ASTM A678 Steel Tube,Pipe, Grade D

ASTM A678 Steel Tube, Grade D Product Information -:- For detailed product information, please contact sales. -: ASTM A678 Steel Tube, Grade D Synonyms -:- For detailed product information, please contact sales. -:

ASTM A678 Steel, Grade D Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: ASTM A678 Grade D High-Strength Structural Steel Plate** **ASTM A678 Grade D** is a high-strength, quenched-and-tempered (Q&T) carbon-manganese-silicon structural steel plate designed for **welded bridges, buildings, and other critical structures requiring superior strength-to-weight ratios and excellent toughness.** It belongs to the ASTM A678 specification, which covers high-strength plates produced to precise heat treatment and compositional controls. Grade D provides **minimum yield strength of 65 ksi (450 MPa)**, making it a premium choice for applications where material weight reduction, durability, and resistance to dynamic loading are paramount. --- ## **International Standard & Key Specifications** * **Primary Standard:** **ASTM A678 / A678M** - Standard Specification for Quenched-and-Tempered Carbon and High-Strength Low-Alloy Structural Steel Plates. * **Governing Standard:** Plates are produced to meet specific mechanical property requirements as defined by the standard, with chemistry secondary to achieving those properties. * **Related Specifications:** * **AASHTO M222M/M222:** Often referenced for bridge construction in the United States (Grade 65). * **AWS D1.1/D1.5:** Governing welding codes for structural and bridge applications. --- ## **Chemical Composition (Weight %, max unless range is specified)** Chemistry is reported but not rigidly specified; the focus is on achieving mechanical properties. The following are typical ranges/limits for Grade D. | Element | Composition (%) | | :--- | :--- | | **Carbon (C)** | ≤ 0.22 | | **Manganese (Mn)** | 1.00 - 1.60 | | **Phosphorus (P)** | 0.035 | | **Sulfur (S)** | 0.040 | | **Silicon (Si)** | 0.15 - 0.50 | | **Copper (Cu)*** | 0.20 min (when specified) | | **Vanadium (V)** | 0.01 - 0.10 (optional, for grain refinement) | | **Columbium (Cb/Nb)** | 0.01 - 0.05 (optional, for grain refinement) | *Note:* Copper is often specified to provide a minimum level of atmospheric corrosion resistance, aligning the steel with "weathering steel" characteristics when required. --- ## **Typical Physical & Mechanical Properties** All plates are supplied in the **quenched and tempered condition**, which gives a uniform tempered martensitic/bainitic microstructure. | Property | Value / Description | | :--- | :--- | | **Tensile Strength** | 570 - 725 MPa (82,500 - 105,000 psi) | | **Yield Strength (min)** | **450 MPa (65,000 psi)** | | **Elongation in 2-in (50 mm) (min)** | 18% | | **Modulus of Elasticity** | ~200 GPa (29 x 10⁶ psi) | | **Poisson's Ratio** | ~0.29 | | **Density** | ~7.85 g/cm³ (0.284 lb/in³) | | **Charpy V-Notch Impact Toughness** | **Test Temperature:** **-40°F (-40°C)**. **Minimum Avg. for 3 Specimens:** 15 ft·lbf (20 J). | | **Brinell Hardness (typical)** | 190 - 240 HBW | --- ## **Product Applications** ASTM A678 Grade D is specified for highly stressed components in major structures where its high strength allows for lighter, more efficient designs. **Primary Industries and Structures:** 1. **Bridge Construction:** * Primary tension members in truss bridges and arch bridges. * Girders and flange plates for long-span plate girder bridges. * Critical components in movable bridges (bascule, lift, swing). * Overpasses and interchange structures requiring high load capacity. 2. **High-Rise & Heavy Industrial Buildings:** * Columns and trusses in skyscrapers and large industrial facilities (power plants, mills). * Crane runway girders and support structures for heavy-duty material handling. * Earthquake-resistant moment frames where high strength and toughness are critical. 3. **Construction & Mining Equipment:** * Booms, arms, and frames for large excavators and cranes. * Chassis and structural components for heavy-duty haul trucks. 4. **Other Structural Applications:** * Penstocks and large-diameter pressure conduits. * Support structures for offshore platforms. * Military and specialized transportation equipment. --- ## **Advantages and Fabrication Considerations** * **Advantages:** * **High Strength-to-Weight Ratio:** Enables lighter, more economical designs with longer spans or higher load capacities. * **Excellent Toughness:** Guaranteed impact properties at -40°C ensure performance in cold climates and under dynamic/shock loads. * **Good Weldability (with proper procedure):** The Q&T process and controlled chemistry allow for successful welding when using low-hydrogen processes and following prescribed procedures. * **Uniform Properties:** The through-thickness quench and temper process provides consistent mechanical properties. * **Critical Fabrication Considerations:** * **Strict Welding Protocols:** **Mandatory use of low-hydrogen electrodes (EXX18) and processes (SAW, FCAW-G).** Detailed Welding Procedure Specifications (WPS) are essential. * **Preheat & Interpass Temperature Control:** Required to prevent hydrogen-induced cracking (HIC) and to avoid forming brittle zones in the Heat-Affected Zone (HAZ). Temperatures are typically in the range of 150-230°C (300-450°F) depending on thickness. * **Limited Thermal Cutting & Forming:** Oxy-fuel cutting may require preheat. Cold forming should be minimized; hot forming or post-forming heat treatment may be necessary. * **No Post-Weld Heat Treatment (PWHT) without approval:** Improper PWHT can destroy the quenched-and-tempered microstructure. Any PWHT must be strictly controlled and approved by the material engineer. **In summary, ASTM A678 Grade D is a premium, quenched-and-tempered structural steel offering an exceptional combination of high yield strength (65 ksi) and reliable low-temperature toughness. It is the material of choice for engineers designing the most critical, weight-sensitive, and dynamically loaded components in modern bridges, skyscrapers, and heavy machinery, where performance and safety are non-negotiable.** -:- For detailed product information, please contact sales. -: ASTM A678 Steel, Grade D Specification Dimensions Size： Diameter 20-1000 mm Length <4514 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: ASTM A678 Steel, Grade D Properties -:- For detailed product information, please contact sales. -:

Applications of ASTM A678 Steel Tube, Grade D -:- For detailed product information, please contact sales. -: Chemical Identifiers ASTM A678 Steel Tube, Grade D -:- For detailed product information, please contact sales. -:

Packing of ASTM A678 Steel Tube, Grade D -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and Steel Tube drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 985 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition