Introduction to Basic Manufacturing Processes and ... - always yours

72 Introduction to Basic Manufacturing Processes and Workshop Technology
at much higher speeds in comparison to high speed steel of 18:4:1 kind. In this steel, cobalt
is added from 2 to 15 per cent in order to increase the cutting efficiency especially at high
temperature. Cobalt high speed steel generally contains 20% W, 4% Cr, 2% V and 12% Co and
remaining Fe. Since the cost of this steel is more, therefore, it is principally used for making
cutting tools for heavy operations which impose high pressure and temperature on the tool.
It is extensively used for making high production tools of heavy work for high production
lathe, planer, shaper, milling and boring machine.
4. Vanadium High Speed Steel
Generally, this steel contains more than 1% V and 0.70% C. This steel possesses better
abrasive resistance in comparison to normal HSS type steel. It is preferred for machining
materials which are highly difficult to machine by conventional means. These steels cutting
tools are close competitors of carbides cutting tools such as drills, reamers, milling cutters
etc. In addition to having heat resistance properties of high speed steels possesses desirable
properties of high hardness, high compressive strength and outstanding wear resistance.
4.3.5.17 Availability of steel in market
Steel are available in market in various rolled forms like sheets, plates, strips, rods,
beams, channels, angles, tees etc. The common structural shapes for market form of supply
are reflected in Fig. 4.5. Steels are generally identified, coded and designated according to
suitable standards by a group of symbols indicating the important characteristics.
Flange
T
Flange
Stem
V
W
L
Leg
T
L
L
D
T
L
D
T
L
Plate
Angle
T-Section
Z-Section
Flange Flange Flange
Web
Web
Web
D D D
W
L L L
W
W
Channel T-Section T-Section
Fig. 4.5 Market forms of steel structure shapes
4.3.5.18 Designation of steels
Bureau of Indian Standards (BIS) designates the various grades of steels by a system of
codification which bears direct relationship with the important characteristics of steel such as