Title of Invention

"AN IMPROVED PROCESS FOR MANUFACTURE OF ALUMINIUM-BRONZE AND PHOSPHOROUS-BRONZE SLIPPER PADS WITH IMPROVED WEAR-RESISTANCE BY SUBJECTING THE CAST SLIPPER PADS WITH HOMOGENISATION TO A STEP OF ALUMINIUM ENRICHMENT FOLLOWED BY HEAT TREATMENT"

Abstract A process for manufacture of wear-resistant Aluminium-Bronze/Phosphorous-Bronze slipper pads with improved wear resistance and in particular to manufacture of aluminium enriched Aluminium-Bronze/Phosphorous-Bronze slipper pads through diffusion annealing and heat treatment. The process involves subjecting the cast slipper pads with homogenisation to a step of aluminium enrichment followed by heat treatment. In particular, the process comprises subjecting the said aluminium-bronze/phosphorous-bronze slipper pads to treatment for enrichment by diffusion of aluminium thereby obtain the aluminium enriched aluminium-bronze and/or phosphorous-bronze slipper pads. The process further involves optimum heat to improve the hardness and hence the wear resistance of such aluminium-bronze/phosphorous bronze alloys. The process provides for an improved process of manufacture of Aluminium-Bronze/Phosphorous Bronze, slipper pads which would improve hardness and wear-resistance as well as achieve smoother lubrication Aluminium enriched aluminium-bronze/phosphorous-bronze slipper pads can be obtained which would have extensive and extended life as compared to the conventional slipper pads presently available The process further provides aluminium-bronze/phosphorous-bronze slipper pads by way of a simple and cost effective process of manufacture which would provide for increasing the productivity and economise the operation of mills.
Full Text The present invention relates to the process for manufacture of wear-resistant Aluminium-Bronze/Phosphorous-Bronze slipper pads with improved wear resistance and in particular to manufacture of aluminium ennched Aluminium-Bronze/Phosphorous-Bronze slipper pads through diffusion annealing and heat treatment
It is presently known to have Aluminium-Bronze (containing 9-11% Al, 1.5-4% Fe and 0 35 Mn and balance Cu) and Phosphorous-Bronze (containing Sn 12%, P 0 50% and balance Cu) slipper pads used extensively in the slabbing mills and hot strip mills of various steel plants
It is found that the average life of the above mentioned slipper pads in roughing stands is usually 2-4 months and for finishing stands only about 3-4 weeks Since, the average wear life of these slipper pads is low, it results in increase in the mill downtime which adversely affected the productivity of the mill
It is thus the basic object of the present invention to provide for an improved process of manufacture of Aluminium-Bronze/Phosphorous Bronze, slipper pads which would improve hardness and wear-resistance as well as achieve smoother lubrication
Another object of the present invention is to provide for an improved process of manufacture of aluminium ennched aluminium-bronze/phosphorous-bronze slipper pads which would have extensive and extended life as compared to the conventional slipper pads presently available
Yet further object of the present invention is directed to the improvement in manufacture of aluminium-bronze/phosphorous-bronze slipper pads treatment cycle, involving optimum heat to improve the hardness and hence the wear resistance of such aluminium-bronze/phosphorous bronze alloys.
Yet further object is directed to the provision of aluminium-bronze/phosphorous-bronze slipper pads by way of a simple and cost effective process of manufacture

2
which would provide for increasing the productivity and economise the operation
of mills

Thus, according to the present invention there is provided an improved process

for manufacture of aluminium-bronze and phosphorous-bronze slipper pads with

improved wear-resistance comprising the steps of diffusion metallisation of homogenised aluminium-bronze/phosphorous-bronze slipper pads with aluminium to obtain aluminium enriched aluminium-bronze and/or phosphorous bronze slipper pads, heat treatment of the aluminium enriched aluminium-bronze and/or phosphorous-bronze slipper pads at a temperature in the range of 820 to 840°C for a period of 0 5 to 1 hr and tempering the slipper pads in the temperature of range of 250 to 350°C for a period of 2 to 3 hrs to thereby obtain the aluminium bronze and/or phosphorous bronze slipper pads with improved wear resistance
In accordance with embodiment preferably prior to said step of aluminium enrichment and heat treatment the cast slippers are subjected to a step of homogenisation comprising subjecting the cast slipper pads to heating at a temperature of 730° to 750°C and soaking for a period of 0 5 to 1 5 hrs
In particular in the above process said step of treatment for enrichment by
diffusion of aluminium comprise
providing an Al-containing pulverulent mixture in a box/container,
providing said cast slipper pads in said box and covering with said pulverulent
mixture ,
heating the said slipper pads covered with said pulverulent mixture in said boxes
by soaking at temperature of 820°C to 840°C for a period of 5 to 7 hrs
The aluminium-bronze slipper pads used preferably comprise 9-11% Al, 1 44% Fe, 0 35 Mn and rest Cu while the phosphorous-bronze slipper pads comprise Sn 12%, P 0 50% and balance Cu

