EN 10357

EN 10357 is a European standard that specifies the dimensions, tolerances, and manufacturing conditions for stainless steel tubes and fittings used in the chemical, food, and pharmaceutical industries. The standard covers welded and seamless tubes and fittings intended to be welded into the tube systems. The standard ensures the tubes are corrosion-resistant and can handle environments where hygiene and resistance to various substances are critical. The key specifications of EN 10357 are:

• Material: Includes the various types of stainless steel tubes, with the steel type depending on application and environment.
• Size and shape: Specifies different sizes and shapes, including round, square, rectangular, and oval, with outlined dimensions and tolerances.
• Welding: Provides specifications for the welding process, including type of weld, quality, and testing.
• Surface condition: Specifies external tube surface conditions without internal surface finish requirements.
• Testing and inspection: Outlines procedures for verifying mechanical properties, corrosion resistance, and dimensional accuracy.
• Marking and packaging: Provides guidelines for proper tube identification and protection during transport.

Note: EN 10357 has replaced DIN 11850 as the standard for stainless steel tubes. The change brings more detailed specifications, welding standards, and testing procedures.

Table of contents

• EN 10357 product order example
• Material
• Manufacturing process requirements
• Testing and inspection documents
• Marking
• Packaging and transport
• Necessary information
• FAQ

EN 10357 product order example

1000 m.Tube EN 10357 — BC - 30 × 1 × 7000 (0/+100) mm - TC1 – EN 10217-7/1.4404 - 3.1.

This is an order for 1000 meters of welded tube. The specifications of this order are as follows:

1. The tube should be manufactured according to EN 10357.
2. The tube should be manufactured using process BC, a specific type of welding process.
3. The tube should have an external diameter of 30 mm and a thickness of 1 mm. This means the tube will be fairly thin and relatively small in diameter.
4. Each tube can be between 7000 mm and 7100 mm long.
5. The tube should meet test category '1' according to EN 10217-7.
6. The tube should be made of grade 1.4404 stainless steel, resistant to corrosion and heat.
7. The tube should come with an inspection certificate 3.1 according to EN 10204. This certificate verifies that the tube has been inspected and meets the requirements laid out in the EN 10204 standard.

The following sections explain each of the above parameters in detail.

Material

According to EN 10357, materials used for manufacturing should be:

• Austenitic stainless steel: Austenitic stainless steel contains a minimum of 16% chromium and 6% nickel, which gives it excellent corrosion resistance. It is also non-magnetic and has good formability and weldability. It's often used in food processing equipment, kitchen utensils, and piping. Stainless steel 304 and 316 are commonly used types of austenitic stainless steel.
• Austenitic-ferritic (Duplex) stainless steel: Duplex type contains roughly equal amounts of austenite and ferrite, which gives it a balance of properties. It has good resistance to stress corrosion cracking, higher strength than austenitic stainless steels, and good weldability. Duplex stainless steels are used in chemical industries, seawater desalination plants, and heat exchangers.
• Ferritic stainless steel: This type contains high levels of chromium but little or no nickel. It has less corrosion resistance than austenitic stainless steel but is still better than ordinary steel. It is magnetic and has good formability and weldability. Ferritic stainless steel is often used in automotive applications, architectural trim, and industrial equipment.

Manufacturing process requirements

Table 1: Manufacturing process and surface characteristics

Manufacturing process	Heat treatment	Surface characteristics and roughness			Symbol
		Internal surface	Internal weld bead	External surface and welding area
From cold rolled material	Not heat treated	Ra < 0.8µm pickled and passivated	Ra < 1.6µm pickled and passivated	Pickled and passivated	CC
				Ground, Ra < 1 µm	CD
From cold rolled material	Heat treated	Ra < 0.8µm pickled and passivated or bright annealed	Ra < 1.6µm pickled and passivated or bright annealed	Pickled and passivated or bright annealed	BC
				Ground, Ra < 1 µm	BD

Note: Ra is the roughness value; it is the average distance between the peaks and valleys on a surface, providing a gauge for the surface's overall smoothness or roughness.

