HIGH STRENGTH HOT DIP GALVANIZED STEEL SHEET AND HIGH STRENGTH GALVANNEALED STEEL SHEET EXCELLENT IN SHAPEABILITY AND PLATEABILITY AND METHODS OF PRODUCTION AND APPARATUSES FOR PRODUCTION OF THE SAME

• US 20100304183A1
• Filed: 07/31/2006
• Published: 12/02/2010
• Est. Priority Date: 01/30/2006
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel Corporation
• Inventors: Ikematsu, Yoichi, Honda, Kazuhiko, Tanaka, Koki, Nishiyama, Tetsuo, Suemune, Yoshihiro, Itoh, Takeo
• Granted Patent: US 8,592,049 B2
• Time in Patent Office: Days
• US Class Current: 428/659
• CPC Class Codes: B32B 15/013 one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
• CPC Class Codes: C21D 8/0263 following hot rolling
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C22C 18/00 Alloys based on zinc
• CPC Class Codes: C22C 18/04 with aluminium as the next major constituent
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C23C 2/0222 in a reactive atmosphere, e.g. oxidising or reducing atmosphere C23C2/024 takes precedence
• CPC Class Codes: C23C 2/024 by cleaning or etching
• CPC Class Codes: C23C 2/06 Zinc or cadmium or alloys based thereon
• CPC Class Codes: C23C 2/261 in a gas atmosphere, e.g. inert or reducing atmosphere
• CPC Class Codes: C23C 2/28 Thermal after-treatment, e.g. treatment in oil bath
• CPC Class Codes: C23C 2/29 Cooling or quenching
• CPC Class Codes: Y10T 428/1266 O, S, or organic compound in metal component
• CPC Class Codes: Y10T 428/12674 Ge- or Si-base component
• CPC Class Codes: Y10T 428/12799 Next to Fe-base component [e.g., galvanized]
• CPC Class Codes: Y10T 428/12972 Containing 0.01-1.7% carbon [i.e., steel]

Abstract

Hot dip galvanized steel sheet excellent in shapeability and plateability comprised of high strength steel sheet according to the present invention can be provided containing, by mass % about, C: 0.05 to 0.25%, Si: 0.3 to 2.5%, Mn: 1.5 to 2.8%, P: 0.03% or less, S: 0.02% or less, Al: 0.005 to 0.5%, N: 0.0060% or less and the balance of Fe and unavoidable impurities. The exemplary steel sheet can have thereon a galvanized layer containing, e.g., about Al: 0.05 to 10 mass % and Fe: 0.05 to 3 mass % and the balance of Zn and unavoidable impurities. Such exemplary hot dip galvanized steel sheet can have oxides containing Si in an average content of about 0.6 to 10 mass % at the crystal grain boundaries and in the crystal grains at the sheet steel side 5 μm or less from the interface between the high strength steel sheet and the plating layer and by the presence of Fe—Zn alloy with an average grain size of about 0.5 to 3 μm at the plating side.

Claims

1-25. -25. (canceled)

26. A hot dip galvanized steel sheet excellent in shapeability and plateability, comprising

at least one high strength steel sheet portion containing approximately, by mass %, C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities,

wherein the at least one high strength steel sheet portion includes (i) a galvanized layer thereon which contains Al;

0.05 to about 10 mass % and Fe;

about 0.05 to 3 mass % and the balance of Zn and unavoidable impurities, (ii) oxides containing Si in an average content of about 0.6 to 10 mass % at crystal grain boundaries and in crystal grains at a side of the at least one high strength steel sheet portion of about 5 μ

m or less from an interface between the at least one high strength steel sheet portion and a plating layer and (iii) Fe—

Zn alloy with an average grain size of about 0.5 to 3 μ

m at a side of the plating layer.

27. The high strength hot dip galvanized steel sheet according to claim 26, wherein the oxides are one or more types selected from SiO₂, FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄.

28. The high strength hot dip galvanized steel sheet according to claim 26, wherein at least one type of the oxides is selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ provided at a surface or a side of the at least one high strength steel sheet portion, and at least one other type of the oxides is SiO₂ provided at an inside surface side of the at least one high strength steel sheet portion.

29. The high strength hot dip galvanized steel sheet according to claim 26, wherein the at least one high strength steel sheet portion provides a relationship between a tensile strength F (MPa) and an elongation L (%) that satisfies the equation L≧

51−

0.035×

F.