3
The said containers/boxes used are preferably fabricated to accommodate at [east two slipper pads at a time kept vertically
The pulverised mixture comprise a selective mix of Al powder 100-150 kq, AI2O3
powder 60-80 kg and NH4CI powder 2-5 kg


4
In the above process the above pulverulent mixture are first thoroughly intermixed and slipper pads kept in said box/container are covered by this mixture and maintained soaked for a period of 5 to 7 hrs. at a temperature of 820 to 840°C in the furnace After the step of soaking of the slipper pads, the same is taken out of the furnace and subjected to air cooling.
Preferably after the said step of diffusion metalization of the bronzes, the aluminium enriched bronzes are hardened by heat treatment to further increase the hardness of the slipper pads. The said step of hardening comprises heating in the temperature of 820 to 840°C preferably for a period of 0 5 to 1.5 hrs After said step of hardening the slipper pads are water quenched Subsequent to said hardening treatment, the thus hardened slipper pads are subjected to tempering and for the purpose are heated in a temperature in the range of 250 to 350°C for a period of 2 00 to 3 00 hours and finally, air cooled
The details of the invention, is objects and advantages are explained hereunder
in greater detail in relation to the non-limiting exemplary embodiment and accompanying drawings biscussed
hereunder
EXAMPLES
I Homogenisation
Al-bronze slipper pads containing 9 to 11% Al, 1 5 to 4% Fe, 0 35% Mn and rest Cu were homogenised first by heating to 740°C, soaking them for 1 hr at that temperature, followed by air cooling It resulted in the increase of the hardness from 54-91 BHN (in the cast pads) to 80-103 BHN (in the case of the homogenised slipper pads).
II Diffusion Metallising
For the purpose the following were carned out A Fabrication of box
A box of appropriate dimensions was made so as to accommodate two
slipper pads at a time, kept vertically as shown in Figs 1 & 2

B Aluminising mixtures
An adequate composition of the mixture required for aluminising slipper pads was evolved after a lot of laboratory scale experiments The same is given below
• Al powder 100-150 kg
• AI2O3 powder 60-80 kg
• NH4CI powder 2-5 kg
Temperature and soaking time
The above pulverulent mixture ingredients were thoroughly intermixed and the two slipper pads were covered all around by this mixture in the packing boxes which were soaked for 6 hours at a temperature of 830°C in the furnace
III Heat Treatment of Al Bronze
A detailed investigation revealed that if the slipper pads are next heat-treated adequately, the hardness and wear resistance is improved significantly The detailed of heat treatment are given below I) Hardening
The slipper pads were hardened to 830°C, soaked for 1 hour and
then water quenched II) Tempering
The hardened slipper pads were heated to 300°C, kept at this
temperature for 2 5 hours and then air cooled
The reaction scheme in the above discussed process of Al enrichment of the slipper pad is as detailed hereunder.
a On heating of the pulverised mix the aluminium chloride decomposes into
ammonia and hydrogen chloride ,
NH4CI NH3 + HCI

b. The evolved gas displaces the air from the container and in reacting with
aluminium, the hydrogen chloride forms aluminium chloride, AI2CI3 in a
gaseous state,
6HCI + 2AI 2AICI3 + 3H2
c At the surface layer of bronzes, an exchange reaction of following type takes
place,
3Cu + 2AICI3 3CuCI2 + 2AI
Thus aluminium precipitated on the surface enters the Al or P bronzes and diffuses inwardly As the time of soaking ts increased, the amount of Al, entering the surface is increased.
The base AI2O3 is needed to prevent the aluminium powder from fusing into a liquid mass. Only separate particles of molten aluminium surround the particles of base AI2O3 and thus the porosity of the mixture remains unchanged or preserved
The values of range of hardness of as cast slipper pads, after homogenisation, metalisation and heat treatment are given in Fig 3 It is observed that the hardness of cast slipper pads (54-91) increases to 130-132 after aluminising ft further increases to 176-195 BHN after heat treatment which has been described in earlier Section
Fig 4 illustrates the microstructure of hardened (830°C) water quenched and tempered (300°C) Al-bronze slipper pads, a (white) and (3 (black) constituents can be observed
In Fig 5 starting of the aluminising process can be observed at the surface of the sample after soaking for one hour at 830°C The core matrix is a + ß with diffusion of Al has started The microstructure of Al-bronze after metalisation at 830°C for 3 hours is shown in Fig 6 This shows the increase in depth of ennchment of aluminium at the surface

