrystallization temperature of nickel-base superalloys

The effects of the amount of γ′ and yttria (Y2O3) content on the secondary recrystallization (SRx) temperature of as-extruded material of the mechanically alloyed nickel-base superalloys based on a superalloy TMO-2 were investigated. It was observed that (1) the primarily recrystallized grain size of the as-extruded material decreased with increasing the γ′ and the yttria content in the material; (2) the SRx temperature decreased with decreasing the yttria content and with increasing the amount of theγ′ up to about 55 vol pct, while (3) the temperature increased for the material containing more than 65 vol pctγ′; and (4) the SRx temperatures of the material containing 75 vol pctγ′ phase with 1.1 wt pct yttria and 55 vol pctγ′ phase with no yttria were identical to theirγ′ solvus. From these results, the following conclusions are drawn: (1) dissolution of theγ′ particles is a necessary, but not a sufficient, condition for the occurrence of secondary recrystallization; (2) secondary recrystallization of a material with sufficiently smaller grain size occurs at a temperature higher than theγ′ solvus and the temperature at which the yttria particles lose their ability to prevent rapid growth of the primarily recrystallized grains; and (3) the SRx temperature of a material with larger grain size depends on grain size.

熱延タングステン板の二次再結晶粒成長に及ぼすドープ剤の影響

In order to understand in detail the secondary recrystallization behaviour of rolled tungsten sheet doped with CaO and/or MgO, the effect of dopants on the secondary grain growth behavior was investigated using EPMA and chemical analyses.It was found that the doping elements (CaO and/or MgO) play an important role in the grain growth of the hot-rolled tungsten, initially restraining growth in the fine-grained primary recrystallized matrix and subsequently promoting the abnormal grain growth of the secondary grain at higher temperatures. Consequently a large-scale single crystal sheet can easily be obtained from a hot-rolled tungsten sheet doped with CaO and/or MgO. Moreover, the temperature at which secondary recrystallization commences on the hotrolled sheet is strongly dependent on the kinds of dopant and is correspondent to their dissociation temperatures. Chemical and EPMA analyses indicate that the particles consisting of CaO and/or MgO are observed much more frequently at the primary grain boundaries than the matrices and survive at high temperatures just below the secondary recrystallization temperature. Those results may be closely related to the dissociation and dissolution mechanisms of the dopants on the secondary grain growth in the hot-rolled tungsten sheet.

Influence of preheating and additional inhibition on the selectivity of secondary recrystallization in 3% Si-Fe

The effect of preheating at temperatures under and over the subsequent secondary recrystallization temperature and the influence of additional inhibition by silicon nitride particles after nitriding 3% Si-Fe decarburized sheets on the selectivity of secondary recrystallization have been investigated. Preheating at a temperature higher than that of the subsequent secondary recrystallization leads to a decrease in the selectivity of secondary recrystallization, whereas preheating at a lower temperature results in an increase in the selectivity, but the highest selectivity has been obtained with secondary recrystallization completed at the lowest temperature. Additional inhibition causes an increase in the selectivity of secondary recrystallization only with insufficiently inhibited materials.

Roles of tin and copper in the 0.23-mm-thick high permeability grain-oriented silicon steel

A study was made in order to make clear the roles of small amounts of tin and copper in the manufacturing process of 0.23-mm-thick steel with excellent magnetic properties. The precipitates in the steel containing 0.1 wt. % tin are smaller in size than those without tin, and provide a stronger inhibiting effect in secondary recrystallization. Such phenomena lead to lowering the secondary recrystallization temperature and improve the secondary grain size distribution. The addition of a small amount of copper improves the quality of a surface glass film.

Preparation of a large-scale molybdenum single-crystal sheet by means of secondary recrystallization

Secondary recrystallization was used to produce a large-scale molybdenum single-crystal sheet. It was found that the presence of dispersed second phases such as calcium and magnesium oxides plays an important role in the grain growth of the rolled molybdenum, initially restraining normal grain growth and hence substantially promoting abnormal grain growth at higher temperatures. The secondary recrystallization temperature was dependent on the amount of the second phase present. Consequently a large-scale single-crystal sheet (2 mm × 40 mm × 180 mm) can easily be produced from a hot-rolled molybdenum sheet doped with CaO and MgO.

Influence of surface condition on the magnetic properties of Fe-3% Si alloy

1. With the use of hydrated magnesium oxide to obtain the magnesium silicate coating on Fe-3% Si alloy the negative influence of the coating on the magnetic properties of this alloy related to the introduction of oxides into the surface of the metal exceeds the positive influence caused by the occurrence of tensile stresses. 2. The magnetic properties of Fe-3% Si alloy given a high temperature anneal without coatings are higher than of the alloy annealed with a coating formed from hydrated magnesium oxide. 3. A decrease in the negative influence of the primer coat may be obtained by selection of an original material for the coating which provides preferential formation of primer coats at temperatures exceeding the temperature of secondary recrystallization of the metal. A decrease in the moisture content in the original material, magnesium oxide, causes an increase in the temperature of formation of the primer coat of magnesium silicate coatings.

Austenite recrystallization diagram for steel R12F4K5

1. A recrystallization diagram was plotted for steel R12F4K5. 2. The secondary recrystallization temperature of high-speed steels with an elevated (over 2–3%) vanadium concentration is 30–50° below the quenching temperature. 3. A method of HTMT was proposed and tested for steel R12F4K5 which ensures an increase of the strength by 20–25% along with high hardness and red hardness.

金属の再結晶におよぼす高温圧縮応力および冷間加工度の影響

The effects of not only degree of cold work but also strain at heating on recrystallization of metals were investigated. First, by comparing the behaviours of secondary recrystallization of Armco iron specimens which were heated freely with those heated under the compressive stress, it was recognized that the secondary recrystallization temperature of Armco iron was reduced by the compressive stress at elevated temperatures. By the hot stage microscopy of the vacuum melted copper specimens compressed to various degrees at room temperature, it was also recognized that the secondary recrystallization temperature was reduced by cold work.Next, the effects of degree of coldw ork on the recrystallization at weld heat-affected zone received the thermal cycle which had characteristics of rapid heating and cooling, were studied after welding actually some kinds of metal specimens cold worked to various degrees.The results obtained were as follows:1) The larger the degree of cold work in aluminum specimens was, the smaller was the size of recrystallized grain at heat-affected zone, except 5% degree of cold work.2) The size of recrystallized grain at coarse grain part of heat-affected zone in stainless steel specimens cold worked to any degree, was always larger than that of 0% degree of cold work. However, the size of recrystallized grain at fine grain part in specimens cold worked to any degree, was always smaller than that of 0% degree of cold work, except 5% degree of cold work.3) On the contrary, the difference of size of recrystallized grain in the various degrees of cold work in mild steel specimens which underwent α-γ transformation, was not recognized.4) The larger the degree of cold work in aluminum and stainless steel specimens was, the larger the width of recrystallized zone at heat-affected zone became.5) However, any change of the width of recrystallized zone at heat-affected zone in mild steel specimens cold worked more than 15% was hardly recognized.