UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 13D
                    UNDER THE SECURITIES EXCHANGE ACT OF 1934



                                 Hydril Company
- --------------------------------------------------------------------------------
                                (Name of Issuer)

                          Common Stock, par value $0.50
- --------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    448774109
- --------------------------------------------------------------------------------
                                 (CUSIP Number)

                            Mr. Fernando R. Mantilla
                      Av. Leandro N. Alem 1067, 27th Floor
                          1001--Buenos Aires, Argentina
                                (54-11) 4018-2254
           (Name, Address and Telephone Number of Person Authorized to
             Receive Notices and Communications)

                                February 11, 2007
                   -----------------------------------------
             (Date of Event which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following
box.

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 (the "Act") or otherwise subject to the liabilities of that section of the
Act but shall be subject to all other provisions of the Act (however, see the
Notes).



CUSIP No. 448774109                                          Page 2 of 11 Pages

- --------------------------------------------------------------------------------
          NAME OF REPORTING PERSONS
   1      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

          Rocca & Partners S.A.
- --------------------------------------------------------------------------------
   2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP              (A) [_]
          (See Instructions)                                            (B) [_]
- --------------------------------------------------------------------------------
   3      SEC USE ONLY
- --------------------------------------------------------------------------------
   4      SOURCE OF FUNDS (See Instructions)

          N/A
- --------------------------------------------------------------------------------
   5      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
          TO ITEMS 2(d) OR 2(e)                                             [_]
- --------------------------------------------------------------------------------
   6      CITIZENSHIP OR PLACE OF ORGANIZATION

          British Virgin Islands
- --------------------------------------------------------------------------------
                       7    SOLE VOTING POWER

                            0
                      ----------------------------------------------------------
                       8    SHARED VOTING POWER
 NUMBER OF SHARES
BENEFICIALLY OWNED          1,035,208
 BY EACH REPORTING    ----------------------------------------------------------
    PERSON WITH        9    SOLE DISPOSITIVE POWER

                            0
                      ----------------------------------------------------------
                      10    SHARED DISPOSITIVE POWER

                            0
- --------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,035,208
- --------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
          (See Instructions)                                                 [_]
- --------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          5.38%
- --------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON (See Instructions)

          CO
- --------------------------------------------------------------------------------

                               Page 2 of 11 Pages


CUSIP No. 448774109                                          Page 3 of 11 Pages

- --------------------------------------------------------------------------------
          NAME OF REPORTING PERSONS
   1      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

          San Faustin N.V.
- --------------------------------------------------------------------------------
   2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP              (A) [_]
          (See Instructions)                                            (B) [_]
- --------------------------------------------------------------------------------
   3      SEC USE ONLY
- --------------------------------------------------------------------------------
   4      SOURCE OF FUNDS (See Instructions)

          N/A
- --------------------------------------------------------------------------------
   5      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
          TO ITEMS 2(d) OR 2(e)                                             [_]
- --------------------------------------------------------------------------------
   6      CITIZENSHIP OR PLACE OF ORGANIZATION

          Netherlands Antilles
- --------------------------------------------------------------------------------
                       7    SOLE VOTING POWER

                            0
                      ----------------------------------------------------------
                       8    SHARED VOTING POWER
 NUMBER OF SHARES
BENEFICIALLY OWNED          1,035,208
 BY EACH REPORTING    ----------------------------------------------------------
    PERSON WITH        9    SOLE DISPOSITIVE POWER

                            0
                      ----------------------------------------------------------
                      10    SHARED DISPOSITIVE POWER

                            0
- --------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,035,208
- --------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
          (See Instructions)                                                 [_]
- --------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          5.38%
- --------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON (See Instructions)

          CO
- --------------------------------------------------------------------------------

                               Page 3 of 11 Pages


CUSIP No. 448774109                                          Page 4 of 11 Pages

- --------------------------------------------------------------------------------
          NAME OF REPORTING PERSONS
   1      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

