- Category
- Hot products
.jpg)
.jpg)
.jpg)
-
【Valve Knowledge】Common Materials for Valve Bodies
-
1. Metal Materials (Mainstream Category, Applicable to Most Industrial/Civilian Working Conditions)
Metal materials are the core choice for valve bodies due to their high strength and good pressure resistance. According to the material properties, they can be divided into cast iron, cast steel, stainless steel, non-ferrous metals and corrosion-resistant alloys.
(1) Cast iron (low cost, easy to cast, suitable for low pressure, room temperature, non-strong corrosion working conditions)
Cast iron is an iron-carbon alloy with a carbon content of >2.11%. It has poor plasticity but good rigidity and is suitable for manufacturing large-diameter low-pressure valve bodies. Common types are as follows:
Gray cast iron (HT200, HT250)
Performance: Lowest price, excellent casting performance, but low strength (tensile strength 200-250MPa), high brittleness, poor corrosion resistance (easy to be corroded by acid and alkali).
Applicable working conditions: working pressure ≤1.6MPa, temperature -10~200℃; medium is water, air, steam (non-corrosive).
Typical Applications: Civilian water supply and drainage valves, HVAC system valves.
Ductile Iron (QT450-10, QT500-7)
Performance: Graphite morphology is improved through spheroidization, resulting in strength (tensile strength 450-500 MPa) and toughness far exceeding that of gray cast iron, slightly better corrosion resistance than gray cast iron, and lower cost than cast steel.
Applicable Operating Conditions: Operating pressure ≤ 4.0 MPa, temperature -30-350°C; media include water, sewage, natural gas, and oil (mildly corrosive or non-corrosive).
Typical Applications: Municipal gas valves, industrial low-pressure oil delivery valves, and large-diameter sewage valves.
Mallable Cast Iron (KTH300-06)
Performance: Made from annealed white cast iron, it offers excellent plasticity (elongation 6%) and easy machining. Its corrosion resistance is similar to that of ductile iron, but its strength is lower.
Applicable Operating Conditions: Low pressure (≤ 1.6 MPa), room temperature, and media include water and air. Typical applications: small low-pressure valves (such as threaded stop valves and check valves).
(2) Cast steel (high strength, good temperature resistance, suitable for medium-high pressure and medium-high temperature working conditions)
Cast steel has a carbon content of <2.11%, high strength and good toughness, and is divided into carbon steel and alloy steel according to chemical composition.
Carbon steel (WCB, ZG230-450)
Performance: Mainly composed of iron and carbon, without alloying elements, medium strength (tensile strength 450MPa), wide temperature resistance range (-29~425℃), general corrosion resistance (easy to rust, requires anti-corrosion treatment).
Applicable working conditions: working pressure 1.6~10MPa, temperature ≤425℃; medium is steam, oil, non-corrosive gas.
Typical applications: industrial steam pipeline valves, petrochemical low-pressure oil valves.
Alloy Structural Steel (WC6, WC9, ZG15CrMo)
Performance: The addition of alloying elements such as Cr and Mo improves high-temperature strength and creep properties (WC6 temperature resistance ≤482°C, WC9 temperature resistance ≤593°C).
The tensile strength is ≥515 MPa, and the corrosion resistance is slightly better than that of carbon steel.
Applicable operating conditions: Medium-high pressure (≤16 MPa), medium-high temperature (≤593°C); media include high-temperature steam, high-temperature oil, and superheated steam.
Typical applications: Steam valves for power plant boilers and valves for high-temperature process pipelines in refineries.
Low-temperature Steel (LCB, LCC, ZG16MnD)
Performance: The addition of elements such as Ni and Mn improves low-temperature toughness and prevents low-temperature brittle cracking (LCB temperature resistance -46°C, LCC temperature resistance -60°C, ZG16MnD temperature resistance -40°C). The strength is close to that of carbon steel. Applicable working conditions: low temperature environment (-60 ~ room temperature), medium and low pressure; medium is liquefied natural gas (LNG), liquid nitrogen, liquid oxygen and other low temperature fluids. Typical applications: LNG storage tank outlet valve, air separation equipment low temperature valve.
(3) Stainless steel (excellent corrosion resistance, suitable for strong corrosion and clean working conditions)
Stainless steel contains Cr ≥ 12%, and achieves corrosion resistance by forming an oxide film (passivation film) by Cr. According to the structure, it is divided into austenite, ferrite and martensite, among which austenitic stainless steel is the most commonly used. Austenitic stainless steel (304, 316, 316L)
304 (06Cr19Ni10): good corrosion resistance (resistant to weak acid and alkali, salt water), temperature resistance - 196 ~ 800 ℃, but not resistant to Cl⁻ corrosion (prone to pitting corrosion);
Applicable media: food, medicine, pure water, weakly corrosive chemical fluids (such as dilute sulfuric acid, dilute nitric acid).
316 (06Cr17Ni12Mo2): Added Mo element, the Cl⁻ corrosion resistance is far superior to 304, temperature resistance -196~800℃;
Applicable media: seawater, salt water, Cl⁻-containing chemical fluids (such as hydrochloric acid, chlor-alkali).
