ArcelorMittal Atlantique Et Lorraine v. AK Steel Corp. ( 2018 )


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  •   United States Court of Appeals
    for the Federal Circuit
    ______________________
    ARCELORMITTAL ATLANTIQUE ET LORRAINE,
    ARCELORMITTAL,
    Plaintiffs-Appellants
    v.
    AK STEEL CORPORATION,
    Defendant-Appellee
    ______________________
    2017-1637
    ______________________
    Appeal from the United States District Court for the
    District of Delaware in No. 1:13-cv-00685-SLR, Judge Sue
    L. Robinson.
    ______________________
    Decided: November 5, 2018
    SEALED OPINION ISSUED: November 5, 2018
    PUBLIC OPINION ISSUED: November 14, 2018 *
    ______________________
    CONSTANTINE L. TRELA, JR., Sidley Austin LLP, Chi-
    cago, IL, argued for plaintiffs-appellants. Also represent-
    ed by HUGH ABRAMS, Shook Hardy & Bacon, LLP,
    * This opinion was originally filed under seal and has
    been unsealed in full.
    Chicago, IL; JEFFREY B. BOVE, Ratner Prestia, Wilming-
    ton, DE.
    CHRISTOPHER NEIL SIPES, Covington & Burling LLP,
    Washington, DC, argued for defendant-appellee. Also
    represented by JEFFREY HOWARD LERNER.
    ______________________
    Before REYNA, WALLACH, and HUGHES, Circuit Judges.
    REYNA, Circuit Judge.
    Appellants appeal from a grant of summary judgment
    of non-infringement. The U.S. District Court for the
    District of Delaware granted summary judgment as a
    matter of law after concluding Appellants’ infringement
    action was collaterally estopped. Because evidence indi-
    cates a material difference in the accused products in this
    action, collateral estoppel does not apply and the entry of
    summary judgment was error. We vacate and remand.
    BACKGROUND
    Plaintiff-Appellants ArcelorMittal Atlantique et Lor-
    raine and ArcelorMittal and Plaintiff-Appellants’ prede-
    cessor in interest, ArcelorMittal France (collectively
    “ArcelorMittal”) own 
    U.S. Patent No. 6,296,805
     (the “’805
    patent”) and two reissues of the ’805 patent, U.S. Patent
    Nos. RE44,153 (the “RE153 patent”) and RE44,940 (the
    “RE940 patent”). This appeal primarily involves the
    RE940 patent.
    1. Hot-Stamped Boron Sheets
    The asserted RE940 patent, issued June 10, 2014, re-
    lates to boron steel sheets with an aluminum-based
    coating that, when hot-stamped, become highly mechani-
    cally resistant. Mechanical resistance, or ultimate tensile
    strength (“UTS”), is measured in megapascals (“MPa”).
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION        3
    Hot-stamping is a thermal treatment process where
    steel blanks are rapidly heated, inserted into a stamping
    machine that contains special dies, stamped into a partic-
    ular shape, and then rapidly cooled, or quenched. See
    ArcelorMittal Fr. v. AK Steel Corp., 
    700 F.3d 1314
    , 1317–
    18 (Fed. Cir. 2012) (“ArcelorMittal I”). The hot-stamping
    process alters the crystalline microstructure of the steel,
    and thereby its UTS, by transforming at least a portion of
    the steel’s microstructure to a form known as martensite.
    
    Id.
     Steel with a martensitic microstructure is capable of
    having a high UTS. See 
    id.
     The hot-stamping process
    gives the steel significantly higher UTS than its pre-
    stamped state. 
    Id.
     Thus, two steel sheets of the same
    composition can have significantly different UTSs depend-
    ing on whether and how they have been thermally treat-
    ed. The high UTS of the hot-stamped steel is desirable for
    use in the production of auto parts.
    Independent claim 17 of the RE940 patent is repre-
    sentative of the asserted product-by-process claims and
    recites:
    17. A hot-rolled coated steel sheet comprising
    a hot-rolled steel sheet coated with an alu-
    minum or aluminum alloy coating, wherein
    said coated steel sheet is in the form of a de-
    livery coil and the steel in the sheet compris-
    es the following composition by weight:
    0.15%2017 WL 239344
    , at *2 & n.6 (D. Del. Jan.