          I.I.I. Industrial Investments Inc.
- --------------------------------------------------------------------------------
   2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP              (A) [_]
          (See Instructions)                                            (B) [_]
- --------------------------------------------------------------------------------
   3      SEC USE ONLY
- --------------------------------------------------------------------------------
   4      SOURCE OF FUNDS (See Instructions)

          N/A
- --------------------------------------------------------------------------------
   5      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
          TO ITEMS 2(d) OR 2(e)                                             [_]
- --------------------------------------------------------------------------------
   6      CITIZENSHIP OR PLACE OF ORGANIZATION

          Cayman Islands
- --------------------------------------------------------------------------------
                       7    SOLE VOTING POWER

                            0
                      ----------------------------------------------------------
                       8    SHARED VOTING POWER
 NUMBER OF SHARES
BENEFICIALLY OWNED          1,035,208
 BY EACH REPORTING    ----------------------------------------------------------
    PERSON WITH        9    SOLE DISPOSITIVE POWER

                            0
                      ----------------------------------------------------------
                      10    SHARED DISPOSITIVE POWER

                            0
- --------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,035,208
- --------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
          (See Instructions)                                                 [_]
- --------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          5.38%
- --------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON (See Instructions)

          CO
- --------------------------------------------------------------------------------

                               Page 4 of 11 Pages


CUSIP No. 448774109                                          Page 5 of 11 Pages

- --------------------------------------------------------------------------------
          NAME OF REPORTING PERSONS
   1      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

          Tenaris S.A.
- --------------------------------------------------------------------------------
   2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP              (A) [_]
          (See Instructions)                                            (B) [_]
- --------------------------------------------------------------------------------
   3      SEC USE ONLY
- --------------------------------------------------------------------------------
   4      SOURCE OF FUNDS (See Instructions)

          N/A
- --------------------------------------------------------------------------------
   5      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
          TO ITEMS 2(d) OR 2(e)                                             [_]
- --------------------------------------------------------------------------------
   6      CITIZENSHIP OR PLACE OF ORGANIZATION

          Luxembourg
- --------------------------------------------------------------------------------
                       7    SOLE VOTING POWER

                            0
                      ----------------------------------------------------------
                       8    SHARED VOTING POWER
 NUMBER OF SHARES
BENEFICIALLY OWNED          1,035,208
 BY EACH REPORTING    ----------------------------------------------------------
    PERSON WITH        9    SOLE DISPOSITIVE POWER

                            0
                      ----------------------------------------------------------
                      10    SHARED DISPOSITIVE POWER

                            0
- --------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,035,208
- --------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
          (See Instructions)                                                 [_]
- --------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          5.38%
- --------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON (See Instructions)

          CO
- --------------------------------------------------------------------------------

                               Page 5 of 11 Pages


ITEM 1.   SECURITY AND ISSUER.

         This statement on Schedule 13D (this "Schedule 13D") relates to the
Common Stock, par value $0.50 per share (the "Common Stock"), of Hydril Company
(the "Issuer"). The principal executive offices of the Issuer are located at
3300 N. Sam Houston Parkway East, Houston, Texas 77032.

         Each share of Class B Common Stock, par value $0.50 per share (the
"Class B Common Stock"), of the Issuer is convertible at the option of the
holder (or upon the occurrence of certain other events) into one Share of Common
Stock. This Schedule 13D is being filed with respect to the Common Stock in
accordance with Rule 13d-3(d)(i).

ITEM 2.   IDENTITY AND BACKGROUND.

         This Schedule 13D is being jointly filed by each of the following
persons pursuant to Rule 13d-1(k): Rocca & Partners S. A., San Faustin N.V.,
I.I.I. Industrial Investments Inc. and Tenaris S.A. ("Tenaris") (collectively,
the "Reporting Persons"). The name, place of organization, principal business
and business address of each Reporting Person is set forth on Schedule I-A and
is incorporated into this Item 2 by reference.

