Introduction to Powder-Cored Wires of Wisdom

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Wisdom has two kinds of metal cored wires. One is solid-cored wire and another is powder-cored one. The basic composition of powder-cored wire can be considered as a tubular electrode consists of outer metal sheath and inner powdered materials. The metal sheath can be cobalt, nickel and iron based. Electrical current is conducted by the sheath during the welding and thermal spraying processes. The internal powder composition is comprised of both elemental and alloyed powders such as cobalt, nickel, chromium, tungsten, molybdenum, and manganese.

The manufacturing process of powder-cored wire is very different from alloyed wires, during which a metal strip is transformed to the outer metallic sheath wrapping the powder inside. On the other side, the powder is fed into the sheath by a specialized feeding process that can ensure the precision. The wire is then rolled into a tubular shape. Finally it is drawn to the required diameter with range from 1.2 mm to 3.2 mm. MIG, MAG, FCA, SAW welding and arc spraying are the typical processes that apply powder-cored wires.

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How to Choose Cobalt based Welding Rods – Regarding Grades, Processes and Applications

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Customers’ requirements are always variable. This article will help you to understand how to choose right alloy rod grades (typically Co1, 6, 12) in consideration of welding processes (OXY, TIG, ERW) in three main applications (valve, engine valve, saw blade).

In order to cater diverse needs of our clients, Wisdom has developed several manufacturing technologies, especially in cobalt based rod production. Therefore, the rods could be slightly different even they are the same grade. We generally classify them as three types, i.e. OXY rod, TIG rod, and ERW rod corresponding to different welding processes. In the following paragraphs, we will discuss the way of choosing the alloy grades & types in certain applications.

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Cobalt Base Investment Casting Components – Production, Advantage & Inspection

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Wisdom has two primary techniques for manufacturing cobalt base components: casting and powder metallurgy. Powder metallurgy is suitable for small and regular dimension while casting can apply to wider situations. There are generally four kinds of casting processes: investment, sand, resin shell and centrifugal. Investment casting is what we mostly use.

Investment casting process uses wax patterns assembled in tree forms on a runner. The completed assembly is coated with ceramic slurries, allowed to dry and then heated to melt out the wax leaving ceramic molds into which the molten alloy is poured. It can be understood from the graph below:

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Differences of 3 Thermal Spray Coatings for Boiler Tubes in Power Plant

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1. Principles

Nickel-Chromium Alloy Coating

Nichrome alloys can form dense chromium oxide surface thereby preventing further oxidation of the metal when it is in the process of heating and oxidation, because Ni-Cr alloys will selectively oxidize due to the considerable affinity of chromium and oxygen. The most frequently used materials are NiCr 80/20 and NiCrTi. Generally, different chromium percentages could lead to diverse performance on oxidation resistance. When the chromium exceeds 20%, Ni-Cr alloys can form continuous and dense chromium oxide protective film in high temperature environment. Once the oxide film is destroyed, the chrome oxide film forms again because of the high ratio of chromium in the alloy, which causes very slow speed of oxidation. NiCrTi (equal to 45CT), as a typical example, is made of nickel-chromium alloy by adding a small amount of titanium element. It is widely used in high-temperature and corrosion-resistant application.

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PTA Welding Machine for Engine Valve

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Since 2008, we have sold 218 sets different kinds of PTA machine including:

  • Long distance valve plate, ring overlay welding machine
  • Short distance valve overlay welding machine(with roll-over table)
  • Automatic double-head Horseshoe valve overlay welding machine
  • Automatic double-head valve ring overlay welding machine
  • Automotive engine valve face welding machine
  • Engine valve stem tip welding machine
  • Vessel engine valve welding machine
  • Triple eccentric butterfly valve welding machine
  • Band saw guide bar dedicated welding machine

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How to Select Arc Spray Coating Materials for different Anti-corrosive Applications?

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Generally, the principle for atmospheric corrosion environment is:

  • pH = 7-12 alkaline environment: pure Zn and Zn alloy
  • pH = 4-7 acidic environment: Al and Al alloy
  • pH = 6-8 neutral environment: Zn-Al alloy

Regarding the bridge and other large steel structures in the ocean atmosphere, industrial city atmosphere and acid rain environment, it is suitable to spray Al and Al alloy coating plus weathering finish top-coat.

Regarding steel structures in the environment of dry area with good quality air, such as television towers and transmission towers, it is appropriate to apply arc spraying with Zn and ZnAl 95/5 alloy.

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Welding & Thermal Spraying Powder – A General Idea from Production Perspectives

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Wisdom’s hardfacing welding and thermal spraying powder is produced by three typical techniques: gas atomization – gas cooling, gas atomization – water cooling, and water atomization – water cooling. After raw materials having been melt, steel water will enter into atomization procedure that is classified as gas and water. The two types use distinct systems as the picture shown: vertical and horizontal.


vertical and horizontal atomisation processes

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Reasons & Solutions for Stellite Tipping Problems on Saw Blade Teeth

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Typical Alloy Grade & Welding Process

Wisdom’s Co1, Co12, Fe306, Fe307 rod are widely used in teeth of band saw blade, the rod size is from 2.4 – 6.4 mm. They are commonly used to extend the service life. Welding process includes TIG, OXY-acetylene, ERW and PTA.

Frequent Applicable Problems

1. Sparking

Reason:
Deposit may increase when steel water in melting furnace runs out, which leads to the less-purity of welding rod. Spark situation then occur in certain situation.

Solution:

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