What is sand casting, and how does it work? Full-time JobDec 14th, 2021 at 04:41 IT & Telecoms Baia Mare 44 views
What is sand casting, and how does it work?
Sand castings are casting process by which sand is used to create a mold, after which liquid metal is poured into this mold to create a part. To learn about the other forms of casting, visit our article on the types of casting processes. Sand is used in this method because it insulates well, it is relatively cheap, and it can be formed into any number of mold shapes. There are defined steps to this process (shown simplified in Figure 1), and this article will walk through each of these steps to illustrate exactly how this casting procedure is conducted.
The first step in the sand casting process involves fabricating the foundry pattern - the replica of the exterior of the casting - for the mold. These patterns are often made from materials such as wood or plastic and are oversized to allow the cast metal to shrink when cooling. They are used to create the sand mold for the final part, and can potentially be reused depending upon the pattern material. Often times, two pattern halves are separately created which provides cavities when put together (shown in Figure 1). Cores are internal mold inserts that can also be used if interior contours are needed, but are typically disposable after one casting. The type of pattern and its material is dictated not only by the desired part dimensions but also by the number of castings needed from each mold.
The second step is the process of making the sand mold(s) from these patterns. The sand mold is usually done in two halves, where one side of the mold is made with one pattern and another side is made using the other pattern (shown in Figure 1). While the molds may not always be in two halves, this arrangement provides the easiest method of both creating the mold and accessing the part, once cast. The top part of the mold is known as the “cope” and the bottom half is the “drag”, and both are made by packing sand into a container (a “flask”) around the patterns. The operator must firmly pack (or “ram”) the sand into each pattern to ensure there is no loose sand, and this can be done either by hand or by machine. After ramming, the patterns are removed and leave their exterior contours in the sand, where manufacturers can then create channels and connections (known as gates/runners) into the drag and a funnel in the cope (known as a “sprue”). These gates/runners and sprues are necessary for an accurate casting, as the runners and gates allow the metal to enter every part of the mold while the sprue allows for easy pouring into the mold.
The third main step in sand casting is clamping the drag and cope together, making a complete mold. If a core is needed for some internal contours, it would be placed into the mold before the clamping step, and any gating/runners are also checked for misalignments.
The fourth step begins when the desired final material (almost exclusively some metal) is melted in a furnace, and is then poured into the mold. It is carefully poured/ladled into the sprue of the mold, where the molten metal will conform to the cavity left by the patterns, and then left to cool completely. After the metal is no longer hot, manufacturers will remove the sand from the mold (via vibrations, waterjets, and other non-destructive means, known as “shakeout”) to reveal the rough final part.
The fifth and final step (not shown in Figure 1) is the cleaning step, where the rough part is refined to its final shape. This cleaning includes removing the gating system and runners, as well as any residual mold/core parts the remains in the final piece. The part is trimmed in areas of excess, and the surface of the casting can be sanded/polished to a desired finish. After major cleaning, each part is inspected for defects and is tested to ensure compliance with the manufacturer’s standards of quality, so that they will perform as intended in their respective applications.
Valves are mechanical or electro-mechanical devices that are used to control the movement of liquids, gases, powders, etc. through pipes or tubes, or from tanks or other containers. In most instances, valve relys on some form of mechanical barrier—a plate, a ball, a diaphragm, for example—that can be inserted and removed from the flow stream of the material passing by. Some valves are designed as on-off varieties, while others allow very fine control of the passage of media.
Material selection and valve parts play an important role in specifying valves to ensure the compatibility of the wetted parts of the valve with the fluid or powder passing through it. Sizing is determined by the pipe or tubing diameter, flow rate, and the width between flanges for pipeline valves being installed as replacements.
Types of Valves and Their Applications
Aerosol Valves are used for dispensing the contents of aerosol cans. They consist of two primary components, the housing and the stem. Key specifications include the intended application, actuator type, output type, valve size, and materials of construction. Media dispensed can be a consideration as well. Aerosol valves dispense liquids, creams and ointments, gases, cleaning agents, and any other product that is packaged in an aerosol can.