         The name, present principal occupation or employment (and the name,
principal business and address of any corporation or other organization in which
such employment is conducted) and citizenship of each director of each Reporting
Person is set forth in Schedule I-B and is incorporated into this Item 2 by
reference. The name, present principal occupation or employment (and the name,
principal business and address of any corporation or other organization in which
such employment is conducted) and citizenship of each executive officer of each
Reporting Person is set forth in Schedule I-B and is incorporated into this Item
2 by reference.

         During the last five years, none of the Reporting Persons, nor, to the
knowledge of the Reporting Persons, none of the persons listed on Schedule I-B
has (i) been convicted in a criminal proceeding (excluding traffic violations or
similar misdemeanors) or (ii) been a party to a civil proceeding of a judicial
or administrative body of competent jurisdiction and as a result of such
proceeding was or is subject to a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to federal
or state securities laws or finding any violation with respect to such laws.

         Information with respect to each of the Reporting Persons is given
solely by such Reporting Person, and no Reporting Person assumes responsibility
for the accuracy or completeness of information given by another Reporting
Person.

ITEM 3.   SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

         The Voting Agreement described in Item 4 of this Schedule 13D (the
terms of which are hereby incorporated by reference) was entered into by
Christopher T. Seaver, Patrick T. Seaver, Richard C. Seaver Living Trust and
Richard C. Seaver (collectively, the "Stockholders") and Tenaris S.A. The
Stockholders entered into the Voting Agreement as an inducement to Tenaris to
enter into the Merger Agreement described in Item 4 (the terms of which are
hereby


                               Page 6 of 11 Pages


incorporated by reference). Tenaris did not pay consideration to the
Stockholders in connection with the execution and delivery of the Voting
Agreement and thus no funds were used for such purpose.

         None of the individuals listed on Schedule I-B has contributed any
funds or other consideration towards the purchase of securities of the Issuer,
nor do the individuals listed on Schedule I-B own any of the Issuer's shares of
Common Stock or Class B Common Stock.

ITEM 4.   PURPOSE OF THE TRANSACTION.

         (a)-(b) On February 11, 2007, the Issuer, Tenaris and Hokkaido
Acquisition, Inc. ("Merger Sub") entered into an Agreement and Plan of Merger,
which provides that Merger Sub will be merged with and into the Issuer (the
"Merger") and the Issuer will become an indirect wholly owned subsidiary of
Tenaris. Pursuant to the Merger, each outstanding share of Common Stock and each
outstanding share of Class B Common Stock will be converted into the right to
receive $97.00 per share in cash. A copy of the Merger Agreement is included as
Exhibit 2.1 hereto and the description of the Merger Agreement herein is
qualified in its entirety by reference to Exhibit 2.1, which is incorporated
herein by reference.

         In connection with the execution of the Merger Agreement, in order to
induce Tenaris to enter into the Merger Agreement, the Stockholders entered into
the Voting Agreement, dated as of February 11, 2007 with Tenaris. Pursuant to
the Voting Agreement, each Stockholder agreed, among other things, to vote (or
cause to be voted), in person or by proxy, the number of shares of Common Stock
and shares of Class B Common Stock listed in the Voting Agreement and any shares
such Stockholder purchases or otherwise acquires beneficial ownership of, or
acquires the right to vote after the execution of the Voting Agreement (i) in
favor of adoption of the Merger Agreement and any other action of the Issuer's
stockholders required in furtherance thereof, (ii) against any action or
agreement submitted for approval of the stockholders of the Issuer that is
reasonably likely to result in a breach of any covenant, representation or
warranty or any other obligation or agreement of the Issuer contained in the
Merger Agreement or of such Stockholder contained in the Voting Agreement or
result in any conditions to Tenaris's obligations under the Merger Agreement not
being satisfied; (iii) against any Acquisition Proposal (as defined in the
Merger Agreement) or any other action, agreement or transaction submitted for
approval to the stockholders of the Issuer that could reasonably be expected to
materially impede, interfere or be inconsistent with, delay, postpone,
discourage or materially and adversely affect the Merger or the Voting Agreement
and (iv) in favor of any other matter required to facilitate the consummation of
the transactions contemplated by the Merger Agreement.

