Description:A composition for manufacturing rotors and pump body, and method thereof
Field of the Invention
This invention relates to metallurgical aspect of components of industrial vacuum pumps. More particularly, this invention relates to composition and method for manufacturing rotors and external body of the pumps.
Background of the Invention
Vacuum pumps come in two basic varieties: the ‘wet’ kind, which is essentially a hydraulic pump, and the pneumatic i.e., ‘dry’ variety. Both are used to create suction, which is imparted onto a dynamic substance in order to ‘pull’ more of that substance from the far end of a tube and generally, to use that same substance in order to perform some sort of work at the tube’s far end. Dry Variety includes pumps such as Dry Screw Vacuum Pump, Booster Vacuum Pump and Vacuum Recompressor pump or any other positive displacement pump which are widely used in chemical, pharmaceutical, petrochemical, food processing, plastics, CD-DVD manufacturing, thin film & wiped film evaporation, food processing industry, electrical industry and many other applications which require a clean and stable vacuum in general and as a central vacuum, are widely used in the above industrial processes to provide a clean and/or low pressure environment and efficient manufacture of products.
However, in the above vacuum pumps, there exist challenges while pumping aggressive gases, vapors or corrosive media through the pump like condensation corrosion and contamination, etc. During pumping sometimes due to condensation of process material or deposition on components surfaces, particle formation starts, if left untreated. These particle traps in between the fine clearances of rotors and results in wear out of material due to abrasion.
While pumping corrosive media, it may by themselves or in combination with others create corrosive elements which can cause degradation of the system and create rust particles. This phenomenon causes material wear out or degradation, specifically the components (Body & Rotor) which are in direct contact of process material while pumping. It ultimately results in component failures or low efficiency of equipment.
In Earlier practice, in order to protect the base material of the rotor surface (surface contact with process media), polymer-based coatings were done. This technique was effective to some extent, but low abrasion resistivity and hardness were still the limitations and resulted in a short life cycle of coating because once the coating wears out of the base metal, the coating material comes in direct contact with process media, hence a direct attack of chemical, vapors and gasses on the surface of material and results in abrasion and corrosion.
In the traditional rotors, SG 450/10 is used as base metal without alloys and a polymer based coating layer of PEEK-polyetheretherketone is coated on the surface. The challenges associated with the above process is that during running of dry screw vacuum pump having the traditional rotors, the polymer-based coating is damaged after a course of time due to abrasive/corrosive process material or process material deposition within the pump due to condensation because the abrasion resistivity of this polymer based coating is low. This results in coating wear out and ultimately the base metal of the rotor comes in direct contact with the process corrosive/abrasive material and starts getting worn out.
To maintain the effective working of equipment and to maintain the desired level of vacuum which is a critical factor for the functioning of the pump, the clearance between the two rotors and in between the rotor and the casing is very narrow. Due to wear out of material from rotor and/or casing, these clearances get disturbed and increased, which result in vacuum drop down resulting in decrease in volumetric efficiency of pump because the backflow/leakages increases due to the material wear out.
There is another problem with regard to the bond strength between the external coating and the rotor, and the casing. In the earlier practice, bonding strength between the coating material and the base material was not sufficient in order to prevent wear out of the material and exposure of the base material for direct attack.
Upon contemplating the above problems in the existing vacuum pumps, there is an unmet need to improve existing rotors used in the pumps for enhancing mechanical properties such as hardness, strength and machinability of the rotors so as to provide extended service life and avoid premature failures. At the same time, there is also a need to provide a protection layer on the base material of rotor and casing which can withstand corrosion as well as abrasion.
Below are the details of the some of the prior arts relevant to the subject matter disclosed in the present invention:
