Stainless Steel Coil Tube — Hard Temper (H) | Fully Cold-Worked Condition

Product Overview

The Stainless Steel Coil Tube in Hard Temper (H) condition represents the highest mechanical strength state achievable through full cold working (充分冷加工) of austenitic stainless steel tubing. This product line is manufactured by Wenzhou Jixing Metal Materials Co., Ltd. and is designed for applications demanding maximum pressure resistance and dimensional stability. The hard temper designation signifies that the material has undergone extensive cold deformation to achieve a fully work-hardened microstructure, resulting in superior yield strength, tensile strength, and resistance to deformation under load.

This product is categorized under the mechanical condition classification system and is specifically limited to prefabricated elbows or straight tube sections, reflecting the inherent trade-off between enhanced mechanical properties and reduced formability characteristic of the fully cold-worked state.

Material & Properties

The Hard Temper (H) condition is achieved through progressive cold reduction of annealed stainless steel coil tube stock. The cold working process introduces dislocation density and strain hardening within the austenitic crystal lattice, fundamentally altering the mechanical response of the material. The resulting microstructure exhibits significant work-hardening characteristics with markedly elevated hardness and strength values compared to the solution-annealed (soft) condition.

Key Mechanical Properties:

Specifications

Parameter Specification Unit Notes
Product Name Coil Tube (盘管) — Product No. 50
Product Category Product Specifications → Mechanical Condition — Hard Temper (H)
Sub-Classification Fully Cold-Worked (充分冷加工) — Maximum cold reduction applied
Hardness (HV) ≥ 280 Vickers Hardness Measured per ASTM E92 / ISO 6507
Elongation at Break (A) ≥ 10 % Minimum residual ductility
Pressure Resistance Maximum (within range) — Highest among all temper grades
Usage Restriction Prefabricated elbows or straight sections only — Not suitable for further forming
Material Grade Austenitic Stainless Steel (e.g., 304, 316, 321) — Per ASTM A269 / A213

Manufacturing Process

The production of Hard Temper (H) stainless steel coil tube involves a multi-stage manufacturing sequence optimized for maximum cold work hardening:

  1. Hot Forming (Initial Shaping): Seamless or welded stainless steel tube blanks are formed to the target outer diameter and wall thickness through hot rolling or hot extrusion processes.
  2. Solution Annealing: The formed tube is subjected to solution heat treatment (typically 1050–1150°C followed by rapid quenching) to achieve a fully annealed, strain-free microstructure with maximum ductility and minimum hardness.
  3. Progressive Cold Drawing / Cold Reduction: The annealed tube undergoes successive passes of cold drawing or cold reduction through a series of dies, each reducing the cross-sectional area incrementally. The cumulative cold work percentage is maximized to achieve the target hardness of HV ≥ 280.
  4. Intermediate Annealing Control: Careful control of intermediate annealing cycles ensures uniform cold work distribution while preventing cracking or excessive strain localization.
  5. Final Dimensional Inspection: The fully cold-worked product undergoes rigorous dimensional, mechanical, and surface quality verification to confirm compliance with Hard Temper specifications.
  6. Coiling and Packaging: The finished hard temper coil tube is wound onto standard cores and packaged for shipment, maintaining the cold-worked condition without subsequent heat treatment.

Applications

The Hard Temper (H) fully cold-worked stainless steel coil tube is specifically engineered for high-pressure and high-stress applications where maximum mechanical strength is the primary design requirement:

Important Usage Restriction: Due to the fully cold-worked condition, this product is limited to prefabricated elbows or straight sections only. Further forming, bending, or cold working operations are not recommended as they may cause cracking or fracture due to the limited residual ductility (elongation ≥ 10%). If additional forming is required, the material must first be stress-relieved or annealed to a softer temper condition.

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality control systems and holds the following certifications to ensure product conformity:

All Hard Temper (H) coil tube products undergo 100% non-destructive testing (NDT), including hydrostatic pressure testing, eddy current inspection, and dimensional gauge verification, to guarantee full compliance with specified mechanical and dimensional requirements prior to shipment.

Unique Selling Points