【Weekly Topic 20101106】Methods and effects of hardening treatment for control valve internals

StelliteNiHCrTiO2Turgston carbideCr2O3 HRC40～4755～6060～6265～6865～7065～72 Thickness (μm)1.5mm500 (max.)30 (max.)300 (max.)300 (max.)300 (max.) Bonding force (kgf/mm2)1085674.2 MethodWeldingPFSPE. PlatingPlasmaDetonationPlasma Self-adhesion!

Deformation refers to the situation where a metal surface is scratched by other materials, stuck together, or its surface becomes spherical. Plastic deformation and scratches can cause: valve jamming, damage to the sealing surfaces, increased friction, and inaccurate positioning of the valve core. In pipeline fluids, the presence of large, hard particles can abrade the valve internals, causing them to become rough and prone to plastic deformation and scuffing. Impact vibration can cause damage to the surfaces of parts that are subjected to impacts as well as to the mating surfaces; it can also lead to plastic deformation and scratches in some cases. Liquid metals, such as sodium and potassium, can remove the oxide layer from metal surfaces. At temperatures of ≥204°C (400°F), scratches are likely to occur and can be quite severe; therefore, materials must be carefully selected to prevent such scratches.

Everyone wants to know about this; those who are aware of it could share their experience. We just buy our control valves and start using them right away – is the hardening treatment done by the manufacturer??