US20100072866A1 discloses a low alloy steel material for generator rotor shafts, which has tensile strength of not less than 700 MPa at room temperature. Preferably the low alloy steel material consists of, by mass percent, 0.15 to 0.35% carbon, 0.01 to 0.10% Si, 0.10 to 0.50% Mn, 1.3 to 2.0% Ni, 2.1 to 3.0% Cr, 0.20 to 0.50% Mo, 0.15 to 0.35% Cu, 0.06 to 0.14% V, and the balance of Fe and unavoidable impurities.
CN103537675A discloses powder metallurgy automotive oil pump internal and external rotors. The powder metallurgy automotive oil pump internal and external rotors are characterized by being manufactured from, by weight, 75-78 parts of iron powder, 7.5-7.8 parts of nickel, 0.5-0.8 part of graphite powder, 3.1-3.4 parts of copper, 9.2-9.6 parts of molybdenum, 0.3-0.5 part of manganese sulfide, 2.5-2.8 parts of paraffin, 8.3-8.7 parts of Cr, 0.4-0.6 part of Sb, 1.3-1.4 parts of Bi, 3.2-3.4 parts of Ti and 2-3 parts of auxiliaries. According to the powder metallurgy automotive oil pump internal and external rotors, the auxiliaries are added, and therefore the alloy powder is scattered evenly, the longitudinal and transverse evenness of the internal structural organization of the products is guaranteed, and the fatigue life of the products is prolonged; besides, the powder metallurgy automotive oil pump internal and external rotors are high in strength, good in impact toughness, high in hardness, and good in abrasion resistance and cutting performance.
CN209604238U discloses a utility model which relates to improved vacuum pumps, improved coating especially for the inner shaft of dry vacuum pump, rotor and/or stator component, it has the first layer including high phosphorus nickel coating (NiP), and wherein the first layer is coated with the second layer, and the second layer includes high phosphorus nickel and nickel phosphorus and fluoropolymer (NiP-PTFE).
GB2551107A discloses a dry pump component coated with a first layer 102 comprising a high phosphorous nickel plating (NiP) of at least 5 μm thickness coated with a second layer 100 comprising a high phosphorous nickel with nickel phosphorous and fluoropolymer (NiP-PTFE) of at least 5 μm thickness, wherein the ratio of the thickness of the first layer of NiP to the thickness of the second layer of NiP-PTFE provides high corrosion resistance and galling resistance. The fluoropolymer in the second layer may include at least one of polytetrafluoroethylene, perfluoroether, and Polyethylenimine. Preferably, the pump component is at least one of a stator component 12, an end plate, a rotor shaft component and a rotor component, where the rotor component has one of a Northey (claw) rotor, a Roots rotor or a Screw rotor profile. A dry vacuum pump comprising the component is also claimed.
US20220331856A1 discloses a high-strength stainless steel rotor and a method for preparing the same, are provided. The high-strength stainless steel rotor, including the following element components by mass percentage: C: 0.03-0.050%, Cr: 14.90-15.80%, Ni: 5.00-5.70%, Cu: 2.20-2.80%, (Nb+Ta): 0.35-0.44%, Mo: 0.45-0.54%, V: 0.06-0.10%, Si: 0.20-0.60%, Mn: 0.40-0.80%, P≤0.010%, S≤0.010%, O≤0.003%, and the balance of iron and inevitable impurities.
In the prior arts, it is also challenging to maintain the desired complex structural configuration of the rotors and casing and yet sufficiently retain their mechanical properties, therefore, in the present invention, the applicant focuses on maintaining desired rotor’s mechanical properties despite their complex shape and configuration.
The compositions and methods disclosed for manufacturing of rotors and casing in the above prior arts do not solve the problems addressed in the present invention. The coatings or the composition used in the rotors do not sufficiently stay intact in the structure of the rotors and may start to deposit on the rotor surface and disturb the clearances between the rotors and casings which damages the internal of the pump and ultimately results in reduced service life of the rotor.
It would be desirable, therefore, to develop an improved and technically advanced composition and method for manufacturing rotors for vacuum pumps that overcome the above drawbacks in the existing rotors and external pump bodies and obviates the challenges that exist in the prior arts leading to premature failure of the pump as cited in the arts above.
Summary of the Invention
Below are various objectives and embodiments of present invention as presented herein are understood to be illustrative and not restrictive and are non-limiting with respect to the scope of the invention.
It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which provides an improved hardness to the rotor’s base material according to the requirements of shape and configuration of the rotor.

