Influence of synthetic slag added during the tapping on inclusion features of a vacuum degassed LCAK steel grade

Melo, Gilberson Mendonça Storck; Silva, Carlos Antonio da; Peixoto, Johne Jesus Mol; Oliveira, Jose Roberto; Silva, Caio Vaccari; Silva, Itavahn Alves

doi:10.1590/0370-44672020730040

Gilberson Mendonça Storck Melo ⁵E-mails: 5 gilberson.melo@gerdau.com.br

Gerdau S.A - Departamento de Pesquisa e Desenvolvimento, Ouro Branco - Minas Gerais - Brasil.

Universidade Federal de Ouro Preto - UFOP/Universidade do Estado de Minas Gerais - UEMG, REDEMAT - Rede Temática em Engenharia de Materiais, Ouro Preto - Minas Gerais - Brasil.

Universidade do Estado de Minas Gerais, Brasil

https://orcid.org/0000-0001-5025-7902

Carlos Antonio da Silva ⁶ 6 casilva@ufop.edu.br

Universidade Federal de Ouro Preto - UFOP, Escola de Minas, Departamento de Engenharia Metalúrgica, Ouro Preto - Minas Gerais - Brasil.

https://orcid.org/0000-0002-2100-9149

Johne Jesus Mol Peixoto ⁷ 7 johnepeix@yahoo.com.br

Universidade Federal de Ouro Preto - UFOP, Escola de Minas, Departamento de Engenharia Metalúrgica, Ouro Preto - Minas Gerais - Brasil.

https://orcid.org/0000-0002-1648-5423

Jose Roberto Oliveira ⁸ 8 jroberto@ifes.edu.br

Instituto Federal do Espírito Santo - IFES, Departamento de Engenharia Metalúrgica, Vitoria - Espirito Santo - Brasil.

https://orcid.org/0000-0003-3785-2306

Caio Vaccari Silva ⁹ 9 caio.vaccari@gmail.com

Instituto Federal do Espírito Santo - IFES, Departamento de Engenharia Metalúrgica, Vitoria - Espirito Santo - Brasil.

https://orcid.org/0000-0003-0851-6098

Itavahn Alves Silva ¹⁰ 10 itavahnufop@yahoo.com.br

Universidade Federal de Ouro Preto - UFOP, Escola de Minas, Departamento de Engenharia Metalúrgica, Ouro Preto - Minas Gerais - Brasil.

https://orcid.org/0000-0002-7048-7163

E-mails: 5 gilberson.melo@gerdau.com.br

6 casilva@ufop.edu.br

7 johnepeix@yahoo.com.br

8 jroberto@ifes.edu.br

9 caio.vaccari@gmail.com

10 itavahnufop@yahoo.com.br

Heat Id	Vacuum treatment time [min]	Circulation flow rate [t/min]	Top slag composition	FeO+MnO in top slag
1	15	130 - 135	Standard	≤ 10%
2			Optimized	≤ 10%
3			Standard	> 10%
4			Optimized	> 10%

Sample	FeO+MnO Level	Top Slag	Heat Id	T [K]	Al₂O₃	CaO	MgO	SiO₂	FeO	MnO
0	≤ 10%	Standard	1	1875	43.09	33.27	6.69	9.66	1.60	5.69
0		Optimized	2	1857	27.96	48.12	7.07	12.87	1.59	2.39
15		Standard	1	1843	42.72	31.87	6.59	11.98	1.41	5.43
15		Optimized	2	1839	29.02	45.02	6.98	12.68	2.35	3.95
0	> 10%	Standard	3	1879	39.69	31.85	7.05	10.08	2.73	8.60
0		Optimized	4	1884	22.97	40.68	6.59	10.20	8.84	10.72
15		Standard	3	1848	41.64	30.37	7.70	9.97	2.31	8.01
15		Optimized	4	1850	24.41	40.11	6.04	9.90	7.35	12.19

Sample	FeO + MnO Level	Heat Id	T [K]	µ [Poise]	Activities
Sample	FeO + MnO Level	Heat Id	T [K]	µ [Poise]	Al₂O₃	CaO	MgO	SiO₂	FeO	MnO
0	≤ 10%	1	1875	1.37	0.0285	0.0235	0.0593	0.0011	0.0371	0.0579
0		2	1857	0.84	0.0042	0.0816	0.1313	0.0002	0.0149	0.0334
15		1	1843	1.84	0.0359	0.0158	0.0509	0.0017	0.0344	0.0482
15		2	1839	0.98	0.0056	0.0603	0.1155	0.0003	0.0303	0.0507
0	> 10%	3	1879	1.23	0.0241	0.0225	0.0665	0.0009	0.0606	0.0847
0		4	1884	0.49	0.0030	0.0745	0.1269	0.0001	0.0963	0.1589
15		3	1848	1.52	0.0270	0.0179	0.0667	0.0011	0.0560	0.0772
15		4	1850	0.59	0.0034	0.0654	0.1102	0.0001	0.0876	0.1761

