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
Claims 42-44 remain withdrawn from further consideration pursuant to 37 CFR 1.142(b), as being drawn to a nonelected arrangement, there being no allowable generic or linking claim. Applicant timely traversed the restriction (election) requirement in the reply filed on 07/06/2026.
The traversal is on the ground(s) that the groups are obvious variants of one another and share the same underlying inventive concept. Examiner notes that unity of invention for 371 applications has different requirements than restriction practice for national applications, where the requirement for lack of unity involves determining why there is no single general inventive concept. Group I is drawn to methods for processing iron ore to obtain steel. Group II is drawn to a smelting furnace arrangement which, while featuring some overlapping terms, does not require the methods of Group I, does not yield the products of Group I, constitutes a separate invention capable of producing steel compositions unique from Group I, and is capable of implementing processes unique from Group I. Therefore, the requirement is still deemed proper and is made final.
Further, as this current application was not filed under 35 U.S.C. § 111 (a) the examiner is not required to demonstrate a "serious burden". Though not required to make such a demonstration, as a courtesy, the examiner asserts that serious burden exists in the differing issues likely to arise during the prosecution of the different inventions and species.
The requirement is still deemed proper and is therefore made FINAL.
Claim Interpretation
The term “basicity” in Claim 1 and Claim 40 is interpreted as “the ratio of calcium oxide (CaO) and magnesium oxide (MgO) to silica (SiO2), i.e. (CaO + MgO/SiO2)” per Page 3 of the instant Specification.
Claim Objections
Claims 26 and 41 are objected to because of the following informalities: Claim 26 recites in Line 3 and Claim 41 recites in Line 3, “Al203” which should be recited as Al2O3. 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 25-41 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 25 and Claim 40 recite “0,015%” “0,8,” and “0,5%” and Claims 26 and Claim 41 recite “10,5%.” It is unclear whether these recitations are intended to convey an individual numeral or a list of numerals as currently presented. Appropriate correction is required.
Claim 25 recites “heap above a slag layer” and Claim 35 recites “heap extending above a slag layer,” presenting the following issues of clarity:
Where applicant acts as his or her own lexicographer to specifically define a term of a claim contrary to its ordinary meaning, the written description must clearly redefine the claim term and set forth the uncommon definition so as to put one reasonably skilled in the art on notice that the applicant intended to so redefine that claim term. Process Control Corp. v. HydReclaim Corp., 190 F.3d 1350, 1357, 52 USPQ2d 1029, 1033 (Fed. Cir. 1999). The term “heap” in Claims 25 and 35 is used by the claim to reference stored sources of direct reduced iron or carbon containing solid while the accepted meaning is “ore pile.” The term is indefinite because the Specification does not clearly redefine the term.
It is further unclear whether the “heap” of Claim 25 is the same “heap” of Claim 35, the same “heap” of Claim 40, or has some other meaning entirely.
These claims are generally narrative and indefinite, failing to conform with current U.S. practice. They appear to be a literal translation into English from a foreign document. Appropriate correction is required.
Claim 25 recites “the smelting” in Line 20 which lacks antecedent basis, rendering the claim indefinite. Previous mention is to “a smelting furnace” in Line 6 and “a smelting process” in Lines 6-7. Appropriate correction is required to establish a nexus between any actionable and repeatable method step involving “smelting.”
Claim 25 recites “introducing carbon so as to increase a carbon content of the obtained intermediate iron product to between 1% - 4% by mass” in Lines 15-16. Claim 40 recites the same at Lines 14-15.The initial amount of carbon in the intermediate iron product is never recited. Accordingly, it is unclear how the carbon content is modified. It is unclear for instance whether the carbon content is modified by the addition of carbon containing solid, or whether just enough carbon is added to increase the carbon content of the mixture, or some other meaning. It is further unclear whether the carbon content of the direct reduced iron is increased, or some other meaning entirely. This recitation “1% - 4% by mass does not sufficiently indicate how the carbon content is modified. Appropriate correction is required to establish an actionable and repeatable method step with specificity such that persons of ordinary skill in the art can ascertain the metes and bounds of the carbon “increase.”