         The Voting Agreement will terminate upon the earlier to occur of (i)
the effective time of the Merger (ii) the date and time of termination of the
Merger Agreement in accordance with its terms and (iii) the date of any
amendment to the Merger Agreement that would reduce the per share merger
consideration to be paid pursuant to the Merger Agreement. A copy of the Voting
Agreement is included as Exhibit 2.2 hereto and the description of the Voting
Agreement contained herein is qualified in its entirety by reference to Exhibit
2.2, which is incorporated herein by reference.


                               Page 7 of 11 Pages


         (c) No determination has been made with respect to the sale or transfer
of a material amount of assets of the Issuer or any of its subsidiaries.

         (d) It is intended that upon consummation of the Merger, the directors
of Merger Sub shall be the directors of the Surviving Corporation (as defined in
the Merger Agreement), until their successors have been duly elected or
appointed and qualified or until their earlier death, resignation or removal.

         (e) No determinations have been made regarding material changes in the
Issuer's present capitalization or dividend policy.

         (f) Upon consummation of the Merger, the Issuer will become a wholly
owned subsidiary of Tenaris.

         (g) Pursuant to the Merger Agreement, upon consummation of the Merger,
the certificate or incorporation of the Issuer will become the certificate of
incorporation of the Surviving Corporation, except that Article Fourth of the
certificate of incorporation shall be amended to read in its entirety as
follows: "The aggregate number of shares that the Corporation shall have the
authority to issue is 1,000 shares of Common Stock, par value $0.50 per share."

         (h) The Merger Agreement provides that the Surviving Corporation shall,
as promptly as practicable after consummation of the merger, cause the shares of
Common Stock to no longer be quoted on NASDAQ.

         (i) Upon consummation of the Merger, the shares of Common Stock will
become eligible for termination of registration pursuant to Section 12(g)(4) of
the Securities Exchange Act of 1934, as amended.

         (j) Other than as described above, the Reporting Persons currently have
no plans or proposals which relate to, or may result in, any of the matters
listed in Items 4(a)-(i) of this Schedule 13D (although the Reporting Persons
reserve the right to develop such plans).

The description contained in this Item 4 of the transactions contemplated by the
Merger Agreement and the Voting Agreement is qualified in its entirety by
reference to the full texts of the Merger Agreement and the Voting Agreement,
the terms of each of which are incorporated herein by reference to Exhibits 2.1
and 2.2 hereto. Except as set forth in this Schedule 13D, the Merger Agreement
and the Voting Agreement, none of the Reporting Persons or, to the best of each
the Reporting Person's knowledge, any of the individuals or entities named in
Schedule I-B hereto, has any plans or proposals which relate to or which would
result in or relate to any of the actions specified in subparagraphs (a) through
(j) of Item 4 of Schedule 13D.

ITEM 5.   INTEREST IN THE SECURITIES OF THE ISSUER.

         (a)-(b) Pursuant to the Voting Agreement, the Stockholders have agreed
to vote 2,956 shares of Common Stock and 1,032,252 shares of Class B Common
Stock in the manner described in Item 4. Based on the Issuer's representation in
the Merger Agreement that there were 18,218,963 shares of Common Stock
outstanding as of February 8, 2007 and assuming 1,032,252 shares of Class B
Common stock are converted into the same number of shares of Common Stock, the
shares subject to the Voting Agreement represent, on an as-converted basis,
approximately 5.38% of the issued


                               Page 8 of 11 Pages



and outstanding shares of Common Stock. The Reporting Persons disclaim
beneficial ownership of the shares subject to the Voting Agreement, and this
Schedule 13D shall not be construed as an admission that any Reporting Person
is, for any or all purposes, the beneficial owner of the securities covered by
this Schedule 13D.