30. A hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

at least one high strength steel sheet containing approximately, by mass %, C;

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities,

wherein the at least one high strength steel sheet portion includes (i) a galvanized layer thereon containing Al;

about 0.05 to 10 mass % and Fe;

about 0.05 to 3 mass % and the balance of Zn and unavoidable impurities, and (ii) oxides containing Si in an average content of about 0.6 to 10 mass % at the crystal grain boundaries and in crystal grains at a side of the at least one high strength steel sheet portion of about 5 μ

m or less from an interface between the high strength steel sheet and a plating layer, and (iii) Fe—

Zn alloy with an average grain size of about 0.5 to 3 μ

m at a side of the plating layer in a ratio of about 1 grain/500 μ

m or more.

31. The high strength hot dip galvanized steel sheet according to claim 30, wherein the oxides are one or more types selected from SiO₂, FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄.

32. The high strength hot dip galvanized steel sheet according to claim 30, wherein at least one type of the oxides is selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ provided at a surface or a side of the at least one high strength steel sheet portion, and at least one other type of the oxides is SiO₂ provided at an inside surface side of the at least one high strength steel sheet portion.

33. The high strength hot dip galvanized steel sheet according to claim 30, wherein the at least one high strength steel sheet portion provides a relationship between a tensile strength F (MPa) and an elongation L (%) that satisfies the equation L≧

51−

0.035×

F.

34. A hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

at least one high strength steel sheet containing approximately, by mass %, C;

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities,

wherein the at least one high strength steel sheet portion includes (i) a galvanized layer thereon containing Al;

about 0.05 to 10 mass % and Mg;

about 0.01 to 5 mass % and the balance of Zn and unavoidable impurities, and (ii) oxides containing Si in an average content of about 0.6 to 10 mass % at the crystal grain boundaries and in the crystal grains at a side of the at least one high strength steel sheet portion of about 5 μ

m or less from an interface between the at least one high strength steel sheet portion and the plating layer.

35. The high strength hot dip galvanized steel sheet according to claim 34, wherein the oxides are one or more types selected from SiO₂, FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄.

36. The high strength hot dip galvanized steel a sheet according to claim 34, wherein at least one type of the oxides is selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ provided at a surface or a side of the at least one high strength steel sheet portion, and at least one other type of the oxides is SiO₂ provided at an inside surface side of the at least one high strength steel sheet portion.

37. The high strength hot dip galvanized steel sheet according to claim 34, wherein the at least one high strength steel sheet portion provides a relationship between a tensile strength F (MPa) and an elongation L (%) that satisfies the equation L≧

51−

0.035×

F.

38. A hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

at least one high strength steel sheet containing approximately, by mass %, C;

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities,

wherein the at least one high strength steel sheet portion includes (i) a galvanized layer thereon containing Al;

about 4 to 20 mass %, Mg;

about 2 to 5 mass %, and Si;

about 0 to 0.5 mass % and the balance of Zn and unavoidable impurities, and (ii) oxides containing Si in an average content of about 0.6 to 10 mass % at crystal grain boundaries and in crystal grains at a side of the at least one high strength steel sheet portion of about 5 μ

m or less from the interface between the at least one high strength steel sheet portion and a plating layer.

39. The high strength hot dip galvanized steel sheet according to claim 38, wherein the oxides are one or more types selected from SiO₂, FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄.

40. The high strength hot dip galvanized steel sheet according to claim 38, wherein at least one type of the oxides is selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ provided at a surface or a side of the at least one high strength steel sheet portion, and at least one other type of the oxides is SiO₂ provided at an inside surface side of the at least one high strength steel sheet portion.

41. The high strength hot dip galvanized steel sheet according to claim 38, wherein the at least one high strength steel sheet portion provides a relationship between a tensile strength F (MPa) and an elongation L (%) that satisfies the equation L≧

51−

0.035×

F.

42. A galvannealed steel sheet excellent in shapeability and plateability, comprising:

at least one high strength steel sheet portion containing approximately, by mass %, C;

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities,

wherein the at least one high strength steel sheet portion includes (i) a zinc alloy plating layer containing Fe and the balance of Zn and unavoidable impurities, (ii) first oxides containing Si in an average content of about 0.6 to 10 mass % at crystal grain boundaries and in crystal grains at a sheet steel side of about 5 μ

m or less from an interface between the at least one high strength steel sheet portion and a plating layer, and (iii) second oxides containing Si in an average content of about 0.5 to 1.5 mass % in the plating layer.

43. The steel sheet according to claim 42, wherein the oxides are one or more types selected from SiO₂, FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄.

44. The steel sheet according to claim 42, wherein at least one first set of the oxides provided in the plating layer and at a surface of the at least one high strength steel sheet portion are selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄,r and at least one second of oxides provided at an inside surface of the at least one high strength steel sheet portion which is SiO₂.

45. The steel sheet according to claim 42, wherein at least one type of the Si oxides is selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ in the plating layer, and wherein at least one other type being SiO₂ at a side of the at least one high strength steel sheet portion and of the plating layer.

