Exhibit 4

                               SECOND AMENDMENT TO
                                CREDIT AGREEMENT


                                      Among


                         ALLEGHENY TELEDYNE INCORPORATED
                                 as the Borrower


                   THE FINANCIAL INSTITUTIONS PARTY THERETO
                                 as the Lenders


            BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION
                            THE CHASE MANHATTAN BANK
                                MELLON BANK, N.A.
                                       and
                         PNC BANK, NATIONAL ASSOCIATION
                               as Managing Agents


                                       and


                         PNC BANK, NATIONAL ASSOCIATION
                as the Documentation and Administrative Agent



                                   Dated as of

                                 March 24, 1998






                      SECOND AMENDMENT TO CREDIT AGREEMENT


            THIS SECOND AMENDMENT TO CREDIT  AGREEMENT (the "Second  Amendment")
made as of March 24, 1998 to that certain  Credit  Agreement  dated as of August
30,  1996 as  amended by the First  Amendment  to Credit  Agreement  dated as of
August 31, 1997 (the Credit  Agreement  together with the exhibits and schedules
thereto and all modifications,  amendments,  extensions, renewals, substitutions
or replacements  prior to the date hereof,  the "Existing  Agreement") among the
FINANCIAL  INSTITUTIONS  listed on the  signature  pages  hereto  and each other
financial  institution  which  from  time to time  becomes  a  party  hereto  in
accordance  with Section 9.6a  (individually  a "Lender"  and  collectively  the
"Lenders"),  BANK OF AMERICA NATIONAL TRUST AND SAVINGS  ASSOCIATION,  THE CHASE
MANHATTAN BANK, MELLON BANK, N.A. and PNC BANK, NATIONAL ASSOCIATION as Managing
Agents  (individually a "Managing Agent" and collectively the "Managing Agents")
and  PNC  BANK,   NATIONAL   ASSOCIATION,   a  national   banking   association,
Documentation  and  Administrative  Agent for the Lenders (in such  capacity the
"Agent").

                                   WITNESSETH:

            WHEREAS,  the Borrower and the initial  Lenders,  the Managing Agent
and the Agent entered into the Existing  Agreement pursuant to which the Lenders
made certain  financial  accommodations  available  to the Borrower  including a
Revolving Credit Commitment;

            WHEREAS,  the Borrower and the Lenders,  the Managing Agents and the
Agent desire to amend the Existing Agreement as set forth herein.

            NOW THEREFORE,  in  consideration  of the mutual premises  contained
herein and other good and valuable consideration, the Borrower and the Bank with
the intent to be legally bound hereby,  agree that the Existing  Agreement shall
be amended as follows:


                                    ARTICLE I

                        AMENDMENTS TO EXISTING AGREEMENT

            SECTION 1.01.  ADDITIONAL  DEFINITIONS.  Section 1.1 of the Existing
Agreement is hereby  amended such that the following  definition  shall be added
thereto in the appropriate alphabetical order:

            "Effective  Time of Merger"  means March 24, 1998 or such other date
and time when the Merger (as defined below) becomes effective.




            "Merger"  means the merger  pursuant  to the  Agreement  and Plan of
Merger  dated as of October 31, 1997 among  OREMET,  the  Borrower  and a wholly
owned Subsidiary of the Borrower pursuant to which (i) a wholly-owned Subsidiary
of the Borrower was merged with and into OREMET, with OREMET being the surviving
corporation of the merger and (ii) with certain limited  exceptions,  each share
of common stock of OREMET outstanding immediately prior to the Effective Time of
the Merger was automatically converted, at the Effective Time of the Merger into
the right to receive shares of the common stock of the Borrower.

