How to buy the right stainless steel tube?

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Introduction

How to buy a stainless steel tube?

Because there are many types of stainless steel tubes. Moreover, its appearance is the same.

And it is difficult for people to recognize with the naked eye.

Besides, the price of the stainless steel tube industry fluctuates frequently.

Therefore, it is not easy for people to buy suitable stainless steel tubes.

So, what aspects should people pay attention to when buying stainless steel tubes?

Let’s take a look together.

buy stainless steel tube

What is a stainless steel tube?

Stainless steel tube is a kind of hollow long round steel. Moreover, a stainless steel tube is economical section steel.

Meanwhile, it usually accounts for about 8% to 16% of the total steel.

And it is widely used in the national economy.

Therefore, it is an important product in the iron and steel industry.

Process flow

The production process of the stainless steel tube is:

slitting → tube making → polishing → packaging → warehousing.

Among them, people need to carry out a quality inspection for each process.

Therefore, its management stage is particularly strict.

process flow

Surface treatment

Stainless steel tubes without surface treatment may leave traces during production and treatment.

Therefore, the stainless steel tube generally has two different surface treatment methods:

  1. Satin Finish: it has a drawing effect. In addition, the grain size distribution is fine.
  2. Bright polishing: it has a secular lustre appearance. Moreover, its mill surface finish is high.

Classification

Generally, stainless steel tubes are classified according to their material and alloy composition.

  1. Stainless steel materials can be divided into 304 stainless steel tube, 316 stainless steel tube, 321 stainless steel tube, 310S stainless steel tube, 317 stainless steel tube, etc.
  2.  According to the different micro-structure, stainless steel can be divided into the following categories:
  3. Ferritic stainless steel
  4. Martensitic stainless steel
  • Austenitic stainless steel
  1. Austenitic ferritic duplex stainless steel
  2. Precipitation hardening stainless steel

After understanding the specific information about the stainless steel tube.

Then, how should we select the appropriate one when buy stainless steel tube?

How to buy stainless steel tube?

For those who don’t know much about the stainless steel tube, it is difficult to buy a good quality stainless steel tube.

However, for stainless steel tube manufacturers know that good stainless steel is produced, not selected.  Moreover, the strict process can ensure that the quality of each stainless steel tube conforms to the industry standard.

So, what are the quality standards of the stainless steel tube?

how to buy

External weld bead

The grinding of the external weld bead should be clean and uniform.

Besides, it has no black line, no pattern.

As for its grinding width, it should be kept within 0.6-0.8cm. Moreover, its thickness should be less than 0.38.Secondly, the position of the weld bead should be on the positive corner of the product, not on both sides of the tube corner.

Moreover, the weld bead must not be crooked.

Otherwise, the back polishing will leave a black line on the product.

About grinding, people have to polish the stainless steel tube three times.

Moreover, the third grinding should cover the first two grinding marks.

Internal weld bead

The inner weld bead should be flat.

What’s more, it doesn’t turn white or change color.

Secondly, each stainless steel pipe must have internal protection.

Tube surface

The size of the tube surface should be uniform, without concave surface, wave, strain, crush, and pressure point.

Moreover, people need to make a drum on a stainless steel tube surface with a thickness of less than 0.5.

And this bulge is even.

Moreover, it should be effectively combined with thickness.

In this way, there is no uneven concave-convex phenomenon after polishing.

different size

Cross-section of nozzle

The cross-section of the nozzle should be flat.

Moreover, there is no undercut, deformation, and residual burr.

Pin

The four formed corners are uniform. Moreover, there is no hook on the corner.

There is no sharp corner on the welding seam corner, and there is no blade shape.

Welded joint

There is no wave in the welded joint after forming.

Diagonal

The diagonal tolerance is within 30.

Embossed stamp

The printed steel seal should be complete and clear. Moreover, each product must have a steel seal.        The steel seal must be in the middle of the pipe surface, not on the pipe corner.

Length

According to the production requirements, the length should be 0.5cm.

Moreover, it can not reduce or exceed product specifications, thickness, length, quantity accuracy.          After understanding these standards, let’s take a look at how engineering procurement should be done?

Four steps for engineering procurement of stainless steel tubes

Generally speaking, engineering procurement has the following steps.

Determine the demand and define the purchase direction

Because there are many kinds of stainless steel tubes.

So, people need to decide what kind of products they need before they buy.

Then, people also need to determine the quantity, size, and specification according to their own needs.

As for the number of purchases, people should have some reservations.

This will prevent the shortage of stainless steel tubes required for procurement.

Generally, the products sold by the wholesale industry of stainless steel tubes will not be returned.