Claim 25, Claim 27, and Claim 40 recite “in connection with.” It is unclear what is meant by this phrase as this can take on a subjective meaning as applied to the claims. The phrase “in connection with” does not impart any actual “connection” with any of the components used in the claimed methods. It is unclear what, if any, of the structures used in the method are physically “connected” or whether this phrase has some other meaning entirely. Appropriate correction is required to establish actionable and repeatable method steps with positive active claim language.
Claim 27 recites, “wherein introducing carbon comprises: introducing a carbon containing gas…in connection with the direct reduction of iron ore.” However, Claim 25 recites, “wherein introducing carbon comprises introducing a carbon containing solid into to the smelting furnace” in Lines 19-20. Claim 25 does not recite introducing carbon in connection with the direct reduction of iron ore. Appropriate correction is required to clearly establish the introduction of carbon and describe actionable and repeatable method steps with positive active claim language.
Claim 28 recites “into a molten bath” in lines 3 and 4. It is unclear whether this is the same molten bath of Claim 25 Line 22, or some separate bath entirely.
Claim 30 recites the limitation "the reduction process" in Line 2 It is unclear whether this is meant to reference “the direct reduction process” of Claim 25 Line 3, or some other process entirely.
Claim 31 recites “a converter, a ladle or an electric arc furnace having 1-3 electrodes.” It is unclear from the structure of the limitation whether “a ladle” references a ladle furnace, a ladle furnace having 1-3 electrodes, a singular ladle, or some other meaning entirely. Appropriate correction is required.
Claim 32 recites “wherein the steel conversion process, the carbon content of the steel obtained is reduced…” in Lines 1-2. It is grammatically unclear in which step or process the carbon content of the steel obtained is reduced. Appropriate correction is required.
Claim 34 recites the limitation “with respect to metallic furnace feed” in Lines 1-2. There is insufficient antecedent basis for this limitation in the claim. There is no support for, or any other reference to “metallic furnace feed.” Further, it is unclear what actionable and repeatable method step is imparted by the phrase “with respect to,” whether this indicates a comparison, a position, or some other meaning entirely. Appropriate correction is required to establish the content of furnace feed as well as identify the source of the feed with specificity.
Claim 35, Claim 36, and Claim 37 recite “the furnace.” It is unclear to which furnace “the furnace” refers, i.e. “the smelting furnace” of Claim 25 on which these claims depend, or some other furnace entirely. Appropriate correction is required.
Claim 35 recites “at least the direct reduced iron is introduced into the furnace” in Lines 1-2, “the at least direct reduced iron” in Line 4, and “wherein the at least direct reduced iron being introduced into the smelting furnace at a position having” in Lines 3-4, rendering the claim indefinite. It is unclear the metes and bounds of what is introduced into the furnace and further unclear to what unstated component the phrase refers. Appropriate correction is required to establish actionable and repeatable method steps with positive active claim language.
Claim 35 recites “the heap extends” in Line 7 and it is unclear how a pile can “extend.” It is unclear whether this ‘extent’ refers to length, height, position, or some other meaning entirely. Appropriate correction is required to establish actionable and repeatable method steps with positive active claim language.
Claim 40 recites “the smelting” in Lines 16 and 21 which lacks antecedent basis, rendering the claim indefinite. Previous mention is to “a smelting furnace” in Line 6 and “a smelting process” in Lines 6-7. Appropriate correction is required to establish a nexus between any actionable and repeatable method step involving “smelting.”
Claims, 29, 33, and 38-39 are rejected for their dependency on a rejected 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.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 25-28, 31-39, and 41 are rejected under 35 U.S.C. 103 as being unpatentable over Gordon et al. US 20050179174 A1 as evidenced by NPL Furlani et al. in view of, NPL Nokhrina et al., NPL Mendes De Paula, Eder et al. US 20120328465 A1, Romenets et al. US 4913734 A, and Iwasaki et a. US 20030047038 A1.
