User:RMcGill33/sandbox

Overview
The Hazelett twin-belt continuous casting machine produces high volume continuous metal bar or strip of constant rectangular cross section. Unlike traditional individual part casting, where molten metal is cooled in stationary mold cavities, the Hazelett twin-belt casting machine employs a moving mold consisting of parallel carbon-steel belts held in tension as top and bottom casting surfaces. Chains of rectangular steel or copper blocks moving with the belts and spaced according to the desired cast width form the sides of the mold.

Molten metal is introduced into the casting machine from a tundish through a nozzle accurately placed between the casting belts. The metal is cooled by direct contact with the belts which are in turn cooled by a high pressure fast-film, recirculating water application, which is a proprietary technology of the Hazelett Corporation. Various proprietary coatings applied to the belt casting surfaces provide specific mold interface characteristics and prevent adhesion.

The cast metal from the twin-belt casting machine is synchronized with, and directly fed into, a hot rolling mill. Combining the casting and rolling operations results in significant energy and cost savings over traditional processes which incorporate intermediate cast and reheat steps.

Capabilities
The twin-belt casting machine is a near net shape casting process, which significantly reduces the need for secondary rolling or forming operations. For example, when casting copper anode plate the cast slab is not rolled but rather sheared into distinct anode plates.

Strip casting dimensions: As-cast dimensions range from 10-35 mm thick, and up to 2035 mm wide. After being directly fed into a hot rolling mill, the as-cast strip is typically rolled down to 1-3 mm thickness strip.

Bar casting dimensions: As-cast dimensions range from 35-75 mm thick, and from 50-150 mm wide. After being directly fed into a hot rolling mill, the as-cast bar is typically rolled into 8 mm diameter rod to be used for wire drawing.

Mold Length: The mold length ranges from approximately 2000 mm for strip casting machines up to 3700 mm for the large copper bar casting machines.

Production rates and speeds: Casting rates range up to 60 tons per hour at speeds up to 14 meters per minute.

Metals Continuously Cast on Twin-Belt Casting Machines:
Copper (Bar, Strip, Anode)

Aluminum (Strip)

Zinc (Strip)

Lead (Strip)

Belt Stabilization
The cooling belts are made of low carbon steel and are held under tension in the casting machine to ensure flatness and accuracy. As a "cold" belt enters the mold region, it is heated in the cast zone and is subject to powerful forces caused by thermal expansion. When casting wide strip, these forces must be controlled to eliminate buckling and reduce thermal distortion of the belt at the mold entrance. These forces are controlled by preheating the belts before mold entry, and by magnetically stabilizing them once they’ve entered the mold.

Belt Preheating: For wide strip casting, an induction belt preheating system is capable of bringing the belt up to 150°C or higher immediately prior to entering the casting mold, reducing the cold framing. Induction heating coils span the full width of each belt. In addition to preventing thermal distortion, the high preheat temperature serves to eliminate any moisture present on the belt surface.

Magnetic Stabilization: When casting wide strip, any tendency of localized thermal distortion is resisted by the use of high-strength, magnetic belt back-up support rolls within the mold region. The moving belt is held against the support rolls by magnetized rotating fins maintaining the belt in a precise flat plane.

Mold Interface
Molten metal progressively solidifies on the mold surfaces as it moves thru the mold region, with a sump of molten metal present between the solidifying outer surfaces. Belt coatings, texture, and gas layer modifications are used to fine tune the heat transfer rate from the cast metal to the belt. Full thickness solidification can occur as early as 30% of the way thru the mold for thin strip, or up to 2 m beyond the mold exit for large bar where exit water spray cooling and roller support are required.

Closed Pool Feeding
When casting lower temperature metals, such as aluminum, lead and zinc, a fully closed pool “injection” metal feeding system can be employed. Here, the metal is introduced under slight pressure into the closed mold cavity. Metal flow is inherently controlled by maintaining a preset level in the tundish. The feed snout, or nozzle, is machined from a special fired ceramic material which is thermally stable and permeable to gases being released from the flowing metal as it cools.

Open Pool Feeding
When casting high temperature metals, such as copper and steel, an open pool feeding system is used. In this case, the upper belt pulley is offset downstream from the bottom pulley. Metal flows through an open trough or tundish into a standing pool of molten metal formed at the convergence of the belts. Shrouding gases may be employed to protect against oxidation.

Mold Tapering
The twin-belt casting machine differs from other moving mold casting machines in that all four mold surfaces are independent. This allows the mold surfaces to be tapered to remain in contact with the cast product as it shrinks. The high velocity, fast-film cooling water, which is continuously applied to the backside of the belt, impinges the belt at a slight angle creating a force on the belt. This force acts to press the belt against the surface of the strip or slab as it shrinks, keeping the belt in intimate contact with the product throughout the mold. Each side of the mold is formed by an endless chain of dam blocks, which are held against the cast strip by adjustable spring-loaded guides.

Molten Metal Level Control
On Hazelett bar and anode casting machines, the straight-through mold allows a bar to be cast at a very high speed while maintaining the liquid sump of the bar under positive pressure. To accommodate high casting speeds and maintain as high a pool level as possible, Hazelett has implemented a unique, non-contact Electromagnetic Metal level Indicator (EMLI) system to sense the pool level in the casting machine.

Hazelett Corporation History
The Hazelett family has been involved in continuous casting since 1919 when Clarence W. Hazelett (XXXX-1956) first began experimenting with continuous metal casting machines. In 1929, Clarence opened the first commercial continuous casting and processing company in the world, using a twin-roll casting machine and in-line stamping to produce lead grids for automotive batteries. He continued to develop continuous casting technology, and in 1948 invented the twin-belt casting machine. Clarence Hazelett's work in continuous metal casting has been recognized in numerous worldwide patents and technical publications.

Clarence W. Hazelett's two sons, R. William “Bill” Hazelett and S. Richard “Dick” Hazelett, carried on the research of their father. In 1956, they founded the Hazelett Strip Casting Corporation and moved the company from Connecticut to its present facilities near Burlington, Vermont.

Bill Hazelett was president from 1956 to 2009, and has over 60 US patents in his name. Bill's son David Hazelett is the current president.