46. The steel sheet according to claim 42, wherein the at least one high strength steel sheet portion provides a relationship between a tensile strength F (MPa) and an elongation L (%) that satisfies the equation L≧

51−

0.035×

F.

47. A method for producing at least one high strength hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

a) continuously hot dip galvanizing the at least one high strength steel sheet containing Si and Mn; and

b) during procedure (a), causing (i) a presence of at least one type of Si oxides selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ at a surface of the at least one high strength steel sheet or an interface of the at least one high strength steel sheet and plating and (ii) a presence of oxides of SiO₂ at an inside surface side of the at least one high strength steel sheet so as to form a galvanized layer or a zinc alloy plating layer on the at least one high strength steel sheet.

48. The method according to claim 47, wherein the high strength hot dip galvanized steel sheet comprises approximately, by mass %, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

49. A method for producing at least one high strength galvannealed steel sheet excellent in shapeability and plateability, comprising:

a) continuously hot dip galvanizing the at least one high strength steel sheet containing Si and Mn;

b) during procedure (a), causing (i) a presence of at least one type of Si oxides selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ at a surface of the at least one high strength steel sheet or an interface of the at least one high strength steel sheet and plating and (ii) a presence of oxides of SiO₂ at an inside surface side of the at least one high strength steel sheet so as to form a galvanized layer on the at least one high strength steel sheet; and

c) galvannealing the at least one high strength steel sheet.

50. The method according to claim 49, wherein the high strength hot dip galvannealed steel sheet comprises approximately, by mass %, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

51. A method for producing at least one high strength hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

a) continuously hot dip galvanizing the at least one high strength steel sheet containing C, Si and Mn; and

b) during procedure (a), causing (i) a presence of at least one type of Si oxides selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ at a surface of the at least one high strength steel sheet or an interface of the at least one high strength steel sheet and plating and (ii) a presence of oxides of SiO₂ at an inside surface side of the at least one high strength steel sheet so as to form a galvanized layer or a zinc alloy plating layer on the at least one high strength steel sheet.

52. The method according to claim 51, wherein the high strength hot dip galvanized steel sheet comprises approximately, by mass %, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

53. A method for producing at least one high strength galvannealed steel sheet excellent in shapeability and plateability, comprising:

a) continuously hot dip galvanizing the at least one high strength steel sheet containing C, Si and Mn;

b) during procedure (a), causing (i) a presence of at least one type of Si oxides selected from FeSiO₃, Fe₂SiO₄, MnSiO₃, and Mn₂SiO₄ at a surface of the at least one high strength steel sheet or an interface of the at least one high strength steel sheet and plating and (ii) a presence of oxides of SiO₂ at an inside surface side of the at least one high strength steel sheet so as to form a galvanized layer on the at least one high strength steel sheet; and

c) galvannealing the at least one high strength steel sheet.

54. The method according to claim 53, wherein the high strength hot dip galvannealed steel sheet comprises approximately, by mass %, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

55. A method for producing at least one sheet which is at least one of (i) at least one high strength hot dip galvanized steel sheet or (ii) at least one high strength galvannealed steel sheet excellent in shapeability and plateability, comprising:

a) continuously hot dip galvanizing the at least one sheet containing C, Si, and Mn;

b) during procedure (a), reducing the at least one sheet in a reduction zone with an atmosphere comprised of H₂ in about 1 to 60 vol % and the balance of one or more of N₂, H₂O, CO₂, CO₂, and CO and unavoidable impurities and controlled to a log PO₂ of oxygen partial pressure in the atmosphere of;

−

0.000034T²+0.105T−

0.2 [Si %]²+2.1 [Si %]−

98.8≦

log PO₂≦

−

0.000038T²+0.107T−

90.4 

 

(equation

     1)

923≦

T≦

1173 

 

(equation

     2)

where,

T;

maximum peak temperature (K) of steel sheet

[Si %];

Si content in steel sheet (mass %).

56. The method according to claim 55, further comprising:

c) oxidizing the at least one sheet in an oxidation zone before the reduction zone in an atmosphere of a combustion air ratio of about 0.9 to 1.2; and

d) reducing the combustion air ratio in the reduction zone.

57. The method according to claim 55, further comprising:

e) oxidizing the at least one sheet in an oxidation zone before the reduction zone in an atmosphere of a dew point of about 273K or more; and

f) reducing the atmosphere in the reduction zone.

