The paper presents experimental results concerning the inhibitor phases generation by microalloying elements utilization. It was made experiments on three silicon steel charges. It was observed that the inhibitor phases have a strong influence on steel sheet structure and its texture. So these phases can by considered like “texture nucleus”

Ana DONIGA

Elisabeta VASILESCU

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
 
 
STUDY OF THE INCLUSIONS FROM THE ORIENTED GRAINS 
SILICON STEELS AND THEIR INFLUENCE ON THE TEXTURE 
 
Ana DONIGA, Elisabeta VASILESCU 
“Dunărea de Jos“University of Galati, 
e-mail: adoniga@ugal.ro
 
ABSTRACT 
 
The paper presents experimental results concerning the inhibitor phases 
generation by microalloying elements utilization. It was made experiments on three 
silicon steel charges. It was observed that the inhibitor phases have a strong 
influence on steel sheet structure and its texture. So these phases can by considered 
like “texture nucleus”. 
 
KEYWORDS: inclusions, oriented grains, silicon steel, texture 
 
 
1. Generalities 
 
 
The extant scattered precipitates in the silicon 
steels have a decisive role, both: in grain forming, 
during secondary annealing and Goss texture 
evolution in the finished strip. The scattered 
precipitates appear in silicon steels as nitrides: NbN, 
AlN, as carbides NbC, TiC and sulphides: MnS, 
against to the added element in the steels to form 
growth “inhibitors” of the grainsize [1]. 
In the paper-framework it was watched the 
influence of the scatter-phase, formed by Niobium 
and Aluminum adding in the steel, on the evolution 
of the structure and Goss texture in silicon steels 
during secondary annealing. The experiments have 
been made on three steel grades with chemical 
composition shown in table 1. 
 
Table 1. Chemical composition of experimental steels 
 
Chemical composition  % Steel State C Si Mn S P Al Nb O2 N2
N1 0.040 3.04 0.080 0.017 0.009 0.002 0.090 0.0073 0.0067 
A2 0.040 3.02 0.070 0.023 0.013 0.070 - 0.0078 0.0065 
M3 
Casted 
0.029 3.04 0.072 0.023 0.009 0.012 - 0.0076 0.0062 
N1 0.004 3.04 0.080 0.015 0.009 0.002 0.090 - - 
A2 0.004 3.02 0.070 0.020 0.013 0.070 - - - 
M3 
Final 
plate 0.003 3.04 0.070 0.022 0.009 0.010 - - - 
 
 
Steels N1 (fig.1.a) and A2 have been 
experimental made by manufacturing of two 50 kg 
ingots, then rolled and thermal treated in the Metal 
Rolling Laboratory from Galati University and M3 
steel was industrial made by MITTAL STEEL S.A. 
 
2. Experimental Researches 
 
The test-specimen taken from those three steel-
grades (hot and cold rolled strips) have been 
submitted to a complete investigations that watched: 
- the nature of the scatter-phases and their role 
in the grain size growth process during primary 
recrystallization (after first rolling) and secondary 
recrystallization (after second rolling) 
- the role of the scatter-phase particles in 
forming and evolution of Goss type crystalographical 
texture 
For study, the optical microscopy, 
electronically micro probe, X ray diffractometry and 
electronically microscopy have been used as 
investigation methods. 
In that rolled strip, the optical microscopy 
distinguished the extant scatter-probe as rare and 
isolated small inclusions or rows of oxides, silicates 
and sulphides types. 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
A more complete analysis was made with 
electronically micro-probes specifying the nature and 
complexity of the scatter-phase particles by 
separation of the main elements in matrix and 
particles (fig. 1). In fig. 1, N1 steel appear about 1μm 
complex particle inclusions containing Mn, Al, Ca. 
Niobium appears isolated or with other elements, 
forming < 1μm diameter complex inclusions (fig 1a). 
In A2 steel are present: Al, Si, Mn (fig 1 d). Same 
type of the complex inclusions, containing Si, Al, 
Mn, appear in M3 steel. X-Ray diffractometry 
analyses distinguished crystalline structure of the 
secondary phase particles and matrix too. The fact of 
the analyses is that each phase characterized by its 
own crystalline net is corresponding to a specific 
system of diffraction lines. The test specimen have 
been taken from those three experimental steels, from 
hot rolled strips and submitted to a CoKa radiation. 
The results are centralized in table 2. 
By this analyses, the evidence of the dispersion 
phase particles, with role of growth inhibitors of the 
grain size in silicon steel strip shave been watched. 
In N1 steel, the microalloying with Niobium is 
determining the forming of the NbN and NbC 
precipitates with CFC type crystalline net. 
In A2 steel, with Aluminum, AlN Al2O3 are 
formed, both with hexagonal net, but in M3 steel is 
MnS present, with CFC type net. As literature of 
specialty shows (2) one of condition that should be 
carried out by the dispersion phase to be inhibitor is 
to create a non coherence degree between crystalline 
net of the particles and matrix. In case of the studied 
steels between ferrite matrix and dispersion phase 
particles: NbN, NbC, AlN, Mn, the complex 
relationship are established due to various crystalline 
net types and differences between values of the net 
parameters. These will determinate the net 
distortions, local elastic deformation and pressure 
exerted by the particles concentration on the grain 
borders, which will have as final effect the delaying, 
or even blocking the growth of the recrystallized 
grains [3]. Electronically microscopy analyses 
allowed for study the shape and size of the secondary 
phase particles in the finished strip. 
 