            "OREMET"   means  Oregon   Metallurgical   Corporation,   an  Oregon
corporation  which prior to the Effective Time of the Merger was a publicly held
corporation  and  at  the  Effective  Time  of  the  Merger,  as  the  surviving
corporation of the Merger, became a wholly-owned Subsidiary of the Borrower. Any
reference to OREMET in the Agreement, in respect of an event or occurrence prior
to the  Effective  Time of the  Merger,  shall be a  reference  to  OREMET  as a
publicly held corporation,  and any reference to OREMET herein, in respect of an
event  or  occurrence  after  the  Effective  Time of the  Merger,  shall  be in
reference to OREMET as a wholly-owned Subsidiary of the Borrower.

            "Second  Amendment"  means the Second  Amendment to Credit Agreement
among the Borrower,  the Lenders,  the Managing Agents and the Agent dated as of
March 24, 1998.

            "Second Amendment Effective Date" shall mean March 24, 1998.

            "Year 2000 Problem" means the risk that computer  applications  used
by or for the  benefit of the  Borrower  and its  Subsidiaries  may be unable to
recognize and perform properly date sensitive  functions involving certain dates
prior to and any date after December 31, 1999.

            SECTION 1.02.  NEW SECTION 3.16.  The Existing Agreement shall be
amended by adding a new Section 3.16 which shall read as follows:

Section  3.16.  YEAR  2000  ANALYSIS.  The  Borrower  and its  Subsidiaries  are
reviewing the areas within their  respective  businesses  and  operations  which
could reasonably be expected to be adversely  affected by, and have developed or
are  developing  programs  to address on a timely  basis the Year 2000  Problem.
Based on such review and programs the Borrower reasonably believes that the Year
2000  Problem  will not have a Material  Adverse  Effect on the Borrower and its
Subsidiaries taken as a whole.

            SECTION  1.03.  AMENDMENT  TO  SECTION  4.11.  Section  4.11  of the
Existing Agreement is amended and restated in its entirety to read as follows:

Section  4.11.  OWNERSHIP  OF ALC, TI AND OREMET.  At all times  during the term
hereof the Borrower shall be the legal and beneficial owner of, and shall retain
all voting rights 
                                       2


relating to, all of the issued and  outstanding  capital stock of ALC and TI. At
all times during the term hereof  after the  Effective  Time of the Merger,  the
Borrower shall be the legal and beneficial owner of, and shall retain all voting
rights relating to, all of the issued and outstanding capital stock of OREMET.

            SECTION 1.04.  NEW SECTION  4.12.  The Existing  Agreement  shall be
amended by adding a new Section 4.12 which shall read as follows:

Section 4.12. YEAR 2000. The Borrower shall take all action  necessary to assure
the Borrower's  and its  Subsidiaries'  computer-based  systems are able, in all
material  respects,  to effectively  process data  including  dates on and after
January 1,  2000,  such that there  will be no  Material  Adverse  Effect on the
Borrower  and its  Subsidiaries  taken as a whole as a result  of the Year  2000
Problem.

            SECTION 1.05. NO OTHER AMENDMENTS OR WAIVERS.  The amendments to the
Existing  Agreement set forth in Sections 1.01 through 1.04  inclusive  above do
not either implicitly or explicitly alter,  waive or amend,  except as expressly
provided in this Second Amendment, the provisions of the Existing Agreement. The
amendments  set forth in Sections 1.01 through 1.04 hereof do not waive,  now or
in the future,  compliance  with any other  covenant,  term or  condition  to be
performed  or  complied  with nor do they  impair any rights or  remedies of the
Lenders  or the Agent  under the  Existing  Agreement  with  respect to any such
violation. Nothing in this Second Amendment shall be deemed or construed to be a
waiver or release of, or a limitation upon, the Lenders' or the Agents' exercise
of any of their respective rights and remedies under the Existing  Agreement and
the other Loan  Documents,  whether  arising as a  consequence  of any Events of
Default which may now exist or  otherwise,  and all such rights and remedies are
hereby expressly reserved.


