Valve sealing surface grinding method and grinding tool material requirements valve suitable for the working temperature and the main part material selection

Valve sealing surface grinding method and grinding tool material requirements valve suitable for the working temperature and the main part material selection

Valve sealing surface is divided into two types of plane and conical sealing surface, which must be ground in valve manufacturing. Manual grinding of valve sealing surfaces is performed using only simple grinding tools. Manual grinding is generally used wet grinding, in the process of wet grinding to often add thin abrasive agent, in order to blunt abrasive particles from the working surface, and constantly add new abrasive particles, so as to get higher grinding efficiency. For sealing surfaces requiring especially high precision and finish, sometimes a pressed sand plate is used for dry grinding.
Requirements for tooling materials
In the grinding process, there are two requirements for the material of the grinding tool: one is that the material of the grinding tool should be easily embedded into the abrasive grain; Second, the grinding tool material should be able to maintain the geometric shape accuracy of the grinding tool for a long time.
In order for the abrasive particles to be easily embedded, the grinding tool material should be softer than the workpiece material. But also not too soft, otherwise the abrasive will be most or all embedded and reduced or lost cutting effect; And too soft giant material will also make the grinding tool wear faster. In order to prevent the grinding tool from losing its geometric precision due to rapid wear, the grinding tool material should have good wear resistance, and its organization should be uniform. The wear of materials with uniform structure is also uniform, which is beneficial to maintain the geometric precision of the tool.
When grinding valve sealing surface, the grinding tool material is used to use gray cast iron. Gray cast iron grinding tool is suitable for grinding sealing surface of various metal materials, it can obtain better grinding quality and higher productivity. The sealing surface of grinding cast iron, copper and austenitic stainless steel is generally made of gray cast iron of HB120-160. Gray cast iron HB150-190 is usually used for the sealing surface of grinding hard alloy and quenched steel, and the commonly used gray cast iron grades are HT150 and HT1200.
Valve sealing surface grinding method
Valve sealing surface is divided into two types of plane and conical sealing surface, which must be ground in valve manufacturing.
Valve sealing surface grinding method has two kinds of manual grinding and mechanical grinding.
(1) Manual grinding of valve sealing surface
Manual grinding of valve sealing surfaces is performed using only simple grinding tools. Manual grinding is generally used wet grinding, in the process of wet grinding to often add thin abrasive agent, in order to blunt abrasive particles from the working surface, and constantly add new abrasive particles, so as to get higher grinding efficiency. For sealing surfaces requiring especially high precision and finish, sometimes a pressed sand plate is used for dry grinding.
① Manual grinding of the sealing plane of the valve body. The valve body seal plane is located in the valve body cavity, grinding is difficult. Usually, a disc-shaped grinding tool with a square hole is used, which is placed on the sealing surface of the inner cavity, and then a long handle with a square head is used to drive the grinding disk for grinding movement. There is a cylindrical boss or guide gasket on the grinding plate to prevent the grinding tool from leaving the ring sealing surface partially during the grinding process and causing uneven grinding. Figure 8-6-5 shows THE diagram OF manual grinding OF THE VALVE body of gate valve and globe valve.
Figure 8. Manual grinding of body plane 1 6 5
Before grinding under the sealing plane of the valve body, the working face of the grinding tool should be wiped with kerosene or gasoline, and the flying edge and burr on the sealing surface of the valve body should be removed, and then coated with a layer of abrasive on the sealing surface. Pestle into the body cavity, to carefully fit on the sealing surface, and then use a long handle to make the pestle plate for positive and negative direction
Turn movement. Rotate clockwise 180°, counterclockwise 90°, and so on. Generally, after turning more than ten times, the abrasive particles in the abrasive agent have been blunted, so the grinding plate should be often lifted to add new abrasive agent.