         (c) Except as described in this Schedule 13D, there have been no
transactions in the shares of Common Stock or Class B Common Stock effected by
the Reporting Persons or, to the best of the Reporting Person's knowledge, any
person or entity identified on Schedule I-B hereto, during the last 60 days.

         (d) Not applicable.

         (e) Not applicable.

ITEM 6.   CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH
          RESPECT TO SECURITIES OF THE ISSUER.

         The information set forth under Items 3, 4 and 5 and the Merger
Agreement and the Voting Agreement set forth on Exhibit 2.1 and Exhibit 2.2,
respectively, are incorporated herein by reference. As described in Item 4,
Tenaris anticipates it will acquire the entire equity interest in the Issuer
pursuant to the Merger Agreement.

         Other than the Merger Agreement and the Voting Agreement, there are no
contracts, arrangements, understandings or relationships (legal or otherwise)
among the Reporting Persons or, to the best of the Reporting Person's knowledge,
any person listed on Schedule I-B hereto, and any person with respect to the
shares of Common Stock or Class B Common Stock.

ITEM 7.   MATERIAL TO BE FILED AS EXHIBITS.

EXHIBIT
NUMBER     TITLE

   1       Merger Agreement, dated as of February 11, 2007, among Hydril
           Company, Tenaris S.A. and Hokkaido Acquisition, Inc. (incorporated
           by Reference to Exhibit 2.1 to the Current Report on Form 8-K of
           Hydril Corporation filed with the Securities and Exchange Commission
           on February 12, 2007)

   2       Voting Agreement, dated as of February 11, 2007, between Tenaris
           S.A. and Christopher T. Seaver, Patrick T. Seaver,  Richard C.
           Seaver Living Trust and Richard C. Seaver (incorporated by reference
           to Exhibit 2.1 to the Current Report on Form 8-K of Hydril Company
           filed with the Securities and Exchange Commission on February 15,
           2007)

   3       Joint Filing Agreement


                                    SIGNATURE

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

February 21, 2007

                                        ROCCA & PARTNERS S.A.

                                        By: /s/ Gianfelice Mario Rocca
                                            ------------------------------------
                                            Name:   Gianfelice Mario Rocca
                                            Title:  President


                                        SAN FAUSTIN N.V

                                        By: /s/ Roberto Bonatti
                                            ------------------------------------
                                            Name:   Roberto Bonatti
                                            Title:  President


                                        I.I.I. INDUSTRIAL INVESTMENTS INC.

                                        By: /s/ Paolo Rocca
                                            ------------------------------------
                                            Name:   Paolo Rocca
                                            Title:  President


                                        TENARIS S.A.

                                        By: /s/ Paolo Rocca
                                            ------------------------------------
                                            Name:   Paolo Rocca
                                            Title:  Chairman and Chief Executive
                                                    Officer



