INVESTMENT CASTING

NTC Machinery is specialised in investment casting which is also called "lost wax casting". A mold is made according to customer's product requirements. Wax is injected into the mold to form a wax pattern and then welded together with gate cups and runners to form a tree. The tree is later coated with multiple layers of refractory slurry and sand to form a shell. The shell will be heated to remove the wax inside and then baked with high temperature. Molten metal will then be poured into the shell. When the molten metal solidifies and cools down, metal parts will be cut off from the tree and cleaned, thus the required products are obtained. Compared with other casting processes, investment casting applies to a wider range of materials and more complex-structured products. After investment casting, the product will gain a high-quality surface finish and high dimensional accuracy. It almost forms the final shape and structure required, without or with very little machining.

HEAT TREATMENT

NTC can perform various types of heat treatment such as solution, quenching, tempering, normalizing, annealing, recarburization hardening and tempering, recarburization normalizing, etc., and is equipped with High-temperature solution treatment furnace that can reach 1250℃ max, and controllable atmosphere multi-purpose furnace that can reach 950℃.

MACHINING

SURFACE TREATMENT

Shot blasting

A high-speed shot flow made of steel shots, iron sand or stainless steel shots is sprayed on the casting surface in the shot blasting machine, to remove surface impurities and get a uniform surface. Further surface treatment is needed to prevent rust if this process is used on the castings made of carbon steel, low and medium alloy steel, or tool steel.

Application: all materials other than nonferrous alloys.

A high-speed sand flow made of quartz sand, brown corundum or glass beads is sprayed on the casting surface with compressed air in the sand spray machine, to remove surface impurities and get a uniform, fine surface. With the effect of the impact, the mechanical properties of the surface of the work piece are improved, so is the fatigue strength. The adhesion between the work piece and the coating can also be increased. Further surface treatment is needed to prevent rust if this process is used on the castings made of carbon steel, low alloy steel, or tool steel.

Application: all materials.

The castings are immersed in passivation solution to remove impurities on the surface and form an oxide film, thus the corrosion and rust resistance of the castings is enhanced. Casting surface after passivation is bright, glossy and aesthetically pleasing.

Application: Stainless Steel, Copper Alloy.

The castings and a lead plate are placed in electrolyte together while the castings act as the anode and the lead plate as the cathode. When DC current is applied, the current density at the positions where burrs and bulges exist on the surface of the product is bigger, and thus burrs and bulges are dissolved faster. This inhomogeneity dissolves the bulges faster and makes the surface smooth and polished. It can improve the surface finish and increase the corrosion resistance of castings. The surface after electropolishing is smooth and with good luster.

Application: Stainless Steel.

It makes a friction between the castings and the grinding blocks under the centrifugal force in a vibrating grinder. The impurities, flashes and parting lines on the surface of the castings can be removed to get a fine surface roughness.

Application: Stainless Steel.

When the polishing wheel rotates at a high speed, friction caused by the force between the casting surface and the wheel generates high temperature at the contacting area and increases the plasticity of the metal. The convex part of the microscopic unevenness flows at the high temperature to the concave part to fill up, thereby the uneven surface is improved. Mechanical polishing is divided into dull polishing and mirror polishing. The surface after dull polishing is smooth, linear, like a foggy film. The mirror polished surface is as bright as a mirror, and the surface roughness can reach ≤ Ra0.2.

Application: stainless steel.

The pre-processed article to be plated is the cathode, the plated metal is the anode, and they are connected by the electrolytic solution composed of the positive ions of the plated metal. After power on, the anode metal will lose electrons, the cathode will get electrons, and the plating metal atoms will accumulate on the surface of the cathode, the plating layer is thus formed. Electroplating can improve the corrosion resistance, hardness and surface looking of castings. At present, the company is capable of blue and white zinc plating, color zinc plating, nickel plating, chrome plating, and KTL coating. The surface after electroplating is smooth and shiny. The surface after white zinc plating is silvery white, the surface of color zinc plating is rainbow with reflection, nickel and chrome plating appears bright white, and KTL coating shows black.

Application: carbon steel, low and medium alloy steel, tool steel.

The paint disperses into uniform and fine fog drops under pressure or centrifugal force in a spray gun or disc type atomizer, and applies to the surface of the castings.

Application: carbon steel, low and medium alloy steel, tool steel.

The casting is placed in a phosphating solution to form a water-insoluble crystalline phosphate film on the surface. It can prevent the casting from rust and certain corrosion.

Application: carbon steel, low and medium alloy steel, tool steel.

Castings are placed in the blackening solution to form an oxide film on the metal surface. It can prevent the casting from rust and certain corrosion.

Application: carbon steel, low and medium alloy steel, tool steel.

Dacromet or Geomet solution is sprayed on pretreated product surface, and then adheres to the surface by drying to form a protective coating with a thickness of around 4 to 8μm. It provides a better anti-corrosion, thermos-stability, permeability and recoat ability, compared with traditional electroplating processes. Geomet solution doesn't contain Chromium element and is called environment-friendly Dacromet. Surface appears sliver white or grey after coating.

Application: all materials.