<PAGE>   1

                                                                     EXHIBIT 4.7

                       SIXTH AMENDMENT TO CREDIT AGREEMENT
                       -----------------------------------


                  THIS SIXTH AMENDMENT TO CREDIT AGREEMENT, dated as of January
15, 2000, (this "Sixth Amendment"), is by and among OLYMPIC STEEL, INC., an Ohio
corporation ("Borrower"), and NATIONAL CITY BANK ("NCB") and the group of other
banks signatory hereto or that become parties to the Credit Agreement hereafter
identified by amendment or supplement thereto (NCB and the banks comprising such
group at any specific time, hereinafter referred to as the "Banks") and NATIONAL
CITY BANK, as agent for the Banks (in that capacity, "NCB-Agent").

                                    RECITALS
                                    --------

                  A. Borrower, the Banks and NCB-Agent entered into a Credit
Agreement, dated as of October 4, 1996 (the "Credit Agreement"), pursuant to
which Borrower may obtain, among other things, (i) loans ratably from the Banks
that are on a revolving credit basis and (ii) subject LCs issued by NCB in which
the Banks agree to ratably share the obligations in respect thereof, in each
case until the expiration date.

                  B. Borrower, the Banks and NCB-Agent entered into the First
Amendment to Credit Agreement, dated as of January 24, 1997 (the "First
Amendment"), in order to increase the amount of the commitments by the Banks for
subject revolving credit loans and additional subject LCs by Ten Million Dollars
($10,000,000) and to permit Borrower to make certain joint venture investments
and guarantees of indebtedness of the joint venture entities.

                  C. Borrower, the Banks and NCB-Agent entered into the Second
Amendment to Credit Agreement, dated as of May 30, 1997 (the "Second
Amendment"), in order to increase the amount of the commitments by the Banks for
subject revolving credit loans and additional subject LCs by Eight Million
Dollars ($8,000,000), to add a commitment by Banks for new Series A term loans
in the amount of Seventeen Million Dollars ($17,000,000), to permit certain
borrowing from other lenders, to permit the Borrower to allow certain of its
property to become encumbered by liens in favor of other lenders and to extend
the expiration date to June 30, 2000.

                  D. Borrower, the Banks and NCB-Agent entered into the Third
Amendment to Credit Agreement, dated as of July 14, 1997 (the "Third Amendment")
in order to add an additional bank as a party to Credit Agreement, to adjust the
ratable share of the obligations among the Banks which were original parties to
the Credit Agreement, to decrease the aggregate amount of the commitments by the
Banks for existing subject LCs, and to make appropriate changes to the Credit
Agreement in recognition that some or all of the proceeds of the subject loans
would be used by a new subsidiary of Borrower, Olympic Steel Iowa, Inc., for the
purpose of acquiring land and constructing a temper mill facility in Bettendorf,
Iowa.

                  E. Borrower, the Banks and NCB-Agent entered into the Fourth
Amendment to Credit Agreement, dated as of December 8, 1998 (the "Fourth
Amendment") in order to authorize Borrower to borrow funds from Mellon Bank,
N.A. ("Mellon"), one of the Banks, pursuant to a discretionary Swing Line of
Credit facility (the "Swing Loan") as an

<PAGE>   2

additional exception to the prohibition against incurring indebtedness under
Section 3D.02 of the Credit Agreement; to grant to Mellon a one-time right to
have the Banks refund the outstanding Swing Loan as a subject revolving credit
loan; and to adjust Mellon's subject commitment with respect to the subject
loans made pursuant to the Credit Agreement until such time as the Swing Loan is
refunded at Mellon's request by a subject revolving credit loan.

                  F. Borrower, the Banks and NCB-Agent entered into the Fifth
Amendment to Credit Agreement dated as of March 10, 1999 (the "Fifth Amendment")
in order to extend the expiration date until June 30, 2002; to increase the
amount of the series A subject term loan commitment by $4,000,000, to waive
certain covenant requirements and exclude certain charges therefrom and modify
the interest rates payable by Borrower based on Borrower's EBIT-to-interest
ratio.

