What Are the Differences between Forged Valves and Cast Valves?
The casting material is integrally cast in a mold, and its stress distribution is uniform. There is no restriction on the compression direction. The forging is pressed by the force in the same direction, so its internal stress is directional and can only bear directional pressure. What are the differences between forged valves and cast valves in detail?
Casting
1. Casting refers to the technological process of melting metal into a liquid that meets certain requirements, then pouring the metal into a mold, experiencing cooling, solidifying and cleaning to obtain casting parts or blanks with predetermined shapes, sizes and properties. It is the basic technology of the modern machinery manufacturing industry.
2. The cost of the blank produced by casting is low, which can show its economy better for parts with complex shapes, especially with complex inner cavities. At the same time, it has wide adaptability and good comprehensive mechanical properties.
3. However, there are many materials (such as metal, wood, fuel, molding materials) and equipment (such as metallurgical furnaces, sand mixers, molding machines, core-making machines, sand dropping machines, shot blasting machines, cast iron flat plates), required for casting production, will produce dust, harmful gas and noise, thus polluting the environment.
4. Casting is an early metal hot working technology mastered by human beings, which has a history of about 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. Between the 13th and 10th centuries BC, China had entered the heyday of bronze castings, and its craftsmanship had reached a fairly high level. For example, Si Muwu Cauldron weighing 875 kg in Shang Dynasty, Marquis Zengyi Plate in Warring States Period and transparent mirrors in Western Han Dynasty are all representative products of ancient castings. The early casting was greatly influenced by pottery, and most of the castings were tools or utensils in agricultural production, religion, life and so on, with a strong artistic flavor. In 513 BC, China cast the earliest recorded iron castings in the world-Jin Kingdom Cast Tripod (weighing about 270 kg). Around the 8th century, Europe began to produce iron castings. After the industrial revolution in the 18th century, castings entered a new period, largely contributing to industrialization. In the 20th century, casting has developed rapidly, producing including ductile cast iron, the malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based, nickel-based alloy and other casting metal materials, and invented a new process for gray 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 casting and shot blasting cleaning had appeared.
5. There are many kinds 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 molding materials, can be divided into two types: special casting with natural mineral sand and gravel as main molding materials, such as investment casting, clay casting, shell casting in the foundry, negative pressure casting, full mold casting, ceramic mold casting, and special casting with metal as main molding materials, such as permanent mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting.
6. Casting process usually includes:
① Preparation of mold (container for making the liquid metal into solid casting), which can be divided into a sand mold, metal mold, ceramic mold, clay mold and graphite mold according to the materials used, and can be divided into the disposable mold, semi-permanent mold and permanent mold according to the times of use. The quality of mold preparation is the main factor affecting the casting quality.
② Melting and pouring of cast metals, which mainly include cast iron, cast steel and cast nonferrous alloys.
③ Casting treatment and inspection
Casting treatment includes removing foreign matter on the core and casting surface, cutting off the riser, relieving burrs, covering seams and other protrusions, as well as heat treatment, shaping, rust prevention and rough machining.
Forging
1. Forging is a processing method that uses forging machinery to exert pressure on metal blank to produce plastic deformation so as to obtain forgings with certain mechanical properties, shapes and sizes.
2. One of the two major components of forging
Forging can eliminate the as-cast porosity of metals and weld holes, and the mechanical properties of forgings are generally better than those of castings made of the same materials. For important parts with high mechanical load and severe working conditions, forgings are mostly used, except for simple rolled plates, profiles or weldments.
3. Forging can be divided into:
① Open forging (free forging)
The metal is deformed between the upper and lower abutments (anvil blocks) by impact force or pressure to obtain the required forgings, mainly including manual forging and mechanical forging.
② Closed die forging
Forgings are obtained by compressing and deforming metal blanks in a forging die bore with a certain shape, which can be divided into die forging, cold heading, rotary forging, extrusion, etc. Forging at deformation temperature can be divided into hot forging (the processing temperature is higher than the recrystallization temperature of the blank metal), warm forging (the processing temperature is lower than the recrystallization temperature) and cold forging (normal temperature).
4. The forging materials are mainly carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, titanium, copper and their matching alloys. The original state of the material includes bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of metal before deformation and after deformation is called the forging ratio. Sufficient consideration of forging ratio plays an important role in improving product quality and reducing cost.
Identification of Castings and Forgings
1. The density of the surface structure of forgings is different. The surface of castings should be thicker, while the machined surface of forgings should be brighter.
2. Cast iron section is dark, while the forged steel section is silver.
3. Listen to the sound. The forging structure is compact, so the sound is crisp after striking, while the sound of the casting is dull.
