GB2125466A - Improvements in and relating to drill pipes - Google Patents
Improvements in and relating to drill pipes Download PDFInfo
- Publication number
- GB2125466A GB2125466A GB08223724A GB8223724A GB2125466A GB 2125466 A GB2125466 A GB 2125466A GB 08223724 A GB08223724 A GB 08223724A GB 8223724 A GB8223724 A GB 8223724A GB 2125466 A GB2125466 A GB 2125466A
- Authority
- GB
- United Kingdom
- Prior art keywords
- members
- connector part
- pipe connector
- recess
- annular zone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000000463 material Substances 0.000 claims abstract description 56
- 238000002844 melting Methods 0.000 claims abstract description 10
- 230000008018 melting Effects 0.000 claims abstract description 10
- 238000000034 method Methods 0.000 claims description 39
- 239000007769 metal material Substances 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 7
- 229910000831 Steel Inorganic materials 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000010959 steel Substances 0.000 claims description 6
- 230000004048 modification Effects 0.000 claims description 4
- 238000012986 modification Methods 0.000 claims description 4
- 239000010432 diamond Substances 0.000 claims description 3
- 239000000155 melt Substances 0.000 claims description 3
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims description 3
- 238000005496 tempering Methods 0.000 claims description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 238000005336 cracking Methods 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
- E21B17/10—Wear protectors; Centralising devices, e.g. stabilisers
- E21B17/1085—Wear protectors; Blast joints; Hard facing
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Earth Drilling (AREA)
Abstract
A drill pipe connector, for example the box 1 of a conventional pin and box connector, is provided with increased wear resistance in an annular zone 3 of the external surface thereof by fixing a plurality of members 4 of hard wear resistant material to the external surface of the pipe connector part in the annular zone 3 using a material 6 having a melting point below that of the material from which the connector part is made. The members 4 and material 6 are both made of a material having a hardness greater than that of the material from which the pipe connector part is made. The members 4 have opposed generally parallel faces, one of which is applied to the surface of the pipe connector part and the other of which is exposed, and a regular, for example rectangular, periphery, and are located in a single or plurality of recesses 5 in the surface of the connector with their exposed surfaces proud of, level with or lying below the adjacent surfaces of the pipe connector part. <IMAGE>
Description
SPECIFICATION
Improvements in and relating to drill pipes
The present invention concerns improvements in and relating to drill pipes for use in drilling wells for example in off-shore operations.
Drill pipes are made up of a plurality of drill pipe sections each of which is formed or provided at each end with part of a pipe connector by which the pipe sections are connected together, the pipe connector having an outer diameter greater than that of the outer diameter of the pipe sections and, as a consequence, during use will come into contact with the well casing. To protect the pipe connectors against wear in use at least one part of each connector is provided on its external surface with a band of a hard wear resistant material.
Conventionally, this band of material is formed by melting the surface metal of the connector part using an electric arc and feeding hard wear resistant particulate material, for example crushed pieces of carbide, into the resulting metal pool.
This provides a hard wear resistant band for the pipe connector which does indeed protect the pipe connector against wear but has at least three substantial disadvantages. Firstly, the characteristics of the metal of the pipe connector are adversely affected by melting the metal in the region of the wear resistant band. Secondly, when the wear resistant band needs to be replaced, further damage is done to the metal of the pipe connector. Thirly, the band has an irregular external surface which itself will wear the casing of the well.
According to one aspect of the present invention there is provided a method of providing a part of a drill pipe connector with increased wear resistance in an annular zone of the external surface thereof, comprising fixing a plurality of members of hard wear-resistant material to the external surface of the pipe connector part in the annular zone, the members having opposed generally parallel surfaces, one of which is applied to the surface of the pipe connector and the other of which is exposed, and a regular periphery, the members being fixed to the external surface of the pipe connector part using a material which melts at a temperature below that of the material from which the pipe connector is made, both the members and the material having a hardness greater than that of the material from which the pipe connector part is made.
The members may be arranged individually or in groups in the annular zone or they may be arranged to form a continuous band in the annular zone.
The members may for example have a generally rectangular periphery with the lateral faces perpendicular to or inclined to the opposed generally parallel surfaces, and they may be arranged to extend parallel to the axis of the pipe connector part.
Each member may be placed in a recess in the exterior surface of the pipe connector part, which recess may for example have been machined in the exterior surface of the pipe connector part, and the depth of the recess may be such that the exposed surface of the member is proud of, level with, or lies below, the level of the adjacent exterior surface of the pipe connector part. A single recess may be provided for all the members or separate recesses may be provided for individual members or groups of members.