Table 1 lists the manufacturing process and surface characteristics of stainless steel tubes.

According to EN 10357, tubes should be manufactured as follows:

• The tubes should be made from a cold rolled plate, sheet, or strip (the metal is shaped at a temperature below its recrystallization point, resulting in increased strength and smooth finish). They should be longitudinally fusion welded, meaning the welding should run along the tube length.
• Tubes without bright annealing or heat treatment should be pickled and passivated inside and out. Pickling and passivation remove impurities and oxidation from the surface of the metal, enhancing its corrosion resistance.
• The weld should be fine-tuned to align with the tube wall and then smoothed out. There should be no overlap between the weld metal and the parent metal.
• The Ra should be measured lengthwise.
• For tubes made using BC and BD processes, the inspection certificate should specify whether the tube has been bright, annealed, heat treated, pickled, and passivated.
• The ends of the tubes should be smooth, without any burrs.

Testing and inspection documents

Tubes made following EN 10357 should be tested in line with the following:

• Testing should be carried out for austenitic and austenitic-ferritic materials as per EN 10217-7, using test categories TC1 or TC2. TC1 involves non-destructive testing, while TC2 involves destructive testing of the tubes.
• Ferrite materials should be tested as per EN 10028-7. A tube having an external diameter of more than 219.1 mm should undergo a transversal weld tensile test. The tensile strength should meet the requirements specified for the base material.
• Tests for intergranular corrosion should be carried out as per the EN 10217-7 standard for austenitic and austenitic-ferritic grades. For ferritic grades, the testing procedure should be agreed upon.
• The roughness should be measured inside the tube, at least 5 mm from the end, according to the ISO 4288 standard. These measurements should be conducted on at least one test run for every 20 tubes in each production batch, and the results should be documented.
• Measurements should be taken on both the welded bead and the base material, and the inspection certificate should confirm that these measurements conform with the standards.

According to EN 10357, tubes should be manufactured and tested as follows:

• In the case of tubes manufactured using the CD and BD processes (Table 1), additional measurements of outside roughness should be taken at least 100 mm from the end of the tube. The frequency of these measurements should match that of the internal ones.
• The appropriate inspection documents should be issued according to EN 10204.

Marking

Each tube should be clearly and permanently marked with the following details:

• The name or trademark of the manufacturer
• EN 10357 TC1 or TC2 to indicate test category 1 or 2, respectively, following EN 10217-7
• The symbol of the manufacturing process (according to Table 1)
• The grade of the steel used
• The dimensions of the tube
• The heat number, which identifies the batch of steel from which the tube was made
• For TC2 tubes, an identification number (such as an order or item number) as per EN 10217-7, which links the product or delivery unit to the relevant document
• The mark of the inspection representative
• If there's a need for a different marking or additional labeling, it should be agreed upon at the time of the order.

Packaging and transport

The tubes should be delivered dry. Those that have been manufactured using the CD or BD process and ground (to smooth their surface) should be protected using PE (polyethylene) sleeves unless a different agreement is made at the time of order. The details of the packaging and transport should be agreed upon when the order is placed.

Necessary information

The supplier should provide the following information at the time of order:

• The quantity (weight, length, and number)
• The reference to standard EN 10357
• Symbol of the manufacturing process and surface characteristics
• Outer diameter and wall thickness
• The length of a single unit and its tolerance
• The steel grade designation according to EN 10217-7, except for ferritic grades
• The steel grade designation, according to EN 10028-7, is only for ferritic grades
• Production and testing according to EN 10217-7 TC1/TC2.

FAQ

What is the EN 10357 standard in stainless steel tubes?

The EN 10357 standard applies to seamless, welded, and longitudinally welded austenitic and duplex stainless steel tubes suitable for the chemical and food industry.