7
After 830°C and 6 hrs soaking the diffusion of aluminium in the bronze sample was adequate and can be seen in Fig. 7 Thus it may be said that a soaking temperature of 830°C of a duration of 6 hrs was found to be optimum
The thus obtained Al enriched slipper pads followed by heat treatment (hardening 830°C/tempenng 300°C) were fitted in finishing stands of Hot Strip Mill, along with conventional slipper pads and industrially tried in identical conditions It was found that wear in new experimental slipper pads was 2 to 3 times less than that in conventional ones
It is thus possible by way of the present invention to have
I) a new pulverulent mixture for aluminising Al & P bronze slipper pads ;
II) an improved process for development of ennchment of aluminium process,
which increased the hardness of as cast phosphorous-bronze slipper pads
from 54-91 to 130-132 BHN. Hardness of aluminium-bronze slipper pads
after heat treatment increased to 178-195 BHN , III) increasing the percentage of aluminium to about 30% in the surface of
slipper pads to thereby improve hardness; iv) evolution of an optimum heat treatment cycle, after a series of laboratory
tnals to improve the hardness & hence the wear resistance
The invention thus clearly provides a process technology to increase the hardness and hence improved wear-resistance of aluminium-bronze and phosphorous-bronze slipper pads thereby improving upon the utilities and cost effectiveness in the use of such slipper pads,

8 WE CLAIM
1 An improved process for manufacture of aluminium-bronze and phosphorous-
bronze slipper pads with improved wear-resistance comprising the steps of
diffusion metallisation of homogenised aluminium-bronze/phosphorous
bronze slipper pads with aluminium to obtain aluminium enriched aluminium-
bronze and/or phosphorous-bronze slipper pads, heat treatment of the
aluminium enriched aluminium-bronze and/or phosphorous-bronze slipper
pads at a temperature in the range of 820 to 840°C for a period of 0 5 to 1 hr
and tempering the slipper pads in the temperature of range of 250 to 350°C
for a period of 2 to 3 hrs to thereby obtain the aluminium bronze and/or
phosphorous bronze slipper pads with improved wear resistance
2 An improved process as claimed in claims 1 wherein said step of treatment
for enrichment by diffusion of aluminium comprise
providing an Al-containing pulverulent mixture in a box/container,
providing said cast slipper pads in said box and covering with said pulverulent
mixture ,
heating the said slipper pads covered with said pulverulent mixture in said
boxes by soaking at temperature of 820°C to 840°C for a period of 5 to 7 hrs
3 A process as claimed in anyone of claims 1 to 2 wherein the aluminium-
bronze slipper pads used comprised 9-11% Al, 1 4-4% Fe, 0 35 Mn and rest
Cu
4 A process as claimed in anyone of claims 1 to 3 wherein the phosphorous-
bronze slipper pads comprised Sn 12%, P 0 50% and balance Cu
3
9
5 .A process as claimed in anyone of claims 1 to 4 wherein the said-*
containers/boxes used are fabricated to accommodate at least two slipper
pads at a time kept vertically
6 A process as claimed in anyone of claims 1 to 5 wherein the said pulverised
mixture comprise a selective mix of aluminium powder AI2O3 powder NH4Cl
powder in the range of 100 to 150 kg 60 to 80 kg 2 to 5 kg respectively
7 A process as claimed in anyone of claims 1 to 6 wherein pulverulent mixture

used comprising Al powder 100-150 Kg, AI2O3 powder 60-80 Kg and NH4CI powder 2-5 Kg
8 A process as claimed in anyone of claims 1 to 7 wherein the above
pulverulent mixture are first thoroughly intermixed and slipper pads kept in
said box/container are covered by this mixture and maintained soaked for a
period of 5 to 7 hrs at a temperature of 820 to 840°C in the furnace
9 A process as claimed in anyone of claims 1 to 8 wherein after the step of
soaking of the slipper pads, the same is taken out of the furnace and
subjected to air cooling
10 A process as claimed in anyone of claims 1 to 11 wherein after the said step
of diffusion metalization of the bronzes, the aluminium enriched bronzes are
hardened by heat treatment to further increase the hardness of the slipper
pads
10
10
11 A process as claimed in claim 10 wherein said step of hardening comprises
heating in the temperature of 820 to 840°C preferably for a period of 0 5 to
15 hrs
12 A process as claimed in claim 11 wherein after said step of hardening the
slipper pads are water quenched
13 A process as claimed in anyone of claims 11 or 12 wherein subsequent to
said hardening treatment, the thus hardened slipper pads are subjected to
tempering and for the purpose are heated in a temperature in the range of

