The Process
In a unique and well proven method, CLADMAX is a sequentially poured centrifugal casting that creates a fully bonded cast cylinder that can be sued as-cast or further processed into the desired dimensional configuration.
The unique CLADMAX™ tubular program begins with the forming of a full metallurgical bond, right at the start of the process. To begin, two ladles of differing steel grades are prepared and refined. A cylindrical mold with the precise OD dimension required is pre-heated and set into a spinning motion along its long axis. The inner surface of the mold is ceramic lined and the ends of the mold each have affixed an “end cap” composed of a ceramic disc with circular openings in the center. The openings on the discs allow for the insertion of the pre-heating gas arc on one end and for the pouring of the liquid steels on the other.
Once the mold has achieved the designed revolutions per minute rate and is pre-heated to the proper temperature, the process of precision casting can begin. The grade designed to become the outer shell is poured into one end of the mold. Centrifugal force and a slight tilt to gravity allow the liquid steel to spread to cover the inside surface of the mold. The end discs contain the flow and allow a layer of steel to build up to the desired thickness for the outer shell of the planned clad tube.
As the first pour cools, but before the grain structure of the steel can fully set, the second pour of the planned inlay grade material is made. As with the first grade, the liquid steel spreads through the inner surface over the shell layer and forms its own layer of steel from end to end of the mold and to the desired thickness. With the mold still spinning at a programmed rate, the materials are allowed to cool together and to solidify.
Currently, we cast hollows in 3 to 4 meter lengths for use in the as-cast condition for heavy wear applications and for further processing into a variety of applications. In mid second quarter 2014 our new 6 meter casting stands will come online. This will allow for a large increase in sizing possibilities for both as-cast and processed materials.
Bonding
As the temperature of the co-joined steel grades begins to drop and the steels go from the liquid state to the solid, a very unique process takes place. Where the two different steels meet, a thin “transition zone” is created. In this zone, the two materials come together at the inter-granular level and bond metallurgically. This zone can vary from 0.5mm to 1.5mm on average depending on the material involved. The balance of each steel grade remains completely separate and pure to the original metallurgy. The bond is complete, permanent and inseparable through mechanical means. Seen below, under extreme magnification, the two grades are joined at the inter-granular level.
Processing
With a full 100% metallurgical bond now achieved, this “hollow” then becomes the pre-material for a variety of product possibilities. After a thorough X-ray inspection to confirm bonding and cast integrity, the hollow is “pre-worked” through machining to clean up all exposed surfaces and to achieve the final desired dimension for further processing. The designed weight of the hollow is calculated to consider the downstream process plan and to allow for the manufacture of specific diameters, overall wall thickness and clad layer ratios required for the finished product.
All CLADMAX™ processing is “linear” in nature. That is to say that this material is processed in a straight line fashion as opposed to rolling, which is based on circumferential processing. Because there are two distinct steels in one wall and each has differing “flow properties” when it comes to hot and cold deformation, the process is best controlled in a linear fashion. This factor allows for two forms of hot processing and one of cold working.
The as-cast hollow can be hot pilgered or hot extruded for those applications where the diameters tend to be larger (150-300mm) and the walls somewhat thicker. These two processes can be used to produce line-pipe, OCTG and tubulars with wear resistant surfaces for application in mining industry. Diameter and wall thickness will vary and lengths will change based on the dimensions and the original weight of the hollow. We publish size and weight/length charts and quote based on customer requirements in a great variety of size configurations.
For precision tube applications, CLADMAX™ can be cold rolled to very tight tolerances and very long lengths. For applications like boiler tubes, heat exchanger tubes and other requirements like hydraulic applications, the cold rolling (roto-rocking) process we use makes a consistent, precision tube every time. Modern certified inspection equipment for X-ray, UT, eddy current and other required inspections are conducted to insure 100% quality in every tube we ship.