                                   ARTICLE II

                   BORROWER'S SUPPLEMENTAL REPRESENTATIONS

            SECTION 2.01  INCORPORATION  BY  REFERENCE.  As an inducement to the
Lenders to enter into this Second Amendment, the Borrower hereby repeats herein,
for the benefit of the Lenders,  the  representations and warranties made by the
Borrower in Sections 3.1 through 3.15, inclusive,  of the Existing Agreement, as
amended  hereby,  except  that for  purposes  hereof  such  representations  and
warranties shall be deemed to extend to and cover this Second Amendment.

                                       3



                                   ARTICLE III

                              CONDITIONS PRECEDENT

            SECTION 3.01.  CONDITIONS PRECEDENT.  Each of the following shall
be a condition precedent to the effectiveness of this Second Amendment:

            (i) The  Lenders  shall  have  received,  on or  before  the  Second
Amendment  Effective  Date, duly executed  counterpart  originals of this Second
Amendment.

            (ii) The  following  statements  shall be true  and  correct  on the
Second Amendment Effective Date:

                  (A) except to the extent  modified in writing by the  Borrower
heretofore  delivered to the Lenders,  the  representations  and warranties made
pursuant  to  Section  2.01 of  this  Second  Amendment  and in the  other  Loan
Documents are true and correct on and as of the Second Amendment  Effective Date
as though made on and as of such date in all material respects;

                  (B) no Event of  Default  or event  which  with the  giving of
notice or passage of time or both would  become an Event of Default has occurred
and is continuing,  or would result from the execution of or  performance  under
this Second Amendment;

                  (C) the Borrower has in all material  respects  performed  all
agreements, covenants and conditions required to be performed on or prior to the
date hereof under the Existing Agreement and the other Loan Documents.


                                   ARTICLE IV

                               GENERAL PROVISIONS

            SECTION 4.01.  RATIFICATION OF TERMS. Except as expressly amended by
this Second Amendment, the Existing Agreement and each and every representation,
warranty,  covenant,  term  and  condition  contained  therein  is  specifically
ratified and confirmed in all material respects.

            SECTION 4.02. REFERENCES. All notices,  communications,  agreements,
certificates,  documents or other  instruments  executed and delivered after the
execution  and  delivery  of  this  Second  Amendment  in  connection  with  the
Agreement,  any of the other Loan  Documents  or the  transactions  contemplated
thereby may refer to the Existing Agreement without making specific reference to
this Second  Amendment,  but nevertheless all such references shall include this
Second  Amendment  unless the  context  requires  otherwise.  From and after the
Second  Amendment  Effective Date, all references in the Existing  Agreement and
each of the  other  Loan  Documents  to the  "Agreement"  shall be  deemed to be
references to the Existing Agreement as amended hereby.

                                       4


            SECTION 4.03. COUNTERPARTS. This Second Amendment may be executed in
different counterparts, each of which when executed by the Borrower and a Lender
shall be regarded as an original, and all such counterparts shall constitute one
Second Amendment.

            SECTION  4.04.  CAPITALIZED  TERMS.  Except for proper  nouns and as
otherwise  defined herein,  capitalized terms used herein as defined terms shall
have the meanings ascribed to them in the Existing Agreement, as amended hereby.

            SECTION 4.05.  GOVERNING LAW.  THIS SECOND AMENDMENT  AND THE RIGHTS
AND OBLIGATIONS  HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY
THE LAWS OF THE  COMMONWEALTH OF  PENNSYLVANIA  WITHOUT REGARD TO THE PROVISIONS
THEREOF REGARDING CONFLICTS OF LAW.

            SECTION 4.06.  HEADINGS.  The  headings  of  the  sections  in  this
Second  Amendment are for purposes of reference  only and shall not be deemed to
be a part hereof.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       5



            IN WITNESS  WHEREOF,  the parties  hereto,  intending  to be legally
bound  hereby,  have caused this Second  Amendment to be duly  executed by their
proper and duly authorized officers the day first above written.