    19, 2017). Evidence about the stamped AXN products
    indicated stamping by a single non-commercial “prototype
    shop” named Vehma. J.A. 1061–62. The evidence indi-
    cated that the stamped AXN product had a UTS that did
    not exceed 1,500 MPa. ArcelorMittal’s own expert testi-
    fied that, after hot-stamping, the AXN product had a UTS
    of 1,442 MPa. ArcelorMittal, 
    2017 WL 239344
    , at *2 &
    n.6. ArcelorMittal’s expert further testified that a UTS of
    1,442 MPa would be “equivalent to something that’s a
    little bit over 1,500 [MPa].” 
    Id. at *2
    . Evidence also
    indicated that Ford Motor Company sought to order steel
    sheets from AK Steel that were to be hot-stamped by a
    commercial hot-stamper for production of automobile
    parts, but that those orders were never fulfilled. 
    Id.
    The 2010 action proceeded to trial and, in January
    2011, resulted in a jury verdict of non-infringement under
    the doctrine of equivalents, “in part based on the lack of
    evidence of the hot-stamped steel sheet meeting the
    district court case, No. 1:13-cv-00685-SLR, filed in 2013
    and involving primarily the RE940 patent. A detailed
    summary of the 2010 action is set out in the opinions of
    this court in the prior appeals. See ArcelorMittal I, 700
    F.3d at 1317–19; ArcelorMittal Fr. v. AK Steel Corp., 
    786 F.3d 885
    , 887–88 (Fed. Cir. 2015); ArcelorMittal v. AK
    Steel Corp., 
    856 F.3d 1365
    , 1367–68 (Fed. Cir. 2017).
    Only the history relevant to this appeal is recited in this
    opinion.
    6       ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    limitation requiring a [UTS] of 1500 MPa.” 
    Id. at *3
    .
    ArcelorMittal appealed, and this court remanded after
    reversing in part on a separate issue.
    3. The 2013 Litigation
    In April 2013, while the 2010 case was on remand,
    ArcelorMittal filed the complaint related to this appeal.
    ArcelorMittal first asserted the RE153 patent and later
    amended the complaint to substitute the RE940 patent.
    AK Steel subsequently filed a motion to dismiss the case
    on the basis of collateral estoppel, arguing that the action
    was estopped by the verdict in the 2010 action. According
    to AK Steel, the accused products in this case—steel
    sheets marketed and sold under the trade name
    ULTRALUME—are the same as the AXN steel sheets in
    the 2010 case.
    In response, ArcelorMittal argued that new evidence,
    obtained after the 2011 verdict, established that AK
    Steel’s ULTRALUME products were materially different
    from the AXN products because the ULTRALUME sheets
    were hot-stamped to achieve a UTS exceeding 1,500 MPa.
    In particular, ArcelorMittal relied on a declaration by its
    employee, Marc Millius. The declaration provided that
    Mr. Millius became aware, as of December 2012, that AK
    Steel was supplying the market with steel sheets that
    were hot-stamped by a commercial hot-stamper 2 to a UTS
    exceeding 1,500 MPa.
    On April 19, 2016, the district court denied AK Steel’s
    motion to dismiss. The court allowed discovery, but
    limited it to a single deposition of an AK Steel representa-
    tive and the production of AK Steel’s manufacturing
    specifications for the period of 2010 to 2013. J.A. 538–39.
    2   The specific hot-stamper is referred to generically
    throughout this opinion to protect information designated
    by the parties as confidential.
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION      7
    The district court reasoned that limited discovery was
    necessary to resolve the question of whether the AK Steel
    products had changed since the 2010 case. 
    Id.
     The
    district court cautioned that it was “reluctant to simply
    open the doors to discovery without some modicum of
    proof (more substantive than the [Millius] declaration
    already submitted) that the accused steel sheet products
    have changed.” 
    Id.
     (emphasis added).
    After limited discovery concluded, AK Steel moved for
    summary judgment based on collateral estoppel. J.A. 1–2.
    In support, AK Steel argued that there was no evidence
    that its pre-stamped steel sheets or its conduct had
    changed since 2010. See J.A. 8–9; 564–66; 582. AK Steel
    reasoned that because the accused products were the
    same products found not to infringe in the 2010 action,
    collateral estoppel applied, and it was entitled to sum-
    mary judgment as a matter of law.