Heat Id	Sampling after de-O agent homogenization		Sampling moment after ladle arrival [min]
	Sampling after de-O agent homogenization		0		5		10		15
	a_O [ppm]	T [K]	a_O [ppm]	T [K]	a_O [ppm]	T [K]	a_O [ppm]	T [K]	a_O [ppm]	T [K]
1	27	1953	6.89	1875	5.93	1865	3.86	1857	3.13	1843
2	16	1957	5.12	1857	3.52	1852	3.41	1843	2.80	1839
3	67	1967	7.89	1879	6.08	1866	4.26	1860	2.77	1848
4	56	1973	8.12	1884	6.51	1870	4.38	1858	3.19	1850

Heat Id	Top Slag	FeO+MnO	$\frac{CaO}{({Al}_{2} O_{3})}$	a_{Al2 O3}	a_CaO	µ [poise]	Inclusion Quantity [-/100mm²]
1	Standard	≤ 10%	0.77	0.0285	0.0235	1.37	195
2	Optimized	≤ 10%	1.72	0.0042	0.0816	0.84	90
3	Standard	> 10%	0.80	0.0241	0.0225	1.23	480
4	Optimized	> 10%	1.77	0.0030	0.0745	0.49	257

Heat Id	Top Slag Type	FeO+MnO Level	$\frac{CaO}{({Al}_{2} O_{3})}$	a_{Al2 O3}	a_CaO	µ [poise]	≤ 4µm Share [%]	Inclusion Density Change [-/mm²]
1	Standard	≤ 10%	0.75	0.0359	0.0158	1.84	58	1.95→0.66
2	Optimized	≤ 10%	1.55	0.0056	0.0603	0.98	76	0.90→0.41
3	Standard	> 10%	0.73	0.0270	0.0179	1.52	41	4.80→0.98
4	Optimized	> 10%	1.64	0.0034	0.0654	0.59	78	2.57→1.12

Type	Inclusion	Class	Rule
Oxide	Alumina	Alumina	Al > 65%
	C3A	Other Oxides	(Ca+Al) ≥ 50% and 0.2 ≤ Al/Ca < 0.4
	C12A7		(Ca+Al) ≥ 50% and 0.4 ≤ Al/Ca < 0.8
	CA		(Ca+Al) ≥ 45% and 0.8 ≤ Al/Ca < 1.5
	CA2		(Ca+Al) ≥ 45% and 1.5 ≤ Al/Ca < 2.5
	CA6		(Ca+Al) ≥ 45% and 2.5 ≤ Al/Ca ≤ 3.0
	Spinel		Al ≥ 35% and Mg/(Al+Mg+Ca) ≥ 0.15 and (Al +Mg) ≥ 70% Mg ≥ 2%
	AlSi		(Al+Si) ≥ 70% and Al ≥ 10% and Si ≥ 10% and Ca < 10%
	MnSi		Mn ≥ 10% and Al ≥ 10% and Si ≥ 10%
	TiAl		Ti ≥ 10% and Al ≥ 10% and (Ti+Al) ≥ 65%
	CaSiAl		Ca ≥ 10% and Si ≥ 5% and Al > 10%
Oxysulfide	AlSi-MnS	Oxysulfide	Mn ≥ 20% and Al ≥ 10% and Si ≥ 10% and S ≥ 10%
	Si-MnS		Mn ≥ 20% and Si ≥ 10% and S ≥ 10% and Al < 5%
	CA-(Mn,Ca)S		(Ca+Al) > 40% and Ca ≥ 20% and Mn ≥ 10% and S ≥ 20%
Sulfides	CaS	Sulfides	Ca ≥ 20% and S ≥ 20% and Si < 5% and (Mn+Al+Mg) < 15%
	MnS		Mn ≥ 10% and S ≥ 10% and (Mn+S) ≥ 50%
	(Ca,Mn)S		Ca ≥ 20% and S ≥ 20% and Mn ≥ 20% and Al < 20%

[1] E-mails: 5 gilberson.melo@gerdau.com.br