The grinding pressure should be uniform and should not be too large. Rough research pressure can be large: fine research should be small. Attention should be paid not to apply pressure and make the grinding tool partially off the sealing plane. After grinding for a period of time, to check the roughness of the workpiece. At this time, you can take out the pestle, wipe the sealing surface with kerosene or gasoline, and then gently put the disc-shaped inspection flat plate on the sealing surface and gently drag it by hand. After taking out the flat plate, contact traces on the sealing surface can be observed. When the ring seal surface shows contact traces evenly, and the ratio of the radial contact width to the sealing surface width (that is, the sealing surface and the test plate of the coincidence) reaches the specified value in the process, the roughness can be considered qualified.
② Manual grinding of gate plate and valve disc seal plane. The seal planes of the gate, disc and seat can be manually ground using a grinding plate. Before the work, the clean plate is evenly coated with a layer of abrasive, and the workpiece is attached to the plate and can be rotated and moved in a straight line by hand, as shown in Figure 8-6-6, or in Figure 8 motion. The grinding efficiency can be improved because the grinding motion direction is changed constantly and the abrasive particles are grinding in the new direction.
Figure 8. Manual grinding of the sealing surface of a 6-6 gate
In order to avoid uneven wear of the grinding plate, do not always grind in the middle of the plate, but should be constantly changing parts on the surface of the plate, otherwise the grinding plate will soon lose plane accuracy.
The DISC and THE VALVE seat dry wedge shape, sealing plane on the circumference of the weight is uneven, grinding should be in its thin end (also known as “small head”) add slightly larger pressure, so that the annular sealing plane pressure uniform, so as not to cause the workpiece wedge Angle change.
Throttle valve disc grinding can be used with a hole ring disk grinding tool, the grinding method and valve sealing surface is basically the same.
Taper sealing surface hand grinding. Grinding the tapered sealing surface requires the use of a tapered rod or sleeve. The TAPER OF THE PESTLE AND the PESTLE SLEEVE SHALL correspond TO THE taper OF the VALVE body sealing face or disc sealing face, respectively. There should be a shallow spiral groove on the cone of the grinding rod and the grinding sleeve of the grinding cock body and the plug to store the excess abrasive agent. When grinding the globe valve body, because the sealing cone is too short and poor stability, it is usually added a guide plate at the flange stop in the valve body to keep the grinding rod stable. Figure 8-6-7 shows the schematic diagram of manual grinding of conical sealing surface.
Figure 8-6-7 Hand grinding of conical sealing surface
When grinding the conical sealing surface, apply a layer of abrasive agent evenly on the wiped grinding tool, lightly put it on the surface of the workpiece, then press the grinding tool by hand and rotate the grinding tool: after 3 to 4 weeks of rotation, the grinding tool can be pulled out to change the circular position before grinding. Abrasives should be added frequently during the grinding process.
The taper of the grinding rod of the grinding cock body and the grinding sleeve of the grinding plug should be consistent, otherwise it will be easy to leak between the tapered sealing surface after grinding.
One of the key considerations in valve design and material selection is the working temperature of the valve. In order to standardize the suitable working temperature of the main material of the valve, the suitable working temperature and related requirements of the main material of the valve are specified from the material properties of various types of steel and No.  for the design, manufacture and inspection of the valve products. In addition, from the aspects of technical management, production management and material procurement, the valve material with the most suitable system configuration is selected.
1 overview
One of the key considerations in valve design and material selection is the valve operating temperature. In order to standardize the suitable working temperature of the main material of the valve, the suitable working temperature and related requirements of the main material of the valve are specified from the material properties of various types of steel and No.  for the design, manufacture and inspection of the valve products. In addition, from the aspects of technical management, production management and material procurement, the valve material with the most suitable system configuration is selected.
2.1 ** temperature valve material
** temperature valve [-254 (liquid hydrogen) ~ -101℃ (ethylene)] the main material must choose face centered cubic lattice austenitic stainless steel, copper alloy or aluminum alloy, its low temperature mechanical properties after heat treatment, especially low temperature impact toughness must meet the requirements of the standard.
The following austenitic stainless steels can be used to manufacture warm valves. ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, ASTM A433 316, 316L, 304, 304L and CF8D (designed by Lanzhou High Pressure Valve Factory, factory standard code GFQ81-93). ** The body, cover, gate or disc of the warm valve must be cryogenized in liquid nitrogen (-196℃) before finishing.