    In opposition, ArcelorMittal argued that the evidence
    before the district court now showed that AK Steel com-
    mercially marketed and supplied steel sheets to various
    auto producers that were hot-stamped to a UTS exceeding
    1,500 MPa. ArcelorMittal pointed to an AK Steel market-
    ing brochure describing how ULTRALUME products
    underwent hot-stamping that converted the steel’s crys-
    talline microstructure into martensite, and that hot-
    stamped steel sheets are sold as auto parts with a UTS of
    “1,400 MPa and higher.” J.A. 1095–1100. ArcelorMittal
    also submitted a supplemental declaration from Mr.
    Millius that provided detail on his observations that AK
    Steel’s sheets were hot-stamped to exceed a UTS of 1,500
    MPa (and supplied to a major auto manufacturer 3 in
    December 2012). The supplemental Millius declaration
    3    As with the hot-stamper referred to above, the
    specific auto manufacturer is referred to generically
    herein.
    8      ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    included an exhibit consisting of a slide from a webinar
    conducted by the auto manufacturer that he personally
    attended, which includes a bar graph that shows the auto
    manufacturer’s various suppliers of 1,500 MPa UTS steel
    sheets, including AK Steel and ArcelorMittal. J.A. 1362–
    66. According to the declaration and as shown on the
    slide, the bar on the graph representing steel supplied by
    AK Steel indicated a tensile strength exceeding 1,500
    MPa.
    Based on the evidence, ArcelorMittal requested addi-
    tional discovery under Federal Rule of Civil Procedure
    56(d). J.A. 1354–60. ArcelorMittal argued that addition-
    al discovery was necessary to present additional facts
    related to the accused products and business conduct
    subsequent to the verdict in the 2010 action. 
    Id.
     The
    district court denied the requested additional discovery
    and granted AK Steel’s motion for summary judgment of
    non-infringement.
    The district court agreed that ArcelorMittal’s in-
    fringement claims with respect to the RE940 patent were
    barred by collateral estoppel. ArcelorMittal, 
    2017 WL 239344
    , at *3–4. The district court found that “the prod-
    uct at issue is the same and cannot—prior to hot stamp-
    ing—be infringing as the steel sheets have a tensile
    strength of about 600 MPa.” 
    Id. at *3
    . The district court
    noted a lack of evidence in the 2010 case that AK Steel’s
    steel sheets were hot-stamped to achieve a UTS exceeding
    1,500 MPa. According to the district court, “[t]hat [AK
    Steel] may ship the steel sheets to a third party hot
    stamper on behalf of its purchaser is of no consequence to
    the infringement analysis.” 
    Id.
     The district court further
    noted that neither the chemistry of the steel sheets nor
    the tensile strength of the sheets as shipped by AK Steel
    were in dispute. 
    Id.
     The district court concluded that
    these facts foreclosed the possibility of direct infringe-
    ment. 
    Id.
     The district court also concluded that with no
    direct infringement, there could be no indirect infringe-
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION       9
    ment. 
    Id.
     at *4 (citing Limelight Networks, Inc. v. Akamai
    Techs., Inc., 
    134 S. Ct. 2111
    , 2115 (2014)).
    In denying ArcelorMittal’s request for additional dis-
    covery under Rule 56(d), the district court reasoned that
    discovery was unnecessary because, in its view, the evi-
    dence showed that auto manufacturers bought the steel
    sheets from AK Steel and shipped them to the hot-
    stampers or had AK Steel ship them on their behalf. 
    Id.
    at *3 & n.9. The district court also rejected ArcelorMit-
    tal’s arguments that its divided or indirect infringement
    theories could justify discovery. Id. at *4.
    DISCUSSION
    We review summary judgment rulings under the law
    of the relevant regional circuit, in this case the Third
    Circuit. See Intellectual Ventures I LLC v. Capital One
    Fin. Corp., 
    850 F.3d 1332
    , 1337 (Fed. Cir. 2017). The
    Third Circuit reviews the grant of summary judgment de
    novo. Gonzalez v. Sec’y of Dep’t of Homeland Sec., 
    678 F.3d 254
    , 257 (3d Cir. 2012). “When reviewing a grant of
    summary judgment, the court must view the facts in the
    light most favorable to the nonmoving party and draw all
    inferences in that party’s favor.” 
    Id.