Investigate the market and understand the situation

Before purchasing, people need to know the market of stainless steel tube.

This includes the type, price, and sales situation required. These aspects need to be examined carefully.

This is the only way to understand the situation. Moreover, people need to record and count the data from the investigation.

In this way, it will be easier for people to buy the right product.

Select reliable manufacturers and conduct an on-the-spot investigation

There are many stainless steel tube manufacturers on the market when people buy stainless steel tube.

So, how to choose a good manufacturer? Generally speaking, people will examine these aspects of manufacturers: strength, reputation, after-sales, quality, price, etc.

Then, people do field trips.

In general, people will look at the output, scale, and personnel of the factory.

On-the-spot investigation can see whether the manufacturer is reliable.

Thus, people decide whether to cooperate with the manufacturer.

reliable

Customization needs and contract signing

Sometimes, people need to customize stainless steel tubes to meet their requirements.

Such as stainless steel tube size, style, and surface treatment. These need people and manufacturers to communicate carefully, to buy the products they need. Then, when people decide to cooperate with manufacturers, they need to write down their customized requirements and specific product conditions in the contract.

Moreover, both parties have reached and signed a contract. This ensures that the products produced are consistent with the products needed.

Moreover, in the event of problems, buyers can also get good protection.

Tips to know when buy stainless steel tube

Now, the application of stainless steel tube is more and more extensive.

Moreover, there are more and more buyers of stainless steel tubes.

So, when buying stainless steel tube, what kind of professional content should people know?

Difference between delivery by actual weight and delivery by theoretical weight for buy stianless steel tube

  1. Delivery according to actual weight: the manufacturer sells stainless steel to others according to the weighed weight.
  2. Delivery by theoretical weight: the manufacturer sells the stainless steel pipe to others according to the weight calculated by the steel calculation formula.

So, what is the formula?

delivery

Calculation formula of theoretical weight of tube

Round tube: (outer diameter thickness) * thickness * 6 * 0.02491;

Square tube: (outer diameter * 4 / 3.14-thickness) * thickness * 6 * 0.02491;

Rectangular tube: [(length + width) * 2 / 3.14-thickness] * thickness * 6 * 0.02491.

Difference between deviation and tolerance

Deviation: in the production process, the actual size of the stainless steel pipe is difficult to meet the requirements of the nominal size.

Therefore, the actual size of the stainless steel pipe will generally be greater than or smaller than the nominal size. This creates a difference.

Meanwhile, if the difference is positive, it is called positive deviation; if the difference is negative, it is called a negative deviation.

Tolerance: the sum of absolute values of positive and negative deviation values specified in the standard is called tolerance. Usually, people also call this tolerance zone. Moreover, the deviation is directional, that is, “positive” or “negative”.

However, tolerances are not directional. Therefore, the term “positive tolerance” or “negative tolerance” is wrong. These are some professional tips.

So, those who are going to buy stainless steel tubes will have a question. That is to go to stainless steel dry manufacturers to buy stainless steel will be cheaper?

Let’s talk about it in detail.

Is it cheaper to buy a stainless steel tube from the factory?

Generally speaking, stainless steel tube manufacturers will receive many orders from agents and engineers. Moreover, there will be some people with less demand to consult stainless steel tube.

However, each manufacturer has its minimum order. If the demand does not meet the manufacturer’s initial order quantity.

Then for the manufacturer, they bear the freight after the profit is not much.

Therefore, general manufacturers will not sell less than the minimum quantity of stainless steel tubes.

What’s more, if people add up the freight and the price in the factory, it’s more expensive than buying directly from the agent.

So, under normal circumstances, the price people buy from manufacturers is not cheaper.

factory

Conclusion

Stainless steel tube is a kind of hollow long round steel. Moreover, the stainless steel buy without surface treatment may leave traces during production and treatment.

Therefore, the stainless steel tube generally has two different surface treatment methods: Satin polishing and bright polishing.

As for its types, generally, stainless steel tubes are classified according to different materials and alloy compositions.

So, there are many kinds of it.

In fact, for those who do not know much about the buy stainless steel tube, it is difficult to buy a good quality stainless steel tube.

However, for  stainless steel tube manufacturers know that good stainless steel is produced, not selected.  People only need to select stainless steel according to the quality inspection standard mentioned in this paper. For engineering procurement, there are generally the following steps:

  1. Determine the demand and define the purchase direction
  2. Investigate the market and understand the situation
  3. Select reliable manufacturers and conduct field investigation
  4. Customization and contract signing

Finally, if the demand is small, buy stainless steel tubes from factories will not be cheaper.

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