            
   a)      b) 
   
  c)      d) 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
 
   
   e)       f) 
 
Fig 1. Complex inclusions in the experimented steels. a) Nb repartition in steel N1;  
b). Mn repartition in steel N1  c). Al repartition in steel N1;  d) variation profile of Si and Al in steel 
A2;  e). variation profile of Mn and Al; f). Al repartition in steel A2 (1200 x increase). 
 
 
At temperature increase a suddenly increase of 
the grain might be produced either due to particle 
coalescence or their dissolving in matrix. For silicon 
steel, the distribution variance is wished to get a solid 
solution with a smallest quantity of inclusions, having 
in view the magnetic characteristics getting using thin 
foils method with transmission electronic microscope, 
the test specimen of N1 steel was analyzed with 
33,000 and 100,000x increase. 
After secondary recrystallization it was 
established it was established that NbN precipitates 
have left as small particle scattered in matrix of about 
400Å, round or elongated shape (fig. 2).
 
 
 
Fig. 2. Inhibitor particles in finished strip of N1 steel (33,000x increase) 
 
Selection of a certain inhibitor should be 
correlated to the temperature of the secondary 
recrystallization too, to assure an advanced 
dissolution of the second phase particles, to get a 
certain grain and stressed Goss texture [4].  
In this direction more ranges of secondary 
recrystallization have been experimented, analyzing, 
finally the percentage of the gotten Goss texture. 
Strip test specimen of 0.35 mm thickness have 
bees used, which have been thermal treated in 
Hydrogen atmosphere at 900°C, 1000°C, 1150°C 
temperature, 6 hours time. Fig. 3 shows the variation 
way of Goss texture component with secondary 
recrystallization temperature. 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
 
 
Fig. 3. Goss texture percentage to the annealing temperature for experimental steels. 
 
 
Could be remarked that from those three steel 
grades, this niobium steel answers the best to the 
requirements imposed to an inhibitor NbN is less 
soluble at lower temperatures (900-1000°C) than 
MnS, therefore, it can keep the grain at small size up 
to the high temperature. In this time, Goss texture 
nucleus could be formed, if deformation degree was 
high enough for (110)[100] texture to store high 
quantity of energy. At temperature over 1200°C, NbN 
particles are solving in higher quantity alloying grain 
growth, characteristic to the secondary 
recrystallization. At 1150°C, 6-8mm diameter grain 
size are formed in Nb steel. While in Mn steel (steel 
M3) very big grain size are forming with 15-20mm 
diameter. It is possible that, due to dissolution of a 
higher quantity of MnS particles, at lower 
temperature (850-900°C), equally, to produce the 
growth of the other texture components in Goss 
texture detriment.  
These suppositions have been confirmed by the 
texture measurements made on the experimental test-
specimen: a percent of 24.8% texture (112)[100] 
resulted at 900°C temperature and 18% (112)[100] at 
1000°C temperature. AlN particle have a stronger 
inhibition effect than NbN, dissolving in smaller 
quantity than NbN, at all temperatures.  
As a result, we have remarked that over 1000°C 
the grains of Al steel (steel A2) remain small enough 
(under 5mm) and Goss texture is weaker. 
In this case, the grain growth process is blocked 
by the presence of Al2O3 particles formed due to 
oxygen high quantity and very harmful by the 
negative influence on the magnetically characteristics 
of the finished strip. Fig 4 shows the macrostructure 
appearance after secondary annealing. 
 