Regarding Claims 25, 28, and 40, Gordon et al. ‘174 teaches a method for processing iron ore to obtain steel comprising introducing direct reduced iron into a smelting process for obtaining an intermediate iron product and slag. Iron ore is introduced into a shaft furnace (meeting the limitation for a gas reduction unit) to subject said iron ore to a direct reduction process for obtaining direct reduced iron [0031]. As evidenced by Furlani et al. the slag ratio is a result-dependent variable impacted by steel production, “One ton of steel implies the production of 130–200 kg of slag,” meeting the limitation of the instant Claim for the ratio of slag to intermediate iron product obtained from the smelting furnace being 0,1, (0.1) or higher. Gordon et al. ‘174 teaches a slag composition wherein the total of CaO, MgO, and SiO2 is 67.3% the total contents thereof, meeting the limitations of the instant Claim for exceeding 2/3 [0046]. As defined by Applicant as set forth in the Claim Interpretation above, the slag has a basicity (CaO+MgO)/SiO2 of approximately 1.98 [0046], meeting the limitations of the instant Claim.
Gordon et al. ‘174 does not expressly teach the composition of its iron ore.
However, NPL Nokhrina et al. teaches direct reduction of an iron ore having an ore content of 52.3% iron, 19.15% SiO2, and 0.072% P2O5 (Table 2).
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to reduce the ore of NPL Nokhrina et al. in the process of Gordon et al. ‘174 in order to increase the processing efficiency of low-grade iron based on the teaching of NPL Nokhrina et al. at (Introduction).
Notwithstanding the 112(b) rejections above, Gordon et al. ‘174 teaches introducing one or more flux materials into the smelting furnace in connection with the smelting process [0044] so as to adjust slag composition wherein the smelting furnace is an electric furnace having a plurality of electrodes.
Gordon et al. ‘174 does not expressly teach the electric furnace is of a non-tilting type or the capacity.
However, NPL Mendes De Paula teaches continuous steelmaking by direct reduction of iron in a conventional gas shaft furnace, and sending the direct reduced iron to a stationary, non-tilting-type electric furnace having a holding capacity of over 1000 tonnes iron (overlapping the instantly claimed range of between 1000 – 3000 tonnes iron (Pages 34-35).
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to conduct the process of Gordon et al. ‘174 in the furnace of NPL Mendes De Paula in order to increase production efficiency.
Gordon et al. ‘174 does not expressly teach adding carbon containing solid to the intermediate iron product.
However, Eder et al. ‘465 teaches admixing dry, fine particulate material containing carbon (introducing carbon) and fine particulate iron ore together with fine particulate direct reduced iron, so as to increase a carbon content of an obtained intermediate iron product produced by direct reduction such that is the composition of dry admixture is maintained below 10% by weight [0013] in order to maintain the strength of the iron product and reduce the need for energy carriers including coal [0011, 0026], overlapping the instantly claimed range.
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to add solid carbon carrier materials to the direct reduced iron of Gordon et al. ‘174 so as to increase a carbon content of the obtained intermediate iron product to be less than 10% by mass, overlapping the instantly claimed range of 1% - 4% by mass, in order to reduce energy consumption based on the teachings of Eder et al. ‘465 at [0011].
As set forth above, the limitation regarding a percentage of carbon is unclear. Nonetheless, adding solid carbon to direct reduced iron is known, and it would have been obvious to one having ordinary skill in the art at the time of filing the invention to add carbon in an amount overlapping the instantly claimed range. See MPEP 2144.05. In cases where claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990). Generally, differences in concentration or temperature will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such concentration or temperature is critical. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation." In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955).
Gordon et al. ‘174 modified with the addition of a carbonaceous reductant teaches the limitations set forth above. Gordon et al. ‘174 does not expressly teach adding carbon containing content to the intermediate iron product.
However, Romenets et al. ‘734 teaches charging solid carbon fuel (a carbon containing solid) together with direct reduced iron reduced iron, such that said carbon is carried along with the direct reduced iron into a molten bath, in order to increase processing efficiency of an intermediate iron product in a continuous steelmaking process (Column 3 Lines 42-46),(Column 4/Lines 45-59).