     (internal quotation
    marks omitted). Similarly, whether collateral estoppel
    applies is a question of law, reviewed de novo. See Jean
    Alexander Cosmetics, Inc. v. L’Oreal USA, Inc., 
    458 F.3d 244
    , 248 (3d Cir. 2006).
    1. Collateral Estoppel of Non-infringement
    A primary issue in a collateral estoppel analysis with
    respect to non-infringement is whether the accused prod-
    uct is the same—i.e., the issue sought to be precluded is
    the same as that involved in the prior action—or whether
    the accused products have materially changed. The
    question on appeal, then, is whether changes, if any, in
    the accused products are “material” for the purpose of
    collateral estoppel application. We conclude that the
    10     ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    evidence in this case supports that the products are not
    materially the same.
    Under Third Circuit law, collateral estoppel applies
    when “(1) the issue sought to be precluded [is] the same as
    that involved in the prior action; (2) that issue [was]
    actually litigated; (3) it [was] determined by a final and
    valid judgment; and (4) the determination [was] essential
    to the prior judgment.” Anderson v. Comm’r, 
    698 F.3d 160
    , 164 (3d Cir. 2012) (quoting In re Graham, 
    973 F.2d 1089
    , 1097 (3d Cir. 1992)). Unless circumstances have
    materially changed such that they constitute controlling
    facts, “collateral estoppel remains applicable.” See Scoop-
    er Dooper, Inc. v. Kraftco Corp., 
    494 F.2d 840
    , 846 (3d Cir.
    1974). Where aspects of collateral estoppel involve sub-
    stantive issues of patent law, we apply Federal Circuit
    precedent. Aspex Eyewear, Inc. v. Zenni Optical Inc., 
    713 F.3d 1377
    , 1380 (Fed. Cir. 2013).
    In the patent context, the Federal Circuit has followed
    Supreme Court precedent and held that defensive collat-
    eral estoppel applies with respect to a patent’s validity if
    (1) the patent was found invalid in a prior case that
    proceeded to final judgment where all procedural oppor-
    tunities were available to the patentee; (2) the issues
    litigated were identical; and (3) the party against whom
    estoppel is applied had a full and fair opportunity to
    litigate. See Abbott Labs. v. Andrx Pharm., Inc., 
    473 F.3d 1196
    , 1203 (Fed. Cir. 2007) (summarizing Blonder–
    Tongue Labs., Inc. v. Univ. of Ill. Found., 
    402 U.S. 313
    ,
    330–33 (1971)). The court should determine “whether a
    patentee has had a full and fair chance to litigate the
    validity of his patent” by considering “whether without
    fault of his own the patentee was deprived of crucial
    evidence or witnesses in the first litigation.” 
    Id. at 333
    .
    Collateral estoppel may bar litigation in cases with differ-
    ent but related patents when there are common issues.
    See Amgen, Inc. v. Genetics Inst., Inc., 
    98 F.3d 1328
    , 1332
    (Fed. Cir. 1996).
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION        11
    With respect to non-infringement, where an alleged
    infringer prevails, the accused products gain non-
    infringing status and the alleged infringer acquires the
    status of a non-infringer to the extent that the accused
    products remain the same. Young Eng’rs, Inc. v. U.S. Int’l
    Trade Comm’n, 
    721 F.2d 1305
    , 1316 (Fed. Cir. 1983). If
    accused devices in a second suit remain “unchanged with
    respect to the corresponding claim limitations at issue in
    the first suit,” then the patentee is precluded from pursu-
    ing her claims a second time. Nystrom v. Trex Co., 
    580 F.3d 1281
    , 1285 (Fed. Cir. 2009). However, “conduct of a
    different nature from that involved in the prior litigation”
    will not be given preclusive effect. Young Eng’rs, 
    721 F.2d at 1316
    .
    Defensive collateral estoppel of non-infringement,
    therefore, may apply in the “limited circumstances[]
    where it is shown that a close identity exists between the
    relevant features of the accused device and the device
    previously determined to be [non-]infringing” such that
    they are “essentially the same.” See Yingbin-Nature
    (Guangdong) Wood Indus. Co. v. Int’l Trade Comm’n, 
    535 F.3d 1322
    , 1333 (Fed. Cir. 2008). “Accused devices are
    ‘essentially the same’ where the differences between them
    are merely ‘colorable’ or ‘unrelated to the limitations in
    the claim of the patent.’” Acumed LLC v. Stryker Corp.,
    
    525 F.3d 1319
    , 1324 (Fed. Cir. 2008) (quoting Foster v.
