STKM11A Heavy Thick-Wall Precision Seamless Steel Tubing — Technical Product Description

Material Overview

STKM11A is a carbon (mild) steel grade under the JIS G 3445 standard, specified for seamless steel tubes used in machine structural applications. It is used for heavy thick-wall tubing in automotive parts and other mechanical components where strength, formability, and consistency are required.

Specifications

Chemical Composition: Comparison Among Similar STKM Grades

Here is a table showing STKM11A and 4 other related STKM grades (used in similar applications) with their chemical composition limits under JIS G 3445.

Mechanical Properties

Below is a table showing mechanical property minima for STKM11A and four other related grades from JIS G 3445, useful for heavy thick-wall applications such as automotive components.

Key Features

• Low Carbon Content → good formability, weldability, machinability. STKM11A’s carbon ≤ 0.12 % makes it relatively mild steel. 

• Good Ductility and Elongation → high elongation (≥ 35 %) allows forming, bending, and deformation without cracking, which is useful in automotive parts where bending or shaping is needed. 

• Adequate Strength for general machine structural parts: tensile ≥ ~290 MPa. Enough for many auto part uses where ultra high strength isn’t necessary.

• Uniformity and Precision: being seamless (no welds), tight tolerances on OD and wall thickness, straightness, surface finish. Useful when assembly, sliding fit, or sealing involved.

• Cost-Effective compared to higher alloys or heat-treated steels. Mild steel grades like STKM11A tend to be less expensive and easier to produce.

Standard / Execution Requirements

• Standard: JIS G 3445 — Carbon steel tubes for machine structural purposes. 

• Dimensional Tolerances: Outside diameter and wall thickness tolerances per divisions defined in JIS G 3445. For example, for OD under 50 mm, tolerance ±0.5 mm; for larger sizes, percentage-based. 

• Mechanical Property Testing: Tensile, elongation, flattening test (e.g., flatten without crack), bending test requirements (degree, radius) stipulated. 

• Appearance: Tubes must be practically straight; ends square to axis; surface free from defects detrimental to use. 

Application Fields

General Application Domains

• Automotive parts

• Machinery components

• Mechanical structures

• Hydraulic or pneumatic systems

• Furniture, appliances

Specific Uses within Automotive / Auto Parts

• Drive shafts and steering shafts (where strength + precise fit matters)

• Tubing for shock absorbers or suspension components (where wall thickness must withstand loads)

• Auto chassis sub-components requiring seamless tubing for durability under vibration

• Bushings, bearing housings, sleeve tubes where precise inner diameter and straightness are needed

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it is according to quantity.

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A: Yes, we could offer the sample for free charge but need pay the cost of freight.

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A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.

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