Skip to main content

General Types Of High Speed Steel And Effects of Alloying elements on HSS :

 There are four general types of  High Speed Steel ,

 1. 18-4-1 High Speed Steel : 

 This Steel, containing 18 per cent tungsten , 4 per cent chromium, and 1 per cent vanadium with about 0.75 per cent carbon is considered to be one of the best of all-purpose tool steels. This steel is extensively used for lathe, planer and shaper tools, drills and milling cutters.

2. Cobalt High Speed Steel :

 This is known as super high speed steel. Normally cobalt is added from 5 to 8 per cent to increase better hot hardness and wear resistance than 18-4-1 type. One analysis of cobalt high speed steel contains 20 per cent tungsten, 4 per cent chromium, 2 per cent vanadium and 12 per cent cobalt.

3. Vanadium High Speed Steel :

 This steel contains 0.70 per cent carbon and more than 1 per cent vanadium. High Vanadium with carbon high speed steel is superior to 18:4:1 type for difficult - to - machine materials. This has excellent abrasive resistance.

4. Molybdenum High-Speed Steel :

This Steel containing 6 per cent molybdenum , 6 per cent tungsten, 4 per cent chromium, and 2 per cent vanadium have excellent toughness and cutting ability



Effect of Alloying Elements on HSS :

Carbon produces carbides and a hardenable matrix. Melting point is decreased with increase in carbon content. A low carbon content increases the impact strength but reduces the matrix hardness.

 Chromium reduces tendency to scaling. It is mainly present in ferrite matrix and is largely responsible for the sir hardening of HSS. 

Vanadium increases the abrasion resistance, cutting quality of the tools and the tendency to air hardening. 

Tungsten provides hot hardness by forming carbides and form - stability. 

Molybdenum increases hardenability , while 

Cobalt improves hot hardness and makes the cutting tool more wear resistant. 

Labels

Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of  detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of  a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of  the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of  electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a  roll. The objec...
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more