The material which is used to fix the members to the connector part is preferably in the form of a powder which is sprayed on using a gas torch.
In a preferred embodiment, the pipe connector part and members are heated slightly to prevent subsequent cold cracking and then the one surface of each member and the corresponding surface of the pipe connector part are coated with the metallic material. The members are then positioned on the surface of the pipe connector part and the metallic powder fused by heating with the gas torch into which further metallic material is injected to fill any gaps around the members.
The exposed surfaces of the members may then be ground to provide a smooth surface in the annular zone.
For use with pipe connectors made of alloy steels having a melting point of about 1 4500C and a hardness of 220/240 BHN, the metallic material may be made of a nickel based powder, typically 93.5% Ni 6% Bo+Si, 0.23% Se, 0. 10% Co and 0.01% C having a melting point of about 1 750C and a hardness of 350/410 BHN.
The members may for example be made of a tungsten carbide material, typically 90.5% C and 9.0% Co with a hardness of 1250 Hv30, which is substantially in excess of that of the alloy steels used.
The members may for example be 3 mm thick, 13 mm long and 5 mm wide.
Where groups or a continuous band of members are provided, the wear resistance may be further increased by providing some of the members with superior wear resistance characteristics, for example by impregnating or facing the exposed surfaces of these members with a harder material, such for example as industrial diamonds. These members with superior wear resistance characteristics may be made with a reduced thickness, for example 2.8 mm thick rather than 3 mm thick so that the exposed surfaces of the adjacent members can be ground down to provide a smooth surface without grinding the surfaces of the members with superior wear characteristics.
It has been found that, where some of the members are provided with the above described superior wear characteristics, the remainder of the members may be made of a material which has improved impact resistance but a reduced hardness value, while of course still having a hardness well in excess of that of the alloy steels used.
According to another aspect of the present invention there is provided a drill pipe connector part which comprises in its external surface an annular zone of increased wear resistance comprising a plurality of members of hard wear resistant material which are fixed to the external surface of the connector part by a material having a melting point below that of the material from which the connector is made, the members having opposed generally parallel faces, one of which is applied to the surface of the pipe connector part, and the other of which is exposed, and a regular periphery, the members and material used for fixing those members to the surface of the connector part both have a hardness which is greater than that of the material of the drill pipe connector part.
The material and members may have the features and characteristics as described above and be arranged on the pipe connector part as described above.
Embodiments according to the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a diagrammatic part axial section through an embodiment of a pipe connector according to the present invention:
Figure 2 is a developed plan view of part of the connector of figure 1;
Figures 3, 4 and 5 show part axial sections through further embodiments according to the present invention; and
Figure 6 shows a developed pian view similar to that of Figure 2 showing a further embodiment according to the present invention.
As shown in Figure 1 , the pipe connector part 1 is the box of a conventional pin and box threaded connector which is made of an alloy steel and which is designed to be welded to one end of a drill pipe section 2. The box is provided with an annular zone 3 having increased wear resistance adjacent that end of the box which is connected to the pipe section 2, so that zone 3 is remote from the parts of the surfaces of the member which are engaged by tongs used for connecting two pipes sections. In the annular zone 3, a plurality of members 4 which are made of a wear resistant material which is harder than that of the material from which the box is made are provided on the external surface of the box.
The members 4 are received in a recess 5 which is machined in box 1, the depth of the recess relative to the thickness of the members 3 is such that the final surface of the members 3 may, as shown, be level with.the adjacent surface of the box 1, or may be poud of, or recessed below, the level of that surface.
The members are fixed in place using a metallic material 5 which has a melting point below that of the material from which the box is made and has a hardness greater than that of the material from which the box is made.
The members 4 are assembled in the recess 6 in the box 1 in batches with the axis of the box 1 horizontal. A batch is arranged on the uppermost part of the surface of the box and the box is then rotated to bring an adjacent part uppermost and another batch of members is arranged on that part. In respect of each batch of members, the box 1 and members are heated slightly, for example to about 3000 C, to prevent subsequent cold cracking. The one surface of each member which is to be applied to the surface of the box, together with the corresponding surface of the box, are then coated with the metallic material which is in the form of a powder and is sprayed onto the surfaces using a gas torch.The batch of members is then assembled on the box 1 and the members are fused to the surface of the box by further heating with the gas torch into which further of the metallic material powder is injected to build up fused metallic material in the gaps surrounding the members.
When the members and box have cooled, the exposed surfaces of the members may be machined to provide them with a smooth surface.
As shown, the members have opposed generally parallel surfaces, one of which is applied to the surface of the box 1 and the other of which is exposed, and a regular periphery. Conveniently the members are rectangular and are arranged with their longer dimension parallel with the axis of the box 1 in axial rows which are off-set relative to each other. Alternatively, longer members 4a (Figure 2) may be used which have a length corresponding to the axial extent of the recess 5.
It will be appreciated that, while for convenience the members are rectangular, they may have other regular shapes, mainly polygonal, which are such that they can be interfitted conveniently.
For a six inch diameter pipe section, the members 4 are preferably about 3 mm thick with a length of 13 mm and a width of 5 mm, the axial extent of the recess being for example 50 mm.
The members may for example be made of a tungsten carbide material comprising for example 90.5% TC and 9.0% Co, which has a hardness of 1250Hv30.
For use with pipe connectors made of alloy steels which have a melting point of about 1 4500C and a hardness of about 220/240 BHN, the metallic material may be made of a nickel based powder, for example comprising 93.5% Ni, 6% Bo+Si, 0.23% Fe, 0.10% Co and 0.01% C, which has a melting point of about 11 750C and a hardness of about 350/41 0BHN.
It has been found that, with the above described arrangement, the life of the zone of increased wear resistance can be increased substantially by providing some of the members 4 with superior wear characteristics, for example by making them of even harder material or by providing them with a facing or coating of harder material, e.g. by impegnating the exposed surfaces with industrial diamonds. With such an arrangement, the remainder of the members can be made of a less hard material without reducing overall the life of the wear resistance.
Where some of the members 4b have superior wear characteristics, it is advantageous to make them of a lesser thickness than the others of the members 4, as shown in Figure 3. For example, the members 4b may be 2.8 mm thick whereas the members 4 are 3 mm thick. When all the members have been assembled, the exposed surfaces of the members 4 are then ground to smooth them and the grinding operation is controlled so that the final thickness of the members 4 is just in excess of that of the members 4b so that the exposed surfaces of the members 4b are not ground, thereby reducing wear of the grinding machine.
While as described above, the members 4 are arranged to provide a continuous band of increased wear resistance in zone 3, in a modification, as shown in Figure 4, 5 and 6, individual members or groups of members may be arranged spaced apart circumferentially in the zone 3, the members being provided in separate recesses or a common recess and fixed to the connector part as described above.
For example, as shown in Figure 4, the connector part 1 is provided with an annular recess 5 in which members 4 are arranged spaced apart around the periphery of the member 1, the members 4 being fixed to the member 1 by the metallic material 5 which is provided to fill the gaps between the members 4. In the embodiments of Figure 5, the connector part 1 is provided with circumferentially spaced recesses 5a in each of which a member 4 is arranged, each member 4 being fixed in place using the metallic material 6. As shown in Figure 6, groups of members 4 are arranged at spaced intervals in a continuous recess 5, the gaps between the members 4 being filled with the metallic material 6.In a modification of this embodiment, as shown by broken lines in Figure 6, the continuous recess 5 may be replaced by individual recesses 5b for each group of members 4. As previously described, one or more of the members 4 of each group may have superior wear characteristics as described in relation to member 4b of Figure 3.
Equally in the embodiments of Figure 4 and 5 the members 4 may also have superior wear resistance properties as described in relation to member 4b of Figure 3. Finally, in each of the embodiments 4, 5 and 6 the member 4 or 4b may have a length corresponding to the length of the zone 3 and, in relation to the embodiment of
Figure 6, each group of members may comprise 1 or more axial rows of members.
It will be appreciated that, with the above described method of creating a wear resistant zone 3, it is a relatively simple matter to replace the members when they become worn. For replacement purposes, connector part 1 is heated to a point at which the metallic material 6 starts to melt and the members 4 are loosened and can be removed. Any material 6 remaining can be removed by heating or by regrinding the or each groove and when this is complete, the operation described above is repeated to replace the members 4. It will be appreciated that, in applying heat at any stage in the method described above, the heat should be applied sufficiently locaily that the bulk of the material of connector part 1 remains well below the upper tempering point and anealing temperature of the steel of member 1.Additionally, when the member is allowed to cool after heating it must be allowed to cool slowly under blanketed conditions.
Claims (Filed on 17 August 1983)
1. A method of providing a part of a drill pipe connector with increased wear resistance in an annular zone of the external surface thereof comprising fixing a plurality of members of hard wear resistant material to the external surface of the pipe connector part in the annular zone, the members having opposed generally parallel surfaces, one of which is applied to the surface of the pipe connector and the other of which is exposed, and a regular periphery, the members being fixed to the external surface of the pipe connector part using a material which melts at a temperature below that of the material from which the pipe connector is made, both the members and the material having a hardness greater than that of the material from which the pipe connector part is made.
2. A method as claimed in claim 1 wherein the members have a polygonal periphery.
3. A method as claimed in claim 2, wherein the members have a rectangular periphery and are arranged to extend generally parallel to the axis of the pipe connector part.
4. A method as claimed in any one of the preceding claims, wherein the members are circumferentially spaced apart in the annular zone.
5. A method as claimed in any one of claims 1 to 3, wherein the members are arranged in groups, the groups being circumferentially spaced apart in the annular zone.
6. A method as claimed in any one of claims 1 to 3, wherein the members are arranged to form a continuous band of members in the annular zone.
7. A method as claimed in any one of the preceding claims, wherein the members are arranged in at least one recess in the surface of the pipe connector part.
8. A method as claimed in claim 7, wherein a plurality of recesses are provided circumferentially spaced apart in the annular zone and at least one member is provided in each recess.
9. A method as claimed in claim 7, wherein a continuous annular recess is provided in the annular zone in which the members are arranged.
10. A method as claimed in any one of claims 7 to 9, wherein the or each recess is machined in the exterior surface of the pipe connector part.
11. A method as claimed in any one of claims 7 to 10, wherein the depth of the or each recess relative to the thickness of the members is such that the exposed surface of at least some of the members is level with the level of the adjacent exterior surface of the pipeconnector part.
12. A method as claimed in any one of claims
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (24)
1. A method of providing a part of a drill pipe connector with increased wear resistance in an annular zone of the external surface thereof comprising fixing a plurality of members of hard wear resistant material to the external surface of the pipe connector part in the annular zone, the members having opposed generally parallel surfaces, one of which is applied to the surface of the pipe connector and the other of which is exposed, and a regular periphery, the members being fixed to the external surface of the pipe connector part using a material which melts at a temperature below that of the material from which the pipe connector is made, both the members and the material having a hardness greater than that of the material from which the pipe connector part is made.
2. A method as claimed in claim 1 wherein the members have a polygonal periphery.
3. A method as claimed in claim 2, wherein the members have a rectangular periphery and are arranged to extend generally parallel to the axis of the pipe connector part.
4. A method as claimed in any one of the preceding claims, wherein the members are circumferentially spaced apart in the annular zone.
5. A method as claimed in any one of claims 1 to 3, wherein the members are arranged in groups, the groups being circumferentially spaced apart in the annular zone.
6. A method as claimed in any one of claims 1 to 3, wherein the members are arranged to form a continuous band of members in the annular zone.
7. A method as claimed in any one of the preceding claims, wherein the members are arranged in at least one recess in the surface of the pipe connector part.
8. A method as claimed in claim 7, wherein a plurality of recesses are provided circumferentially spaced apart in the annular zone and at least one member is provided in each recess.
9. A method as claimed in claim 7, wherein a continuous annular recess is provided in the annular zone in which the members are arranged.
10. A method as claimed in any one of claims 7 to 9, wherein the or each recess is machined in the exterior surface of the pipe connector part.
11. A method as claimed in any one of claims 7 to 10, wherein the depth of the or each recess relative to the thickness of the members is such that the exposed surface of at least some of the members is level with the level of the adjacent exterior surface of the pipeconnector part.
12. A method as claimed in any one of claims
7 to 10, wherein the depth of the recess in relation to the thickness of the members is such that the exposed surface of at least some of the members is proud of the level of the adjacent exterior surface of the pipe connector part.
1 3. A method as claimed in any one of claims 7 to 10, wherein the depth of the recess relative to the thickness of the members is such that the exposed surface of at least some of the members lies below the level of the adjacent exterior surface of the pipe connector part.
14. A method as claimed in any one of claims 7 to 13, wherein some of the members have a lesser thickness than others of the members.
1 5. A method as claimed in any one of the preceding claims, wherein the members are made of a tungsten carbide material.
1 6. A method as claimed in any one of the preceding claims, wherein the exposed surfaces of some of the members are impregnated or faced with a harder material, e.g. industrial diamonds.
17. A method as claimed in claim 16, wherein the members having a harder exposed surface have a lesser thickness than the other members and the surfaces of the other members are ground to smooth them.
18. A method as claimed in any one of the preceding claims, wherein the material fixing the members to the pipe connector part is in the form of a powder which is sprayed on using a gas torch.
19. A method as claimed in any one of the preceding claims, wherein during assembly of the members with the pipe connector part, the surface of the pipe connector part and the members are heated slightly, the one surface of each member and the corresponding surface of the pipe connector part are coated with the fixing material, the members are positioned on the surface of the pipe connector part, the fixing material is heated to fuse it, and further fixing material is provided to fill any gaps around and between the members.
20. A method as claimed in claim 19, including grinding the exposed surfaces of at least some of the members to smooth them.
21. A method of providing a part of a drill pipe connector with increased wear resistance substantially as herein described with reference to the accompanying drawings.
22. A drill pipe connector part comprising on its external surface an annular zone of increased wear resistance comprising a plurality of members of hard wear resistant material which are fixed to the external surface of the connector part by a material having a melting point below that of the material from which the connector is made, the members having opposed generally parallel faces, one of which is applied to the surface of the pipe connector part, and the other of which is exposed, and a regular periphery, the members and material used for fixing the members to the surface of the connector part both having a hardness which is greater than that of the material of the drill pipe connector part.
23. A drill pipe connector part comprising in its external surface an annular zone of increased wear resistance and made by a method according to any one of claims 1 to 21.
24. A drill pipe connector part comprising in its external surface an annular zone of increased wear resistance substantially as herein described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08223724A GB2125466B (en) | 1982-08-18 | 1982-08-18 | Improvement in and relating to drill pipes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08223724A GB2125466B (en) | 1982-08-18 | 1982-08-18 | Improvement in and relating to drill pipes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2125466A true GB2125466A (en) | 1984-03-07 |
| GB2125466B GB2125466B (en) | 1986-02-05 |
Family
ID=10532366
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08223724A Expired GB2125466B (en) | 1982-08-18 | 1982-08-18 | Improvement in and relating to drill pipes |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2125466B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE1014478A3 (en) * | 2000-11-17 | 2003-11-04 | Baker Hughes Inc | DRILL STEEL BODY scraping. |
| FR3015546A1 (en) * | 2013-12-20 | 2015-06-26 | Vallourec Drilling Products France | DRILL LINING ELEMENT HAVING AN IMPROVED REFILL LAYER |
| CN105537586A (en) * | 2015-12-14 | 2016-05-04 | 中国石油大学(北京) | Machining method for boss type diamond composite material anti-abrasion belt, mould and anti-abrasion belt |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1496641A (en) * | 1975-07-21 | 1977-12-30 | Christensen Inc | Tool joint wear protectors |
| GB2041427A (en) * | 1978-11-01 | 1980-09-10 | Nl Industries Inc | Insert for tool wear surfaces and method of manufacture |
-
1982
- 1982-08-18 GB GB08223724A patent/GB2125466B/en not_active Expired
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1496641A (en) * | 1975-07-21 | 1977-12-30 | Christensen Inc | Tool joint wear protectors |
| GB2041427A (en) * | 1978-11-01 | 1980-09-10 | Nl Industries Inc | Insert for tool wear surfaces and method of manufacture |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE1014478A3 (en) * | 2000-11-17 | 2003-11-04 | Baker Hughes Inc | DRILL STEEL BODY scraping. |
| US6651756B1 (en) | 2000-11-17 | 2003-11-25 | Baker Hughes Incorporated | Steel body drill bits with tailored hardfacing structural elements |
| FR3015546A1 (en) * | 2013-12-20 | 2015-06-26 | Vallourec Drilling Products France | DRILL LINING ELEMENT HAVING AN IMPROVED REFILL LAYER |
| WO2015092340A3 (en) * | 2013-12-20 | 2015-12-03 | Vallourec Drilling Products France | Drill string element having an improved refill layer |
| US10202810B2 (en) | 2013-12-20 | 2019-02-12 | Tuboscope Vetco (France) Sas | Drill-string liner element furnished with an improved hardbanding layer |
| CN105537586A (en) * | 2015-12-14 | 2016-05-04 | 中国石油大学(北京) | Machining method for boss type diamond composite material anti-abrasion belt, mould and anti-abrasion belt |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2125466B (en) | 1986-02-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19970818 |