It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which provides high resistance to corrosion and abrasion in the rotors.

It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which provides protection layer on the rotor surface for maintaining its hardness.

It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which helps in increasing service life of the rotor.

It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which has a negligible mean time between failures.

It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps which improves self-lubricating properties of the rotor and casing.
It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps, and external vacuum pump body which has improved lattice structure with the desired hardness.
It is an objective of the present invention to provide a method and composition for manufacturing rotors and casing to be used in vacuum pumps wherein the surface finish of rotor and casing is improved with high Ra value thus helping to increase the bonding between the base metal surface and protection layer.
In the present invention, the improved bond strength adhesion of ENP on metal surface enhance the plating life and ultimately increases the rotor and product life.
In the present invention, the base material is improved by adding alloys within the casting which improve the rotor hardness, lattice structure and the surface finish of rotor by increasing the Ra value which further help in increase the bonding between the base metal surface and protection layer (Electroless nickel plating).
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component.
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein the components comprise of rotor and casing of the vacuum pump.
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein said alloy includes 0.1 – 1.2 % of Ni and 0.2 – 0.6 % Mo.
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein said alloy includes 0.1 – 1.2 % of Ni, 0.1 - 0.6 % Cu and 0.2 – 0.6 % Mo.
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein said alloy includes 0.8 – 1.0 % of Ni, 0.3 - 0.5 % Cu and 0.2 – 0.3 % Mo
In accordance with one preferred embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein the said alloy includes 0.4 – 0.6 % of Ni, 0.2 - 0.5% Cu and 0.2 – 0.3 % Mo.
In accordance with another preferred embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein said alloy includes 0.4 – 0.6 % of Ni, 0.2 - 0.5 % Cu and 0.2 – 0.3 % Mo.
In accordance with another preferred embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein said alloy includes 0.8 – 1.0 % of Ni, 0.5 - 0.8 % Cu and 0.3 – 0.5 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 0.1 – 3.0 % of Ni and 0.2 – 1.0 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 1.0 – 3.0 % of Ni and 0.5 – 1.0 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 0.8 – 1.0 % of Ni and 0.2 – 0.3 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 0.5 – 1.0 % of Ni and 0.3 – 0.5 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 1.0 – 2.0 % of Ni and 0.5 – 1.0 % Mo.
In accordance with one of the above embodiments of the present invention, said alloy includes 0.4 – 0.6 % of Ni and 0.25 – 0.3 % Mo.
In accordance with one embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein the composition is having semi-metals and transition metals including 3 - 4% C, 1.5 - 2.5% Si, 0.1 - 1.0% Mn, 0.01 – 0.2% S and 0.01 – 0.2% P.
In accordance with one preferred embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein the composition is having semi-metals and transition metals includes 3.5 – 3.51% C, 1.9 - 2.2% Si, 0.1 – 0.5% Mn, 0.02 – 0.05% S and 0.04 – 0.05% P.
In accordance with one preferred embodiment of the present invention, there is provided a composition for manufacturing components of vacuum pumps, comprises of ductile or cast iron forming a base material of the components of the vacuum pumps, and an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components, wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component, wherein the composition is having semi-metals and transition metals includes 3.1 – 3.4 % C, 1.6 - 2.0 % Si, 0.6 – 0.8 % Mn, 0.06 – 0.15% S and 0.01 – 0.15% P.
Detailed Description of the Invention
In accordance with another embodiment of the present invention, there is provided a method of manufacturing components of vacuum pumps, comprises of forming base material by casting ductile or cast iron along with one or more semi-metals and transition metals including 3 - 4% C, 1.5 - 2.5% Si, 0.1 - 1.0% Mn, 0.01 – 0.2% S and 0.01 – 0.2% P, and adding an alloy of 0.1 – 3.0 % of Ni, 0.2 – 1.0 % Mo and/or 0.1 - 0.8 % Cu to the base material at the time of casting iron to form the component characterized by having smooth surfaces with negligible porosity and high Ra value so as to allow an effective adhesion of electroless nickel plating for providing a layer of protection.
In accordance with another embodiment of the present invention, there is provided a method of manufacturing components of vacuum pumps, comprises of forming base material by casting ductile or cast iron along with one or more semi-metals and transition metals including 3 - 4% C, 1.5 - 2.5% Si, 0.1 - 1.0% Mn, 0.01 – 0.2% S and 0.01 – 0.2% P, and adding an alloy of 0.1 – 3.0 % of Ni, 0.2 – 1.0 % Mo and/or 0.1 - 0.8 % Cu to the base material at the time of casting iron to form the component characterized by having smooth surfaces with negligible porosity and high Ra value so as to allow an effective adhesion of electroless nickel plating for providing a layer of protection, wherein Vickers Hardness number of the coating upon electroless nickel plating of the rotor varies between 850-860.
In accordance with the above embodiments, the disclosed method followed to manufacture the Rotor of Dry Screw Vacuum Pumps, Vacuum Booster and Vacuum Recompressors include advanced metallurgy i.e. alloying of cast steel followed by Ni plating & heat treatment on internal process contact material so as to provide an extra layer of protection to components and ensure protection of the base metal from corrosion/abrasion and ultimately leads to increased product life.
Further, in the above embodiments, the alloys with the composition as stated above are added at the casting stage itself to improve one or more physical properties of the base material such as corrosion resistance, abrasion resistance (hardness) and also improves self-lubrication properties of the rotor. Furthermore, these special alloys improve iron lattice structure and improve the physical properties of the formed rotor material like hardness.
In accordance with one of the above embodiments of the present invention, said base material is majorly made of SG 450/10 or CI FG 260.
In the present invention, mechanical properties of the rotor is impacted by molybdenum’s content as yield strength and tensile strength are both increased with increasing molybdenum content. Further, the tensile strength of 579 MPa for a nodular iron increases up to 20% for a nodular iron with 0.380 % molybdenum. However, the values of yield strength increased up to 10% in this case.

