FABRICATION PROCESS OF COATED STAMPED PARTS AND PARTS PREPARED FROM THE SAME
First Claim
1. A manufacturing process of a hot stamped coated part comprising the following successive steps, in this order:
- providing a hot rolled or cold rolled steel sheet comprising a steel substrate and an aluminium-silicon alloy precoating, said precoating containing more than 50% of free aluminium and having a thickness selected to enable alloying with said steel substrate, said thickness being preferably comprised between 15 and 50 micrometers, thencutting said steel sheet to obtain a precoated steel blank, thenheating said blank under a non protective atmosphere up to a temperature Ti near the melting temperature of said precoating, said temperature Ti being preferably comprised between Te−
10°
C. and Te, where Te is the eutectic or solidus temperature of said precoating, thenheating said blank from said temperature Ti up to an austenitization temperature Tm of said steel substrate, said temperature Tm being preferably comprised between 840 and 950°
C., under a non-protective atmosphere at a heating rate V comprised between 30°
C./s and 90°
C./s, V being the heating rate between said temperature Ti and said temperature Tm, in order to obtain a coated heated blank, thensoaking said coated heated blank at said temperature Tm for a time tm, comprised between 20 s and 90 s, thenhot stamping said blank in order to obtain a hot stamped coated part, then—
cooling said stamped part at a cooling rate in order to form a microstructure in said steel substrate comprising at least one constituent chosen among martensite or bainite.
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Accused Products
Abstract
A manufacturing process of a hot stamped coated part comprising the following successive steps, in this order: providing a hot rolled or cold rolled steel sheet comprising a steel substrate and an aluminium-silicon alloy precoating, the precoating containing more than 50% of free aluminium and having a thickness comprised between 15 and 50 micrometers, then cutting the steel sheet to obtain a precoated steel blank, then heating the blank under non protective atmosphere up to a temperature Ti comprised between Te−10° C. and Te, Te being the eutectic or solidus temperature of the precoating, then heating the blank from the temperature Ti up to a temperature Tm comprised between 840 and 950° C. under non protective atmosphere with a heating rate V comprised between 30° C./s and 90° C./s, V being the heating rate between the temperature Ti and the temperature Tm, in order to obtain a coated heated blank, then soaking the coated heated blank at said temperature Tm for a time tm comprised between 20 s and 90 s, then hot stamping the blank in order to obtain a hot stamped coated part, then cooling said stamped part at a cooling rate in order to form a microstructure in the steel substrate comprising at least one constituent chosen among martensite or bainite.
19 Citations
14 Claims
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1. A manufacturing process of a hot stamped coated part comprising the following successive steps, in this order:
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providing a hot rolled or cold rolled steel sheet comprising a steel substrate and an aluminium-silicon alloy precoating, said precoating containing more than 50% of free aluminium and having a thickness selected to enable alloying with said steel substrate, said thickness being preferably comprised between 15 and 50 micrometers, then cutting said steel sheet to obtain a precoated steel blank, then heating said blank under a non protective atmosphere up to a temperature Ti near the melting temperature of said precoating, said temperature Ti being preferably comprised between Te−
10°
C. and Te, where Te is the eutectic or solidus temperature of said precoating, thenheating said blank from said temperature Ti up to an austenitization temperature Tm of said steel substrate, said temperature Tm being preferably comprised between 840 and 950°
C., under a non-protective atmosphere at a heating rate V comprised between 30°
C./s and 90°
C./s, V being the heating rate between said temperature Ti and said temperature Tm, in order to obtain a coated heated blank, thensoaking said coated heated blank at said temperature Tm for a time tm, comprised between 20 s and 90 s, then hot stamping said blank in order to obtain a hot stamped coated part, then—
cooling said stamped part at a cooling rate in order to form a microstructure in said steel substrate comprising at least one constituent chosen among martensite or bainite. - View Dependent Claims (2, 3, 10)
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4. A manufacturing process of a hot stamped coated part, comprising the following successive steps, in this order:
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providing a hot rolled or cold rolled steel sheet comprising a steel substrate and an aluminium-silicon alloy precoating, said precoating containing more than 50% of free aluminium and having a thickness selected to enable alloying with said steel substrate, said thickness being preferably comprised between 15 and 50 micrometers, then cutting said steel sheet to obtain a precoated steel blank, then heating said steel blank under a non-protective atmosphere at a heating rate V up to a temperature Tm, in order to transform, preferably fully transform, the steel substrate microstructure into austenite and to obtain, immediately after heating and prior to ulterior soaking, a limited proportion of liquid phase on the surface of said precoating, said proportion being preferably comprised between 10 and 60%, then, transforming said liquid phase of the precoating at the temperature Tm during a soaking period tm in order to obtain a coated heated blank with a coating having between 0 and 30% of liquid phase on its surface at the end of said soaking period, and comprising by weight between 20 and 50% Fe on said surface, then hot stamping said blank in order to obtain a hot stamped part, then cooling said stamped part in order to form a microstructure in said steel substrate comprising at least one constituent chosen among martensite or bainite. - View Dependent Claims (5, 6, 7, 8, 9)
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11. A hot stamped coated part comprising a steel substrate having a microstructure comprising at least one constituent chosen among bainite or martensite, and a coating on each one of the two sides of said substrate, said coating being composed of the following layers containing Si in solid solution, starting from the layer contiguous to said steel substrate:
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a Fe3Al layer a FeAl or τ
1 or τ
2 layer atop of the said Fe3Al layeran external layer composed of more than 70% of FeAl3 or Fe2Al5, said FeAl3 or Fe2Al5 layer containing a discontinuous minor phase of FeAl, or τ
1 or τ
2, said external layer having more than 70% of crystals on its surface. - View Dependent Claims (12, 13, 14)
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Specification