Gate valve raw materials Valve body materials Carbon steel gate valve raw materials steel annealing

Gate valve raw materials Valve body materials Carbon steel gate valve raw materials steel annealing

Can be used for non-corrosive substances, in some special conditions such as in a certain range of temperature, concentration value environment, can be used for some corrosive substances. Available temperature -29~425℃. Valve body, single flow valve and gate valve (piston valve) look more complex, so the general use of casting parts. Only some caliber valves or gate valves with unique working condition standards use cast steel parts.
Most of the valve body, single flow valve and gate valve (piston valve) look more complex, so the general use of casting parts. Only some caliber valves or gate valves with unique working condition standards use cast steel parts.
Carbon steel
Can be used for non-corrosive substances, in some special conditions such as in a certain range of temperature, concentration value environment, can be used for some corrosive substances. Available temperature -29~425℃
Carbon cast steel parts
At present, the implementation standard used in our country is GB12229 — 89 “General valve, carbon steel casting Technical Conditions”, material brand is WCA, WCB, WCC. The standard is in accordance with the foreign material testing association standard ASTMA216-77 “high temperature fusible carbon steel Castings standard specification”. The standard has been modified at least twice, but my GB12229-89 is still in use, and the newer version I see at the present stage is Astma216-2001. It differs from Astma 216-77 (that is, from GB12229-89) in three ways.
A: The 2001 requirements added a requirement for WCB steel, that is, for every 0.01% reduction in the very large carbon limit value, the very large magnesium limit value can be increased by 0.04% until the maximum value is 1.28%.
B: The sundries Cu of WCA, WCB and WCC models: 0.50% in 77, adjusted to 0.30% in 2001; Cr: 0.40% in 77 and 0.50% in 2001; Mo: It was 0.25% in ’77 and 0.20% in 2001.
C: The residue element synthesis should be less than or equal to 1.0%. In 2001, when there is a carbon equivalent standard, this clause is not suitable, and the maximum carbon equivalent of the three models is required to be 0.5 and its carbon equivalent calculation formula.
Q&A
A: Qualified casting parts must be qualified in organic chemical composition, structural mechanical properties, and meet the requirements, especially the residue element manipulation, otherwise it will harm the welding performance.
B: The organic chemical composition specified in the code is still the maximum. In order to obtain good welding performance and achieve the required structural mechanical properties, it is necessary to establish the internal control standards of components and carry out the correct heat treatment process for the casting parts and test rods. Otherwise, the production and manufacture of unqualified casting parts. For example, WCB steel carbon content standard ≤0.3%, if the smelter out WCB steel carbon content of 0.1% or lower from the composition to see is qualified, but the structural mechanical properties do not meet the requirements. Carbon content if equivalent to 0.3% also qualified but welding properties
Poor, carbon control to 0.25% is more appropriate. Want to be an “entry and exit,” some investors will clearly put forward carbon control regulations.
C: Temperature categories relating to carbon steel valves
(a) JB/T5300 — 91 “Universal valve materials” requirements of carbon steel valve available temperature of -30℃ to 450℃.
(b) SH3064-94 “petrochemical steel general valve selection, inspection and acceptance” requirements of carbon steel valve available temperature of -20℃ to 425℃ (the application of low limit provisions for -20℃ is in order to unify with GB150 steel pressure vessel)
(c) ANSI 16·34 “flange and butt welding end valve” working pressure – temperature rated current value standard requirements WCB A105 (carbon steel) available temperature range including -29℃ to 425℃, can not be used above 425℃ for a long time. Solid carbon steel tends to graphitize at about 425℃.
Gate valve raw material of steel annealing complete annealing (recrystallization annealing) : the steel slow heating to Ac3 (hypoeutectoid steel) above 30~50℃, to ensure a moderate time, then slow refrigeration out. For common steel, according to the heating process of ferrite into martensite (back change recrystallization) and the refrigeration process in addition to the second change recrystallization, the crystal fine, thick layer, uniform structure of ferrite. Gray cast iron annealing: the steel is heated to a temperature of 30 ~ 50℃ above Ac1, and then slowly cooled out.
