Which is better, forged steel valves or cast steel valves?
Cast steel valves are the steel used to cast castings. A type of cast alloy. Cast steel is divided into three categories: cast carbon steel, cast low alloy steel and cast special steel. Cast steel refers to a kind of steel casting produced by casting method. Cast steel is mainly used to manufacture parts that are complex in shape, difficult to forge or cut, and require high strength and plasticity.
Forged steel refers to various forgings and forgings produced by forging. The quality of forged steel parts is higher than that of steel castings, and it can withstand large impact forces. The plasticity, toughness and other mechanical properties are also higher than those of steel castings. Therefore, forged steel parts should be used for some important machine parts.
The difference between forged steel valves and cast steel valves:
The quality of forged steel valves is better than that of cast steel valves, and they can withstand large impact forces. The plasticity, toughness and other mechanical properties are also higher than those of cast steel valves, but the nominal diameter is relatively small, generally below DN50. The pressure rating of cast valves is relatively low, and the commonly used nominal pressures are PN16, PN25, PN40, 150LB-900LB. Forged steel valve grade: PN100, PN160, PN320, 1500LB-3500LB, etc. Cast steel is mainly used to manufacture parts that are complex in shape, difficult to forge or cut, and require high strength and plasticity.
Casting is liquid forming, while forging is a plastic deformation process. Forging and forming workpieces can improve the internal structure of the organization, with good mechanical properties and uniform grains. Important and demanding workpieces must be forged. Casting will cause structural segregation and structural defects. Of course, casting has its advantages. , Forming complex workpiece forging is not easy to open the mold, casting has been adopted.
Introduction of forged valve (forged steel valve):
1. Forging can be divided into:
(1) Closed mode forging (die forging). It can be divided into die forging, rotary forging, cold heading, extrusion, etc., and forgings are obtained by placing metal blanks in a forging die with a certain shape and deforming under pressure. According to the deformation temperature, it can be divided into cold forging (the forging temperature is normal temperature), warm forging (the forging temperature is lower than the recrystallization temperature of the blank metal), and hot forging (the forging temperature is higher than the recrystallization temperature).
(2) Open forging (free forging). There are two methods of manual forging and mechanical forging. The metal blank is placed between the upper and lower anvils (iron) and the impact force or pressure is used to deform the metal blank to obtain the required forging.
2. Forging is one of the two major components of forging. Forgings are mostly used for important parts with high loads and severe working conditions in machinery. Forgings with simpler shapes can be rolled weldments, except for profiled plates. Welding holes and as-cast porosity of metal materials can be eliminated by forging.
3. The correct choice of forging ratio has a lot to do with improving product quality and reducing costs. Forging materials are mainly carbon steel, stainless steel and alloy steel. The forging ratio refers to the ratio of the cross-sectional area of the metal before deformation to the die area after deformation. The original state of the material includes ingot, bar, liquid metal and metal powder.
4. The mechanical properties of forgings are generally better than castings of the same material. Forging is a processing method that applies pressure to metal blanks through forging machinery to cause plastic deformation of metal blanks to obtain a processing method with a certain shape and size and good mechanical properties.
Casting valve (cast steel valve) detailed introduction:
1. There are many types of casting, according to the molding method, ordinary sand casting and special casting:
① Ordinary sand casting, including dry sand mold, wet sand mold and chemically hardened sand mold.
② Special casting, according to the mold material, it is divided into two types: special casting of ore and special casting of metal material;
Special casting with metal as mold material, including: pressure casting, metal mold casting, low pressure casting, continuous casting, centrifugal casting, etc.
Special casting with natural mineral sand as mold material, including: real mold casting, investment casting, foundry shell casting, mud casting, negative pressure casting, ceramic casting, etc.
3. Casting is a metal thermal processing process. Casting production has good comprehensive mechanical properties. Casting production has wide adaptability and low blank cost. It is more suitable for parts with complex shapes, especially complex internal structures. It can show the economy of foundry production.
4. Casting is the basic process of modern machinery manufacturing industry. It is to smelt metal into liquid and pour it into casting mold, and then take out the casting after cooling and solidification, and then get the casting with predetermined size, shape and mechanical properties (blank or parts).
5. The casting process usually includes:
① Prepare the casting mold (the mold used to make the liquid metal into a solid casting, the quality of the casting mold directly affects the quality of the casting), the casting mold can be divided into one-time type, multiple type and permanent type according to the number of uses, casting Molds are divided by material: metal mold, sand mold, mud mold, ceramic mold, graphite mold, etc.
② Melting and pouring of cast metal, cast metal mainly includes cast iron, carbon steel and stainless steel;
③ Processing and acceptance of castings. Casting processing includes removal of foreign objects and cores on the surface of castings, treatment of protrusions (removal of burrs, removal of pouring risers, and treatment of draping seams, etc.), heat treatment of castings, shaping, rough machining and anti-rust treatment wait.
6. Disadvantages of casting production methods, casting will produce noise, harmful gases and dust, etc., which will pollute the environment, and the required materials (such as modeling materials, metal, fuel, wood, etc.) and equipment (such as core making machines, metallurgical furnaces, etc.) molding machine, sand mixer, shot blasting machine, etc.)
7. Cast steel is divided into three categories: cast carbon steel, cast low alloy steel and cast special steel.
① Cast carbon steel. Cast steel with carbon as the main alloying element and small amounts of other elements. Cast low-carbon steel with a carbon content of less than 0.2%, cast medium-carbon steel with a carbon content of 0.2% to 0.5%, and cast high-carbon steel with a carbon content of more than 0.5%. As the carbon content increases, the strength of cast carbon steel increases and the hardness increases. Cast carbon steel has high strength, plasticity and toughness, and low cost. It is used in heavy machinery to manufacture parts that bear heavy loads, such as rolling mill frames, hydraulic press bases, etc.; Parts that are also subject to impact such as bolsters, side frames, wheels and couplers, etc.