Further, increase of hardness in ferrite and pearlite phases is based according to the amount of molybdenum present in the iron, wherein higher values of 206 and 411 Vickers hardness numbers corresponded to ferrite and pearlite respectively for nodular iron containing 0.380 % molybdenum.

In one of the embodiments, it was observed that molybdenum, when in suitable amounts, has a marked effect on the interlayer spacing of pearlite, therefore, further increasing the property of tensile strength and yield strength of the material.

In one of the embodiments, the presence of Copper in Gray Cast Iron impacts the physical properties of the rotor, wherein Copper is mild graphitiser and it promotes pearlite formation, copper in gray iron upto 0.5% increase the yield strength and tensile strength as well as hardness increases as the proportion of the copper increases.

In one of the embodiments, the addition of Nickel results in slight increase in nodule counts, refines graphite and increases in strength and hardness, and the alloy of Ni, Cu, Mo improves corrosion resistance and cast structure of the base metal, provide rotor with improved material properties and diminish the possibility of creation of porosity and pitting which is usually seen after casting.
Further, post machining the outer surface of the Rotor, a protection layer is coated on to the rotor by way of Electroless Nickel Plating (ENP) which contains Phosphorus in high content, which results in enhanced hardness, high abrasion and corrosion resistance, wherein ENP (HighP) Plating is the process of deposition of Nickel and Phosphorus on the base metal substrate by utilizing an autocatalytic chemical reaction to deposit a reliable, repeatable plating of uniform thickness. Since the process is electroless, it ensures uniform plating of ENP on all surfaces that are dipped into the solution, wherein the plating is done on all the pump's wetted parts with medium to high ENP plating, wherein ENP plating provides a unique advantage of even thickness over all the surfaces of the component regardless of the shape, and may be selected as a very useful choice for use in pumps that are being operated in harsh environments in the process industry, wherein the ENP plating is extremely resistant to corrosion and will therefore extend the lift of everything that it coats, hence making it ideal for parts that are being exposed to harsh process conditions.
In accordance with another embodiment of the present invention, a heat treatment of Ni plated Rotor is performed to further improve the hardness and stress relieving and ENP plated parts, in general, have a hardness of 550-650 HV 0.1, as plated and this hardness goes up to 900-1000 HV 0.1 after Heat Treatment, wherein heat treatment also relieves the stress within the coating layer and improves the properties of ENP protection layer.
Experimental results
Table 1: Various Composition used in the manufacture of the rotors:
Composition C (%) Si (%) Mn (%) S(%) P (%) Ni (%) Cu (%) Mo (%)
C1 3.50-3.51 1.9-2.2 0.1-0.5 0.02-0.05 0.04-0.05 - - -
C2 3.50-3.51 1.9-2.2 0.1-0.5 0.02-0.05 0.04-0.05 1.0-3.0 - 0.5-1.0
C3 3.50-3.51 1.9-2.2 0.1-0.5 0.02-0.05 0.04-0.05 0.8-1.0 - 0.2-0.3
C4 3.50-3.51 1.9-2.2 0.1-0.5 0.02-0.05 0.04-0.05 0.4-0.6 0.2-0.5 0.2-0.3
Table 2: Hardness of the rotor corresponding to each of the composition along with Ni, Cu and Mo:
Composition Hardness (HB)
C1 160-190
C2 210-240
C3 210-220
C4 220-240
Table 3: Various Composition used in the manufacture of the casing:
Composition C (%) Si (%) Mn (%) S(%) P (%) Ni (%) Cu (%) Mo (%)
C1 3.10-3.4 1.6-2.0 0.6-0.8 0.06-0.15 0.01-0.15 - - -
C2 3.10-3.4 1.6-2.0 0.6-0.8 0.06-0.15 0.01-0.15 1.0-2.0 - 0.5-1.0
C3 3.10-3.4 1.6-2.0 0.6-0.8 0.06-0.15 0.01-0.15 0.8-1.0 - 0.2-0.3
C4 3.10-3.4 1.6-2.0 0.6-0.8 0.06-0.15 0.01-0.15 0.4-0.6 0.2-0.5 0.25-0.3
Table 4: Hardness of the casing corresponding to each of the composition along with Ni, Cu and Mo:
Composition Hardness (HB)
C1 180-230
C2 250-260
C3 210-230
C4 235-250

Table 5: Vickers Hardness number upon Electroless Nickel Plating (high Phosphorus)

Table 6: Real photographs of rotor part showing no white and red rust at the end of 500hrs of testing

Table 7: Experimental Test for Corrosion Resistance

In accordance with one of the embodiment of the present invention, there is provided a rotor for a dry screw vacuum pump, wherein the rotor has a front surface and a rear surface, each specially designed to secure an open machined balancing pocket, a screw main body having helically designed conveyor grooves with variable pitch, wherein said open machined balancing pockets that are engraved during casting followed by machining of the rotors for counterbalancing of the dynamic and static imbalance produced in the rotors.
In accordance with another embodiment of the present invention, there is provided a rotor which is having at least a couple of hollow lobes having non-circular annulus, wherein each said rotor is provided with an irremovably solid rotor shaft along its axis of rotation on its two opposite ends, wherein each said rotor is provided with an internal balancing cavity longitudinally designed along and on its axis of rotation, wherein a bi-lobe is provided in each of the rotor, and inner longitudinal profile of one lobe is designed symmetrically on and along the axis of rotation and consistently with the non-circular annulus of the lobe so as to optimize mass distribution of the rotor assembly.
In the present invention, the process steps followed to manufacture the rotors of the structural configuration explained in the above embodiments is critical as a very specific composition and method produces rotor of the above structure with the desired mechanical properties. Even a slight change in the composition and method can impact or may deteriorate the mechanical features of the rotor.
In accordance with one of the preferred embodiments of the present invention, the method and composition for manufacturing rotors is specific to the manufacturing of the rotors having structural configuration as disclosed in the above embodiments.
In the present invention, the terms such as “casing” or “body” or “pump body” or “pump casing” should be interpreted to have the same meaning in context of the vacuum pump.
While the invention is amenable to various modifications and alternative forms, some embodiments have been illustrated by way of experimental results in the tables and are described in detail above. The intention, however, is not to limit the invention by those experimental results and the invention is intended to cover all modifications, equivalents, and alternatives to the embodiments described in this specification.

The embodiments in the specification are described in a progressive manner and focus of description in each embodiment is the difference from other embodiments. For same or similar parts of each embodiment, reference may be made to each other.

It will be appreciated by those skilled in the art that the above description was in respect of preferred embodiments and that various alterations and modifications are possible within the broad scope of the appended claims without departing from the spirit of the invention with the necessary modifications.

