Custom Size GB/T 3639 Cold Finished Steel Tube for Shock Absorber Components

• Customization: Available
• After-sales Service: Free
• Warranty: Free
• Model NO.: GB3639
• Type: Seamless
• Technique: Cold Drawn
• Material: Carbon Steel
• Surface Treatment: Oiled
• Usage: Hydraulic/Automobile Pipe, Machinery Industry, Construction & Decoration, Special Purpose
• Section Shape: Round
• IATF16949: Od15-70
• Od: 15-80mm
• Thinckness: 1-20mm
• Customized: Yes
• Transport Package: Bundle
• Specification: 15-75
• Trademark: bluesky pipe
• Origin: China
• HS Code: 7304319000
• Production Capacity: 50000 Ton/Year

Product Description

Product Description

Define the Precision Requirement Under GB/T 3639

GB/T 3639-2021 is the current Chinese recommended national standard for seamless cold-drawn or cold-rolled steel tubes for precision applications.

The order should combine grade, manufacturing route, dimensions, tolerance basis, delivery condition, surface, inspection and documentation. This page presents the confirmed factory range without assigning one universal tolerance to every size and condition.

Product focus: precision seamless tube supplied by a cold-drawn or cold-rolled route as agreed. Hydraulic-cylinder ID finishing and special application standards require separate review.

DIMENSIONS AND TOLERANCES

Order the Dimension That Controls the Finished Component

GB/T 3639 enquiries should identify whether OD, ID, wall or a combination is the primary acceptance basis.

≡ OD  Outside Diameter  :       State the nominal size and ordered tolerance basis.
≡ ID    Inside Diameter     :       Control directly where component fit or machining stock requires it.

≡ WT  Wall Thickness      :       Confirm nominal wall and allowable variation before production.

≡ O     Roundness             :       Review for chucking, forming, sealing and component assembly.

≡ S     Straightness           :      Define the inspection method and application requirement on the order.

≡ Ra  Surface Quality       :      State visual, roughness or downstream-finishing requirements where needed.

Specification

IMPORTANT PARAMETERS
Confirmed factory capability and purchasing controls for GB/T 3639 precision seamless tube.
Product type	Cold-drawn or cold-rolled precision seamless steel tube
Standard focus	GB/T 3639-2021, current order basis
Grade direction	Carbon or higher-strength grade stated by the buyer and confirmed before quotation
Outside diameter	15-70 mm
Wall thickness	1-14 mm
Length	Random, fixed or precision cut length according to order
Delivery conditions	Cold-worked or heat-treated condition according to the ordered grade
Dimensional basis	OD x wall, OD x ID or ID x wall as agreed
Surface	Bare, oiled, phosphated or order-specific finish where available
Documentation	Chinese-standard material and inspection documentation as specified
Not every OD and wall combination is available in every grade, condition or tolerance class. Final feasibility is confirmed against the complete purchase specification.

Mechanical properties
Steel grade	Minimum values for the delivery condition
	+C	+LC	+SR	+A	+N
	Rm     /   A Mpa    /  %	Rm    /    A Mpa   /   %	Rm   / Reh  /  A Mpa  /  Mpa /%	Rm    /    A Mpa   /   %	Rm    Mpa	Reh  /   A Mpa /  %
	min				——	min
10	430/8	380/10	400/300/16	335/24	320~450	215/27
20	550/5	520/8	520/375/12	390/21	440~570	255/21
35	590/5	550/7	——/——/——	510/17	≥460	280/21
45	645/4	630/6	——/——/——	590/14	≥540	340/18
25Mn	650/6	580/8	580/450/10	490/18	——	——/——
Q355B	640/4	580/7	580/450/10	450/22	490~630	355/22
Q420B	750/4	620/8	690/590/12	520/22	550~700	425/22
25CrMo	720/4	670/6	——/——/——	——/——	——	——/——
42CrMo	720/4	670/6	——/——/——	——/——	——	——/——

Applications

Precision Tube for Automotive and Mechanical Components

≡ 01     Automotive Parts                                         Sleeves, supports and precision tube components

≡ 02     Shock Absorber Parts                                 Tube blanks for suspension components

≡ 03     Hydraulic Components                                Precision blanks for fluid-power applications

≡ 04     Motorcycle Parts                                         Steering, suspension and structural components

≡ 05     Machine Parts                                              Hollow shafts, spacers and precision members

≡ 06     Bushings and Sleeves                                 Cut and machined annular parts

≡ 07     Instrument Components                             Small precision tubular parts where feasible

≡ 08     Custom Fabrication                                     Drawing-based tube and hollow-shaft components

Move From GB Precision Tube to Finished Part

Drawing-based processing can combine precision tube supply with controlled cutting and machining.

Precision Cutting and Chamfering:

Fixed and cut-to-length supply

CNC Machining  :

Turning , Milling and Drilling

Honing and Skived & Roller Burnished   :

Precision internal surface

Custom Machining:

Components according to drawings

INSPECTION AND TRACEABILITY

Trace the Chinese Grade, Process Route and Inspection Lot

≡ Material identity                                  ≡ Chemical composition

≡ Tensile properties                              ≡  Hardness where required

≡ OD / ID / wall                                       ≡   Roundness

≡ Straightness                                        ≡  Surface inspection

≡ Roughness if ordered                        ≡  NDT if ordered

Global Precision Steel Tube Standards and  Product Network

Each page answers a different market and purchasing intent while sharing one precision-tube manufacturing framework.

Different standards define different scopes, grades, manufacturing routes and acceptance rules. Similar grade names or historical references must not be treated as automatic equivalents.The finished store structure can connect standard pages to processing and application products.

GB/T 3639 Precision Seamless Steel Tube Purchasing Questions

Q: Is GB/T 3639-2021 currently valid?

A:  Yes. The national standards platform lists GB/T 3639-2021 as current, replacing GB/T 3639-2009.

Q: Does GB/T 3639 cover cold drawing and cold rolling?

A:  Yes. Its scope covers seamless cold-drawn or cold-rolled steel tubes for precision applications.

Q: What is the confirmed factory size range?

A:  The confirmed range is 15-70 mm outside diameter and 1-14 mm wall thickness, subject to grade and order review.

Q: Can EN or DIN grades be substituted directly?

A: No. Cross-standard supply requires a documented comparison of chemistry, properties, condition, dimensions and acceptance rules.

Q:Can the tube receive honing or SRB processing?

A: These internal finishing operations can be reviewed from the required ID, wall, allowance, length, roughness and application.

Q:What information is needed for quotation?

A:  Provide GB/T 3639-2021, complete grade, dimensions, process and delivery condition, tolerances, length, quantity, tests and application.