② cast low alloy steel. Cast steel containing alloying elements such as manganese, chromium, and copper. The total amount of alloying elements is generally less than 5%, has greater impact toughness, and can obtain better mechanical properties through heat treatment. Cast low-alloy steel has better performance than carbon steel, which can reduce the quality of parts and increase the service life.
③ cast special steel. There are many varieties of alloy cast steel refined to meet special needs, and usually contain one or more high-alloying elements to obtain certain special properties. For example, high manganese steel containing 11% to 14% manganese is resistant to impact and wear, and is mostly used for wear-resistant parts of mining machinery and construction machinery; various stainless steels with chromium or chromium-nickel as the main alloying element are used in corrosion or 650 Parts that work under high temperature conditions above ℃, such as chemical valve bodies, pumps, containers, or steam turbine casings for large-capacity power stations.
Valve casting process:
1. Casting: It is the process of smelting metal into a liquid that meets certain requirements and pouring it into a mold, cooling and solidifying, and cleaning to obtain a casting (part or blank) with a predetermined shape, size and performance. The basic technology of modern machinery manufacturing industry.
2. The cost of the blank produced by casting is low, and it can show its economical efficiency for parts with complex shapes, especially those with complex inner cavities; at the same time, it has wide adaptability and good comprehensive mechanical properties.
3. Materials (such as metal, wood, fuel, molding materials, etc.) and equipment (such as metallurgical furnace, sand mixer, molding machine, core making machine, shakeout machine, shot blasting machine, cast iron plate, etc.) required for casting production ) more, and will produce dust, harmful gases and noise to pollute the environment.
4. Casting is an earlier metal thermal processing technology mastered by humans, with a history of about 6,000 years. Bronze frog castings appear in Mesopotamia 3200 BC. From the 13th century BC to the 10th century BC, China has entered the heyday of bronze castings, and the craftsmanship has reached a very high level, such as the Simuwufang Ding weighing 875 kg in the Shang Dynasty, the Zenghou Yizun plate in the Warring States Period and the Western Han Dynasty. The light-transmitting mirror and so on are all representative products of ancient casting. Early casting was greatly influenced by pottery, and most of the castings were tools or utensils for agricultural production, religion, and daily life, with a strong artistic color. In 513 BC, China cast the world's first iron casting found in written records - Jin Guozhu Ding (about 270 kg in weight). Around the 8th century AD, iron castings began to be produced in Europe. After the industrial revolution in the 18th century, castings entered a new era of serving large industries. In the 20th century, the development of casting was very fast. Ductile iron, malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloys, titanium-based, nickel-based alloys and other casting metal materials were developed successively. A new process for inoculation of cast iron. After the 1950s, new technologies such as wet sand high-pressure molding, chemically hardened sand molding and core making, negative pressure molding, and other special castings and shot blasting appeared.
5. There are many types of casting, which are customarily divided into:
① Ordinary sand casting, including wet sand mold, dry sand mold and chemically hardened sand mold.
② Special casting, according to the molding material, can be divided into special casting with natural mineral sand and stone as the main molding material (such as investment casting, mud casting, foundry shell casting, negative pressure casting, solid casting, ceramic casting etc.) and special casting with metal as the main casting material (such as metal casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).
6. The casting process usually includes:
① Preparation of casting molds (containers that make liquid metal into solid castings). According to the materials used, casting molds can be divided into sand molds, metal molds, ceramic molds, mud molds, graphite molds, etc., and can be divided into disposable types and semi-permanent types according to the number of uses And permanent type, the pros and cons of mold preparation is the main factor affecting the quality of castings;
② Melting and pouring of cast metals, cast metals (cast alloys) mainly include cast iron, cast steel and cast non-ferrous alloys;
③ Casting treatment and inspection. Casting treatment includes removal of foreign objects on the core and casting surface, removal of sprue risers, shovel grinding of burrs and seams and other protrusions, as well as heat treatment, shaping, anti-rust treatment and rough machining. Imported pump valve
Valve forging process:
1. Forging: It is a processing method that uses forging machinery to apply pressure to metal blanks to cause plastic deformation to obtain forgings with certain mechanical properties, certain shapes and sizes.
2. One of the two major components of forging. The as-cast looseness and welding holes of metal can be eliminated by forging, and the mechanical properties of forgings are generally better than castings of the same material. For important parts with high load and severe working conditions in machinery, forgings are mostly used except for plates, profiles or weldments that can be rolled with simple shapes.
3. Forging can be divided into:
① Open forging (free forging). Using impact force or pressure to deform the metal between the upper and lower irons (anvils) to obtain the required forgings, there are mainly two kinds of manual forging and mechanical forging.
② Closed mode forging. Metal blanks are compressed and deformed in a forging die chamber with a certain shape to obtain forgings, which can be divided into die forging, cold heading, rotary forging, extrusion, etc. According to the deformation temperature, forging can be divided into hot forging (processing temperature higher than the recrystallization temperature of the blank metal), warm forging (lower than the recrystallization temperature) and cold forging (normal temperature).
4. Forging materials are mainly carbon steel and alloy steel with various components, followed by aluminum, magnesium, titanium, copper and their alloys. The original state of the material includes bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. The correct choice of forging ratio has a lot to do with improving product quality and reducing costs.