58. The method according to claim 55, wherein the at least one sheet is comprised, by mass % approximately, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

59. A method for producing at least one high strength hot dip galvanized steel sheet excellent in shapeability and plateability, comprising:

a) final rolling a steel slab containing C, Si, and Mn at an Ar₃ point or more in temperature;

b) cold rolling the at least one sheet by about 50 to 85%;

c) hot dip galvanizing the at least one sheet;

d) during step (c), using a continuous hot dip galvanization facility having a reduction zone with an atmosphere comprised of H₂ in about 1 to 60 vol % and the balance of one or more of N₂, H₂O, O₂, CO₂, and CO and unavoidable impurities and controlled to a log PO₂ of oxygen partial pressure in the atmosphere of;

−

0.000034T²+0.105T−

0.2 [Si %]²+2.1 [Si %]−

98.8≦

log PO₂≦

0.000038T²+0.107T−

90.4 

 

(equation

     1)

923≦

T≦

1173 

 

(equation

     2)

where,

T;

maximum peak temperature (K) of steel sheet

[Si %];

Si content in steel sheet (mass %);

e) annealing the at least one sheet in a dual-phase coexisting temperature range of ferrite and austeniste of about 1023K to 1153K;

f) cooling the at least one sheet from a maximum peak temperature to about 923K by an average cooling rate of about 0.5 to 10 degree/second;

g) further cooling the at least one sheet from about 923K to 773K by an average cooling rate of about 3 degree/second or more and further from about 773K by an average cooling rate of about 0.5 degree/second or more for hot dip galvanization so as to thereby form a hot dip galvanized layer on the surface of a cooled-rolled steel sheet; and

h) controlling a cooling time from about 773K to the 623K after plating to about 25 seconds to 240 seconds.

60. The method according to claim 59, wherein the at least one sheet is comprised, by mass % approximately, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

61. A method for producing at least one high strength galvannealed steel sheet excellent in shapeability and plateability, comprising:

a) final rolling a steel slab containing C, Si, and Mn at an Ar₃ point or more in temperature;

b) cold rolling the at least one sheet by about 50 to 85%;

c) hot dip galvanizing the at least one sheet;

d) during step (c), using a continuous hot dip galvanization facility having a reduction zone with an atmosphere comprised of H₂ in about 1 to 60 vol % and the balance of one or more of N₂, H₂O, O₂, CO₂, and CO and unavoidable impurities and controlled to a log PO₂ of oxygen partial pressure in the atmosphere of;

−

0.000034T²+0.105T−

0.2 [Si %]²+2.1 [Si %]−

98.8≦

log PO₂≦

−

0.000038T²+0.107T−

90.4 

 

(equation

     1)

923≦

T≦

1173 

 

(equation

     2)

where,

T;

maximum peak temperature (K) of steel sheet

[Si %];

Si content in steel sheet (mass %),

e) annealing the at least one sheet in a dual-phase coexisting temperature range of ferrite and austeniste of about 1023K to 1153K;

f) cooling the at least one sheet from a maximum peak temperature to about 923K by an average cooling rate of about 0.5 to 10 degree/second;

g) further cooling the at least one sheet from about 923K to 773K by an average cooling rate of about 3 degree/second or more and further from about 773K by an average cooling rate of 0.5 degree/second or more down to about 693K to 733K and maintaining the cooling rate from 773K to a plating bath for about 25 seconds to 240 seconds;

h) hot dip galvanizing the at least one sheet so as to form a hot dip galvanized layer on a surface of a cold rolled steel sheet; and

i) alloying the at least one sheet on which the hot dip galvanized layer is formed so as to form a zinc alloy plating layer on the surface of at least one sheet,

wherein procedure (h) is performed in a hot dip galvanization bath of a composition comprised of an effective bath Al concentration of about 0.07 to 0.105 wt % and the balance of Zn and unavoidable impurities, and

wherein procedure (c) is performed at a temperature T (K) satisfying the following

720≦

T≦

690×

exp(1.35×

[Al %])

wherein, [Al %];

effective bath Al concentration in galvanization bath (wt %).

62. The method according to claim 61, wherein the at least one sheet is comprised, by mass % approximately, of C:

0.05 to 0.25%, Si;

0.3 to 2.5%, Mn;

1.5 to 2.8%, P;

0.03% or less, S;

0.02% or less, Al;

0.005 to 0.5%, N;

0.0060% or less, and the balance of Fe and unavoidable impurities.

63. The method according to claim 61, further comprising:

j) annealing the at least one sheet;

k) cooling the at least one sheet to about 673K to 723K; and

l) reheating the at least one sheet to a temperature of about 703K to 743K for galvannealing.

64. The method according to claim 61, further comprising controlling the time from plating to cooling to about 673K or less in temperature to about 30 seconds to 120 seconds.

65. A production facility for hot dip galvanized steel sheet, comprising:

a furnace which is at least one or nonoxidizing or direct-fired which is structured to at least one of produce or accept at least one continuously hot dip galvanizing steel sheet; and

a device provided in the furnace for introducing a gas comprised of CO₂ in about 1 to 100 vol % and the balance of N₂, H₂O, O₂, CO and unavoidable impurities.