4. Grind with a grinder to see the difference in spark between the two materials (spark of forgings can be brighter).
Casting
1. Casting refers to the technological process of melting metal into a liquid that meets certain requirements, then pouring the metal into a mold, experiencing cooling, solidifying and cleaning to obtain casting parts or blanks with predetermined shapes, sizes and properties. It is the basic technology of the modern machinery manufacturing industry.
2. The cost of the blank produced by casting is low, which can show its economy better for parts with complex shapes, especially with complex inner cavities. At the same time, it has wide adaptability and good comprehensive mechanical properties.
3. However, there are many materials (such as metal, wood, fuel, molding materials) and equipment (such as metallurgical furnaces, sand mixers, molding machines, core-making machines, sand dropping machines, shot blasting machines, cast iron flat plates), required for casting production, will produce dust, harmful gas and noise, thus polluting the environment.
4. Casting is an early metal hot working technology mastered by human beings, which has a history of about 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. Between the 13th and 10th centuries BC, China had entered the heyday of bronze castings, and its craftsmanship had reached a fairly high level. For example, Si Muwu Cauldron weighing 875 kg in Shang Dynasty, Marquis Zengyi Plate in Warring States Period and transparent mirrors in Western Han Dynasty are all representative products of ancient castings. The early casting was greatly influenced by pottery, and most of the castings were tools or utensils in agricultural production, religion, life and so on, with a strong artistic flavor. In 513 BC, China cast the earliest recorded iron castings in the world-Jin Kingdom Cast Tripod (weighing about 270 kg). Around the 8th century, Europe began to produce iron castings. After the industrial revolution in the 18th century, castings entered a new period, largely contributing to industrialization. In the 20th century, casting has developed rapidly, producing including ductile cast iron, the malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based, nickel-based alloy and other casting metal materials, and invented a new process for gray 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 casting and shot blasting cleaning had appeared.
5. There are many kinds 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 molding materials, can be divided into two types: special casting with natural mineral sand and gravel as main molding materials, such as investment casting, clay casting, shell casting in the foundry, negative pressure casting, full mold casting, ceramic mold casting, and special casting with metal as main molding materials, such as permanent mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting.
6. Casting process usually includes:
① Preparation of mold (container for making the liquid metal into solid casting), which can be divided into a sand mold, metal mold, ceramic mold, clay mold and graphite mold according to the materials used, and can be divided into the disposable mold, semi-permanent mold and permanent mold according to the times of use. The quality of mold preparation is the main factor affecting the casting quality.
② Melting and pouring of cast metals, which mainly include cast iron, cast steel and cast nonferrous alloys.
③ Casting treatment and inspection
Casting treatment includes removing foreign matter on the core and casting surface, cutting off the riser, relieving burrs, covering seams and other protrusions, as well as heat treatment, shaping, rust prevention and rough machining.
Forging
1. Forging is a processing method that uses forging machinery to exert pressure on metal blank to produce plastic deformation so as to obtain forgings with certain mechanical properties, shapes and sizes.
2. One of the two major components of forging
Forging can eliminate the as-cast porosity of metals and weld holes, and the mechanical properties of forgings are generally better than those of castings made of the same materials. For important parts with high mechanical load and severe working conditions, forgings are mostly used, except for simple rolled plates, profiles or weldments.
3. Forging can be divided into:
① Open forging (free forging)
The metal is deformed between the upper and lower abutments (anvil blocks) by impact force or pressure to obtain the required forgings, mainly including manual forging and mechanical forging.
② Closed die forging
Forgings are obtained by compressing and deforming metal blanks in a forging die bore with a certain shape, which can be divided into die forging, cold heading, rotary forging, extrusion, etc. Forging at deformation temperature can be divided into hot forging (the processing temperature is higher than the recrystallization temperature of the blank metal), warm forging (the processing temperature is lower than the recrystallization temperature) and cold forging (normal temperature).
4. The forging materials are mainly carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, titanium, copper and their matching alloys. The original state of the material includes bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of metal before deformation and after deformation is called the forging ratio. Sufficient consideration of forging ratio plays an important role in improving product quality and reducing cost.
Identification of Castings and Forgings
1. The density of the surface structure of forgings is different. The surface of castings should be thicker, while the machined surface of forgings should be brighter.
2. Cast iron section is dark, while the forged steel section is silver.
3. Listen to the sound. The forging structure is compact, so the sound is crisp after striking, while the sound of the casting is dull.
4. Grind with a grinder to see the difference in spark between the two materials (spark of forgings can be brighter).
