COLD MILLING WORK ROLLS FOR 2-Hi,
4-Hi AND SKIN PASS MILLS

The experience acquired in the field of the heat treatments, together with a wide knowledge of the characteristics of the steels and machining cycles allow B.S.A. to produce forged rolls of low, medium and high alloyed tool steels.
The reference market is that of the medium and small size rolls, with high precision mechanical machining for the cold milling of narrow and thin strips of ferrous and non-ferrous metals.

The maximum dimensions for the rolls supply are:

Work rolls: Ømax ~300 mm, maximum weight: 2500kg
Back-up rolls: Ømax ~600 mm, maximum weigth: 3500kg

The great accuracy of the grinding step and the high surface hardness of the work rolls allow the customer to get strips with a high degree of precision and a very good surface finishing.


MACHINING CYCLE

The machining cycle of the rolls starts with the order to selected suppliers of the forged, rough on drawings blanks, which are quenced and tempered in accordance with the hardness calculated by B.S.A. in order to guarantee the mechanical characteristics (i.e. impact strength, toughness and wear resistance) necessary for the best performance of the rolls.
After an accurate U.S. check to control the inner quality of the rough materials coming from the steel suppliers, we go on with the machining cycle which includes different steps (i.e. turning, boring, milling, drilling and grinding).
However, the most important step is the induction deep hardening heat treatment performed by the sister company TERMOSTAHL.
The machining cycle ends up with the final test to check the rolls hardness in different points, the dimensional matching with the drawings, the perfect surface conditions (roughness and roundness) and, finally, with the punching with our trade mark . Logo Termostahl


ROLL GRADE DESCRIPTION

B.S.A. has developed its production plan in the light of the many trials made by the end users, that have been able to select high quality rolls after years of experiments.
The material used have all been forged and vacuum degassed; only sometimes Electro Slag Remelted (ESR) steel is used.

Forget blanks for rolls
Forged blanks for rolls
Deep induction hardening
Deep induction hardening

WORK ROLLS GRADES

STEEL GRADE MAIN ALLOY % SURFACE HARDNESS BARREL HARDNESS
100CrMo7 2% Cr 62÷65 HRc 270÷330 HB
86CrMoV7 2% Cr 62÷66 HRc 280÷340 HB
X63CrMoV51 5% Cr - 1% Mo 60÷64 HRc 300÷350 HB
X155CrMoV121 12% Cr - 1% Mo 60÷63 HRc 56÷58 HRc

BACK-UP ROLLS GRADES

STEEL GRADE MAIN ALLOY % SURFACE HARDNESS BARREL HARDNESS
86CrMoV7 2% Cr 56÷60 HRc 310÷350 HB
56NiCrMo7 2% Cr 54÷58 HRc 320÷380 HB
90MnVCr8 2% Mn 54÷59 HRc 310÷350 HB


Hereafter you can find some information regarding the characteristics and the suggested instructions for use for each kind of steel grade, with a notice: there is no standard rule to determine which is the grade that can guarantee the best performance. The choice depends on many use conditions, among which: the kind of rolled steel and the relevant hardness, the kind of roll cooling, the rolling speed, the maximum reduction per pass, the presence/absence of vibrations or impacts and the surface condition of the strip.

Magnetoscope check 100%
Magnetoscope check 100%

Besides, it is the most suitable for deep hardening induction reatments (>20 mm) and keeps the surface toughness of the rolls. This grade can be widely employed and many applications are to be found in the field of the cold milling on 2-Hi, 4-Hi and Tandem mills.
It's application can be standard unless performance problems (i.e. vibrations or impact) suggest a change of grade. The materials of the rolled strips vary from the low Carbonium steels to the non-ferrous metals like alluminium, copper, bronze and alloys.

Back-up rolls induction hardened
Back-up rolls Ø760 mm in 86CrMoV7 medium frequency induction hardened



CHARACTERISTICS AND APPLICATIONS FOR WORK GRADES

100CrMo7
86CrMoV7
X155CrMoV121
63CrMoV51



PRODUCTION EXAMPLES

Small size cold milling work rolls 2% Cr
Small size cold milling work rolls 2% Cr
Work rolls 5% Cr
Work rolls 5% Cr for cold milling of high resistance narrow strips
Work rolls 2% Cr for reversible 4-Hi mill
Work rolls 2% Cr for reversible 4-Hi mill
Induction hardened back-up rolls in 2% Cr steel
Induction hardened back-up rolls in 2% Cr steel