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to charge carbon containing solid into the smelting furnace of Gordon et al. ‘174 together with direct reduced iron in order to increase processing efficiency.
Notwithstanding the 112(b) rejections above, Romenets et al. ‘734 teaches charging solid carbon fuel (a carbon containing solid) together with direct reduced iron reduced iron, but does not expressly teach the materials are stored separately.
However, Iwasaki et al. ‘038 teaches a method and apparatus for charging multiple raw materials, stored separately before being introduced into an electric arc furnace with a feed chute (meeting the limitation for a feed tube) and the raw materials are stored in material receiving hoppers (meeting the limitation for a heap above a slag layer) [0402, 0278, 0770].
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to store the charge materials of the process of modified Gordon et al. ‘174 separately as a heap above a slag layer in order to improve the efficiency of steelmaking. The charging chute of Iwasaki et al. ‘038 entrains the materials which are mixed prior to introduction into a smelting furnace and are fed into a molten bath [0755], meeting the limitations of instant Claims 25, 28, and 40.
Regarding Claim 26, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0046] an exemplary slag obtained from the smelting process comprises a calcium oxide (CaO) content of 34.7, an aluminum oxide (Al2O3) content of 12.0, a silica (SiO2) content of 22.6%, and a magnesium oxide (MgO) content of 10.0%, meeting the limitations of the instant Claim.
Regarding Claim 27, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches gas-based direct reduction at [0043], meeting the limitations of the instant Claim.
Regarding Claim 31, modified Gordon et al. ‘174 teaches the limitations set forth above. Notwithstanding the 112(b) rejections above, Gordon et al. ‘174 further teaches at [0023] carrying out steel conversion in a ladle furnace.
Further, Ito et al. ‘539 teaches [0083] conducting continuous steel conversion in a converter, meeting the limitations of the instant Claim.
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to conduct continuous steel conversion in a converter in order to reduce costs and increase efficiency, meeting the limitations of the instant Claim.
Regarding Claim 32, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0046] a carbon content of 0.10% by weight. As set forth above, Ito et al. ‘539 teaches adding carbonaceous materials, introducing carbon, so as to increase a carbon content of an obtained intermediate iron product produced by direct reduction such that it is maintained below 4.5% [0058] in order to maintain the strength of the iron product, meeting the limitations of the instant Claim for reducing carbon content of the steel obtained to no more than 25% by weight of the original carbon content of the intermediate iron product.
Regarding Claim 33, modified Gordon et al. ‘174 teaches the limitations set forth above.
Gordon et al. ‘174 does not expressly teach subjecting the intermediate iron product to a desulphurization process.
However, Ito et al. ‘539 teaches desulfurizing the intermediate iron product within a continuous smelting process prior to introduction into the steel conversion unit [0007-0008].
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to desulfurize the intermediate iron product of Gordon et al. ‘174 prior to introduction into the steel conversion unit, in order to increase the material strength of the intermediate iron product and improve the quality of the product, based on the teachings of Ito et al. ‘539 at [0007-0008].
Regarding Claim 34, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0037] charging up to 20% of external scrap into the smelting furnace, overlapping the instantly claimed range of no more than 1% of external scrap, meeting the limitations of the instant Claim.
See MPEP 2144.05. In cases where claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990). Generally, differences in concentration or temperature will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such concentration or temperature is critical. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation." In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955).
Regarding Claim 35, Gordon et al. ‘174 modified by Iwasaki et al. ‘038 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at (Figure 1) direct reduced iron is introduced into the furnace between an electrode and a lateral wall. Gorden et al. ‘174 teaches charging direct reduced iron from one or more hoppers vertically above the electric arc furnace charging ports, but does not detail the spacing dimensions.
