This article is about the differences between forged steel valves and cast steel valves. Which one is good?
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cast steel valve is one kind of cast alloy. Cast steel can be divided into cast carbon steel, cast low alloy steel and cast special steel. Cast steel is a kind of steel casting produced by the casting method. Cast steel is mainly used to manufacture some parts with complex shapes, which are difficult to forge or machine. It requires high strength and plasticity.
Forged steel refers to all kinds of forging materials and forgings produced by the forging method. Forged steel is higher in quality than cast steel. It can withstand a large impact. Its plasticity, toughness and other aspects of mechanical properties are higher than that of cast steel. Therefore, some important machine parts should use forged steel.
The quality of forged steel valves is better than that of cast steel valves. It can withstand a large impact. The plasticity, toughness and other aspects of mechanical properties are also higher than that of cast steel. However, the nominal diameter is relatively small, which is generally below DN50. The pressure grade of cast steel valves is relatively low. The common nominal pressures are PN16, PN25, PN40 and 150lb-900lb. The pressure grades of forged steel valves are PN100, PN160, PN320, 1500lb-3500lb, etc. Cast steel is mainly used to manufacture some parts with complex shapes, which are difficult to forge or machine high strength and plastic components.
Casting is liquid forming and forging is a plastic deformation process. The forging forming workpiece can improve the organization structure. The mechanical performance is good.
Forged steel valves
1. Forging can be divided into:
(1) Closed forgin. It can be divided into die forging, rotary forging, cold heading, extrusion, etc. The metal blank is placed in the forging die with a certain shape and deformed under pressure to obtain the forging. According to the deformation temperature, it can be divided into cold forging (forging temperature is normal temperature), warm forging (forging temperature is lower than the recrystallization temperature of the billet metal), hot forging (forging temperature is higher than the recrystallization temperature). The casting can cause tissue segregation, tissue defects, but casting has its advantage. The forging forming complex workpiece is not easy to open mold.
(2) Open forging (free forging). There are two ways of manual forging and mechanical forging. The metal billet is put on two anvil blocks (iron) between the use of impact force or pressure to make the metal billet deformation to obtain the required forgings.
2. Forging is one of the two major components of forging. The simple shape of forgings can be rolled into welding parts, except the profile plate. The weld holes and loose cast state of metal materials can be eliminated by forging.
3. The correct choice of forging ratio can improve product quality and reduce costs. Forging materials are mainly carbon steel, stainless steel and alloy steel. Forging ratio refers to the ratio of the cross section area of metal before deformation and the die section area after deformation. The original states of the material are ingot, bar, liquid metal and metal powder.
4. The mechanical properties of forgings are generally better than those of castings of the same material. Forging is a machining method that exerts pressure on the metal blank by forging and pressing machinery to produce plastic deformation of the metal blank to obtain a certain shape, size and better mechanical properties.
Cast steel valves
1. There are many kinds of casting. According to the modeling methods, it can be divided into ordinary sand casting and special casting:
(1) Ordinary sand castings include dry sand type, wet sand type and chemical hardening sand type.
(2) Special castings, according to the casting material, are divided into two categories: the special casting of ore and the special casting of metal materials.
If the metal is as casting materials of special castings, it includes pressure castings, metal mold castings, low pressure castings, continuous castings, centrifugal castings, etc.
If natural mineral sand and stone are as casting materials of special castings, it includes truthful casting, investment casting, casting shop shell casting, mud casting, negative pressure casting, ceramic casting, etc.
2. Casting is a kind of metal hot processing process. The casting production has good comprehensive mechanical properties. The casting production adaptability is wide, and the blank cost is low. For the shape is more complex, especially the parts with complex internal structure, more of them can visualize the economy of casting production.
3. Casting is the basic process of the modern machinery manufacturing industry.
4. The casting process usually includes the following steps:
(1) Prepare the casting mold (The mold can be used to make liquid metal into solid castings. The merits and disadvantages of the casting mold directly affect the casting quality). The casting mold can be divided into one-time type, multiple type and permanent type according to the number of use. The casting mold can be divided into metal type, sand type, mud type, ceramic type, graphite type, etc.
(2) The melting and casting of casting metals, casting metals are mainly cast iron, carbon steel and stainless steel.
(3) Casting processing and collection. The casting processing includes the removal of foreign bodies and core on the surface of the casting, processing of protrusions (shovel grinding burr, removal of pouring riser and processing of the seam, etc.), casting heat treatment, shaping, rough processing and rust treatment, etc.
5. The disadvantages of the mode of casting production, casting will produce noise, harmful gas, dust and pollution of the environment. The required materials (such as molding materials, metal, fuel, wood, etc.) and equipment (such as core making machine, metallurgical furnace, molding machine, sand mixing machine, shot blasting machine, etc.).
6. Cast steel can be divided into cast carbon steel, cast low alloy steel and cast special steel.
(1) Cast carbon steel. It is the cast steel that the carbon is as the main alloying element and with a small amount of other elements. Carbon contains less than 0.2% for casting low carbon steel. And carbon contains 0.2% ~ 0.5% for casting medium carbon steel. Carbon contains more than 0.5% for casting high carbon steel. With the increase of carbon content, the strength and hardness of cast carbon steel increase. Cast carbon steel has high strength, plasticity and toughness and low cost. In heavy machinery, carbon steel is used to manufacture parts bearing large loads, such as rolling machine frame, hydraulic press base, etc. The carbon steel is used in railway vehicles to manufacture large force and impact bearing parts such as bolsters, side frames, wheels and couplings, etc.
(2) Casting low alloy steel. Cast steel contains manganese, chromium, copper and other alloying elements. The total amount of alloying elements is generally less than 5%, with greater impact toughness, and it can obtain better mechanical properties through heat treatment. Cast low alloy steel has better service performance than carbon steel, which can reduce the quality of parts and improve the service life.
(3) Casting special steel. A variety of alloy cast steels are made to meet special needs, usually containing one or more high amounts of alloying elements to obtain a particular property. For example, high manganese steel containing 11% ~ 14% manganese can withstand impact wear. It is mostly used for wear-resistant parts of mining machinery and engineering machinery. Stainless steel with chromium or chromium-nickel as the main alloying element, used in corroded or high-temperature conditions above 650℃ parts, such as the chemical valve, pump, vessel or turbine casing of large capacity power station, etc.
