FeTiP or Fe(Ti+Nb)P precipitates were observed in each sample, while much more incidence was that of the precipitates with niobium as without it. Precipitates without niobium FeTiP were observed only in 5 samples, in a ratio of 8:1,the Fe(Ti+Nb)P being the one with greater values. Oval shapes of Fe(Ti+Nb)P were observed after recrystallization annealing at the grain bounadries and also inside the grain itself. At the grain boundary in the sample with a lower coiling temperature of 565 °C was observed TiC precipitate (Fig.5). The precipitates were not distributed equally, but in both samples it was possible to observe the tendency of Fe(Ti+Nb)P precipitates to form clusters. In most cases the grain boundaries were more densely occupied by precipitates at Tcoil = 700 °C than at Tcoil = 565 °C.The question is, whether the Fe(Ti+Nb)P precipitates of size from 10 nm and bigger will affect the recrystallization processes. The impact of coiling temperatures on the recrystallization kinetics influence significantly even the changes of mechanical properties. Greater the coiling temperature, lower the values of the yield strength and the tensile strength. For example, the sample A with the coiling temperature of 500 °C during the annealing of 650 °C has a yield strength of Rp0,2 = 202 MPa and with coiling temperature of 700 °C has a yield strength of Rp0,2 = 166 MPa. With the increased annealing temperature the number of differences increased as well. On the sample A with the coiling temperature of 500 °C annealed at Trec = 850 °C was measured Rp0,2 = 611 MPa and within the same sample but with the coiling temperature of 700 °C was measured Rp0,2 = 367 MPa. When the annealing temperature increased, the values of yield strength increased as well. The increase of yield strength in sample A with Tcoil = 500 °C at annealing temperature from 650 to 850 °C was 409 MPa. The influence of the coiling temperature on the elongation is not so significant. Much more significant on the elongation was the influence of recrystallization annealing temperature. The increase of the annealing temperature from 650 to 850 °C causes a decrease in elongation from 42,8 to 12,9% that can be considered as a
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This weakened effect manifests at lower annealing temperatures of about 650 °C. As the results of the static tensil test shows in Tab.3. The values of a mechanical characteristics such as yield strength and tensile strength are on the same level with conventional IF steels at that temperature. This fact is more significant in the case of higher coiling temperature. During the increase of the annealing temperature , the strengthening is more obvious. Annealing at 850 °C with low coiling temperature at 500 °C causes an increase of yield strength up to 600 MPa. Those values along with low elongation would mean the exclusion from deep-drawing steel qualities and, on the contrary, they would be regarded as high strength steel. This assertion is supported by the values of elongation at the level of 10%. Also a change in size of grain in the range of 10 μm was observed during the process of annealing. The higher the level of temperature of annealing , the greater the size of the grain even to about 22 μm. The strengthening operates in a opposite direction from the size of a grain to the annealing temperature is probably overlapped by precipitation strengthening.The results of electron microscopic analysis confirms, that the sumárna plošná početnosť of precipitated particles in steel
This weakened effect manifests at lower annealing temperatures of about 650 °C. As the results of the static tensil test shows in Tab.3. The values of a mechanical characteristics such as yield strength and tensile strength are on the same level with conventional IF steels at that temperature. This fact is more significant in the case of higher coiling temperature. During the increase of the annealing temperature , the strengthening is more obvious. Annealing at 850 °C with low coiling temperature at 500 °C causes an increase of yield strength up to 600 MPa. Those values along with low elongation would mean the exclusion from deep-drawing steel qualities and, on the contrary, they would be regarded as high strength steel. This assertion is supported by the values of elongation at the level of 10%. Also a change in size of grain in the range of 10 μm was observed during the process of annealing. The higher the level of temperature of annealing , the greater the size of the grain even to about 22 μm. The strengthening operates in a opposite direction from the size of a grain to the annealing temperature is probably overlapped by precipitation strengthening.The results of electron microscopic analysis confirms, that the sumárna plošná početnosť of precipitated particles in steel