316L (022Cr17Ni12Mo2): Low carbon version of 316, stronger resistance to intergranular corrosion (avoids corrosion after welding), suitable for welded valve bodies; Application: Chemical industry, marine engineering, nuclear power field, strong corrosion conditions.
Ferritic stainless steel (430)
Performance: does not contain Ni, low cost, corrosion resistance is better than carbon steel but weaker than 304, temperature resistance -40~800℃, and brittleness is relatively large.
Applicable working conditions: low pressure, weak corrosive media (such as fresh water, air), cost-sensitive scenarios.
Typical applications: civil water heater valves, low-end chemical low-pressure valves.
(4) Nonferrous metals and corrosion-resistant alloys (high performance, high cost, suitable for extreme working conditions)
These materials are designed for extreme working conditions such as strong corrosion, high temperature, and high pressure. They are expensive and are only used in special scenarios.
Copper and copper alloys (brass H62, bronze QAl9-4)
Performance: Brass (copper-zinc alloy) is easy to process, resistant to low temperatures, and has medium corrosion resistance (not resistant to strong acids); bronze (copper-aluminum alloy) has high strength and wear resistance.
Applicable working conditions: low pressure (≤1.6MPa), room temperature, media such as water, gas, and refrigerants (such as R22).
Typical applications: household gas valves, air conditioning and refrigeration system valves.
Titanium and titanium alloys (TA2, TC4)
Performance: extremely strong corrosion resistance (resistant to strong acids, strong alkalis, and seawater, only not resistant to hydrofluoric acid), high strength (TA2 tensile strength ≥485MPa), temperature resistance -253~600℃, but expensive (about 5-8 times that of 316L).
Applicable Operating Conditions: Extremely corrosive environments (such as concentrated nitric acid, hydrochloric acid, and offshore oil and gas development).
Typical Applications: Chemical reactor outlet valves subject to severe corrosion, deep-sea oil and gas production valves.
Nickel-Based Corrosion-Resistant Alloys (Hastelloy C-276, Monel 400)
Hastelloy C-276: Corrosion resistance reaches its ceiling, resistant to almost all inorganic acids (including hydrochloric acid and sulfuric acid) and organic acids, with a temperature resistance range of -29°C to 1093°C. Applications: High-end chemical, nuclear power, and aerospace industries.
Monel 400 (nickel-copper alloy): Resistant to seawater, hydrochloric acid, and hydrofluoric acid, with high strength. Applications: Offshore engineering and fluorine chemical valves.
2. Non-metallic Materials (Excellent corrosion resistance, low cost, suitable for low-pressure, mildly corrosive environments)
Non-metallic materials are lightweight and offer excellent corrosion resistance, but they also have low strength and poor pressure and temperature resistance, making them suitable only for low-pressure (≤1.0 MPa) and room-temperature (≤100°C) applications.
(1) Plastics (PVC, PP, PTFE)
PVC (polyvinyl chloride): low cost, acid and alkali resistance (not resistant to strong oxidizing acids), temperature resistance ≤60℃;
application: civil chemical wastewater valves, laboratory low-pressure valves.
PP (polypropylene): temperature resistance ≤100℃, better corrosion resistance than PVC (resistant to most acids and alkalis), good toughness;
application: chemical low-pressure acid and alkali delivery valves.
PTFE (polytetrafluoroethylene, "plastic king"): extremely corrosion-resistant (resistant to all acids and alkalis), temperature resistance -200~260℃, but low strength and easy to deform;
application: laboratory strong corrosion valves, high-end seals (valve body linings).
(2) Ceramics (alumina ceramics, silicon nitride ceramics)
Performance: high hardness (Mohs hardness 9, second only to diamond), extremely strong corrosion resistance (resistant to all acids and alkalis), but brittle and poor impact resistance.
Applicable working conditions: low pressure, strong corrosion, abrasive media (such as acid and alkali wastewater containing particles).
Typical applications: Chemical wastewater valves containing particles, desulfurization system valves.
(3) Rubber (natural rubber, nitrile rubber)
Performance: good elasticity and wear resistance, but poor temperature resistance (≤80℃) and corrosion resistance (only resistant to weak alkali). Usually used as valve body lining (such as rubber-lined valves) rather than as the entire valve body material.
Application: Water supply and drainage, sewage treatment valves (rubber-lined valve body, improved corrosion resistance).
3.Composite materials (taking into account both metal strength and non-metallic corrosion resistance)
Composite materials combine the advantages of "metal matrix + non-metallic lining/coating" and are a cost-effective choice for medium and low pressure corrosion conditions.
(1) Lined valve (metal matrix + plastic/rubber lining)
Structure: The valve body matrix is cast iron/cast steel (to ensure strength), and the interior is lined with PVC, PP, PTFE or rubber (to provide corrosion resistance).
Applicable working conditions: low pressure (≤1.6MPa), strong corrosive media (such as acid and alkali solutions).
Typical applications: chemical low-pressure acid and alkali transfer valves.
(2) Coated valves (metal substrate + anti-corrosion coating)
Common coatings: epoxy resin (weak corrosion resistance, temperature resistance ≤120°C), polytetrafluoroethylene coating (strong corrosion resistance, temperature resistance ≤260°C).
Applications: municipal sewage valves, chemical low-pressure valves (substrate is cast iron/cast steel, reducing costs).