SCHEDULE I-A ------------ PLACE OF PRINCIPAL NAME OF REPORTING PERSON ORGANIZATION BUSINESS ADDRESS OF PRINCIPAL OFFICE - --------------------------------------------------------------------------------------------------- ROCCA & PARTNERS S.A. British Virgin Holding company Vanterpool Plaza, 2nd Floor, Islands Wickhams Cay I, Road Town, Tortola, British Virgin Islands SAN FAUSTIN N.V. Netherlands Holding company Berg Arrarat I, Curacao, Antilles Netherlands Antilles I.I.I. INDUSTRIAL Cayman Islands Holding company 69 Dr. Roy's Drive, INVESTMENTS INC. Georgetown, Grand Cayman, Cayman Islands TENARIS S.A. Luxembourg Holding company 46 A Ave John F Kennedy of steel tube - 2nd floor L-1855 manufacturing Luxembourg companies
SCHEDULE I-B ROCCA & PARTNERS SA DIRECTORS OF ROCCA & PARTNERS SA - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Gianfelice Rocca Italian Via Monterosa 93 President of Rocca & Partners, Milan, Italy Chairman of San Faustin Anna Maria Rocca Bonatti Italian Via Maggiolini 1, Milan, Director of Rocca & Partners Italy Marcella Rocca Italian Gaspar Campos 325, 1638 Director of Rocca & Partners Vicente Lopez -Buenos Aires - Argentina Giovanni Sardagna Italian Av. Leandro N. Alem 1067, Director of San Faustin Buenos Aires - Argentina OFFICERS OF ROCCA & PARTNERS SA - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Gianfelice Rocca Italian Via Monterosa 93 President of Rocca & Partners, Milan, Italy Chairman of San Faustin Guido Bonatti Italian Via Monterosa 93 Treasurer of Rocca & Partners Milan, Italy Fernando R. Mantilla Argentinean Av. Leandro N. Alem 1067, Secretary of Rocca & Partners Buenos Aires - Argentina Andres Pineyro Argentinean Cerrito 1266, Buenos Assistant Secretary of Rocca & Aires, Argentina Partners Ursula Rosa Geiser Swiss Villa Maggio 2 Assistant Secretary of Rocca & Lugano, Switzerland Partners Cinzia Della Santa Swiss Villa Maggio 2 Assistant Secretary of Rocca & Lugano, Switzerland Partners Umberto Bocchini Swiss Av. Leandro N. Alem 1067, Assistant Secretary of Rocca & Buenos Aires - Argentina Partners
SAN FAUSTIN N.V. DIRECTORS OF SAN FAUSTIN N.V. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Gianfelice Rocca Italian Via Monterosa 93 President of Rocca & Partners, Milan, Italy Chairman of San Faustin Giansandro Bassetti Italian Via Monterosa 93 Vice Chairman of San Faustin Milan, Italy Guido Bonatti Italian Via Monterosa 93 Financial Advisor Milan, Italy Marco Drago Italian Via Monterosa 93 Chairman, Milan, Italy De Agostini SpA, Novara Vincenzo Figus Italian Via Monterosa 93 Attorney-at-Law Milan, Italy Gabriele Galateri Italian Via Monterosa 93 President, Mediobanca, Milan Milan, Italy Bruno Marchettini Italian Via Carnaghi 2 Director, Tenaris Milan, Italy Andres Pineyro Argentinean Cerrito 1266, Buenos President, Meridium SA, Buenos Aires, Argentina Aires Ludovico Rocca Italian Av. Leandro N. Alem 1067 Attorney-at-Law Buenos Aires, Argentina Paolo Rocca Italian Av. Leandro N. Alem 1067 Chairman and Chief Executive Buenos Aires, Argentina Officer of Tenaris Giovanni Sardagna Italian Av. Leandro N. Alem 1067 Attorney-at-Law Buenos Aires, Argentina OFFICERS OF SAN FAUSTIN N.V. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Roberto Bonatti Italian Av. Leandro N. Alem 1067 President of San Faustin N.V. Buenos Aires, Argentina Paolo Rocca Italian Av. Leandro N. Alem 1067 Vice President of San Faustin Buenos Aires, Argentina N.V., Chairman and Chief Executive Officer of Tenaris Pierluigi Molajoni American Via Monterosa 93 General Manager of San Faustin Milan, Italy N.V. Carlos Enrique Zandona Argentinean Av. Leandro N. Alem 1067 Treasurer of San Faustin N.V. Buenos Aires, Argentina Fernando R. Mantilla Argentinean Av. Leandro N. Alem 1067 Secretary of San Faustin N.V. Buenos Aires, Argentina Umberto Bocchini Italian Av. Leandro N. Alem 1067 Assistant Secretary of San Buenos Aires, Argentina Faustin N.V. Stefano Gnecchi Ruscone Italian Via Monterosa 93 Assistant Secretary of San Milan, Italy Faustin N.V.
