FIELD OF INVENTION
The present invention relates to a new manufacturing process of cold drawn telescopic front fork tubes adaptable to two wheelers appliances.
BACKGROUND OF THE INVENTION
The conventional process routes for manufacturing Telescopic front fork tubes are long and a time consuming, (Fig 1). These tubes are adapted for making the components of two wheelers which require having a good combination of properties, i.e. strength, elongation and surface finish. The Steel grade used for this is commercially known as grade SAE 1541, the specified composition of such steel is shown in Table 1. The Conventional manufacturing process includes a long processing route i.e, a double cold drawing with two times normalizing and surface treatment followed by tempering. The conventional process route manufacturing of Telescopic front fork tubes are shown in Fig. 1. The overall process has inherent drawbacks like poor material yield due to higher level of rejection, lower productivity and complicated shop logistics.

OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a new manufacturing process of cold drawn telescopic front fork tubes which minimizes the lengthy manufacturing process route in the existing state of art.
Another object of the present invention is to propose a new manufacturing process of cold drawn telescopic front fork tubes which improves the material properties.
A further object of the present invention is to propose a new manufacturing process of cold drawn telescopic front fork tubes, which increases material yield and productivity and decreases production time.
A still further object of the present invention is to propose a new manufacturing process of cold drawn telescopic front fork tubes which saves cost due to reduction in processing stages.
Yet further object of the present invention is to propose a new manufacturing process of cold drawn telescopic front fork tubes which is easy logistics and easy processing.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
Fig.1 shows a flow diagram of conventional process route for producing TFF
tubes.
Fig.2 shows a flow diagram of modified process route for producing TFF tubes.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
A modified process route for producing TFF tubes are mentioned below and also
shown Fig. 2:
i) Making liquid steel in a LD Converter followed by further processing in a ladle
furnace to achieve a commercial grade specification of SAE 1541 and required
cleanliness level.
ii) Casting the liquid metal into a Slab having 210mm size.
iii) Rolling the slab to convert strip coil according Specific thickness.
iv)Slitting the strip coil in required width.
v) Forming the tube from Slitted Steel Coil by welding.
vi)Normalizing the tube at a temperature between 850°-950°C.
vii) Treating the tube surface chemically.
viii) Cold drawing of tube.
ix) Cleaning the tube surface chemically.
x) Tempering clean tube at a temperature between 550°C-650°C.

xi) Cutting Standard length size. Experiments And Results: -
At the beginning of the experimentation, a hot rolled strip of SAE 1541 steel
rolled for processing with the conventional process routes as shown in Fig.l were
taken for experimentation. Subsequently two trials were made to compare the
development of properties of the tubes with reduced modified process steps.
Details of the trials conducted are mentioned in Table 2.
Initially, few tubes were processed in cold draw line with two stage deformation.
In first stage high (33%) deformation and in a second stage low(18%)
deformation and properties were examined in the un-tempered condition.
In the next trial, few tubes were processed with a maximum possible
deformation of 33% and then tempered along with the other material in a
furnace and tested the properties. Results of industrial trial are shown in table 3
which represents the properties of the first trial tubes (two stage drawings
without tempering) are not satisfactory due to poor elongation.
However the result of the second trial (Single drawing and tempering) was
satisfactory.
Subsequently, to improve the elongation values, tempering parameters were
improved cold drawn tube samples were heat treated in laboratory muffle
furnace at various temperature and time and properties were measured (Table-
4). Results of the tempering experiments are given in Table 4. Based on these
results, the temperature of the existing process could be increased.

Based on the above results, process route was modified as shown in fig-2 which is much shorter route than that of conventional process fig-1. Results of the commercial trial made with the modified process steps are show in Table 5. Mechanical properties and surface roughness required were fully achieved even with the reduced processing steps. Moreover, the surface Ra values and elongations were found to be better than conventional routes.
Table 5: Results of commercial trial made at tubes division with single stage drawing


WE CLAIM
1. A new manufacturing process of cold drawn telescopic front fork tubes
adaptable to two wheeler appliances comprises the steps of:-
- making a liquid steel in a LD converter followed by further processing in a ladle furnace to achieve the commercial grade specification SAE 1541 and required cleanliness level:
- casting the liquid metal into a 210 mm slab;
- rolling the slab to convert in to a steel Strip coil;
- slitting the Steel strip coil in required coil width;
- making the hollow tube from Slitted Steel strips by forming and welding;
- normalizing the tubes at a temperature between 850°-950°C;
- treating the tube surface chemically;
- cold drawing of the tubes;
- further cleaning the tube surface chemically;
- tempering tubes at a temperature between 500°-600°C;
- cutting the tube in stand size;
2. The process as claimed in claim 1 where in the liquid steel produced having a
composition in (wt%) C-0.36 - 0.44, Si-0.15 - 0.3, Mn-1.35-1.65, S-0.04max, P-
0.05max.

3. The process as claimed in claim 1 wherein the steel tubes produced having a yield strength 800-850 MPa , UTS 900-950 MPa and elongation 15 to 19%;
4. The process as claimed in claim 1, wherein the steel tubes produced having a Ra in < 0.60 urn in internal diameter (ID) surface.

The present invention relates to a new manufacturing process of cold drawn telescopic front fork tubes comprises the steps of making a liquid steel in LD converter followed by further processing in a ladle furnace to achieve a commercial grade specification of SAE 1541 and casting the liquid steel into a 210mm slab and rolling the slab to convert into a steel strips coil and slitting the steel strip coil in required width and forming the hollow tube from slitted steel strips by welding and then normalizing the tubes at a temperature between 850° - 950°C and treating the tube surface chemically and cold drawing of the tubes and further cleaning the tube surface chemically and tempering tubes at a temperature between 500°-600°C and cutting the tubes in size.