    Hallco Mfg. Co., 
    947 F.2d 469
    , 480 (Fed. Cir. 1991)); see
    also Brain Life, LLC v. Elekta Inc., 
    746 F.3d 1045
    , 1055
    (Fed. Cir. 2014) (observing that products that were not
    “materially different” from products at issue in prior
    litigation would bar the subsequent assertion of the same
    claims). The proponent of claim or issue preclusion bears
    the burden of showing that the accused devices are essen-
    tially the same as those in the prior litigation. See Young
    Eng’rs, 
    721 F.2d at 1316
     (claim preclusion); In re Katz
    Interactive Call Processing Patent Litig., 
    639 F.3d 1303
    ,
    1311 (Fed. Cir. 2011) (issue preclusion).
    12     ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    2. Evidence of Material Differences
    We conclude that AK Steel failed to meet its burden
    that the ULTRALUME products in the present action are
    materially the same as the AXN products in the 2010
    action, especially when the facts are viewed in the light
    most favorable to the non-movant, ArcelorMittal. In the
    2010 action, there was no evidence that the AK Steel AXN
    products met the “in excess of 1,500 MPa” UTS limitation
    or that any AXN products were commercially stamped
    and supplied to an auto manufacturer at all. In this
    action, there is evidence that AK Steel is a supplier of
    such products to at least one major auto manufacturer.
    The September 2016 supplemental Millius declaration
    supports the allegation that AK Steel is a supplier of steel
    sheets that have a UTS exceeding 1,500 MPa to the auto-
    producing industry. J.A. 1362–66. The declaration was
    supported by an exhibit of a presentation slide taken from
    a December 2012 auto manufacturer-hosted webinar that
    provided tensile test information for hot-stamped steel
    from several of the auto manufacturer’s suppliers. 
    Id.
    The auto manufacturer’s webinar slide, entitled “Tensile
    Strength Comparison by Supplier,” includes a bar graph
    representing tensile strengths of steel sheets that, accord-
    ing to the declaration, correspond to each supplier, includ-
    ing ArcelorMittal and AK Steel.           
    Id.
        For both
    ArcelorMittal and AK Steel, the graph indicates a UTS in
    excess of 1,500 MPa. 
    Id.
     Although the parties dispute
    the significance of the auto manufacturer’s tensile test
    data, it is significant that the auto manufacturer’s own
    2012 test data shows that AK Steel’s products were
    thermally treated to achieve a UTS in excess of 1,500
    MPa. J.A. 1364 ¶ 5, 1366. This evidence, when viewed in
    the light most favorable to ArcelorMittal as the non-
    movant, reflects a material difference in the accused
    product and AK Steel’s conduct since the 2011 verdict.
    See Anderson v. Liberty Lobby, Inc., 
    477 U.S. 242
    , 255
    (1986).
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION          13
    We disagree with AK Steel’s argument that this slide
    is “identical to the testing introduced in the [2010] [c]ase.”
    Appellee Br. 46. AK Steel points to testimony from Arce-
    lorMittal’s expert in the 2010 action who heat treated and
    tested several steel sheets from various suppliers, using
    what he called a “conservative heat treatment” that
    resulted in a UTS of 1,442 MPa. J.A. 705. But the auto
    manufacturer’s test data shows strengths of steel hot-
    stamped by a commercial hot-stamper (as named in the
    first Millius declaration) to meet the auto manufacturer’s
    commercial specifications. AK Steel in attorney argument
    characterizes the auto manufacturer’s test data as “exper-
    imental,” but there is no evidence supporting such a
    characterization. Compare Appellee Br. 46, with J.A.
    1364 ¶ 4. AK Steel’s attorney argument is not sufficient
    to rebut ArcelorMittal’s evidence. See Icon Health &
    Fitness, Inc. v. Strava, Inc., 
    849 F.3d 1034
    , 1043 (Fed. Cir.
    2017). In addition, that the auto manufacturer’s test data
    was prior to the RE940 patent’s issue date is not material.