However, such a change would constitute a rearrangement of parts obvious to one of ordinary skill at the time of filing the invention. See MPEP 2144.04VI A., C. It would have been obvious to one having ordinary skill in the art at the time of filing the invention to charge the material of the hoppers of modified Gordon et al. ‘174 at a distance above the slag layer, and at a position having a distance from the lateral wall that is closer to the wall than to the electrodes, in order to not interfere with the electrodes of the furnace, and to ensure sufficient melting. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation." In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955).
Regarding Claim 36, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0032] the furnace is an open slag bath furnace, meeting the limitations of the instant Claim.
Regarding Claim 37, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at (Figure 1) the furnace has six electrodes arranged in a six-in-line configuration, meeting the limitations of the instant Claim.
Regarding Claim 38, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0019] the furnace has a width dimension and a length dimension, wherein the length (27 meters) is 3 times the width dimension (9 meters), meeting the limitations of the instant Claim for at least 2.5 times the width dimension.
See MPEP 2144.05. In cases where claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990). Generally, changes in shape will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such shape is critical. See MPEP 2141.01(a) I.
Regarding Claim 39, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0019] an electric arc furnace of a rectangular shape, meeting the limitations of the instant Claim.
Regarding Claim 41, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 further teaches at [0046] an exemplary slag obtained from the smelting process comprises a calcium oxide (CaO) content of 34.7%, an aluminum oxide (Al2O3) content of 12.0%, a silica (SiO2) content of 22.6%, and a magnesium oxide (MgO) content of 10.0%, meeting the limitations of the instant Claim.
Claims 29 and 30 are rejected under 35 U.S.C. 103 as being unpatentable over Gordon et al. US 20050179174 A1 as evidenced by NPL Furlani et al. in view of, NPL Nokhrina et al., NPL Mendes De Paula, Eder et al. US 20120328465 A1, Romenets et al. US 4913734 A, and Iwasaki et a. US 20030047038 A1 as applied to claims 25-28, 31-39, and 41 above, further in view of NPL Mathieson et al.
Regarding Claim 29, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 does not expressly teach the carbon containing solid is of a non-fossil or recycled origin.
However, NPL Mathieson et al. teaches at (Section 19.1.2) using biomass as a carbon containing solid within the direct reduction of iron in order to reduce carbon dioxide emission.
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to utilize biomass as the carbonaceous material in the direct iron reduction process of Gordon et al. ‘174 in order to reduce carbon dioxide emissions based on the teachings of NPL Mathieson et al. at (Sections 19.1.1-2), meeting the limitations of the instant Claim.
Regarding Claim 30, modified Gordon et al. ‘174 teaches the limitations set forth above. Gordon et al. ‘174 does not expressly teach the contents of gas used in the reduction process.
However, NPL Mathieson et al. teaches at (Section 19.1.1) using hydrogen as reducing gas the direct reduction of iron in order to reduce carbon dioxide emission.
It would have been obvious to one having ordinary skill in the art at the time of filing the invention to utilize hydrogen as the reductant in the reduction process of Gordon et al. ‘174 in order to reduce carbon dioxide emissions based on the teachings of NPL Mathieson et al. at (Sections 19.1.1-2), meeting the limitations of the instant Claim.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure:
US 3912501 A teaches forming a homogeneous admixture of ore and coal in the direct reduction of iron.
Liang, Zhikai, et al. "A novel and green metallurgical technique of highly efficient iron recovery from refractory low-grade iron ores." ACS Sustainable Chemistry & Engineering 7.22 (2019): 18726-18737. Teaches iron recovery from ultra-low grade iron ore by injecting coal into the ore.
EP 2851436 B1 teaches a method for charging a blast furnace with a rotating chute.
Jiang, Yi, et al. "Characteristics of steel slags and their use in cement and concrete—A review." Resources, Conservation and Recycling 136 (2018): 187-197. teaches designs for a standard ladle furnace and standard electric arc furnace used in the process of steelmaking.
EP 1445334 A1 teaches a longstanding practice of dual hopper charging into a blast furnace.
US 20040076539 A1 teaches carburizing reduced iron to decrease the melting point.
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/M.S.S./Examiner, Art Unit 1733
/Tima M. McGuthry-Banks/Primary Examiner, Art Unit 1733
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