1) Definition: Temperature the parts to 30 ~ 50℃ above the critical temperature, heat insulation for a period of time, and then with the furnace refrigeration. (Critical temperature: the temperature at which the internal structure of the steel changes)
2) Objectives: (1) Reduce strength and improve grinding performance;
(2) Refine the grain, improve the structure and distribution of cementite in steel, and lay the foundation for the final heat treatment process;
(3) Remove thermal stress, remove the thermal stress caused by shape change production processing, grinding processing or electric welding and the residual thermal stress in the casting parts, to reduce deformation and avoid dry cracking;
(4) spherification of cementite to reduce strength;
⑤ Improve and eliminate all kinds of organizational shortcomings formed in steel forging, calcination and welding operation, to avoid causing small white spots.
4) Type: In production, annealing process is used very much. According to the product workpiece annealing effect is not the same, there are many kinds of annealing process standards, commonly used are complete annealing, gray cast iron annealing, or to the ground stress annealing
(1) Complete annealing (recrystallization annealing) : the steel slow heating to Ac3 (hypoeutectoid steel) above 30~50℃, to ensure a moderate time, then slow refrigeration out. For common steel, according to the heating process of ferrite into martensite (back change recrystallization) and the refrigeration process in addition to the second change recrystallization, the crystal fine, thick layer, uniform structure of ferrite.
② Gray cast iron annealing: the steel is heated to a temperature of 30 ~ 50℃ above Ac1, and then slowly cooled out. The ferrite structure becomes spheroidal and granular, and the low and medium carbon steel with this kind of structure has low strength, strong drilling ability and strong cold bending ability. For alloy steel, this kind of structure is a better initial structure before heat treatment. (Sample shaft CrWMn, guide shaft Tenon GCr15)
Complete annealing and isothermal annealing
Complete annealing — heating to Ac3 20~30℃, heat insulation after cold furnace — refers to heating to complete austenization
Objective: According to thorough recrystallization fine grain, symmetrical structure, improve performance
Application: hypoeutectoid steel, low carbon steel: reduce strength, improve drilling performance. Organization: F P
Isothermal process annealing — heating to Ac3 (Ac1) 20~50℃,
Thermal insulation is followed by air cooling after the following isothermal process in Ar1: with thorough annealing for easy control
Application: medium and ferritic stainless steel
Organization: F P or Fe3C P
Gray cast iron annealing and spread annealing
Gray cast iron annealed – heated to Ac1 20~30
Objective: To obtain spherical Fe3C, soft
Application: eutectoid, eutectoid steel
Tissue: spherical P
Spread annealing — heating to 100-200 degrees below the solid line, long-term thermal insulation (10-15h) after slow cooling
Objective: symmetrical composition
Suitable for: stainless steel castings
Microstructure: Coarse grain – after spread annealing the thorough annealing or quenching – optimization
Destress annealing and work hardening annealing
De-stress annealing — heating to Ac1-100~200℃, heat insulation after the furnace cold
Objective: To remove thermal stress and stabilize the organization
Application: cold drawing parts, heat treatment parts
Organization: It won’t change
Work hardening annealing — heating to t and then 150~250℃, heat insulation after air cooling
Objective: To reduce strength and enhance plasticity
Application: work hardening product workpiece
Structure: equiaxed grain
Work hardening temperature: T re =T melting × 0.4 (temperature)
quenching
Normalizing – heating to Ac3(Accm) 30~50℃, heat insulation after air cooling
Objective: Refine grain, improve performance
Application: high carbon steel HB↑ → Improve the cutting properties of carbon (aluminum alloy) steel refining grain symmetry organization (heat treatment, heat treatment before) hypereutectoid steel → clear mesh structure Fe3CⅡ, laying the foundation for spheroidization treatment of parts with lower requirements → mechanical equipment performance final heat treatment process.