Metal-sealed ball valve hardening process Brief description of how ball valves break out in the gate valve industry?
In thermal power plants, petrochemical equipment system software, energy and chemical industry high viscous fluid, with soot and solid particles of the combination of liquid, strong corrosion of liquid and other media, ball valves must use metal materials hard seal gate valve valve, so the use of appropriate metal materials hard seal gate valve ball valve ball and seat hardening process is very important.
1. Brief Introduction
In thermal power plants, petrochemical equipment system software, energy and chemical industry high viscous fluid, with soot and solid particles of the combination of liquid, strong corrosion of liquid and other media, ball valves must use metal materials hard seal gate valve valve, so the use of appropriate metal materials hard seal gate valve ball valve ball and seat hardening process is very important.
2, metal material hard seal gate valve ball valve ball and seat hardening method
At present, the common hardening process on the surface of metal hard seal gate valve ball valve is mainly as follows:
(1) The ball surface spray welding (or spray welding) cemented carbide tool, the hardness can reach about 40HRC, the ball surface spray welding cemented carbide tool process is complicated, the production and manufacturing efficiency is not high, and the large-scale spray welding is easy to make parts deformation, now the ball surface hardening process application is less.
(2) The ball surface hard oxidation, hardness can reach 60 ~ 65HRC, thickness 0.07 ~ 0.10mm, stainless steel layer high hardness, wear resistance, corrosion resistance and can always keep the surface bright, simple process, low cost. However, the hardness of hard chromium coating will be rapidly reduced by the release of its thermal stress when the temperature rises, and its operating temperature can not be higher than 427℃. In addition, the combination of stainless steel layer is low, and the coating is easy to fall down.
(3) The surface of the ball is plasma nitriding, the surface hardness can reach 60 ~ 65HRC, the thickness of nitriding treatment layer is 0.20 ~ 0.40mm, low temperature plasma nitriding treatment hard substrate process because of its weak corrosion resistance, can not be applied in chemical plant strong etching and other industries.
(4) Ball surface supersonic spraying (HVOF) process, the hardness is very high, can reach 70 ~ 75HRC, high strength, thickness 0.3 ~ 0.4mm, supersonic spraying is the key process of ball surface hardening. High viscous fluid in thermal power plants, petrochemical equipment system software, energy and chemical industry; This hardening process is used in most of the composite liquid, highly corrosive fluid media with soot and solid particles.
The supersonic spraying process is a process in which the combustion of oxygen fuel causes the high pressure gas to accelerate the impact of powder particles on the workpiece surface of the product and produces a high density surface coating. In the collision link, because the particle speed is fast (500-750m /s) and the particle temperature is low (-3000℃), the coating with high bonding strength, low porosity and low metal oxide relative content can be obtained after the collision on the workpiece surface. The characteristic of HVOF is that the particle speed of alloy powder exceeds the speed of sound, even 2 ~ 3 times of the speed of sound, and the average speed of cyclone is 4 times of the speed of sound.
HVOF is a new production and processing technology, paint thickness 0.3 ~ 0.4mm, between the coating and the workpiece mechanical bonding, high bonding strength (77MPa), coating porosity is low (< 1%). The process of product workpiece heating temperature is low (< 93℃), the product workpiece does not wrinkle, can be cold spraying. Spray paint, powder particle rate is high (1370m/s), no welding heat affected zone, workpiece composition mechanism does not change, coating hardness is high, can be machining.
Spray welding is a process of arc spraying on the surface of metal composite materials. It is through the pyreogen powder (metal powder, alloy powder, ceramic powder can be) heating to melt or do high plasticity, with the cyclone to it gushing, accumulated on the surface of the product after prior treatment, forming a layer and product workpiece surface (plate) solid fusion coating (welding) layer.
Spray welding and spray welding hardbase process alloy and substrate have melting process, carbide cutting tool and substrate have hot melt zone, in order to completely achieve spray welding or spray welding carbide cutting layer characteristics, prevent after treatment welding hot melt zone for metal material contact area, proposed spray welding or spray welding carbide cutting tool thickness must be more than 3mm above.
3. The hardness of the contact area of the hard seal gate valve ball valve and the valve seat is compatible with each other
The sliding contact surface of metal materials needs to have a certain hardness, otherwise it is easy to produce the situation of death. In specific applications, the hardness difference between the general valve ball and the valve seat is 5 ~ 10HRC, and the hardness differential ball valve can have a good service life. Because the ball production and processing complex, high production cost, in order to protect the ball is not easy to suffer damage and damage, generally choose the hardness of the ball is higher than the hardness of the seat surface.
Ball and valve seat contact surface hardness collocation is better for the two kinds of hardness to cooperate with each other: (1) Valve ball surface hardness 55HRC, valve seat surface 45HRC, valve ball surface can adopt supersonic spraying Stellite20 aluminum alloy, valve seat surface can take spray welding Stellite12 aluminum alloy, the hardness of mutual coordination is metal seal ball valve widely used hardness coordination, can meet the basic damage requirements of metal material hard seal gate valve ball valve; The surface hardness of valve ball is 68HRC, the surface of valve seat is 58HRC, the surface of valve ball can be subsonic spraying tungsten carbide, the surface of valve seat can be supersonic spraying Stellite20 aluminum alloy, the hardness is used with the energy and chemical industry, with high wear resistance and service life.
Overseas, the valve ball and valve seat surface match with each other with the same hardness. All the valve ball and valve seat surface adopt subsonic spraying tungsten carbide process, and the surface hardness is more than 72HRC. Even under the premise of extremely high hardness, the valve ball and valve seat touch the surface and are not easy to kill. But at present our valve ball making surface hardness of more than 72HRC valve ball, valve seat is not perfect grinding technology, it is difficult to ensure the valve ball and valve seat cooperation, application is less.
