Everything about the Deep Drawing Stainless Steel Coil

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Introduction

Deep drawing is a common technology widely used in the stainless steel industry. Know more about deep drawing stainless steel coil in this article.

What is a deep drawing stainless steel coil?

To answer the question, we need to know first what deep drawing is. And then, as a result of the process, a deep drawing stainless steel coil.

So, deep drawing a sheet metal forming process, which have the sheet metal drawn into a forming die. And the mechanical action of a punch makes it happen.

Thus, deep drawing is a process to transform the shapes of the metal material. But the material retains.

When the process applies to stainless steel, then the processed stainless steel gets the name as deep drawing stainless steel.

Wait, where is the “coil” then? In fact, the deep drawing stainless steel coil is the product of deep drawing stainless steel. Similar to a roll of paper, when the paper is long enough, we roll it for easier storage and transportation.

A deep drawing happens when the depth of the drawn part is longer than its diameter.

The manufacturing process of deep drawing stainless steel coil

In many cases, the process to produce deep drawing stainless steel coils involve complex geometries like straight sides and radii.

In this case, people often introduce the term “stamping”. The purpose is to distinguish between the deep drawing and stretch-and bend components.

Deep drawing requires radial tension-tangential compression, while stretch-and bend works along the straight sides.

Also, deep drawing often comes with other forming techniques within the press.

These forming techniques include:

  • Beading: Displace the material to create a larger, or smaller, diameter ring of material beyond the original body diameter of a part. This method is often used to create O-ring seats.
  • Bottom Piercing: When the drawn part is complete, cut a shaped portion of the metal, a round piece for example.
  • Bulging: In the bulging process, a portion of the part’s diameter protrudes from the surrounding geometry by forces.
  • Coining: The coining process enables stainless steel material to form specific shapes.
  • Curling: Roll the stainless steel under a curling die to create a rolled edge.
  • Extruding: It will cause the metal to expand and grow in length.
  • Ironing/Wall Thinning: A process to reduce the wall thickness of the metal parts.
  • Necking: Reduce a portion of the part in diameter to less than the major diameter.
  • Notching: To cut a notch into the open end of the metal part. Usually, the notch is round, square, or other shapes accordingly.
  • Rib Forming: During the drawing process, rib forming involves creating an inward or outward protruding rib.
  • Side Piercing: Pierce holes in the sidewall of the drawn part.
  • Stamping / Marking: This process is usually used to put identification on a part, such as a part number or supplier identification.
  • Threading: Form the threads into a part by a wheel and arbour. That way, the production of threaded parts can complete within the stamping press.
  • Trimming: The trimming process cuts away the excess metal from the finished part.

Manufacturers often partially produce deep drawing stainless steel components. This is to create a series of diameters throughout the component.

And the method is common to see since it saves more cost than the turned parts. Plus, it requires much less raw material.

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Wrinkles during the process of deep drawing stainless steel coil

It’s common to see wrinkles during the process of deep drawing stainless steel coil.

And the deep drawing process involves a bunch of other complex processes to take place. Below are several instances to explain why wrinkles happen.

Wrinkles can occur in both the side-wall and flange area.

The stress state of the flange area is similar to the Yoshida buckling test.

The tensile stress comes along the tangent direction. And the compressive stress generates along the circumferential direction.

However, the compressive stress in the deep drawing is often uneven along the circumferential direction. This is because the normal constraint induces the friction.

In the tube shear-bending process, a shear force can enforce the tube in the vertical segment.

In the shear deformation zone, both sides of the tube are subjected to compressive stress.

Thus, wrinkles are likely to occur due to the above factors.

Moreover, during the tube rotary draw-bending process, the clamp die bends the tube. As a result, the compressive stress concentrates at the inner ridge along a tangent direction during the process.

This is why you can find wrinkles often at the inner side of the bending region.

Similarly, during the tube hydroforming process, the axial direction of the feeding of punch generates the compressive stress.

Then it forms wrinkles combined with the internal and external pressure.

Generally speaking, compressive instability exists in most metal forming processes.

So, it is important to find a reliable supplier to ease your purchase for the deep drawing stainless steel coil.

Which type of stainless steel is suitable for deep drawing?

Austenitic Stainless Steels

Austenitic stainless steels have exceptional ductility.

So, they have excellent formability.

While drawing is the most common cold-forming procedure, it’s useful to distinguish two modes.

The first one is deep drawing. In the deep drawing process, manufacturers use a die to pull the flat blank freely.

This happens with the action of a punch and with no added restraint.

The second type of drawing restrains the periphery of the blank. Then the metal is stretched into the die. This is drawing by expansion.