250 to 350°C for a period of 2 to 3 hours and finally, air cooled
14 A process as claimed in anyone of claims 1 to 13 wherein prior to said step of
aluminium enrichment and heat treatment the cast slippers are subjected to a
step of homogenisation
15 A process as claimed in claim 13 wherein said step of homogenisation
comprises subjecting the cast slipper pads to heating at a temperature of 730
to 750°C and soaking for a period of 0 5 to 1 5 hrs
16 A process for producing aluminium-bronze/phosphorous-bronze slipper pads
with improved hardness substantially as herein described and illustrated with
reference to the accompanying figures and examples
Dated this 25th day of January 2001

A process for manufacture of wear-resistant Aluminium-Bronze/Phosphorous-Bronze slipper pads with improved wear resistance and in particular to manufacture of aluminium enriched Aluminium-Bronze/Phosphorous-Bronze slipper pads through diffusion annealing and heat treatment. The process involves subjecting the cast slipper pads with homogenisation to a step of aluminium enrichment followed by heat treatment. In particular, the process comprises subjecting the said aluminium-bronze/phosphorous-bronze slipper pads to treatment for enrichment by diffusion of aluminium thereby obtain the aluminium enriched aluminium-bronze and/or phosphorous-bronze slipper pads. The process further involves optimum heat to improve the hardness and hence the wear resistance of such aluminium-bronze/phosphorous bronze alloys. The process provides for an improved process of manufacture of Aluminium-Bronze/Phosphorous Bronze, slipper pads which would improve hardness and wear-resistance as well as achieve smoother lubrication Aluminium enriched aluminium-bronze/phosphorous-bronze slipper pads can be obtained which would have extensive and extended life as compared to the conventional slipper pads presently available The process further provides aluminium-bronze/phosphorous-bronze slipper pads by way of a simple and cost effective process of manufacture which would provide for increasing the productivity and economise the operation of mills.

Documents:

00042-cal-2001-abstract.pdf

00042-cal-2001-claims.pdf

00042-cal-2001-correspondence.pdf

00042-cal-2001-description(complete).pdf

00042-cal-2001-drawings.pdf

00042-cal-2001-form-1.pdf

00042-cal-2001-form-18.pdf

00042-cal-2001-form-2.pdf

00042-cal-2001-form-3.pdf

00042-cal-2001-pa.pdf

42-cal-2001-granted-abstract.pdf

42-cal-2001-granted-acceptance publication.pdf

42-cal-2001-granted-claims.pdf

42-cal-2001-granted-correspondence.pdf

42-cal-2001-granted-description (complete).pdf

42-cal-2001-granted-drawings.pdf

42-cal-2001-granted-examination report.pdf

42-cal-2001-granted-form 1.pdf

42-cal-2001-granted-form 18.pdf

42-cal-2001-granted-form 2.pdf

42-cal-2001-granted-form 3.pdf

42-cal-2001-granted-letter patent.pdf

42-cal-2001-granted-pa.pdf

42-cal-2001-granted-reply to examination report.pdf

42-cal-2001-granted-specification.pdf


Patent Number 194766
Indian Patent Application Number 42/CAL/2001
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 09-Sep-2005
Date of Filing 25-Jan-2001
Name of Patentee STEEL AUTHORITY OF INDIA LIMITED
Applicant Address RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA, RANCHI-834 002
Inventors:
# Inventor's Name Inventor's Address
1 MEDIRATTA SHREE RAM DIRECTOR GENERAL, INSTITUTE FOR STEEL DEVELOPMENT & GROWTH, ISPAT NIKETAN, 1ST FLOOR, 52/1A, BALLYGUNGE CIRCULAR ROAD, CALCUTTA
2 SINGH SUKH DEO RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834 002
3 RAI DAMODAR RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834 002
4 CHATTERJEE TULSI DAS RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834 002
5 RAI DAMODAR R
PCT International Classification Number C22F 1/00; C22F 1/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA