This application is an addition of Indian Application 201621003959 which has filing date of February 04, 2016.

Field of the invention

The present invention relates to a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven-sacks and Cops/Bobbins/Pirns for synthetic yarn and more particularly it relates to a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for winding varieties of flat tape yarn i.e. PP (Polypropylene), HDPE (High Density Polyethylene) and Cops/Bobbins/Pirns for winding Nylon (Polyamide) and Polyester etc. in synthetic yarn.

Background and prior art of the invention

Woven Sacks Industry has gained importance in past two decades for packaging of cement, fertilizer, sugar, chemicals, food grains and Atta.

The woven sacks are manufactured by granules of PP (Polypropelyne) & HDPE (High Density Polyethylene). The same are extruded in thin sheet form followed by slitting into flat tape. Flat tape when extruded is wound on the Cheese Tubes/Pipes, Jumbo Tubes/Pipes and then is taken on the loom for weaving. The bags woven out of the same are called Woven Sacks.

Since the woven sacks are utilized mainly for packaging, it requires excellent strength as also other properties since the commodity packed in the same has to remain intact for reasonably long time.

Synthetic yarns have become popular on account of their ideal characteristics for clothes which mainly includes more compact molecular structure, creases can be heat-set at higher temperatures, better weathering properties; better sunlight resistance, superior colourfastness, excellent abrasion resistance, greater elasticity and elastic recovery.

The Cheese Tubes/Pipes play important role for winding varieties of flat tape yarn i.e. PP (Polypropylene), HDPE (High Density Polyethylene) in woven sacks and Cops/Bobbins/Pirns for winding Nylon (Polyamide) and Polyester etc. in synthetic yarn. For manufacturing end products, an extrusion plant is used which produces varieties of yarn i.e. PP (Polypropylene), HDPE (High Density Polyethylene) Nylon and Polyester etc. that is required to be wound on cylindrically round tubes and these tubes are called Cheese Tubes/Pipes or Jumbo Tubes/Pipes or Cops/Bobbins/Pirns as the case may be.

Further, due to winding of varieties of flat tape yarn and shrinkage of Nylon yarn, high pressure and crushing load is exerted on the Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns so that the Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns tends to bulge. The steel Cheese Tubes/Pipes are manufactured with thickness from 0.70 mm to 1.50 mm, the steel Cops/Bobbins/Pirns having thickness 0.70 mm to 1.30 mm and the Jumbo Tubes having thickness 1.50 mm to 2.00 mm. So, that it is required to minimize the weight and cost of steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn to reduce the time and cost of manufacturing the same.

Though, the steel Cheese Tubes/Pipes of thickness from 0.70 mm to 1.50 mm, provides sufficient tensile strength and yield strength, there is still room for reducing the thickness of steel Cheese Tubes/Pipes to achieve sufficient higher tensile strength to withstand the pressure exerted on steel Cheese Tubes/Pipes. So, that the cost and the time for manufacturing steel Cheese Tubes/Pipes, Jumbo Tubes/Pipes and Cops/Bobbins/Pirns can be reduced. Therefore, it can be seen that a need yet exists for an improved manufacturing process for steel Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bibbins/Pirns which can reduce the overall cost and time for manufacturing the same. Hence, there is an instant need to provide a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn which is economical for manufacturing the same.

Object of invention

The main object of the present invention is to provide a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbin/Pirns for synthetic yarn.

Another object of the present invention is to provide a process for manufacturing steel Cheese Tubes/Pipes having sufficient higher tensile strength and yield strength with thickness 0.70 mm to 1.50 mm.

Another object of the present invention is to provide a process for manufacturing steel Jumbo Tubes/Pipes having sufficient higher tensile strength and yield strength with thickness from 1.50 mm to 2.00 mm.

Yet, another object of the present invention is to provide a process for manufacturing steel Cops/Bobbins/Pirns having sufficient higher tensile strength and yield strength with thickness from 0.70 mm to 1.30 mm. Still, object of the present invention is to provide a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn that reduces the overall cost of manufacturing the steel Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns.

Still, another object of the present invention is to provide a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn that reduces the overall time for manufacturing the steel Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns.

Further object of the present invention is to provide a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns that acquires sufficient higher tensile strength and yield strength to withstand crushing load of flat tape yarn for pressure exerted on steel Cheese Tubes/Pipes and Jumbo Tubes/Pipes and crushing load of Nylon and Polyester yarn on steel Cops/Bobbins/Pirns.

Summary of invention

The present invention relates to a process for manufacturing steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and s/Bobbins/Pirns for synthetic yarn. The present invention provides steel Cheese Tubes/Pipes having thickness 0.70 mm to 1.50 mm, Jumbo Tubes/Pipes having thickness 1.50 mm to 2.00 mm and Cops/Bobbins/Pirns having thickness 0.70 mm to 1.30 mm to reduce the time and overall cost for manufacturing of steel Cheese Tubes/Jumbo Tubes/Pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn. The present invention utilizes the steel strip of one of grades SAE 1020, SAE 1026, SAE 1541, ST 52, ST 52.3 and MC 11 and similar or equivalent grades. The steel strip undergoes the forming process to form steel tube and faying edges of said tube undergoes electrical resistance welding (ERW) to obtain primary tubes. The primary tubes thus prepared are subjected to heat treatment process i.e. induction hardening process by passing the primary tubes through the induction hardening coil to achieve sufficient high tensile strength, yield strength and improved elongation. After induction hardening, the steel tubes/pipes to be used for cheese tubes/pipes and jumbo tubes/pipes are further subjected to coating i.e. powder coating, cathode electro deposition (CED), blackodizing and polyurethane coating. Thus, the steel cheese tubes/jumbo tubes/pipes and Cops/Bobbins/Pirns after induction hardening achieves sufficient high tensile strength and yield strength to resist the crushing load of yarn and to withstand the pressure exerted on steel cheese tubes/pipes having thickness 0.70 mm to 1.50 mm, jumbo tubes/pipes having thicknessl.50 mm to 2.00 mm and Cops/Bobbins/Pirns having thickness 0.70 mm to 1.30 mm

Detailed description of the invention

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the description. The invention is capable of other embodiments, as depicted in description as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

The dimensions and weight of steel cheese tubes/pipes used conventionally varies as per the ultimate applications. The outer diameter of steel cheese tubes/pipes, Cops/Bobbins/Pirns and jumbo tubes/pipes ranges from 34 mm - 40 mm, 45 mm - 51 mm and 58 mm - 118 mm respectively. The length of steel cheese tubes/pipes, Cops/Bobbins/Pirns and jumbo tubes/pipes ranges from 218 mm - 230 mm, 305 mm -450 mm and 270 mm - 330 mm respectively. The inner diameter depends on the ultimate thickness and uniformity of the steel cheese tubes/pipes and steel Cops/Bobbins/Pirns. The thickness of steel cheese tubes/pipes, Cops/Bobbins/Pirns and jumbo tubes/pipes ranges from 0.7 mm - 1.50 mm, 0.7 mm - 1.30 mm and 1.50 mm - 2.00 mm respectively. Based on the varying dimension, weight of steel cheese tubes/pipes, Cops/Bobbins/Pirns and jumbo tubes/pipes is in the range of 150 gm - 300 gm, 300 gm - 750 gm and 600 gm - 1200 gm respectively.

The process for manufacturing steel cheese tubes/jumbo tubes/pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn uses basic steel strips as feed stock. This steel strip undergoes the forming process to form the steel tubes and faying edges of said steel tubes undergoes electrical resistance welding (ERW) to obtain primary tubes. This welding process provides seam welding to flange of strips by producing coalescence of surfaces where heat to form the weld is generated by the electrical resistance welding process (10000 Amp). The principal of welding is based on material deformation with the time and the force used to hold the materials together during welding. This welding process ultimately gives tube with basic characteristic of basic steel. Different grades of steels have different tensile strength, hardness and % elongation. The requirement of further processing is needed as basic raw material doesn't have requisite characteristics for steel cheese tubes/pipes manufacturing. The present process is investigated on various steel grades SAE 1020, SAE 1026, ST 52, ST 52.3, SAE 1541, and MC 11 and similar or equivalent grades.. These steel grades are evaluated for improvement in tensile strength, hardness and % elongation.

In the process for manufacturing of steel Cheese Tubes/Jumbo Tubes/Pipes and Cops/Bobbins/Pirns, basic strips of steel are selected as feed stock or raw material. The strips are subjected to slitting in predefined width which will undergo forming of primary tubes/pipes and sealing the faying edges of the steel strips using electrical resistance welding (ERW). The steel tubes/pipes are having tensile strength in range of 400 - 700 MPa depending on the different grades of steel.

The composition and tensile strength of various steel grades is given in table 1 as below.

Table - 1

* 'Grades are denoted as per the standards of SAE societies. These mechanical properties are enhanced for making steel Cheese Tubes/Jumbo Tubes/Pipes to achieve improved eventual product with high tensile strength and light weight for woven sacks and Cops/Bobbins/Pirns for synthetic yarn. Further, during welding,the outer diameter dimensional tolerances achieved are very wide. The ERW steel Tubes/Pipes are then straightened on hyperbolic Tubes/Pipes straightening machine to relieve undesirable stress as well as improve outside diameter tolerances. This process is done with tubes/pipes inputs from one end and if required the tubes direction is reversed to pass again through the straightening machine with a view to make sure that desired straightness is achieved.

Thereafter, for achieving desirable mechanical properties of the resultant straightened Tube/Ppipe, the heat treatment process i.e. induction hardening is carried out in order to generate fine grains in the re-crystallization and to increase the enduring strength of steel tubes. In hardening process, the steel Tubes/Pipes are heated at about 900°C - 950°C. The time generally depends upon the dimension and thickness of the steel Tubes/Pipes, after which tensile strength shall be in the range from 750-1800 MPa and percentage elongation is limited to a level of 8% to 15%. This hardening process is carried out by induction hardening. After induction hardening, the steel Tubes/Pipes to be used for Cheese Tubes/Pipes and Jumbo Tubes/Pipes is subjected to suitable coating i.e. powder coating, cathode electro deposition (CED), blackodising and poly urethane coating.

The induction hardening process is carried out by passing the ERW steel tubes/pipes through induction hardening coil (Eddy current coil) so that the produced induction hardened steel tubes/pipes would have higher tensile strength, yield strength and improved elongation to resist the crushing load of flat tape yarn and to withstand the pressure exerted on the steel cheese tubes/jumbo tubes/pipes during winding of the yarn in woven sacks and Cops/Bobbins/Pirns for winding Nylon (Polyamide) and Polyester in synthetic yarn.

The present process for manufacturing provides steel cheese tubes/jumbo tubes/pipes and Cops/Bobbins/Pirns having enhanced tensile strength, yield strength and improved elongation by following steps:

(a) The strip of basic steel grade is selected as a feed stock or raw materials;

(b) Said strip undergoes forming process to form steel tube and faying edges of the steel tube are welded through electrical resistance welding (ERW) to form the primary tube; (c) The ERW tube is further straightened on hyperbolic tube/pipe straightening machine and cut in to desired length;

(d) The tube obtained in step (c) is hardened by induction hardening at 900°C-950°C to achieve high tensile strength, yield strength and improved elongation;

(e) The hardened tube obtained in step (d) is subjected to coating i.e. powder coating, cathode electro deposition (CED), Blackodising and poly urethane coating for preparing cheese tube/pipe and jumbo tube/pipe for woven-sacks. Coating is not required for Cop/Bobbin/Pirn for synthetic yarn.

The invention is illustrated more in details in the following examples. The example describes and demonstrates embodiments within the scope of the present invention. This example is given solely for the purpose of illustration and is not to be construed as limitations of the present invention, as many variations thereof are possible without departing from spirit and scope.

Example 1: a) The suitable steel strip of grade of SAE 1020 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel Tube/Pipe and the faying edges of the Tube/Pipe were welded through electrical resistance welding to form primary tube of SAE 1020. c) The ERW (electrical resistance welded) tube was straightened on hyperbolic Tube/Pipe straightening machine and then cut into 218 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The Tube/Pipe obtained in step (d) was subjected to powder coating. f) The tube obtained in step (e) was the Cheese Tube/Pipe.

Table - 1

Example 2: a) The suitable steel strip of grade of SAE 1026 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel tubes and the faying edges of said tubes were welded through electrical resistance welding to form the primary tube of SAE 1026. c) The ERW (electrical resistance welded) tube/Pipe was straightened on hyperbolic Tube/Pipe straightening machine and then cut into 230 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The tube obtained in step (d) was subjected to cathode electro deposition (CED) coating. f) The tube obtained in step (e) was the Cheese Tube/Pipe.

Table - II

Segment of Tensile % Elongation Hardness Yield 0.2% Process strength HV- 10 Proof

(MPa) scale Stress MPa

After rolling 490 12 to 15 200-225 415 (ERW)

After Induction 800-850 8 to 12 325-375 700-750 hardening Example 3: a) The suitable steel strip of grade of ST-52 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel tubes and the faying edges of said tubes were welded through electrical resistance welding to form the primary tube of ST-52. c) The ERW (electrical resistance welded) Tube/Pipe was straightened on hyperbolic Tube/Pipe straightening machine and then cut into 363 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The tube obtained in step (d) was undergoing further assembly of components to from the Cops/Bobbins/Pirns.

Table - III

Example 4: a) The suitable steel strip of grade of ST-52.3 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel tubes and the faying edges of said tubes were welded through electrical resistance welding to form the primary tube of ST-52.3. c) The ERW (electrical resistance welded) tube was straightened on hyperbolic tube/pipe straightening machine and then cut into 397 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The tube obtained in step (d) was undergoing further assembly of components to from the Cops/Bobbins/Pirns.

Table - IV

Example 5: a) The suitable steel strip of grade of SAE 1541 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel Tubes/Pipes and faying edges of said Tubes/Pipes were welded through electrical resistance welding to form the primary tube of SAE 1541. c) The ERW (electrical resistance welded) tube was straightened on hyperbolic tube/pipe straightening machine and then cut into 275 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The tube obtained in step (d) was subjected to cathode electro deposition (CED) coating. f) The tube obtained in step (e) was the Jumbo Tube/Pipe.

Table - V

After Induction 1600-1800 10 to 14 500-575 1200-1400 hardening

Example 6: a) The suitable steel strip of grade of MC 11 was taken as feed stock or raw material. b) Said strip underwent a forming process to form steel Tubes/Pipes and the faying edges of said Tubes/Pipes were welded through electrical resistance welding (ERW) to form the primary tube of MC 11. c) The ERW (electrical resistance welded) tube was straightened on hyperbolic tube/pipe straightening machine and then cut into 330 mm length. d) The tube obtained in step (c) was subjected to induction hardening at temperature 900 °C-950 °C. e) The tube obtained in step (d) was subjected to polyurethane coating. f) The tube obtained in step (e) was the Jumbo Tube/Pipe.

Table - VI (MPa) scale Stress MPa

After rolling 700-730 8 to 12 350 600-620 (ERW)

After Induction 1600-1800 5 to 8 510-580 1250-1450 hardening

Result and Discussion:

The result shown in table (I-VI) provides the clear indication about the improvement in the requisite characteristics for woven sacks and synthetic yarn. Tensile strength of each steel grade is improved with respect to primary tubes or ERW tubes. The achieved tensile strength after induction hardening is sufficiently higher to resist the crushing load of flat tape yarn and to withstand the pressure exerted on the steel cheese tubes/jumbo tubes/pipes during winding of the flat tape yarn in woven sacks and Cops/Bobbins/Pirns for winding of Nylon (polyamide) and Polyester in synthetic yarn. Further, the steel cheese tubes/pipes of thickness 0.7 mm - 1.50 mm, the Cops/Bobbins/Pirns of thickness 0.7 mm - 1.3 mm and the jumbo tubes of thickness 1.50 mm - 2.00 mm were produced in short period of time. The process of the present invention reduces the weight, overall cost and overall time for manufacturing steel cheese tubes/jumbo tubes/pipes for woven sacks and Cops/Bobbins/Pirns for synthetic yarn. The induction hardening of ERW tubes/pipes provide improved elongation of 10-14% and enhanced tensile strength of 750 Mpa to 1800 Mpa respectively. It is to be noted that hardness increases with the tensile strength of the steel tube.

Advantages of the process:

Steel cheese tubes/jumbo tubes/pipes produced by this process provides exceptional high tensile strength with improved elongation which provides better ductility and lesser weight product. Reduction in weight and thickness achieved by this process is 25% - 40% with respect to conventional process. If the improvement is calculated on practical basis then weight reduction for each steel cheese tube/jumbo tube/pipe will reflect in making process economical in terms of lower maintenance, lower electricity consumption and lower handling efforts. The high tensile strength provides better durability and long life to the steel cheese tubes/jumbo tubes/pipes and Cops/Bobbins/Pirns which also provides multiple usage capability. Therefore the process of the present invention provides economical significance with respect to current state of art.

The steel cheese tubes/jumbo tubes/pipes and Cops/Bobbins/Pirns according to present invention have excellent ductility, reduced weight, higher tensile strength and proof stress in resultant product for woven sacks and synthetic yarn application.

While various embodiments of the present invention have been described in details, it is apparent that modification and adaptation of those embodiments will occur to those skilled in the art. It is expressly understood, however, that such modifications and adaptations are within the spirit and scope of the present invention as set forth in the following claims.