CN114905174A

CN114905174A - Plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fitting

Info

Publication number: CN114905174A
Application number: CN202210537442.4A
Authority: CN
Inventors: 于浩楠; 李智; 赵子俊; 孙俪峰; 金泽坤; 周秉强; 温晶雯
Original assignee: Northeast Petroleum University
Current assignee: Northeast Petroleum University
Priority date: 2022-05-18
Filing date: 2022-05-18
Publication date: 2022-08-16

Abstract

The invention belongs to the technical field of nuclear power pipe fitting cutting, and discloses a plasma-flame coaxial composite cutting process for a nuclear power thick-wall stainless steel complex pipe fitting, which comprises the following steps: providing a composite cutting torch, wherein the composite cutting torch comprises a plasma cutting torch and a flame torch coaxially sleeved on the periphery of the plasma cutting torch; the flame torch is of an external mixing structure and is respectively communicated with an oxygen source and a fuel gas source; the composite cutting torch is used as a cutting source to cut the complex stainless steel pipe fitting to be cut, and therefore the nuclear power thick-wall complex stainless steel pipe fitting can be cut. The plasma cutting capability and quality are improved by coaxially compounding with flame, and the thickness indexes of thick-wall stainless steel main pipelines, super pipelines and the like of AP1000 nuclear power in China and groove cutting are realized; the composite cutting torch is connected with a robot arm arranged at the lower end of the gantry stand column, so that the all-position cutting of the nuclear power thick-wall stainless steel complex pipe fitting can be realized.

Description

Plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fitting

Technical Field

The invention relates to the technical field of nuclear power pipe fitting cutting, in particular to a plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fittings.

Background

In 2014, a new forming process of 'axial material supplement and radial extrusion' of AP1000 nuclear power stainless steel main pipe fittings and complex pipe fittings is provided by the technical personnel in the field. Compared with the forging forming of the traditional nuclear power pipe fitting, all parts of the metal continuously deform in the extrusion forming process, and the forming time is short, so the extrusion forming has remarkable advantages in the aspects of improving the product quality and shortening the manufacturing period.

The excessive parts such as a pipe connecting nozzle and the like of an extrusion-molded pipe fitting need to be cut off, the thin-wall part can be cut by adopting a universal plasma power supply device, the plasma cutting technology for cutting the stainless steel material depends on the power of the plasma power supply at present, the cutting capability of the power supply cannot meet the requirement for cutting the pipe fitting with the thick wall due to the particularity of the stainless steel material 316LN for nuclear power, and only large-scale machining equipment can be adopted for processing, so that a large amount of time and cost are consumed.

In order to further reduce the production cost, improve the efficiency and realize the near-net-shape manufacturing of the connecting pipe nozzle of the nuclear power complex pipe fitting, a special high-power plasma cutting process technology and equipment thereof are urgently needed.

Therefore, the invention provides a plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fittings.

Disclosure of Invention

In order to solve the defects in the prior art, the invention provides a plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fittings.

The plasma-flame coaxial composite cutting process for the nuclear power thick-wall stainless steel complex pipe fitting is realized by the following technical scheme:

a plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fittings comprises the following steps:

providing a composite cutting torch, wherein the composite cutting torch comprises a plasma cutting torch and a flame torch coaxially sleeved on the periphery of the plasma cutting torch; the flame torch is of an external mixing structure and is respectively communicated with an oxygen source and a fuel gas source;

the composite cutting torch is used as a cutting source to cut the stainless steel complex pipe fitting to be cut, and during cutting, plasma jet flow is jetted out of a plasma cutting torch in the composite cutting torch through a nozzle of the plasma cutting torch; meanwhile, the flame torch jets out a flame heat source of oxygen and fuel gas, so that the plasma arc jet flow is isolated from cold air, heat energy is injected, and the shock wave loss of the plasma arc jet flow is reduced.