                                          ALLEGHENY TELEDYNE INCORPORATED


                                          By    /S/ R. S. PARK
                                                --------------------------------
                                          Name  R. S. PARK
                                                --------------------------------

                                          Title VICE PRESIDENT, TREASURER
                                                --------------------------------


PNC BANK, NATIONAL ASSOCIATION,           BANK OF AMERICA NATIONAL
as Lender, Managing Agent and Agent       TRUST AND SAVINGS ASSOCIATION,
                                          as Lender and Managing Agent


By    /S/ DAVID B. GOOKIN                 By    /S/ M. A. DETRICK
      ----------------------------              --------------------------------
Name  DAVID B. GOOKIN                     Name  M. A. DETRICK
      ----------------------------              --------------------------------
Title VICE PRESIDENT                      Title VICE PRESIDENT
      ----------------------------              --------------------------------


THE CHASE MANHATTAN BANK,                  MELLON BANK, N.A.,
as Lender and Managing Agent               as Lender and Managing Agent


By    /S/ JAMES H. RAMAGE                 By    /S/ ROGER N. STANIER
      ----------------------------              --------------------------------
Name  JAMES H. RAMAGE                     Name  ROGER N. STANIER
      ----------------------------              --------------------------------
Title VICE PRESIDENT                      Title VICE PRESIDENT
      ----------------------------              --------------------------------


THE BANK OF NEW YORK                      MORGAN GUARANTY TRUST
                                          COMPANY OF NEW YORK

By    /S/ ROBERT J. JOYCE                 By    /S/ CHRISTOPHER C. KUNHARDT
      ----------------------------              --------------------------------

Name  ROBERT J. JOYCE                     Name  CHRISTOPHER C. KUNHARDT
      ----------------------------              --------------------------------
Title VICE PRESIDENT                      Title VICE PRESIDENT
      ----------------------------              -------------------------------

                       [SIGNATURES CONTINUED ON NEXT PAGE]



                                       6




                        [CONTINUATION OF SIGNATURE PAGE]

NATIONSBANK, N.A.                         THE TORONTO-DOMINION BANK


By    /S/ PHILIP DURAND                   By    /S/ DAVID G. PARKER
      ----------------------------              --------------------------------
Name  PHILIP DURAND                       Name  DAVID G. PARKER
      ----------------------------              --------------------------------
Title VICE PRESIDENT                      Title MANAGER CREDIT ADMINISTRATION
      ----------------------------              --------------------------------


BANK OF TOKYO-MITSUBISHI TRUST            CORESTATES BANK, N.A.
COMPANY


By    /S/ M.R. MARRON                     By    /S/ DONNA J. EMHART
      ----------------------------              --------------------------------

Name   M. R. MARRON                       Name  DONNA J. ENHART
      ----------------------------              --------------------------------

Title VICE PRESIDENT                      Title VICE PRESIDENT
      ----------------------------              --------------------------------


THE FIRST NATIONAL BANK OF                 NATIONAL CITY BANK OF
CHICAGO                                    PENNSYLVANIA
                                        
By    /S/ KENNETH J. KRAMER               By    /S/ WILLIAM S. HARRIS
      ----------------------------              --------------------------------

Name  KENNETH J. KRAMER                   Name  WILLIAM S. HARRIS
      ----------------------------              --------------------------------
Title AS AUTHORIZED AGENT                 Title VICE PRESIDENT
      ----------------------------              --------------------------------

THE FUJI BANK LIMITED, NEW YORK           UNION BANK OF SWITZERLAND,
BRANCH                                    NEW YORK BRANCH


By    /S/ RAYMOND VENTURA                 By    /S/ HAMILTON W. BULLARD
      ----------------------------              --------------------------------
Name  RAYMOND VENTURA                     Name  HAMILTON W. BULLARD
      ----------------------------              --------------------------------
Title VICE PRESIDENT AND MANAGER          Title ASSISTANT TREASURER 
      ----------------------------              --------------------------------

                                          By    /S/ PAUL R. MORRISON
                                                --------------------------------
                                          Name  PAUL R. MORRISON
                                                --------------------------------
                                          Title DIRECTOR
                                                --------------------------------