                  G. Borrower, the Banks and NCB-Agent desire to again amend the
Credit Agreement by this Sixth Amendment in order to change the Interest Rate
and Letter of Credit Commission and to modify the Interest Coverage requirements
of the Credit Agreement.

                                    AGREEMENT
                                    ---------

         Accordingly, the parties have agreed and do hereby agree as follows:

                  1. Subsection 2B.07 INTEREST RATES AND LETTER OF CREDIT
COMMISSIONS of the Credit Agreement shall be deleted in its entirety and the
following shall be substituted in place thereof:

                  2B.07 INTEREST RATES AND LETTER OF CREDIT COMMISSIONS - (a)
          Effective as of December 1, 1999 and thereafter until maturity, the
          principal of subject revolving credit loans and term loans shall bear
          interest at the per annum rates and the commissions on the subject
          letters of credit (in both cases, computed in accordance with
          subsection 8.10) as calculated based on the following:

                  (i) Prime rate loans shall bear interest at a fluctuating rate
         equal to the prime rate from time to time in effect, with each change
         in the prime rate automatically and immediately changing the rate
         thereafter applicable to the prime rate loans plus the applicable prime
         rate margin as determined in accordance with the following table;

                  (ii) LIBOR loans shall bear interest at a rate equal to the
         LIBOR pre-margin rate in effect at the start of the applicable contract
         period (except that any change in the FRB reserve percentage shall
         automatically and immediately change the LIBOR pre-margin rate
         thereafter applicable to the LIBOR loans) plus the applicable LIBOR
         margin as determined in accordance with the following table;

                  (iii) Commissions on existing subject LCs have been paid in
         advance through the respective dates set forth on EXHIBIT 2(B).07(iii).
         Commencing after such dates commissions on all subject LCs shall be
         adjusted quarterly on the last business day of


<PAGE>   3


         each March, June, September and December of each year on the basis of
         the applicable percentage as determined in accordance with the
         following table:
<TABLE>
<CAPTION>

----------------------------------------------------------------------------------------------------------------------

      If the Borrower's              and the Borrower's         Then, both the applicable LIBOR          And the
     Liabilities-to-Worth          EBIT-to-Interest Ratio     margin and the applicable letter of      applicable
          Ratio is:                         is:               credit commission shall be equal to:     Prime rate
                                                                                                     margin equals:
----------------------------------------------------------------------------------------------------------------------
<S>                             <C>                           <C>                                    <C>
less than or equal to           Greater  than  or  equal      75 basis points                               0
 .75:1                           to 3.50:1
----------------------------------------------------------------------------------------------------------------------
greater than .75:1 but less     Less than 3.50:1 but          100 basis points                              0
than or equal to 1.25:1         greater than or equal to
                                2.75:1
----------------------------------------------------------------------------------------------------------------------
Greater than 1.25:1 but less    Less than 2.75:1 but          125 basis points                              0
than or equal to 1.75:1         greater than or equal to
                                2.25:1
----------------------------------------------------------------------------------------------------------------------
greater than 1.75:1             Less than 2.25:1 but          175 basis points                              0
                                greater than or equal to
                                2.00:1
----------------------------------------------------------------------------------------------------------------------
greater than 1.75:1             Less than 2.00:1              200 basis points                              0
----------------------------------------------------------------------------------------------------------------------
</TABLE>

          Both the liabilities-to-worth ratio and EBIT-to-interest ratio must be
         satisfied in order for the corresponding applicable prime rate margin,
         applicable LIBOR margin and applicable letter of credit commission to
         be effective, and if either the specific liabilities-to-worth ratio or
         EBIT-to-interest ratio is not satisfied, then the next highest prime
         rate margin, LIBOR margin or applicable letter of credit commission
         shall be applicable.

