DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Election/Restrictions
Applicant’s election without traverse of Group I, claims 1-6, in the reply filed on 1/28/2026 is acknowledged. The restriction requirement has been withdrawn in the interests of compact prosecution because there is no serious search and/or examination burden in examining the Groups of invention together.
Claim Objections
Claim 4 is objected to because of the following informalities: Claim 4 recites “a number density of retained austenite in a range of 1.0 μm from the prior γ grain boundary”. This should be “retained austenite in a range within 1.0 μm from the prior γ grain boundary”. Appropriate correction is required.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION —The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claims 2 and 7-11 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Claim 2 recites “R/t, which is a ratio of a limit bend R to a sheet thickness at 90° V-bending is 5.0 or less”. This limitation is indefinite because it fails to specify what R and t are in the ratio R/t. For purposes of examination, it is presumed this limitation was intended to be “a ratio of a limit bend radius R to a sheet thickness t”.
Claim 7 recites “a hot rolling process of directly or once cooling and then heating a cast slab”. It is unknown what is meant by “directly or once cooling”. What is being cooled, and from what? What exactly is “directly cooling” and what is “once cooling” in the context of the claimed process? For purposes of examination, it is presumed that a cast slab was at one point cooled and then heated. Dependent claims 8-11 not addressed are indefinite by virtue of dependence from an indefinite claim.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-11 are rejected under 35 U.S.C. 103 as being unpatentable over Tobata et al. (US 2025/0223662) in view of Nishio et al. (US 2022/0333221).
Regarding claims 1, 3-4, and 7-8, Tobata discloses a cold-rolled steel sheet having the following composition, as compared to the claimed composition (¶ 17):
Claims 1&7
Tobata (¶ 17)
C
0.140%-0.400%
0.030%-0.500%
Si
≤1.00%
0.50%-2.50%
Mn
1.30%-4.00%
1.50%-5.00%
P
≤0.100%
≤0.100%
S
≤0.010%
≤0.0200%
Al
≤0.100%
≤1.00%
N
≤0.0100%
≤0.0100%
Ti
≤0.050%
≤0.200%
Nb
≤0.050%
≤0.200%
V
≤0.50%
≤0.200%
Cu
≤1.00%
≤1.00%
Ni
≤1.00%
≤1.00%
Cr
≤1.00%
≤1.00%
Mo
≤0.50%
≤1.00%
B
≤0.0100%
≤0.0100%
Ca
≤0.0100%
≤0.0100%
Mg
≤0.0100%
≤0.0100%
REM
≤0.0500%
≤0.0100%
Bi
≤0.050%
≤0.200%
Fe
Remainder
Remainder
Claims 3&8 (one or more)
Ti
0.001%-0.050%
0.001%-0.100% (¶ 34)
Nb
0.001%-0.050%
0.001%-0.100% (¶ 34)
V
0.01%-0.50%
0.001%-0.100% (¶ 34)
Cu
0.01%-1.00%
0.01%-1.00% (¶ 38)
Ni
0.01%-1.00%
0.01%-1.00% (¶ 36)
Cr
0.01%-1.00%
0.01%-1.00% (¶ 36)
Mo
0.01%-0.50%
0.01%-1.00% (¶ 36)
B
0.0001%-0.0100%
0.0003%-0.010% (35)
Ca
0.0001%-0.0100%
0.0005%-0.0100% (¶ 41)
Mg
0.0001%-0.0100%
0.0005%-0.0100% (¶ 41)
REM
0.0005%-0.0500%
0.0005%-0.0100% (¶ 41)
Bi
0.0005%-0.050%
0.001%-0.200% (¶ 44)
Microstructure (claims 1&7)
r-Austenite
1.0%-8.0%
3%-15% (¶ 48)
t-Martensite
≥80.0%
≥80.0% (¶¶ 47&52 martensite & t-martensite)
Ferrite & Bainite
≤15.0%
≤10% (¶ 50)
Martensite
≤5.0%
≥80.0% (¶¶ 47&52 martensite & t-martensite)
The microstructure phases are measured at a depth at ¼ sheet thickness from the surface (¶ 51). The prior art steel composition and microstructure overlap the claimed steel composition and microstructure, creating a prima facie case of obviousness. See MPEP 2144.05 I. While Tobata does not explicitly differentiate between tempered martensite and martensite, the claimed ratio is expected to be present in the prior art steel based on the similar manufacturing processes, as will be discussed below. Tobata teaches the prior austenite grain size is 20 μm or less (¶ 53), which overlaps the claimed grain size, creating a prima facie case of obviousness. See MPEP 2144.05 I.
Tobata does not expressly disclose the number density of retained austensite on prior austenite grain boundaries. However, given the similar manufacturing process, one of ordinary skill in the art would expect the claimed number density to be present in Tobata. The claimed manufacturing process of claim 7 is compared to the process of Tobata:
Claim 7
Tobata
Cooling and heating a cast slab having the composition of claim 1 to 1,100°C or higher and hot rolling
Heating a slab to 1,100°C or higher, followed by hot rolling (¶ 61). Since the slab is cast (¶ 61), it inherently must have been cooled from the molten state.
