The necessary basis of M.Y. to produce high quality products is it's complete automatic tube production line integrating all the procedures and know-how. The 4 major process is melting, casting, machining and welding, each stage equipped with the machines of latest and state-of-the-art technologies.

Production Line Chart


Melting

To gain the purified metal liquid in the very beginning of production, minimize the formation of non-metallic inclusions, pin holes, sand inclusions in the cast tubes, and reach a homogeneous and solid chemical composition and mechanical properties throughout each job, M.Y. takes following measures:

• Internal (confidential) standards of chemical compositions are applied, with much more stringent requirements comparing with customers' specifications, and careful considerations of balanced ratio of different alloy elements.
  
• Formal, continuous and stable sources of raw material supply.
  
• Preheating of raw materials to eliminate moisture and other inclusions.
  
• Inert gas protection during melting when high purity of molten metal is required.
  
• Special slag-off process.
  
• Know-how of addition of micro alloy elements.

Centrifugal Casting

To realize the soundness and superior properties of the spun tubes, M.Y. introduced the art centrifugal casting machines and technologies, of which main characteristics are:

• Foundation of special designs to accommodate the additional weight and vibrations that are imparted during casting, leading to smooth and high speed rotation of mould, thus make possible casting longer tubes and structure soundness throughout the whole tube length.
  
• Very high rotation speed up to 2400 ~ 3000 rpm, resulting in bigger centrifugal force, propelling the molten metal flowing quickly, so that compact and homogenous structure can be obtained.
  
• Preheating of mold in 3 sections, with temperature gradient automatically kept constant via infrared sensing programmable controllers. Such will compensate the heat loss of molten metal, and homogeneous structure is guaranteed. This is also critical to control the ratio of equiaxe and columnar structure.
• To ensure the consistency of products, all critical parameters - mould preheat temperature, rotation speed, wash thickness, pouring temperature etc - at M.Y. are controlled by real time process control devices.
  
• During each pouring, the metal temperatures are monitored by disposable and accurate thermocouples. These temperatures are critical to establish the distribution and extent of shrinkage porosity in the tube.
  
• Special mould wash is used and application of it is preset and mechanically controlled, to eliminate the variability of thickness that can negatively influence structure or tube quality.

Machining

Apart from lathes, beveling machine, special requirements of inside machining quality for petrochemical tubes necessitate the application of pull boring machine, the customer engineered and unarguably the best for inside machining, with capability to accept tube diameters up to 8" diameter, and a length of 7 meters. The pull boring allows to obtain machined tubes with very low eccentricity (≤0.25mm).

The main characteristics that make our pull boring machine unique are: optimization between longitudinal feed and cross feed to ensure the required surface RMS of 125 to 63, safety device on the oil pump which stops boring if any anomaly is detected in the oil circuit pressure (two sets of pumps), and cast iron bed with quenched guide ways and sliding drill head with antifriction material.

Welding

In the fabrication shop, all tube to tube assemblies use automatic TIG welding process, by direct fusion of base metal without adding wires. This means much similar properties of welds as base metal, and the inside protrusion is limited.

In similar fashion as TIG, the filler passes are made exclusively using computerized automatic MIG on closure welds and couplings. By doing such, operator intervention to the fabrication operation is minimized, and high quality of welds is reproducible with more than 99% of Class I films, reduced the repairing rate almost to zero.

Static Casting

At M.Y., mainly sand mould method is applied for production of different static casting parts.

M.Y. is capable to produce castings of different shapes. The production of most shapes such as simple return bends, elbows and Y castings are routine at M.Y. and thus are made by established practices proven over years of production experience. A broad base of production and service history exists with integrally cast hangers, lugs, and bosses to validate the successful design integrity of cast components.

Fittings design incorporates directional solidification principles to ensure progressive solidification properties are achieved to obtain optimum casting soundness. The casting production design method is engineered to balance the part design requirements with the optimum production techniques to assure features to provide maximum service performance.

These types of common components have simple design calculations common throughout M.Y. In similar fashion the methods of producing fittings are standardized and selected with the customer use in mind.

Whenever possible fitting production is restricted to the bottom pouring technique. Without exception, all M.Y. fittings are poured through a standard filter system to ensure maximum metal cleanliness. Combined with bottom pouring, this allows for the use a slightly non-pressurized pouring system. All these are consistent with achieving optimum metal cleanliness and production of castings free from weld repairs. Practices common to other suppliers such as use of gas flow off rings at bevel sites or ingating at bevels for bottom gating practices are not allowed as these increase grain size and reduce ductility locally. Under certain conditions, they will make castings easier to produce but they will reduce weldability in the fittings.