         (b)      After maturity (whether occurring by lapse of time or by
                  acceleration), the prime rate loans shall bear interest at a
                  fluctuating rate equal to the prime rate from time to time in
                  effect plus two percent (2%) per annum; PROVIDED, that in no
                  event shall the rate applicable to the prime rate loans after
                  the maturity thereof be less than the rate applicable thereto
                  immediately before maturity and each LIBOR loan shall bear
                  interest computed and payable in the same manner as in the
                  case of prime rate loans EXCEPT that in no event shall any
                  LIBOR loan bear interest after maturity at a lesser rate than
                  that applicable thereto immediately before maturity.

         2.       Subsection  3B.03 INTEREST  COVERAGE of the Credit  Agreement
shall be deleted in its entirety and the following substituted in place thereof:

                  3B.03 INTEREST COVERAGE - On a consolidated statement basis,
         Borrower will not, as at the end of the fiscal quarter during any
         fiscal year of Borrower (commencing December 31, 1999), suffer or
         permit its EBIT-to-interest ratio to be less


<PAGE>   4


         than 1.50:1 except as hereinafter provided. The Banks waive Borrower's
         compliance with the EBIT-to-interest ratio requirement as of
         September 30, 1999 provided such ratio was not less than 1.75:1.
         Further, notwithstanding the foregoing, Borrower's EBIT-to-interest
         ratio for the fiscal quarter ending on September 30, 2000 shall be not
         less than 1.75:1 and for the fiscal quarters ending on and after
         December 31, 2000 shall be not less than 2.25:1.

         3. Borrower shall pay or cause to be paid to NCB-Agent an amendment fee
in the amount of $85,000.00 to be shared ratably among the Banks.

         4. From and after the effective date of this Sixth Amendment,
references in the Credit Agreement and the subject notes (as amended by the
First Amendment, the Second Amendment, the Third Amendment, the Fourth
Amendment, the Fifth Amendment and this Sixth Amendment thereto or pursuant to
such amendments) to the Credit Agreement shall be deemed to be references to the
Credit Agreement as amended by all such amendments (unless otherwise expressly
indicated).

         5. Borrower restates and reaffirms all of its representations and
warranties set forth in Section 4B of the Credit Agreement as of the date
hereof.

         6. This Sixth Amendment and the modifications set forth herein shall be
and become effective as of the date hereof.

         7. The Credit Agreement, as amended by the First Amendment, the Second
Amendment, the Third Amendment, the Fourth Amendment, the Fifth Amendment and
this Sixth Amendment, is hereby ratified and confirmed.

         8. This Sixth Amendment may be executed in one or more counterparts,
each counterpart to be executed by Borrower, by NCB-Agent and by one or more or
all of the Banks. Each such executed counterpart shall be deemed to be an
executed original for all purposes but all such counterparts taken together
shall constitute one agreement, which agreement constitutes the entire agreement
among the parties hereto with respect to the subject matter hereof.

         9. This Sixth Amendment may be executed by representatives of the Banks
using facsimile signatures and facsimilied signature pages shall in all respects
be binding on all parties hereto and thereto as if such signature pages were
originally delivered. Original signature pages for all facsimilied signature
pages shall be delivered to NCB-Agent.


<PAGE>   5



         In WITNESS WHEREOF, the parties have executed this Sixth Amendment as
of the date first above written.
<TABLE>
<CAPTION>

<S>                                                         <C>
NATIONAL CITY BANK, AGENT                                   OLYMPIC STEEL, INC.


By:                                                         By:
    -------------------------------------------------          --------------------------------------------
Printed Name:                                               Printed Name:
              ---------------------------------------                     ---------------------------------
Title:                                                      Title:
       ----------------------------------------------             -----------------------------------------


NATIONAL CITY BANK                                          MELLON BANK, N.A.


By:                                                         By:
    -------------------------------------------------          --------------------------------------------
Printed Name:                                               Printed Name:
              ---------------------------------------                     ---------------------------------
Title:                                                      Title:
       ----------------------------------------------              ----------------------------------------


COMERICA BANK                                               PNC BANK, NATIONAL ASSOCIATION


By:                                                         By:
    -------------------------------------------------          --------------------------------------------
Printed Name:                                               Printed Name:
              ---------------------------------------                     ---------------------------------
Title:                                                      Title:
       ----------------------------------------------               ---------------------------------------
</TABLE>