I.I.I. INDUSTRIAL INVESTMENT INC. DIRECTORS OF I.I.I. INDUSTRIAL INVESTMENTS INC. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Giansandro Bassetti Italian Av. Leandro Alem 1067, Vice-Chairman of San Faustin Buenos Aires, Argentina Guido Bonatti Italian Via Monterosa 93 Financial Advisor Milan, Italy Roberto Bonatti Italian Av. Leandro N. Alem 1067 President of San Faustin Buenos Aires, Argentina Gianfelice Rocca Italian Via Monterosa 93 Chairman of San Faustin Milan, Italy Paolo Rocca Italian Av. Leandro N. Alem 1067 Chairman and Chief Executive Buenos Aires, Argentina Officer of Tenaris Carlos Manuel Franck Argentinean Av. Leandro N. Alem 1067 President of Santa Maria Buenos Aires, Argentina S.A.I.F. OFFICERS OF I.I.I. INDUSTRIAL INVESTMENTS INC. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Guido Bonatti Italian Via Monterosa 93 Vice-president of I.I.I. Milan, Italy Industrial Investments Inc. Ursula Rosa Geiser Swiss Villa Maggio 2 Treasurer & Assistant Lugano, Switzerland Secretary of I.I.I. Industrial Investments Inc. Fernando R. Mantilla Argentinean Av. Leandro N. Alem 1067 Secretary of I.I.I. Industrial Buenos Aires, Argentina Investments Inc. Umberto Bocchini Italian Av. Leandro N. Alem 1067 Assistant Secretary of I.I.I. Buenos Aires, Argentina Industrial Investments Inc. Caledonian Bank & Trust Ltd Cayman Island Caledonian House - George Assistant Secretary of I.I.I. Town, Grand Cayman, Industrial Investments Inc. Cayman Island
TENARIS S.A. DIRECTORS OF TENARIS S.A. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Roberto Bonatti Italian Av. Leandro Alem 1067, President of San Faustin Buenos Aires Argentina Carlos Manuel Franck Argentinean Av. Leandro N. Alem 1067, President of Santa Maria Buenos Aires S.A.I.F. Argentina Bruno Marchettini Argentinean Via Carnaghi 2 Board member of San Faustin, Milan, Italy Ternium and Siderar Robert Monti Argentinean Talcahuano No 826 Non-executive chairman of Piso 6 Trefoil Limited and member of Buenos Aires Argentina the board of Directors of Petrobras Energia, Transocean Offshore Drilling and of John Wood Group PLC Paolo Rocca Italian Av. Leandro N. Alem 1067, Chairman and Chief Executive Buenos Aires - Argentina Officer of Tenaris Gianfelice Rocca Italian Via Monterosa 93 Chairman of San Faustin Milan, Italy Jaime Serra Puche Mexican Prol. Paseo de la Reforma Chairman of SAI Consultores No 600-103 Piso 1 Santa Fe CP 01210. Mexico, D.F. Amadeo Vazquez y Vazquez Argentinean Austria No 2670 Buenos Chairman of the board of Aires - Argentina directors of Telecom Argentina S.A. Guillermo F. Vogel Mexican Campos Eliseos 400 Piso Vice Chairman of Tamsa 17 Col. Chapultepec Polanco. CP 11560. Mexico, D.F. OFFICERS OF TENARIS S.A. - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Paolo Rocca Italian Av. Leandro N. Alem 1067, Chairman and Chief Executive Buenos Aires - Argentina Officer of Tenaris Alberto Valsecchi Italian Av. Leandro N. Alem 1067, Chief Operating Officer of Buenos Aires - Argentina Tenaris Carlos Condorelli Argentinean Av. Leandro N. Alem 1067, Chief Financial Officer of Buenos Aires - Argentina Tenaris Alejandro Lammertyn Argentinean Av. Leandro N. Alem 1067, Supply Chain Director of Buenos Aires - Argentina Tenaris