    In the 2010 action, the evidence was that the AXN prod-
    ucts were of “experimental grade,” i.e., not for sale, and
    were thermally treated by the Vehma “prototype shop,”
    i.e., non-commercial hot-stamper; there was no evidence
    that those products were supplied to an auto manufactur-
    er. See ArcelorMittal, 
    2017 WL 239344
    , at *2, 1061–63;
    see also, e.g., J.A. 1065 (“The Vehma trial was rudimen-
    tary. . . . [It] should not, by any means, be used as a mass
    production trial.”). The evidence in this case indicates
    that the production process is no longer “rudimentary,”
    that commercial stampers are utilized, and that the
    stamped steel is being commercialized. This crucial
    evidence represents a material difference in the accused
    products and did not exist during the 2010 action.
    Finally, AK Steel’s own product brochure, made after
    the verdict in the 2010 action, lends further support to
    ArcelorMittal’s contention that AK Steel’s conduct and
    the accused products have changed. The brochure ex-
    14     ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    plains that blanks produced from ULTRALUME are hot-
    stamped to undergo “a phase transformation” to its micro-
    structure that results in “a high strength phase – marten-
    site.” J.A. 1089. The brochure advertises that this
    process “increases the tensile strength of the steel from
    approximately 600 MPa to 1,400 MPa and higher.” 
    Id.
    (emphasis added). AK Steel’s brochure is evidence in this
    action that supports an allegation that AK Steel is com-
    mercially marketing and supplying steel sheets to auto
    manufacturers that may exceed 1,500 MPa UTS after hot-
    stamping.
    At minimum, this evidence contravenes the undisput-
    ed evidence in the 2010 action that AXN steel sheets hot-
    stamped by Vehma did not exceed 1,500 MPa UTS, and
    that none of the stamped AXN sheets were supplied to, or
    used by, auto manufacturers. In aggregate, this evidence
    constitutes, as the district court put it, more than a modi-
    cum of proof that the accused products materially differ
    from those in the 2010 action with respect to claimed
    limitations. Differences with respect to the claimed
    limitations constitute changes in controlling facts, such
    that collateral estoppel does not apply. See Scooper
    Dooper, 
    494 F.2d at 846
    . For this reason, the district
    court erred in finding that the accused products cannot as
    a matter of law infringe and granting summary judgment
    of non-infringement on the basis of collateral estoppel.
    We express no opinion on whether the RE940 patent is
    actually infringed or who might infringe it, only that
    there is now evidence that the accused products, the
    stamped steel sheets originating from AK Steel and
    supplied to auto manufacturers, are materially different
    from the products in the 2010 action.
    3. The Relevance of Hot-Stamping
    The parties dispute the extent to which there may be
    differences in the chemical composition between the AXN
    and ULTRALUME products and the effect of those differ-
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION          15
    ences, but those are not the only facts relevant to the
    claim limitations at issue. Consistent with the claim
    language of the patent, the mechanical resistance of the
    accused products after the claimed thermal treatment,
    i.e., hot-stamping, which transforms the crystalline mi-
    crostructure of the steel (as opposed to its chemical com-
    position), is also relevant to the claim limitations at issue.
    The district court erred when it focused solely on the
    pre-stamped product and stated “[t]hat [AK Steel] may
    ship the steel sheets to a third party hot stamper on
    behalf of its purchaser is of no consequence to the in-
    fringement analysis.” ArcelorMittal, 
    2017 WL 239344
    , at
    *3. The asserted product-by-process claims are not di-
    rected to unstamped blanks that have not yet been sub-
    ject to the claimed thermal treatment process step. It is
    well established that “[e]ach element contained in a
    patent claim is deemed material to defining the scope of
    the patented invention.” Warner-Jenkinson Co. v. Hilton
    Davis Chem. Co., 
    520 U.S. 17
    , 29 (1997). As we have
    previously affirmed, “process terms in product-by-process
    claims serve as limitations in determining infringement.”
    Abbott Labs. v. Sandoz, Inc., 
    566 F.3d 1282
    , 1293 (Fed.
    Cir. 2009) (en banc) (quoting Atl. Thermoplastics Co. v.
    Faytex Corp., 
    970 F.2d 834
    , 846–47 (Fed. Cir. 1992)). An
    “inventor is absolutely free to use process steps to define
    [a] product” and “will not be denied protection.” Id. at
    1294. The court cannot ignore the inventor’s definition of
    her product. Id. In view of the claim language, the
    claimed thermal treatment process step, i.e., hot-
    stamping, and resulting UTS, is of significant conse-
    quence to the infringement analysis.