Air Logic Valves
Air Logic Valves are mechanical or electro-mechanical devices used to regulate the flow of air in pneumatic systems and can be used in place of electrical control in instances such as hazardous atmospheres or where electrical control is impractical. Key specifications include actuator type, number of ports, materials of construction, switching speed, port thread size, pressure ratings, and input voltage. Air logic valves are applied to pneumatic systems as e-stops, pilot valves, one-shot valves, etc.
Balancing Valves are used to control fluid flow by dividing flow evenly in multiple flow branches. Key specifications include the number of ports, port connections, valve size, and materials of construction. Balancing valves are used primarily in HVAC applications and fluid power systems. For example, they can be used in commercial heating/cooling systems to adjust water temperatures under varying loading conditions. They can also be used to provide a counterbalancing force for double acting cylinders.
Forged flange is defined as a plate type device, normally round, that is attached to the end of a pipe, fitting, valve or other object to facilitate the assembly and disassembly of a piping system.
Forged steel flanges made of carbon steel or stainless steel, the materials conform to the JIS, ASTM A182,A105, DIN17100 ST-2 and BS standard. Dimension to be in accordance with JIS ANSI DIN BS standard accordingly.
The flanges are suitable for connection of steel pipes conveying mediums such as steam, oil, air and water. They are widely used in Chemical industry and Shipbuilding . And the flanges are suitable for welding. The flanges mainly include Welding Neck, Blind, Slip-on, Lap-Joint, Socket, Spectacle, Forged, Reducing and Threaded.
What is Forging?
Forging, a metal shaping technique using compressive, localized forces, has been a staple metal fabrication technique since the time of the ancient Mesopotamians. Since its origins in the fertile crescent, forging has experienced significant changes, resulting in a more efficient, faster, and more durable process. This is because today, forging is most commonly performed with the use of forging presses or hammering tools that are powered by electricity, hydraulics or compressed air. Some of the common materials used for forging are carbon steel, alloy steel, microalloy steel, stainless steel, aluminum, and titanium.
What is the purpose of forging?
The purpose of forging is to create metal parts. Compared to other manufacturing methods, metal forging produces some of the sturdiest manufactured parts available. As metal is heated and pressed, minor cracks are sealed, and any empty spaces in the metal close.
The hot forging process also breaks up impurities in the metal and redistributes such material across the metalwork. This vastly reduces inclusions in the forged part. Inclusions are compound materials implanted inside steel throughout manufacturing that cause stress points in the final forged parts.
While impurities should be managed during the initial casting process, forging further refines the metal.
Another way that forging strengthens metal is by alternating its grain structure, which is the metal material's grain flow as it deforms. Through forging, a favorable grain structure can be created, making the forged metal sturdier.
The forging process is highly multipurpose and can be used on small parts just a few inches in size to large components that weigh up to 700,000 lbs. It is used to produce critical aircraft parts and transportation equipment. Forging is also used to fortify hand tools such as chisels, rivets, screws, and bolts.
What are the different types of forging?
The pounding action of forging deforms and shapes the metal, which results in unbroken grain flow. This causes the metal to retain its strength. Ancillary effects of this unique grain flow include the elimination of defects, inclusions, and porosity in the product. Another advantage of forging is the relatively low costs associated with moderate and long production runs. Once the forging tools have been created, products can be manufactured at relatively high speeds with minimal downtime.There are two main types of forging: hot and cold.
Hot forging requires the metal to be heated above its recrystallization temperature. This can mean heating metals up to 2,300 degrees Fahrenheit. The main benefit of hot forging is the decrease in energy required to form the metal properly. This is because excessive heat decreases yield strength and improves ductility. Hot forged products also benefit from the elimination of chemical inconsistencies.
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Cold forging typically refers to forging a metal at room temperature, though any temperature below recrystallization is possible. Many metals, such as steel high in carbon, are simply too strong for cold forging. Despite this hindrance, cold forging does edge out its warmer equivalent when it comes to standards of dimensional control, product uniformity, surface finish, and contamination. Cold forging encompasses numerous forging techniques, including bending, extruding, cold drawing, coining, and cold heading. However, this increased versatility comes at a cost, because cold forging requires more powerful equipment and may call for the use of intermediate anneals.