Further, the distance between the nozzle of the plasma cutting torch and the nozzle of the flame torch is 10-20 mm, so that the plasma cutting torch protective cap is exposed.

Further, the flow ratio of the oxygen introduced into the flame torch to the fuel gas is 3: 1.

Further, the fuel gas is propane gas.

Further, when the stainless steel plate is cut, the working pressure of oxygen in the flame is 0.5-0.8 MPa, and the working pressure of fuel gas is 0.4-0.6 MPa.

Further, when a stainless steel plate with the thickness of 120 mm-140 mm is cut, the working pressure of oxygen in the flame torch is 0.5-0.6 MPa, and the working pressure of fuel gas is 0.4-0.5 MPa.

Further, when a stainless steel plate with the thickness of 140 mm-160 mm is cut, the working pressure of oxygen in the flame torch is 0.6-0.8 MPa, and the working pressure of fuel gas is 0.5-0.6 MPa.

Further, when a stainless steel plate having a thickness of 160mm or more is cut, the operating pressure of oxygen in the torch is 0.8MPa, and the operating pressure of fuel gas is 0.6 MPa.

Compared with the prior art, the invention has the following beneficial effects:

the technology of the invention is a new process for plasma cutting of thick-wall stainless steel nuclear power pipelines and complex pipe fittings developed aiming at a new extrusion forming process of nuclear power pipe fittings, compared with forging forming of nuclear power pipe fittings, the process has the advantages that all parts of metal are continuously deformed in the extrusion forming process, the forming time is short, the deformation with large deformation amount can be realized in 1 pass, the deformation is uniform, and the control of the grain size is facilitated, so the extrusion forming has remarkable advantages in the aspects of improving the product quality and shortening the manufacturing period. The manufacturing method solves the manufacturing problem of large complex pipe fittings for nuclear power and power generation equipment in China, improves the matching process level and the manufacturing capability of heavy forging forming equipment in China, meets the requirements of fields such as power generation equipment, ships and the like on the large complex pipe fittings with high efficiency, high quality, low cost and long service life, and enables the manufacturing technology of the large complex pipe fittings in China to reach the international advanced level.

The plasma cutting capability and quality are improved by coaxially compounding with flame, and the thickness index of the groove cutting of the AP1000 nuclear power thick-wall stainless steel pipe fitting in China is realized; the technology is connected with a robot arm and is inversely installed at the lower end of a gantry upright post, so that the all-position cutting of nuclear power thick-wall stainless steel complex pipe fittings can be realized.

Compared with the existing turning processing, the plasma cutting efficiency is greatly improved. Taking simple machining of the end face of the inclined tee joint as an example, the placing and machining time (the machining difficulty of stainless steel materials is high, and the tools are changed for many times in the midway) of a turning workpiece is about 5 hours, and the plasma cutting is about 15 minutes (the teaching efficiency is higher for batch production without each time); the non-orthogonal branch pipes (the extension lines and the axes do not intersect) on the super pipeline and the main pipeline are longer due to the fact that the workpiece placing and processing difficulty is increased, and the plasma cutting time is basically the cutting after teaching.

The cost is greatly reduced. The stainless steel cutting tool is high in price, and due to the fact that the nuclear power pipeline is large in wall thickness, the frequency of replacement of the cutting tool is high, and huge cost is caused; time costs, labor costs and material waste costs are also enormous due to the low machining efficiency.

The whole manufacturing process is different, and the bottleneck of manufacturing nuclear power pipe fittings in China is broken through.

Drawings

FIG. 1 is a schematic structural diagram of an AP1000 nuclear power main pipe fitting;

FIG. 2 is a schematic diagram of the cutting process of the present invention;

FIG. 3 is a schematic view showing the positional relationship between the injection port of the plasma cutting torch and the injection port of the flame torch according to the present invention;

FIG. 4 is a schematic view of the positional relationship of the oxygen port outlet and the gas port outlet in a flame torch of the invention;

FIG. 5 is a schematic view of the composite torch of the present invention in full position cutting.

Detailed Description

As described in the background art, in the prior art, the forged pipeline integral structure is machined by machining processes such as boring and turning; the extrusion molding proposed in China at present directly extrudes a pipeline, and only redundant filler necks need to be removed.

However, the inventor finds that the sizes of pipe fittings such as nuclear power main pipe fittings, super pipe fittings and inclined tee joints are large; for example, the maximum total length of an AP1000 nuclear power main pipe fitting (shown in figure 1) is 8000mm, the maximum end surface diameter is 2000mm, and the maximum wall thickness is 120mm, the main pipe fitting cannot be turned over during cutting, only a robot arm can be used for fixedly cutting the pipe fitting at each position, and the cutting position is not fixed, so that the cutting at any position in a placing area is required to be completed. Although the plasma cutting can solve the all-position cutting problem to a certain extent, the pipeline with the thickness of 160mm can be theoretically realized by the power supply cutting capacity with the maximum power at home and abroad at present, the all-position cutting needs horizontal or even vertical upward cutting, and the upward cutting thickness can only reach 120 mm. For thick-wall stainless steel pipes, the wall thickness is generally 80-120 mm, but as the filler neck is required to be welded, groove cutting is required for cutting, and the maximum theoretical cutting thickness can reach 170mm (45-degree groove), so that the cutting requirement of 170mm cannot be met by single plasma cutting. In the prior art, large-scale machining equipment is adopted for turning, and because the hardness of the steel 316LN typical for nuclear power is high, the machining difficulty is high, a large number of cutters are consumed for machining, and the cost is overhigh; the nuclear power pipe fitting is large in size, needs a large-scale multi-shaft machining center to machine, and is very difficult to clamp; the wall thickness of the pipe fitting is large, the removal amount of the groove is large, and the machining efficiency is extremely low; the above disadvantages are not acceptable for new technologies of extrusion forming nuclear power tube developed for improving production efficiency and reducing cost.

Based on the above, the plasma-flame coaxial composite cutting process for the nuclear power thick-wall stainless steel complex pipe fitting is provided, the plasma cutting capability and quality are improved by coaxially compounding with flame, and the thickness index of the groove cutting of the AP1000 nuclear power thick-wall stainless steel pipe fitting in China is realized; the technology is connected with a robot arm, so that the all-position cutting of the nuclear power thick-wall stainless steel complex pipe fitting can be realized. Therefore, the defect of the existing domestic and foreign high-power plasma cutting capability is overcome, and the problem of cutting the all-position groove of the stainless steel plasma with the thick wall of 80-120 mm in nuclear power is solved.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 2, fig. 2 is a schematic diagram of a plasma-flame coaxial composite cutting process for a nuclear power thick-wall stainless steel complex pipe provided by the present invention, and the cutting process of the present invention includes:

s1, providing a composite cutting torch, as shown in figure 2, the composite cutting torch comprises a plasma cutting torch 1 and a flame torch 2 coaxially sleeved on the periphery of the plasma cutting torch 1;

the specific connection mode between the flame 2 and the plasma cutting torch 1 is not limited in the present invention, as long as the flame 2 can be sleeved on the periphery of the plasma cutting torch 1 and the flame 2 and the plasma cutting torch 1 are coaxially disposed.

In the embodiment, the vertical position relationship between the flame torch 2 and the plasma cutting torch 1 can be adjusted in a small range according to actual conditions, so that the distance between the jet orifice of the plasma cutting torch 1 and the jet orifice of the flame torch 2 is 10-20 mm, as shown in fig. 3, to expose the protective cap of the plasma cutting torch, thereby avoiding shielding the protective cap and the nozzle (the protective cap and the nozzle are generally made of materials with excellent thermal conductivity, such as red copper and the like) and influencing cutting torch cooling; and the flame heat source 5 which is formed by oxygen and fuel gas and is jetted by the flame torch 2 at high speed can have the cooling function on the plasma electrode, the nozzle and the protective cap of the plasma cutting torch 1, and can further cool the vulnerable parts.

Optionally, in this embodiment, the flame torch 2 of the present invention is preferably an external mixing type flame torch, and the flame torch 2 adopts a special channel design, as shown in fig. 4, the oxygen channel outlet 21 of the flame torch 2 is located at the inner side, the gas channel outlet 22 is located at the outer side, and both the oxygen channel and the gas channel are inclined channels, and a specific inclination angle of the channel is not limited in this embodiment, as long as both the oxygen channel outlet 21 and the gas channel outlet 22 are inclined and point at the axis of the plasma cutting torch 1, so that after the flame torch 2 is respectively communicated with the oxygen source 3 and the gas source 4, oxygen and gas are not premixed in the flame torch 2 and respectively flow out from respective channels, thereby ensuring that the oxygen channel and the gas channel do not intersect inside the flame torch 2. They are mixed and burned in the atmosphere after they are ejected out of the flame torch 2, thereby contributing to an increase in flame burning length.

The fuel gas of the invention is preferably propane gas, and the flow ratio of the oxygen introduced into the flame torch 2 to the fuel gas is preferably 3:1 when cutting is performed. The oxygen gas preferably adopts liquid oxygen or oxygen gas with the purity of more than or equal to 99.5 percent, and the fuel gas preferably adopts propane gas with the purity of more than or equal to 95 percent.

S2, cutting the complex stainless steel pipe to be cut by using the composite cutting torch as a cutting source, so that the nuclear power thick-wall complex stainless steel pipe can be cut;

it should be noted that, when cutting is performed, the height of the nozzle of the composite cutting torch (i.e. the height of the composite cutting torch and the upper surface of the workpiece) is the same as the height of the nozzle when cutting is performed by using a single plasma cutting torch in the prior art, and therefore, the detailed description is omitted here and those skilled in the art should know it.

When cutting is carried out, firstly, the flame torch 2 is started, a gas valve is opened, gas is introduced, the pressure is adjusted to be 0.4-0.5 MPa according to the cutting thickness, an oxygen valve is opened after ignition, the oxygen pressure is adjusted from small to large, the flame is adjusted to be neutral flame or weak oxidizing flame, then, the plasma cutting torch 1 is started, and cutting is carried out from the edge of a workpiece. The high-power plasma arc jet flow 6 is compressed by the nozzle of the plasma cutting torch 1 and then is ejected at high speed, and when the high-power plasma arc jet flow leaves the nozzle, the high-power plasma arc jet flow reacts with surrounding cold air to generate shock wave phenomenon, so that an arc column is expanded, the kinetic energy of plasma is converted into internal energy, the speed is rapidly reduced, the power density is reduced, and the impact force of the plasma arc jet flow 6 is reduced; meanwhile, the plasma arc is subjected to annular protection by using an external additional coaxial flame heat source 5 (as shown in figure 2), heat energy is injected while cold air is isolated, and jet flow resistance is reduced; the energy loss of the plasma arc jet flow 6 caused by the shock wave phenomenon is weakened, the energy flow density of the plasma arc jet flow 6 is improved, the energy of the ion arc jet flow 6 is more concentrated, the impact force is larger, and therefore the plasma cutting capability is improved.

According to the plasma cutting torch, the oxygen-gas (propane gas) flame heat source 5 is added to the plasma cutting torch 1 for coaxial compounding, so that the temperature difference in the thickness direction of a cutting workpiece is reduced, the cooling time difference in the thickness direction of a cut is shortened, the temperature in the thickness direction of the cut is more uniform, the cutting 'penetration' is improved, and the quality and the speed of plasma cutting of medium and heavy plates are improved. The speed and impact force of the plasma jet depend on the electric field intensity and the current density field, and the motion of charged particles in the plasma arc is actually thermal motion under the combined action of electric field force, thermal expansion force, self-magnetic compression force and the like. The additional flame heat source 5 can enhance the thermal motion, change various characteristics of jet flow particles, improve the fluidity of molten metal and be beneficial to further improving the plasma cutting capacity and quality.

It should be noted that, when the groove position with the thickness of the stainless steel material (aluminum alloy or carbon steel) exceeding 120mm is cut, different oxygen and gas pressures can be selected according to the actual thickness of the stainless steel material:

when a stainless steel plate with the thickness of 120 mm-140 mm is cut, the working pressure of fuel gas in a flame torch 2 is 0.5-0.6 MPa and 0.4-0.5 MPa. (ii) a

When a stainless steel plate with the thickness of 140 mm-160 mm is cut, the working pressure of oxygen in the flame torch 2 is 0.6-0.8 MPa, and the working pressure of fuel gas is 0.5-0.6 MPa;

when a stainless steel plate with a thickness of 160mm or more is cut, the operating pressure of oxygen in the flame torch 2 is 0.8MPa, and the operating pressure of fuel gas is 0.6 MPa.

When the process is used for cutting, the composite cutting torch can be arranged on a robot arm 8 at the lower end of a gantry stand column 7 to be connected, as shown in fig. 5, a plasma cutting torch 1 is communicated with a plasma power supply, a flame torch 2 is communicated with an oxygen source and a fuel gas source, the robot arm 8 is electrically connected with a robot control cabinet 9, and the robot arm 8 is controlled by the robot control cabinet 9 to move according to actual cutting requirements, so that the all-position cutting of nuclear power thick-wall stainless steel complex pipe fittings can be realized. The invention does not limit the type of the robot control cabinet, and can be realized by the prior art as long as the driving robot arm can move correspondingly according to the actual requirement, and the invention is not described again as long as the driving robot arm can move correspondingly.

It is to be understood that the above-described embodiments are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims

1. A plasma-flame coaxial composite cutting process for nuclear power thick-wall stainless steel complex pipe fittings is characterized by comprising the following steps:

the composite cutting torch is used as a cutting source to cut the complex stainless steel pipe fitting to be cut, so that the nuclear power thick-wall complex stainless steel pipe fitting can be cut;

when cutting, the plasma cutting torch in the composite cutting torch jets plasma arc jet flow from the nozzle of the plasma cutting torch; meanwhile, the flame torch jets out a flame heat source formed by oxygen and fuel gas, so that the plasma arc jet flow is isolated from cold air, heat energy is injected, and the shock wave loss of the plasma arc jet flow is reduced.

2. The cutting process according to claim 1, wherein the distance between the nozzle of the plasma cutting torch and the nozzle of the flame torch is 10 to 20 mm.

3. The cutting process of claim 1, wherein the flame torch is fed with oxygen and fuel gas at a flow ratio of 3: 1.

4. The cutting process of claim 1, wherein the fuel gas is propane gas.

5. The cutting process according to claim 1, wherein the operating pressure of oxygen in the flame is 0.5 to 0.8MPa when cutting the stainless steel sheet;

the working pressure of the fuel gas is 0.4-0.6 MPa.

6. The cutting process according to claim 5, wherein when a stainless steel plate having a thickness of 120mm to 140mm is cut, the operating pressure of oxygen in the torch is 0.5 to 0.6 MPa;

the working pressure of the fuel gas is 0.4-0.5 MPa.

7. The cutting process according to claim 5, wherein when a stainless steel plate having a thickness of 140mm to 160mm is cut, the operating pressure of oxygen in the torch is 0.6 to 0.8 MPa;

the working pressure of the fuel gas is 0.5-0.6 MPa.

8. The cutting process according to claim 5, wherein when a stainless steel plate having a thickness of 160mm or more is cut, the operating pressure of oxygen in the torch is 0.8MPa and the operating pressure of fuel gas in the torch is 0.6 MPa.