Stainless steel, specifically grades 304, 316, and 430, are commonly used for refrigerator construction due to their corrosion resistance. Sheet steel is produced through rolling processes such as hot rolling, cold rolling, and galvanization. Rolling is the most popular technique due to its low cost and ability to produce large quantities with precise dimensions and uniform properties. Defects can occur from issues like roll misalignment but modern rolling processes aim to minimize variations and improve productivity while lowering energy usage and maintenance needs.

1. Production of Sheet Steel for
Refrigerator Body
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2. Material for refrigerator body
There are two types of metal mostly used on the interior and exterior of
refrigeration body are aluminum and steel.
The most common type of steel used in commercial refrigeration
construction is stainless steel. This includes
1. 300-series stainless steel, an austenitic alloy of at least 16 percent chromium,
no more than 0.15 percent carbon, and nickel.
2. 400-series stainless steel, which is made with a larger amount of carbon.
The most commonly used types of stainless steel for refrigeration equipment
are 304, 316, and 430.
Another type of steel found in commercial refrigeration is galvanized steel.
It is not as strong as stainless steel, so it is frequently only used on the less
vulnerable sections such as the top, bottom, and back.
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3. Why Stainless Steel Sheet
Comparatively cheap
Highly strong
Corrosion resistant.
VCM film on steel plate make the appearance of the refrigerator more
beautiful.
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4. What Is Sheet Metal?
Sheet metal is metal formed by an industrial process into thin, flat
pieces. These metal has a thickness in between 0.5 to 0.6 millimeters or less.
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5. Why Sheet Metal
Sheet metal has a low weight to thickness ratio.
Sheet metal is extremely strong and durable.
Sheet metal is malleable, which means it can be formed, cut, bent or stretched
easily.
Sheet metal can also be repaired relatively easily.
Its relatively low cost.
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6. Production process of steel sheet for
refrigerator body
Deep Drawing
Hydroforming
Ironing
Laser Cutting
Photochemical Machining
Rolling
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7. Among all of these processes, Rolling is the most popular technique
for the production of sheet steel. Because it is,
More economic.
It can be used to roll large ingots from half a meter thickness down to a
few microns.
A very wide variety of forms, widths and thicknesses can be
manufactured.
High productivities.
Extremely efficient , capable of processing over a million tons of steel
sheet per year.
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8. Production process of steel sheet by rolling
Hot rolling
Cold rolling
Coated by
galvanized
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9. Various Rolling configuration
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10. Mostly used configuration
Four-high Tandem type rolling mill
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11. Hot Rolling
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12. Cold Rolling
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13. Coated by
galvanizing
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14. Hot-Rolled vs Cold-Rolled Steel Sheet
Hot Roll Cold Roll
Hot rolling process can go less then 3 mm for
stainless steels.
Cold rolling only goes up to 3 mm.
Porosity can be closed up, grain size reduced by
recrystallization and coarse particles broken up
leading to stronger, tougher alloys.
Cold rolling can also be used to increase strength
by work hardening.
No need of extra annealing. Intermediate softening operations by annealing
are necessary to continue rolling.
In hot rolled steels, after cooling, the steel shrinks
slightly and the shape might change a little.
Control over the final dimensions.
Comparatively cheap. Comparatively costly.
Rough finished surface. Smooth surface.
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16. Microstructural difference
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17. Annealing for Cold Rolling Process
• The formability of products is
determined by annealing. Because
cold rolling significantly increases
material hardness, making forming
difficult, annealing is performed to
improve ductility by inducing a
recrystallized structure in the steel.
As the annealing process, coils are
piled and covered by the box and
annealed and this is called the batch
annealing. The other is the
continuous annealing process, in
which coils are continuously treated.
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18. Defects of Rolling in Steel Sheet Production
Defects Related to Roll Cambering
Fins
Defects by Roll Misalignment
Alligatoring
Blistering
Inclusion Related Defects
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19. Defects Related to Roll Cambering
Roll bending can produce in sheets with varying thickness.
 To counter this effect, rolls are usually cambered (crowned) as shown in Fig
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20. If the rolls are over-cambered, as shown in Fig, the residual stress pattern is the
opposite. Centerline compression and edge tension may cause edge cracking,
lengthwise splitting and a wavy center.
 Can minimize with multistand continuous rolling, interstand tension is adjusted to
maintain the rolling load to a constant value and so achieve a flat surface.
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21. Fins
Fins are caused by trying to push too much metal into the rolling groove.
Attempting too large reduction can cause rolls are forced apart and excess metal is
squeezed outside as figure
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22. Defects by Roll Misalignment
• Misalignment of the rolls leads either to curvature of the strip to one side as it comes
out of the roll gap, if it is relatively thick, or to a wavy edge on one side if it is thin
strip.
• To avoid this type defect proper adjustment of the roll screws to give a parallel roll
gap is essential.
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23. Alligatoring
A pipe is the funnel like depression at the top of a cast ingot that results from
shrinkage during solidification. When the ingot is subsequently rolled, this will give a
center line defect along sheet.
 This can lead to a splitting apart of strip and sheet during subsequent rolling, a defect
known as 'alligatoring‘.
To avoid such problem, the region containing the pipe should be dropped off before
working and recycled as scrap of known quality.
Alligatoring type defect in rolling.
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24. Blistering
Blistering on the surface of sheet and strip may be caused by gas porosity trapped
in the cast stock or arising from reactions with the atmosphere during annealing
treatments.
This problem can be avoided by control of casting or annealing conditions.
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25. Inclusion Related Defects
Inclusions in the cast stock are insoluble particles such as oxides and silicides.
These can lead to problems of cracking during working or to the formation of hard
spots that can affect the quality of final polished surfaces.
Regular inspection of crucibles and furnace linings, cleanliness of working
surroundings and a consideration of possible reactions is important if inclusions are
to be kept to a minimum. 25

26. Modern Rolling Process for Steel Sheet
Features
 High mill availability coupled
with high productivity and
high yields.
 Meeting the need of low
maintenance.
 Meeting the need of lower
energy consumption.
 Close dimensional tolerances.
 No variation in dimensions
throughout the length.
 Uniform physical properties.
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27. Conclusion
• Cold rolled steel sheets offer a variety of outstanding properties,
including easy formability and a smooth, clean surface, and so is now
mostly used commercial process of steel sheet production for
refrigerator body.
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