Cold drawn or cold-rolled precision seamless steel tubes

Relative standard :

GB/T222 permissible tolerance for chemical composition of steel products.

GB/T223.5 Steel and iron-Determination of acid-soluble silicon and total silicon content-Reduced molybdosilicate spectro photometric method(GB/T223.5-2008,ISO 4829-1:1986,ISO 4829-2:1988,MOD)

Mechanical properties

Steel grade 10# 20# 35# 45# Q345B

Deliver condition:

Cold working/Hard condition:+C

No heat treatment after the final cold working process.

Cold working/Soft condition:+LC

After the final treatment there is a suitable cold working process

Stress relieving annealed conditio:+SR

After the final cold working process there is a stress relief heat treatment in a controlled atmosphere

Annealed condition:+A

After the final cold working process the tubes are fully annealed in a controlled atomosphere.

Normalised condition:+N

After the final cold working operation the tubes are normalized in a controlled atomosphere.

The permissible tolerances of the internal and external diameter unit:mm

Length is 2000-12000mm Fixed length and multiple length is available.

Tolerance for length , a)the length ≤5000mm +5,0mm

B)the length ＞5000mm +10,0mm

Every multiple length should leave incision margin according to the following requirement for the steel tubes delivered by multiple length.

1. External diameter≤159mm:5mm~10mm
2. External diameter＞159mm:10mm~15mm

Curvature:≤3.0mm/m

The steel tubes’ total length curvature external diameter ≥16mm

• ReH≤500Mpa,≤0.15%L
• ReH＞500Mpa,≤0.20%L

QUALITY CONTROL

1~ Incoming Raw Material Inspection
2~ Raw Material Segregation to avoid steel grade mix-up
3~ Heating and Hammering End for Cold Drawing
4~ Cold Drawing and Cold Rolling, on line inspection
5~ Heat Treatment, +A, +SRA, +LC, +N, Q+T
6~ Straightening-Cutting to specified length-Finished Measuring Inspection
7~ Machanical Testing in own labs with Tensile Strength, Yield Strength, Elongation, Hardness, Impact, Mictrostruture etc
8~ Packing and Stocking.

100% of our steel tubes are dimensionally checked
100% of our steel tubes are visually checked to assure they have a perfect surface condition and no surface defects.
100% eddy current test and ultrosonic test to eliminate longitudinal and transversal defects.