Based on the description of disclosed embodiments, persons skilled in the art can implement or apply the present disclosure. Various modifications of the embodiments are apparent to persons skilled in the art, and general principles defined in the specification can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments in the specification but intends to cover the most extensive scope consistent with the principle and the novel features disclosed in the specification. , C , Claims:We Claim:
1. A composition for manufacturing components of vacuum pumps, comprises of:
ductile or cast iron forming a base material of the components of the vacuum pumps; and
an alloy containing Ni, Mo and/or Cu, for improving lattice structure of the base material and mechanical properties of the components,
wherein the alloy forms 0.1-5% and the base material forms rest of the composition of the component.
2. The composition as claimed in claim 1, wherein the components comprise of rotor and casing of the vacuum pump.
3. The composition as claimed in claim 1, wherein said alloy includes 0.1 – 1.2 % of Ni, 0.1 - 0.6 % Cu and 0.2 – 0.6 % Mo.
4. The composition as claimed in claim 1, wherein said alloy includes 0.8 – 1.0 % of Ni, 0.3 - 0.5 % Cu and 0.2 – 0.3 % Mo
5. The composition as claimed in claim 1, wherein the said alloy includes 0.4 – 0.6 % of Ni, 0.2 - 0.5% Cu and 0.2 – 0.3 % Mo.
6. The composition as claimed in claim 1, wherein said alloy includes 0.4 – 0.6 % of Ni, 0.2 - 0.5 % Cu and 0.2 – 0.3 % Mo.
7. The composition as claimed in claim 1, wherein said alloy includes 0.8 – 1.0 % of Ni, 0.5 - 0.8 % Cu and 0.3 – 0.5 % Mo.
8. The composition as claimed in claim 1, wherein said alloy includes 0.1 – 3.0 % of Ni and 0.2 – 1.0 % Mo.
9. The composition as claimed in claim 1, wherein said alloy includes 1.0 – 3.0 % of Ni and 0.5 – 1.0 % Mo.
10. The composition as claimed in claim 1, wherein said alloy includes 0.8 – 1.0 % of Ni and 0.2 – 0.3 % Mo.
11. The composition as claimed in claim 1, wherein said alloy includes 0.5 – 1.0 % of Ni and 0.3 – 0.5 % Mo.
12. The composition as claimed in claim 1, wherein said alloy includes 1.0 – 2.0 % of Ni and 0.5 – 1.0 % Mo.
13. The composition as claimed in claim 1, wherein said alloy includes 0.4 – 0.6 % of Ni and 0.25 – 0.3 % Mo.
14. The composition as claimed in claim 1, wherein the composition is having semi-metals and transition metals including 3 - 4% C, 1.5 - 2.5% Si, 0.1 - 1.0% Mn, 0.01 – 0.2% S and 0.01 – 0.2% P.
15. The composition as claimed in claim 1, wherein said semi-metals and transition metals includes 3.5 – 3.51% C, 1.9 - 2.2% Si, 0.1 – 0.5% Mn, 0.02 – 0.05% S and 0.04 – 0.05% P.
16. The composition as claimed in claim 1, wherein said semi-metals and transition metals includes 3.1 – 3.4 % C, 1.6 - 2.0 % Si, 0.6 – 0.8 % Mn, 0.06 – 0.15% S and 0.01 – 0.15% P.
17. The composition as claimed in claim 1, wherein the hardness of the components varies between 160-260 HB.
18. The composition as claimed in claim 1, wherein the hardness of the components varies between 220-240 HB.
19. The composition as claimed in claim 1, wherein the hardness of the components varies between 250-260 HB.
20. A method of manufacturing components of vacuum pumps, comprises of:
forming base material by casting ductile or cast iron along with one or more semi-metals and transition metals including 3 - 4% C, 1.5 - 2.5% Si, 0.1 - 1.0% Mn, 0.01 – 0.2% S and 0.01 – 0.2% P; and
adding an alloy of 0.1 – 3.0 % of Ni, 0.2 – 1.0 % Mo and/or 0.1 - 0.8 % Cu to the base material at the time of casting iron to form the component characterized by having smooth surfaces with negligible porosity and high Ra value so as to allow an effective adhesion of electroless nickel plating for providing a layer of protection.
21. The method as claimed in claim 1, wherein Vickers Hardness number of the coating upon electroless nickel plating of the component varies between 850-860.
22. The method as claimed in claim 1, wherein the components comprise of rotor and casing of the vacuum pump, wherein the rotor is characterized by having open machined balancing pockets at its two ends that are engraved during casting followed by machining of the rotors for counterbalancing of the dynamic and static imbalance produced in the rotors.
23. The method as claimed in claim 1, wherein the components comprise of rotor and casing of the vacuum pump, wherein the rotor is characterized by having an irremovably solid rotor shaft along its axis of rotation on its two opposite ends, wherein said rotor is provided with an internal balancing cavity longitudinally designed along and on its axis of rotation and a bi-lobe with non-circular annulus is provided in the rotor, and inner longitudinal profile of one lobe is designed symmetrically on and along the axis of rotation and consistently with the non-circular annulus of the lobe so as to optimize mass distribution of the rotor.