LEAF SPRING
Serves to support vehicle weight, absorb bumps and locate axle
to the vehicle
RAW MATERIAL
During the serves cycle, leaf spring must not exceed certain
level of stress to avoid settling or premature failure.
Therefore, the choice of chemical composition of the spring
steel should be such to get sufficient harness to bear the
required level of stress. Spring steel flats are available in
various chemical compositions of alloy steel. The most common
ones are -
GRADE
C
Si
Mn
S
P
Cr
V
EN 45A
0.55-0.65
1.70-2.10
0.70-1.00
0.040 Max
0.040 Max
-
-
55 Si7
0.55-0.60
1.50-1.80
0.70.1.00
0.045 Max
0.045 Max
-
-
60 Si7
0.55-0.65
1.50-2.00
0.80-1.00
0.040 Max
0.040 Max
-
-
65 Si7
0.60-0.68
1.50-1.80
0.70-1.00
0.050 Max
0.050 Max
-
-
55 Si
Cr7
0.50-0.60
0.70-1.00
0.50-1.80
0.025 Max
0.025 Max
0.20-0.40
-
60 Si
Cr7
0.57-0.65
1.50-1.80
0.70-1.00
0.030 Max
0.030 Max
0.20-0.40
-
65 Si
Cr7
0.60-0.68
1.50-1.80
0.00-1.00
0.050 Max
0.050 Max
0.20-0.40
-
50 Cr
V4
0.47-0.55
0.15-0.40
0.70-1.00
0.035 Max
0.035 Max
0.90-1.20
0.10-0.20
Other grades can be used according to customer requirements.
PRODUCTION PROCESS
The desired grade of spring steel, of required width and
thickness is cut to specification. Than passing through the
processes that are industry recognized and ultimate, quality
leaf springs are produced without variation.
PRODUCTION CYCLES
HEAT TREATMENT CYCLE
Paragon is on record as being the first Leaf Spring
manufacturing plant to run the heat treatment cycle on
Compressed Natural Gas (CNG). Not only being an Eco-friendly
fuel, CNG also has an undisputed edge over other fuels such as
LDO / Furnace Oil used to run the heat treatment cycle in
producing quality. The hardening and tempering furnaces run on
CNG, controls the de-carbonization limits of the finished
product to minimum, thereby giving more value for money to its
customers.
ON GAS
ON LDO
2% Wital 200%
2% Wital 200%
Microstructure
Tempered
Tempered
De-Carbonized Layer Hardness
0 - 0.1mm
0.1 - 0.3mm
Surface
HRC 38(BHN - 364)
HRC 32(BHN - 302)
Core
HRC 45(BHN - 430)
HRC 45(BHN - 430)
The above record has been validated through a test conducted by
Process & Product Development Centre (A Government of India
Society, Ministry of Industry).
QUALITY
Hardness Testing
Range of hardness after heat treatments :
50Cr4V2
409 to
485 HB
60Cr4V2
432 to
485 HB
55Si7
378 to
432 HB
60Si7
363 to 435 HB
65Si7
363 to 432 HB
Variation in hardness of any one leaf does not
vary by more than 7% of the range specified above.
Hardness Testing does according to IS: 1500 : 1983.
Load Testing
Downward load test load applied to test
stress equal to 90% of the yield stress of
the spring leaf material in its heat treated condition.
All Leaf
Springs are tested for minor and major
defects.