OFFICERS OF TENARIS S.A. (CON'T) - --------------------------------------------------------------------------------------------------------- RESIDENCE OR BUSINESS PRESENT PRINCIPAL NAME CITIZENSHIP ADDRESS OCCUPATION - --------------------------------------------------------------------------------------------------------- Marco Radnic Argentinean Av. Leandro N. Alem 1067, Human Resources Director of Buenos Aires - Argentina Tenaris Marcelo Ramos Argentinean Dr. Jorge A. Simini 250, Quality Director of Tenaris Campana Buenos Aires -Argentina German Cura Argentinean Av. Leandro N. Alem 1067, Commercial Director of Tenaris Buenos Aires - Argentina German Cura Argentinean 2200 West Loop South, North American Area Manager of 8th floor Tenaris Houston, TX -USA Sergio de la Maza Mexican Km. 433.7 Carr. Central American Area Manager Mexico-Veracruz Via of Tenaris Xalapa, Veracruz-Mexico Guillermo Noriega Argentinean Dr. Jorge A. Simini 250, South American Area Manager of Campana Tenaris Buenos Aires -Argentina Vincenzo Crapanzano Italian Piazza Caduti 6 Luglio European Area Manager of 1944, 1 Tenaris Bergamo-Italy Claudio Leali Italian 1-10 Minamiwatarida, Managing Director, Japanese Kawasaki-ku, Kanagawa, Operations of Tenaris Kawasaki-Japan Tulio Chipoletti Brazilian Av. Dr. Gastao Vidigal Area Manager, Brazil, of Neto, 475 Cidade Nova Tenaris Pindamonhangaba Sao Paulo-Brazil Emyr Berbare Brazilian Av. Dr. Gastao Vidigal Director, Confab Equipamentos Neto, 475 Cidade Nova of Tenaris Pindamonhangaba Sao Paulo-Brazil Sergio Tosato Italian Piazza Caduti 6 Luglio Industrial Coordination 1944, 1 Director of Tenaris Bergamo-Italy Giancarlo Miglio Italian Av. Leandro N. Alem 1067, Information Technology Buenos Aires - Argentina Director of Tenaris Carlos Pappier Argentinean Av. Leandro N. Alem 1067, Planning Director of Tenaris Buenos Aires - Argentina Carlos San Martin Argentinean Dr. Jorge A. Simini 250, Technology Director of Tenaris Campana Buenos Aires -Argentina
                                                                      Exhibit 3


                             JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on Schedule 13D filed herewith
(and any amendments thereto), relating to the Common Stock, par value $0.50 per
share, of Hydril Company, is being filed jointly with the Securities and
Exchange Commission pursuant to Rule 13d-1(k)(1) under the Securities Exchange
Act of 1934, as amended, on behalf of each such person.

Dated: February 20, 2007

                                        ROCCA & PARTNERS S.A.

                                        By: /s/ Gianfelice Mario Rocca
                                            ------------------------------------
                                            Name:   Gianfelice Mario Rocca
                                            Title:  President


                                        SAN FAUSTIN N.V

                                        By: /s/ Roberto Bonatti
                                            ------------------------------------
                                            Name:   Roberto Bonatti
                                            Title:  President


                                        I.I.I. INDUSTRIAL INVESTMENTS INC.

                                        By: /s/ Paolo Rocca
                                            ------------------------------------
                                            Name:   Paolo Rocca
                                            Title:  President


                                        TENARIS S.A.

                                        By: /s/ Paolo Rocca
                                            ------------------------------------
                                            Name:   Paolo Rocca
                                            Title:  Chairman and Chief Executive
                                                    Officer