The surfacing welding electrode for D502 valves complies with GBEDCr-A1-03 specifications: D502 is a 1Cr13 type valve surfacing welding electrode with a titanium-calcium flux coating; it can be used with both AC and DC power, and offers good welding properties. The surfacing metal is 1Cr13 semi-ferritic high-chromium steel. The surfacing layer possesses air-quenching properties; workers at ASCO Pulse Valve Manufacturing Company say that in such cases heat treatment is generally not required. The hardness remains uniform, and it can also be softened by annealing at 750–800°C. It can be hardened again after being heated to 900–1000°C and then cooled either in air or by oil quenching. Purpose: This is a general-purpose welding rod for surface cladding, used for cladding shafts and valves made of carbon steel or alloy steel in working temperatures below 450°C. The surfacing welding electrode for D507 valves complies with GBEDCr-A1-15 specifications: D507 is a 1Cr13 valve surfacing welding electrode with a low-hydrogen sodium-type coating, and direct current reverse polarity is used. The surfacing metal is 1Cr13 semi-ferritic high-chromium steel. The surfacing layer possesses air-quenching properties; generally, no heat treatment is required. It has uniform hardness, and can also be softened by annealing at 750–800°C. It can be hardened again after being heated to 900–1000°C and then cooled in air or by oil quenching. Experts from ASCO on solenoid valves explain its purpose: This is a general-purpose welding rod for surface cladding, used for cladding shafts and valves made of carbon steel or alloy steel in applications where the operating temperature is below 450°C. The surfacing welding electrode for D507Mo valves complies with GBEDCr-A2-15; it is a 1Cr13 valve-type surfacing welding electrode with a low-hydrogen sodium-based coating. The surfacing metal is 1Cr13 semi-ferritic high-chromium steel. The surfacing layer exhibits air-quenching properties, while the surfacing metal possesses high medium-temperature hardness, good thermal stability, and erosion resistance. When used in combination with D577 welding rod, it provides excellent scratch resistance. The surfacing process is simple: no preheating is required before welding, and no heat treatment is needed after welding; direct current in reverse polarity is used. Purpose: Used for surfacing the sealing surfaces of medium-temperature and high-pressure stop valves operating at temperatures below 510°C. For the sealing surfaces of gate valves, this welding electrode should be used in combination with D577 welding electrode (the valve seat and the valve disc are each coated with these two types of welding electrodes). The D507MoNb valve surfacing welding electrode complies with GBEDCr-A1-15 specifications: D507MoNb is a 1Cr13-type valve surfacing welding electrode with a low-hydrogen sodium-based flux; direct current reverse polarity is used in its application. Due to the inclusion of appropriate amounts of strengthening and stabilizing elements such as Mo and Nb in the flux, the surfacing metal exhibits good oxidation resistance and crack resistance. Purpose: Used for surfacing welding the sealing surfaces of medium and low pressure valves operating at temperatures below 450°C. The surfacing welding electrode for D512 valves complies with GBEDCr-B-03 specifications: D512 is a 2Cr13 type valve surfacing welding electrode with a titanium-calcium flux coating; it can be used with both AC and DC power, and offers good welding properties. The surfacing metal is 2Cr13 martensitic high-chromium steel. The surfacing layer possesses air-quenching properties; it generally does not require heat treatment, has uniform hardness, can be annealed and softened at 750–800°C, and can be re-hardened by air cooling or oil quenching when heated to 950–1000°C. According to ASCO’s representatives, D512 is a general-purpose welding rod for surface cladding. The cladding layer produced with this rod is harder and more wear-resistant than that of D502; it is also more difficult to work with. It is used for cladding carbon steel or low-alloy steel shafts, valve components used in superheated steam systems, mixer blades, and screw conveyor blades. The surfacing welding electrode for D516MA valves complies with GBEDCrMn-A-16. Description: D516MA is a surfacing welding electrode made of high-chromium-manganese steel, with a low-hydrogen potassium-type flux; the metal of the surfacing layer possesses excellent wear resistance, heat resistance, corrosion resistance, and resistance to thermal cracking. The welding process is simple – no preheating is required before welding, and no heat treatment is needed after welding. The surfacing layer can be machined. Purpose: Used for surfacing components that are exposed to water, steam, or petroleum-based fluids and operate at working temperatures below 450°C, such as cast steel grade 25 and the sealing surfaces of high and medium pressure valves. The surfacing welding electrode for D517 valves complies with GBEDCr-B-15 specifications: D517 is a 2Cr13 type valve surfacing welding electrode with a low-hydrogen sodium flux, and direct current reverse polarity is used. The surfacing metal is 2Cr13 martensitic high-chromium steel. The surfacing layer possesses air-quenching properties; it generally does not require heat treatment, has uniform hardness, can be annealed and softened at 750–800°C, and can be re-hardened by air cooling or oil quenching when heated to 950–1000°C. Purpose: D517 is a general-purpose welding rod for surface cladding. The cladding layer produced with this rod is harder and more wear-resistant than that of D502, but it is more difficult to work with. It is used for cladding carbon steel or low-alloy steel shafts, valve components used in superheated steam systems, mixer blades, screw conveyor blades, etc. The surfacing welding electrode for D547 valves complies with GBEDCrNi-A-15 specifications: D547 is a CrNiSi-type valve surfacing welding electrode with a low-hydrogen sodium-coated alloy steel core, and direct current reverse polarity is used. The surfacing metal is strengthened by silicon, resulting in an austenitic structure with a certain amount of ferrite, which confers it good properties such as scratch resistance, corrosion resistance, and oxidation resistance. Purpose: Used for surfacing the valve sealing surfaces and other sealing components of power plant high-pressure boiler systems that operate at temperatures below 570°C. The surfacing welding electrode for D547Mo valves complies with GBEDCrNi-B-15 specifications: D547Mo is a CrNiSiMo-type valve surfacing welding electrode with a low-hydrogen sodium flux. Reverse DC connection is used. The surfacing metal possesses excellent properties such as resistance to scratching and erosion at high temperatures, high hardness at high temperatures, as well as good thermal stability and fatigue resistance. The age-hardening effect of the surfacing metal is significant; as the aging time increases, both hardness and scratch resistance further improve. Purpose: Used for surfacing welding the sealing surfaces of high-pressure valves operating at temperatures below 600°C. The surfacing welding electrode for D557 valves complies with GBEDCrNi-C-15 specifications: D557 is a CrNiSi-type valve surfacing welding electrode with a low-hydrogen sodium-based coating. The surfacing metal is strengthened by a high content of silicon, resulting in an austenite-ferrite structure; as the aging time increases, its hardness and scratch resistance further improve. The surfacing metal possesses good erosion resistance, oxidation resistance, and corrosion resistance, and direct current reverse polarity is used during welding. Purpose: Used for surfacing welding the sealing surfaces of high-pressure valves operating at temperatures below 600°C. The surfacing welding electrode for D577 valves complies with GBEDCrMn-C-15 specifications: D577 is a chromium-manganese type surfacing welding electrode for valves, featuring a low-hydrogen sodium-coated alloy steel core. With direct current in reverse polarity, the surfacing metal is a high-chromium-manganese austenitic steel; hence, cold working hardening occurs significantly, resulting in good scratch resistance. It possesses moderate hardness at medium temperatures as well as good thermal stability. When used in combination with D507Mo, excellent scratch resistance is achieved. This welding rod has good crack resistance, the surfacing process is simple – no preheating is required, and no heat treatment is needed after welding. The surfacing metal also exhibits good machinability. Purpose: Used for surfacing the sealing surfaces of medium-temperature and high-pressure valves operating at temperatures below 510°C. When used in gate valves in combination with D507Mo, it extends the service life further. Instructions for using welding electrodes for valve surfacing: In accordance with the GB984-2001 standard, surfacing is a welding process in which a metal layer with properties such as wear resistance, corrosion resistance, and heat resistance is deposited on the surface or edges of a workpiece. It offers significant economic benefits by restoring and extending the service life of parts, utilizing materials efficiently, improving product performance, and reducing costs. The surfacing work and its working conditions are highly complex; when carrying out surfacing, it is necessary to select the appropriate welding electrode based on different requirements. Different workpieces and surfacing electrodes require different surfacing processes in order to achieve satisfactory surfacing results.

I also want to learn about the hardening treatment of valve internal components

For corrosion-resistant materials, grades 316L and higher are usually chosen, including medium-grade duplex steel, high-grade duplex steel, and super duplex steel. All of these steels can withstand harsh conditions such as strong acids and bases. Of course, if hardness is required, it’s worthwhile to invest in tungsten carbide or Stellite alloys as well. This is my personal opinion; if there are any mistakes, I hope experts can point them out

I want to know, that’s why I’m replying. It’s meant for mutual learning* – why impose restrictions?