4, hard seal gate valve ball valve ball and seat hardening pay attention to the problem
Raw materials of hard metal seal gate valve ball and valve seat are generally selected stainless steel plate or corrosion resistant raw materials, otherwise carbide tool and valve seat (or ball) combination layer is easy to be corroded by substances, resulting in carbide tool layer fall down, harm the service life of the ball valve.
In addition, according to different valve seat (or valve ball) raw materials should choose their own hardening process, in the field of energy and chemical industry is applied to dual-phase steel raw materials, dual-phase steel raw materials have better corrosion resistance fatigue and wear corrosion characteristics.
Two-phase steel raw material is a kind of steel with both metallographic structure and austenitic structure, the microstructure and austenitic structure of about 50%, and the two-phase mechanism does exist, its performance characteristics are both low alloy steel and 430 stainless steel characteristics. In 430 stainless steel characteristics, when the temperature is 400 ~ 500℃ range, long-term thermal insulation will produce a certain aging, this situation is generally called 475℃ aging; When the temperature exceeds 400 ~ 500℃, the characteristics of two-phase steel can be destroyed.
If spray welding or spray welding carbide cutting tool process is used for biphase steel raw materials, the process of melting process of carbide cutting tool and substrate (ambient temperature is generally more than 900℃), will damage the alloy composition of biphase steel raw materials, so the biphase steel raw materials should not use spray welding (or spray welding) carbide cutting tool hardening process. The supersonic spraying process is suitable for the surface hardening process of biphase steel raw materials. The hardening process should ensure that the alloy composition of biphase steel raw materials cannot be damaged.
5. Closing Remarks
Scientific and reasonable hardening process is selected for the ball and valve seat of metal hard sealed gate valve ball valve, which can directly determine the service life and performance index of metal hard sealed gate valve, and scientific and reasonable hardening process can reduce the cost. With the emergence of new technologies, there will inevitably be more curing processes. It is a very complex problem that the hardening process and hardness of metal hard seal gate valve cooperate with each other. Therefore, sufficient attention should be paid to the coordination of the design, material type, hardening process and hardness of the hard seal gate valve.
How do ball valves break out in the gate valve industry? In the 1950s, ball valves gradually appeared in the industrialized production of western countries. And its utilization gradually continued to rise, by others continue to carry out various features of improvement. Now in our country, ball valve key used in pharmaceutical machinery, petroleum refining, hydraulic engineering chemical plants, electric power municipal engineering paper industry steel products and other fields, these industries have an important position in the social and economic development, thus, ball valve are indispensable machines and equipment in these industries.
In the 1950s, ball valves gradually appeared in the industrialized production of western countries. And its utilization gradually continued to rise, by others continue to carry out various features of improvement. Now in our country, ball valve key used in pharmaceutical machinery, petroleum refining, hydraulic engineering chemical plants, electric power municipal engineering paper industry steel products and other fields, these industries have an important position in the social and economic development, thus, ball valve are indispensable machines and equipment in these industries.
Ball valve how to excel
In the field of gate valves, there are a variety of gate valves. The reason why ball valves can stand out and are frequently used in various fields is that they cannot be replaced without their advantages. So, what are the advantages of ball valves?
First, the ball valve can not be ignored advantage is wear resistance. According to the industry professional and technical personnel detailed introduction, for the gate valve, wear resistance is the key factor to measure the quality of the gate valve, the rubber sealing ring of the ball valve is carbon steel spray welding, and the general valve sealing ring is plastic or other alloys, a variety of materials are not the ball valve carbon steel surfacing wear resistance.
“As we all know, the gate valve is a switch, which must be opened and closed at the same time, but at the same time, the sealing ring will be greatly damaged, but the sealing ring of the ball valve is not prone to such a situation.” If the industry is indicating.
Second, the ball valve sealing is very good. According to statistics, the sealing of ball valve is not by equipment grinding, but by artificial grinding, to ensure that the level of compliance is higher, so the sealing is very reliable.
In addition, ball valve service life is particularly long. It is also a manufacturing enterprise for the production line equipment very much attention.
“Because the need is often used in multiple areas of critical production, of course, if its service life is not long enough, often need to be replaced, will become very troublesome, will lead to a lot of mistakes.”
Ball valve model selection skills to share
Ball valve as a rely on valve seat opening and closing parts, the quality of its machine stability is very important. So in the model selection to comply with some details, in order to really achieve the actual needs.
Attach importance to the selection of specifications. According to statistics, ball valve fluid density is generally not large, the safety channel and pipeline is basically the same, so it can be used in some areas particularly sensitive to the working condition of the material. When selecting this kind of gate valve, we must pay attention to the selection of specifications. The specifications are not the same as the net weight, and the effect can be achieved is not the same.
Effective consideration of price. In the selection of valves, in addition to shopping around, we should also pay attention to rationality, as long as it can meet the specific needs of the can, do not have to choose large specifications or net significant is the best selection.
In addition, fixed ball valves are closed valve chambers. If they are used in low-temperature media or natural environments that may produce vaporization, gate valves containing release devices must be selected. When appropriate, the ball valve needs to be changed into a disc valve or cut-off valve.
The industry emphasizes that this kind of gate valve in general can be used for pipe disconnection without ball standard. If necessary, the selection of this kind of valve can also be selected according to the needs of the construction of the safety channel, which can ensure that it can meet the needs of several safety channels and reduce the total number of applications of the valve as far as possible.
It is worth reminding you that the selection of ball valves also values the selection of well-known brands and their prices. It is a wise choice to choose the most cost-effective gate valve.
Post time: Mar-10-2023
