Heat treatment of carbon steel for gate valve raw material

Heat treatment of carbon steel for gate valve raw material

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℃..
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. 1, the implementation standard of carbon cast steel parts used in our country is GB12229 — 89 “Universal valve, Technical standard of carbon steel casting parts”, the 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.
Common problems: A: Qualified casting parts must be qualified in organic chemical composition, physical properties, and meet the requirements, especially the residue element manipulation, otherwise harm the weldability. B: The organic chemical composition specified in the code is still the maximum. In order to obtain good weldability and achieve the required physical properties in the manufacturing process, it is necessary to establish the internal control standards of the components and carry out the correct heat treatment of 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 physical performance does not meet the requirements. If the carbon content is equivalent to 0.3%, but the weldability is poor, the carbon content control is more appropriate to 0.25%. Want to be an “entry and exit,” some investors will clearly put forward carbon control regulations.
C: Temperature category of carbon steel valves
(a) JB/T5300 — 91 “Universal valve material” requirements carbon steel valve available temperature of -30℃ to 450℃.
(b) SH3064-94 “petrochemical steel general valve selection, inspection and acceptance” requirements carbon steel valve available temperature of -20℃ to 425℃ (the application of the low limit of -20℃ is to be unified 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. Carbon solid steel has a graphitization tendency at about 425℃. Heat treatment of metal materials is one of the important processing technologies in the manufacture of mechanical equipment. Compared with other manufacturing processes, heat treatment generally does not change the shape and overall composition of the workpiece, but by changing the internal microstructure of the workpiece, or adjusting the composition of the workpiece surface, to give or improve the performance index of the workpiece. Characteristic is to improve the most essential quality of the workpiece, however, this is generally not visible to the human eye.
Heat treatment technology characteristics:
Heat treatment of metal materials is one of the important processing technologies in mechanical equipment manufacturing. Compared with other manufacturing processes, heat treatment generally does not change the shape and overall composition of the workpiece, but by changing the internal microstructure of the workpiece, or adjusting the composition of the workpiece surface, to give or improve the performance index of the workpiece. Characteristic is to improve the most essential quality of the workpiece, however, this is generally not visible to the human eye.
– Solid, according to heating, heat insulation, refrigeration, change the mechanism to obtain the required characteristics of the processing process.
Features: Only parts of the workpiece can be changed in SSDS, no shape specifications can be changed
Objective: To improve the application and performance of raw materials
Basically the whole process: heating → heat insulation → refrigeration
Categorize:
1 General heat treatment
quench
Heat treatment and quenching
2 Surface heat treatment
Induction hardening
Organic chemical heat treatment
Phase transition point during heating and cooling
A chemical produced by the dissolution of an ionic crystal C in the lattice constant of Fe (an aluminum alloy phase in which solution molecules are incorporated into the lattice constant of an organic solvent while remaining an organic solvent)
Metallographic (F) C dissolved in α-Fe resulting in void ionic crystals
A void ionic crystal resulting from the dissolution of austenite (A) C in Y-Fe
Pearlite (FeC) A metallic compound formed of Fe and C
Ferrite (P) metallographic structure and pearlite formed chemical (FFeC)
45 Steel: initial mechanism Metallographic structure (F) ferrite (P)
General heat treatment process of steel
General parts manufacturing technology:
Production and manufacture of wool embryos — preparation for heat treatment — mechanical processing — final heat treatment — mechanical finishing
Preparation for heat treatment: quenching; Quenching, heat treatment
** Final heat treatment: heat treatment; quenching
The change of steel when it is heated
The effect of heating process: obtain austenite
Austenite production process:
Subcooling of composition — subcooling of composition at the F/Fe3C phase interface
Energy source growth — F→ A lattice constant reconstructs Fe3C melting and C→ A spreading
3 Residual Fe3C melting
Plan of austenite production process
Influence factors on austenite grain size
Austenite homogenization
P-eutectoid steel: P F
For eutectoid steel: P Fe3CⅡ
Effect of heat insulation process flow:
Obtain uniform austenite, remove thermal stress, promote the spread
Factors affecting austenite grain size:
Heating temperature ↑, holding time ↑→ A grain grow fast
Heating speed ↑→ A crystal fine
Carbon containing ↑→ A crystal fine
Initial mechanism fineness → A crystal fineness
The change of steel during cooling
Low temperature austenite: No variable unstable austenite appears below A1.
Analysis of eutectoid C curve
Three kinds of variation
Continuous high temperature change zone: P – type change
Atmospheric pressure variation zone: Type B variation
Ultra-low temperature variation zone: M type variation
Ferrite change
Ferrite composition: machine mixture of F and Fe3C
Under solid state drives, the composition is supercooled and the growth is diffusion-type change
3 Shape:
block
A1~650℃ : ferrite P
650~600℃ : Trostenite S (fine P)
600~550℃ : Trotensite T (ultra fine P also known as trotensite)