Both ferritic stainless steel and carbon steel are doing well in deep drawing. The reason is the anisotropic nature of flat-rolled b.c.c. structures resist thinning in the thickness direction. Thus, it gives them a drawability beyond their inherent ductility.

Austenitic stainless steels are to a first approximation isotropic.

So, they don’t enjoy much of that benefit. But their exceptional ductility can make up for it.

On the other hand, the work hardening rate is critical in expansion forming.

It is because localized thinning would lead to fracture.

The strength in the critical location would increase. In this location, the stretching is the greatest.

Plus, the controllably high work hardening rate of austenite is a great advantage. And it permits extraordinary stretch formability.

Austenitic stainless steels have less stable austenite, 301 stainless steel for example (17% chromium, 7% nickel). And items like sinks will use these kinds of steels. It is because part geometry lends itself to stretch forming.

High aspect ratio cylindrical parts use richer grades to lessen or completely eliminate martensite formation. As an example, 305 stainless steel represents that extreme. And the structure of 305 stainless steel comprises up to 19% chromium and 13% nickel

Popular types of Austenitic Stainless Steels

201 stainless steel

Type 201 Stainless Steel is a popular austenitic stainless steel.

The material is a lower-cost alternative to conventional Cr-Ni stainless steels such as 304 stainless steel. The reason is the structure of 201 stainless steel contains less nickel (an expensive material).

Instead, the production of 201 stainless steel uses more manganese and nitrogen.

So, it is also a type of high-manganese stainless steel.

201 stainless steel serves a bunch of applications especially for indoor use with not many requirements for food safety.

However, the type 201 remains less resistant than its counterparts, such as the popular 304 stainless steel.

304 stainless steel

As a food-grade member, 304 stainless steel is far better than 201 in the performance of corrosion resistance.

Thus, 304 stainless steel is common to see in places with a complex environment.

And it is a great choice for kitchen applications such as appliances, sinks, pots, pans and more.

That’s why the price of 304 stainless steel is higher than 201 stainless steel.

You can also find the usage of 304 stainless steel in:

As a result, it is one of the most widely-used austenitic stainless steels today.

316 stainless steel

The looks of 304 stainless steel and 316 stainless steel are pretty much alike. And they are both austenitic and non-magnetic stainless steel.

Also, both 304 and 316 stainless steel resists corrosion.

However, the critical difference lies in their structures: the molybdenum in 316 stainless steel make it stand out.

By adding molybdenum, the anti-corrosion performance of the 316 stainless steel remains excellent.

That’s why 316 stainless remains more ideal for acidic environments than 304 stainless steel.

Plus, the stainless steel grade 316 is more suitable for marine applications. And seawater environments as well.

Due to its greater resistance to oxidations, it’s common to see 316 stainless steel in the following situations:

  • refining equipment
  • fasteners
  • pulp and paper processing equipment
  • pharmaceutical processing equipment
  • surgical instrumentation

After all, the excellent performance of 316 stainless steel comes with a more expensive price.

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More about the industry

What is the metal drawing process?

Drawing is a metalworking process. It uses tensile forces to stretch the materials.

The metal stretches thinner by the drawing process, hence, to be in a desired shape and thickness.

Other than metal, the drawing process is also applicable to other materials like glass and plastic.

Generally, there are 2 types of metal drawing:

  • sheet metal drawing
  • wire, bar, and tube drawing

Sheet metal drawing involves deformation over a curved axis.

While wire, bar, and tube drawing draw the starting stock through a die to reduce the diameter and increase the length.

Drawing is usually complete at room temperature, thus known as a cold working process.

On the other hand, the work can take place at elevated temperatures to hot work large wires, rods or hollow sections. The purpose is to reduce forces.

Unlike rolling, the transmission of pressure depends on the force applied locally near the area of compression.

Instead, the pressure of rolling is transmitted through the turning action of the mill.

This means the tensile strength of the material can limit the amount of possible drawing force.

It is obvious in drawing thin wires.

Meanwhile, it is interesting to know the hot-rolled stock of a suitable size is the starting point of cold drawing.

The surface finish treatment for stainless steel

Besides drawing, the surface finish treatment is another key consideration for stainless steel.

The common surface finish treatments today include:

Know more about the popular surface finish treatment on the stainless steel market today.

Conclusion

So, we’ve learned several things about the topic of deep drawing stainless steel coil in this article:

  • the meaning of deep drawing stainless steel coil
  • stainless steel that is suitable for deep drawing
  • and the popular surface finish treatment for stainless steel

If you want to know more about the stainless steel industry, keep following our blogs. And don’t forget to share with your friends if you like this article.

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