 
 
 
 
   a)      b) 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
 
   c)       d) 
 
   e)       f) 
 
Fig. 4. Macrostructure of the strip after secondary annealing 
a). steel N1 – annealing at 1150°C, 6 hours, b). steel N1 - 1000°C, 6 hours, c). steel A2 - 1150°C, 6 
hours, d). steel A2 - 1000°C, 6 hours, e). steel M3 - 1150°C, 6 hours, f). steel M3 - 1000°C, 6 hours 
 
Table 2. Crystalline nets characteristics of the dispersion phase – particles and matrix in the 
experimental steels. 
 
Steel Phase 2 θ (grades) D/n hkl 
Crystalline net 
type 
Crystalline 
net 
parameter 
Fe3C 44.08 2.38 (012) Orthorhombic - 
Ferită 52.74 2.02 (11) CVC 2.98 
SiC 86.90 1.31 (201) Hexagonal - 
NbN 105.13 1.125 (400) NaCl cubic type 1.10 
NbC 107.94 1.09 (400) CFC 4.47 
1 
NbC 130.00 0.993 (420) CFC 4.47 
AlN 44.38 2.37 (101) Hexagonal 5.12 
Al2O3 50.97 2.08 (102) Hexagonal - 
Ferită 54.00 2.02 (110) CVC 2.98 
SiC 72.00 1.54 (110) Hexagonal - 
AlN 74.25 1.50 (233) Hexagonal 5.12 
AlN 98.30 1.186 (202) Hexagonal 5.12 
2 
Al2O3 101.96 1.144 (131) Hexagonal - 
Ferită 53.20 2.02 (110) CVC 2.98 
MnS 58.35 1.85 (220) CFC 5.22 
Ferită 77.44 1.42 (200) CVC 2.98 
MnS 89.26 1.12 (42) CFC 5.22 
3 
SiC 110.30 1.087 (203) Hexagonal - 
 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 2 – 2006 
 
 
From made researches resulted that inhibitor 
particles have an important influence on the texture 
[5]. It is possible that type of the crystalline net net-
parameter, generally, non-coherence degree 
established between particles and matrix to influence, 
positively, the forming and growth of Goss texture 
nucleus. By the fact that in Nb steel is remarked the 
highest level of goss texture, it results that NbC or 
NbN inhibitor particles have the best influence on 
Goss texture. From here, could be concluded that the 
particles so called “inhibitors” of the grain size 
growth are, in fact “generator” of Goss texture too, 
acting as “texture nucleus” [6]. 
From those shown in this chapter results that the 
existence of the dispersion phases in silicon steels is a 
complex phenomenon with many implications on the 
structure and characteristics of the finished products. 
Therefore, in the manufacturing process the 
following aspect, regarding the added elements for 
dispersion – phase – forming, should be taken into 
consideration: 
- the accurate control of the chemical 
composition high purity and a very good steel 
dezoxidation to stumble oxides formation which 
would limit phase forming with inhibitor role and 
texture nucleus; 
- against to the technology used, chemical 
element (elements) choosing for dispersion phase 
forming; 
- rigorous control of C and N contents, as 
dispersion phase to be, mainly, carbide and nitride, 
these being the most efficient; 
- existence of the highest precision equipment 
to determinate nitrogen and oxygen contents from 
steel both in making process and finished strip as 
well. 
 
References 
 
[1]. J. May, D.Turnbull - Influence of impurities on second 
recrystallization of silicon iron - Journal of Appl.Phys. nr.4- 1959 
[2]. S. Gadea, M.Petrescu- Metalurgia fizica si studiul metalelor 
vol 3 EDP-Bucuresti 1988 
[3]. H. Stuart- Niobium - Proceedings of the International 
Symposium  San Francisco -California 1981 
[4]. J. Walter, C. Dunn - Growth of (110)[100] oriented grains in 
high purity silicon - a unique form of secondary recrystallization - 
Transaction of AIME vo1218 -1960 p.1053 
[5]. T. Matsuoka - Effect of Impurities on the Development of 
(110)[100] Secondary Recristallization Texture in 3%Si Iron -  
Transaction ISIJ vo17, 1967, p19 
[6]. A. Doniga - "Cercetari privind otelurile silicioase pentru 
transformatoare " Teza de doctorat -Galati 1998 
 
 
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Study of the Inclusions from the Oriented Grains Silicon Steels and their Influence on the Texture

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Study of the Inclusions from the Oriented Grains Silicon Steels and their Influence on the Texture

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