The development and production of nonmagnetic hard alloy materials are significant manifestations of new hard alloy materials. Hard alloy is made by sintering the refractory metal carbides of the IV A, V A, and VI A groups in the periodic table of elements (such as tungsten carbide WC), and the transition metal of the iron group (cobalt Co, nickel Ni, iron Fe) as the bonding phase through powder metallurgy industry. The above tungsten carbide is nonmagnetic, while Fe, Co, and Ni are all magnetic. Using Ni as a binder is a necessary condition for producing nonmagnetic alloys.
There are the following methods for obtaining WC Ni series nonmagnetic hard alloys:1. Strictly control carbon content
Like WC Co alloy, carbon content is the main factor affecting the solid solution capacity of W in the bonding phase of WC Ni alloy. That is, the lower the carbon content of the carbon compound phase in the alloy, the greater the solid solution capacity of W in the Ni bonding phase, with a variation range of approximately 10-31%. When the solid solution of W in the Ni bonded phase exceeds 17%, the alloy becomes demagnetized. The essence of this method is to obtain nonmagnetic hard alloys by reducing carbon content and increasing the solid solution of W in the bonding phase. In practice, WC powder with a carbon content lower than the theoretical carbon content is usually used, or W powder is added to the mixture to achieve the goal of producing low-carbon alloys. However, it is very difficult to produce nonmagnetic alloys solely by controlling carbon content.
2. Add chromium Cr, molybdenum Mo, tantalum Ta
A high carbon WC-10% Ni (wt% by weight) alloy exhibits ferromagnetism at room temperature. If more than 0.5% Cr, Mo, and 1% Ta are added in metal form, the high carbon alloy can transition from ferromagnetism to non-magnetism. By adding Cr, the magnetic properties of the alloy are independent of carbon content, and Cr is the result of a large amount of solid solution in the bonding phase of the alloy, like W. The alloy with Mo and Ta can only transform into a non-magnetic alloy at a certain carbon content. Due to the low solid solution of Mo and Ta in the bonding phase, most of them only capture the carbon in WC to form corresponding carbides or carbide solid solutions. As a result, the alloy composition shifts towards the low-carbon side, resulting in an increase in the solid solution of W in the bonding phase. The method of adding Mo and Ta is to obtain a non-magnetic alloy by reducing the carbon content. Although it is not as easy to control as adding Cr, it is relatively easier to control the carbon content than pure WC-10% Ni alloy. The range of carbon content has been expanded from 5.8-5.95% to 5.8-6.05%.
Email: oiltools14@welongpost.com
Contact: Grace Ma
Post time: Oct-09-2023