    The district court recognized that the jury verdict was
    based on a lack of evidence that AK Steel’s 2010 hot-
    stamped steel sheet met the claimed thermal treatment
    limitation requiring a UTS of 1,500 MPa. Yet in conclud-
    ing that the product now at issue cannot infringe, the
    district court instead focused on the accused product prior
    16     ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    to hot-stamping, having the same composition as the 2010
    products and a tensile strength of about 600 MPa. By
    simply focusing on the composition and mechanical re-
    sistance of the pre-processed, blank steel sheets, and by
    ignoring the claimed thermal treatment process step
    conducted by hot-stampers and the resulting UTS, the
    district court erred in determining whether a material
    claimed element in the patent as defined by the inventor
    had changed in the accused products. See ArcelorMittal,
    
    2017 WL 239344
    , at *3–4. Indeed, it is the thermal
    treatment and resulting UTS claim elements that Arce-
    lorMittal contends have changed since the 2011 jury
    verdict, making the now-accused products materially
    different from the products in the 2010 action.
    Contrary to the district court’s finding, that the ther-
    mal treatment is performed by a third party hot-stamper
    does not foreclose the possibility of direct infringement
    here. See 
    id.
     If the third party hot-stampers produce
    steel sheets with a UTS exceeding 1,500 MPa after ther-
    mal treatment, as ArcelorMittal alleges, the hot-stampers
    might very well directly infringe the RE940 patent.
    Therefore, the district court erred in dismissing Arce-
    lorMittal’s potential indirect infringement claims due to a
    lack of direct infringement. See 
    id.
     at *4 (citing Limelight
    Networks, 
    134 S. Ct. at 2115
    ).
    4. Additional Discovery Is Warranted
    In granting summary judgment, the district court de-
    nied ArcelorMittal’s request for additional discovery to
    oppose AK Steel’s motion for summary judgment under
    Rule 56(d). The district court based its decision on its
    finding that “the product at issue [in this case] is the
    same [as the product at issue in the 2010 case] and can-
    not—prior to hot stamping—be infringing as the steel
    sheets have a tensile strength of about 600 MPa.” Arce-
    lorMittal, 
    2017 WL 239344
    , at *3.
    ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION       17
    The standard of review for the district court’s deci-
    sions related to discovery under Rule 56(d) in the Third
    Circuit is abuse of discretion. Renchenski v. Williams,
    
    622 F.3d 315
    , 339 (3d Cir. 2010). To disturb such a deci-
    sion, “[a]ppellants must demonstrate that the district
    court’s action made it impossible to obtain crucial evi-
    dence.” Wisniewski v. Johns-Manville Corp., 
    812 F.2d 81
    ,
    90 (3d Cir. 1987) (internal quotation marks omitted).
    Additionally, “[a]n abuse of discretion may be established
    under Federal Circuit law by showing that the court made
    a clear error of judgment in weighing the relevant factors
    or exercised its discretion based on an error of law or
    clearly erroneous fact finding.” Wind Tower Trade Coal.
    v. United States, 
    741 F.3d 89
    , 95 (Fed. Cir. 2014) (quoting
    Qingdao Taifa Grp. Co. v. United States, 
    581 F.3d 1375
    ,
    1379 (Fed. Cir. 2009).
    As explained above, we conclude that new evidence of
    material differences in the accused products exists. This
    means that the district court erred in limiting discovery
    on the basis of the issues presented in the 2010 action.
    The denial of ArcelorMittal’s requested discovery kept it
    from obtaining crucial evidence. See Wisniewski, 
    812 F.2d at 90
    .
    Discovery is necessary to determine whether and to
    what extent AK Steel supplied auto manufacturers with
    steel sheets with a UTS in excess of 1,500 MPa after
    thermal treatment, its knowledge and intent in doing so,
    and the nature of the relationships between AK Steel, the
    hot-stampers, and the auto manufacturers during the
    relevant timeframe. On remand, we direct the district
    court to allow discovery as requested by ArcelorMittal
    under Rule 56(d) in its opposition to summary judgment.
    CONCLUSION
    Because evidence shows material differences between
    the accused product in this action and the product in
    18      ARCELORMITTAL ATLANTIQUE v. AK STEEL CORPORATION
    earlier litigation, the district court erred in applying
    collateral estoppel. We vacate and remand.
    VACATED AND REMANDED
    COSTS
    No costs.