370 Steels: Metallurgy and Applications750
700650
600E^550
~,,500
.=
450
400
350
300
250
200
150-- ~ ~" ~ Ultimate tensile
_ /i / strength
~ //.~<//- ~ NNNX x
_ x ~ ~ 0.2% Proof stress
"- 1t ~" \ ~~ o '/o Elongation _
-ti ~, -,
9 1 ...... "1Impact strength
1 2
% Boron8C7C6(]50 ~
8
4o302010- 220
- 200
-18o
-160
--140 "~
120 ~-
-100 e-
Jr-- 80 o c-
-- 60 z O
:::) i- 40
- 20
3 -0
Figure 4.41 Effect of boron on the mechanical properties of Type 304 steel (After King
and Wilkinson 37)Corrosion/abrasion-resistant grades
Large quantities of wear-resistant materials are used for the handling of bulk
solids in industries such as steelmaking, coal mining, quarrying and power
generation. Many of the requirements are satisfied by quenched and tempered
low-alloy steels, with hardness values in the range 360-500 B HN, and provide
long life and satisfactory performance under a wide range of operating conditions.
However, under wet corrosive conditions, corrosion losses can contribute
significantly to the wear process. Additionally, corrosion in low-alloy steel linings
can increase friction and prevent the free flow of material in chutes and bunkers,
causing metering and blockage problems. Under such conditions, stainless steels
become attractive alternatives to low-alloy wear-resistant grades.
One interesting example of the use of stainless steel in this field is as a
composite material bonded to a thick resilient rubber backing. Both ferritic
(Type 409) and austenitic (Type 304) stainless steels are used in such appli-
cations, the rubber backing reducing the amount of steel required and also the
level of noise generated. Ferritic stainless steel has been used very successfully
in such composites for lining coal silos in British Steel plant and many of the
installations have handled over 2 million tonnes of coal. 38
Austenitic stainless steels are generally used in situations where the conditions
are very corrosive but the high rate of work hardening in these materials also