Coiling at 550°C or lower
Coiling at 350°C-650°C (¶ 61)
Descaling followed by cold rolling
Pickling (¶ 62) and cold rolling (¶ 63)
Annealing at a soaking temperature of 820°C-880°C with an average heating rate slower than 10°C/s above 700°C for 30-200 seconds
Annealing at a temperature of 750°C-950°C for 10-1000 seconds (¶¶ 65-66)
Bending-Bending back deformation at 90° or more within the range of 700°C -800°C one or more times using a roll with a radius of 850 mm or less while applying a tension of 3 kN or more
Bending-unbending with a roll having a radius of 800 mm or less 1-15 times within the annealing temperature of 750°C-950°C (¶ 67)
Bending-Bending back deformation at 90° or more within the range of 50°C -350°C one or more times using a roll with a radius of 850 mm or less while applying a tension of 3 kN or more
Bending-unbending with a rolling having a radius of 800 mm or less 1-15 times within a temperature of the cooling stop temperature to the Ms temperature (¶ 74). The cooling stop is in the range of 100°C to the Ms-80°C (¶ 76), and the Ms temperature is ~320°C (see Table 3). The applied tension is 5-100 MPa (74).
Cooling at a rate of 5°C/s or faster between 700°C-600°C and 450°C-350°C
Cooling rate between 700°C-600°C is at least 20°C/s (¶ 69), cooling rate between 499°C-Ms temperature is at least 20°C/s (¶ 70)
Tempering at 200°C-350°C for at least 1 second
Tempering at cooling stop temperature to 450°C for 10-1000 seconds (¶¶ 77-78)
Tobata teaches the bending and unbending is performed by bending the steel in one direction and then cancelling the bend (¶ 68), which implies a bending degree of 180°. Tobata teaches a tension applied during bending/unbending is 5-100 MPa (¶ 74). Based on a steel sheet width of 25 mm (¶ 89) and a steel sheet thickness of 0.6-2.2 mm (¶ 85), the force applied is equivalent to 75 N to 5.5 kN. While Tobata does not expressly disclose a tension for the first bending-unbending treatment, one of ordinary skill in the art would expect the tension at this step to be similar to the tension at the second bending-unbending treatment since these steps are being performed continuously on a steel sheet, absent objective evidence to the contrary. See MPEP 2112.
Tobata does not expressly disclose a heating rate to the annealing temperature. Nishio teaches a steel sheet having a similar composition and manufacturing process to that of Tobata (¶¶ 22-32). Nishio teaches a heating rate of 1-50 °C/s within the temperature range of 550°C -750°C to reach the annealing temperature (¶ 149). It would have been obvious at the effective time of filing for one of ordinary skill in the art to adopt the heating rate taught by Nishio in the process of Tobata because Nishio teaches this heating rate ensures improved strength, hole expandability, and bendability (¶ 150). The process parameters of the prior art combination are substantially similar to, and overlap, the claimed process parameters, creating a prima facie case of obviousness. See MPEP 2144.05 I. Accordingly, because the process of the prior art combination is substantially similar to the claimed process which is used to make the claimed product, one of ordinary skill in the art would expect the steel sheet of the prior art combination to exhibit the same number density of retained austenite at prior austenite grain boundaries as claimed, absent objective evidence to the contrary. See MPEP 2112.
Regarding claim 2, Tobata teaches the steel has a tensile strength of at least 1180 MPa (¶15) and a R/t V-block bend ratio of 6.0 or less (¶ 90). This overlaps the claimed ranges, creating a prima facie case of obviousness. See MPEP 2144.05 I. Nishio teaches a uniform elongation of 5% or more (¶ 33). One of ordinary skill in the art would expect the steel sheet of the prior art combination to exhibit the claimed properties given the substantial similarities in composition and manufacturing processing parameters, absent objective evidence to the contrary. See MPEP 2112.
Regarding claims 5-6, Tobata teaches forming a hot-dip galvanizing or galvannealing layer on the steel (¶ 83).
Regarding claim 9, Tobata teaches an average cooling rate in the temperature range from Ms to cooling stop temperature is 5-120°C/s or less (¶ 73). This overlaps the claimed range, creating a prima facie case of obviousness.
Regarding claims 10-11, Tobata teaches forming a hot-dip galvanizing layer during the post-anneal cooling process, with a subsequent alloying treatment (¶ 83). Nishio teaches the steel is galvanized during the cooling after annealing step by immersing in a hot dipping bath when the steel is at a temperature range of 450°C -600°C (¶ 155). It would have been obvious at the effective time of filing for the claimed invention for one of ordinary skill in the art to adopt the galvanizing temperature of Nishio in the process of Tobata because this is a conventional temperature for galvanizing a steel sheet.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. US 2022/0081734 discloses a method of making a steel sheet including a bending-unbending deformation during annealing, but does not teach or suggest the claimed number density of retained austenite, or the process including the bending-unbending deformation at a lower temperature or the tension applied during bending-unbending deformation. US 2023/0160032 discloses a method of making a steel sheet including a bending-unbending deformation from the annealing temperature to the cooling stop temperature, but discloses a different microstructure. US 2014/0227555 and US 2014/0287263 also disclose similar bending-unbending deformation process steps but teach away from the claimed microstructure.
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/XIAOBEI WANG/Primary Examiner, Art Unit 1784