Bethlehem Steel Sheet,Plate RQC ASTM A678 RQC90, Steel Sheet,Plate

Bethlehem Steel Sheet/Plate RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, Steel Sheet/Plate plate Product Information -:- For detailed product information, please contact sales. -: Bethlehem Steel Sheet/Plate RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, Steel Sheet/Plate plate Synonyms -:- For detailed product information, please contact sales. -:

Bethlehem Steel RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, steel plate Product Information -:- For detailed product information, please contact sales. -: ## **Product Datasheet: Bethlehem Steel RQC ASTM A678 RQC90 Steel Plate** **Product Overview** Bethlehem Steel RQC ASTM A678 RQC90 represents the pinnacle of the proprietary RQC (Rapid Quenched Carbon) series, engineered as an ultra-high-strength, quenched and tempered (Q&T) structural steel plate. This grade is designed to push the boundaries of commercially available structural steel performance, delivering a guaranteed **90 ksi minimum yield strength** while maintaining the exceptional low-temperature toughness characteristic of the RQC family. Through a rigorously controlled heat treatment process producing a refined tempered martensitic microstructure, RQC90 provides an unmatched strength-to-weight ratio alongside superior resistance to fracture and fatigue. This plate is available in thicknesses ranging from **3/16 inch (4.8 mm) to 1-1/2 inches (38.1 mm)**. **Key International Standards & Specifications** * **Performance Benchmark:** **ASTM A678 / A678M** - While "RQC90" is a proprietary designation exceeding the standard's highest grade (Grade D, 80 ksi), its manufacturing philosophy and quality controls are aligned with the stringent principles of ASTM A678 for Q&T steel. * **Proprietary Certification:** The **"RQC90"** trademark signified Bethlehem Steel's capability to produce a 90 ksi yield strength plate with certified, high-level toughness—a combination rarely achieved in standard specifications. * **Mandatory Enhanced Requirements:** Due to its premium nature, certification was comprehensive: * **ASTM A6 S1 (Charpy V-Notch Impact Testing):** Guaranteed at specified temperatures, often **-40°F / -40°C** or lower, with high minimum energy requirements. * **ASTM A6 S4 (Ultrasonic Examination):** Performed to stringent quality levels (ASTM A578 Level B or A) to ensure flawless internal soundness. * **ASTM A6 S5 (Maximum Carbon Equivalent):** Critically controlled, though inherently higher due to strength requirements. * **Additional Bethlehem Protocols:** May have included **Jominy Hardenability Tests** and **Fracture Mechanics Testing** (CTOD or K1C) for critical applications. * **Industry Context:** Positioned beyond standard structural grades, it served applications where **ASTM A514** or similar 100 ksi yield steels were considered, but where better weldability and guaranteed low-temperature toughness were required. **Chemical Composition (Weight % - Typical RQC90 Aim)** Chemistry is meticulously designed for extreme hardenability and strength, utilizing a sophisticated balance of alloys to achieve 90 ksi yield while preserving as much toughness and weldability as possible. | Element | Typical RQC90 Aim / Range | Key Purpose | | :--- | :--- | :--- | | **Carbon (C)** | 0.16 - 0.21% | Higher than lower RQC grades for strength, but controlled to mitigate weldability loss. | | **Manganese (Mn)** | 1.40 - 1.70% | Elevated for solid solution strengthening and hardenability. | | **Phosphorus (P)** | ≤ 0.010% | Ultra-low for fracture resistance. | | **Sulfur (S)** | ≤ 0.005% | Ultra-low, calcium-treated for superior ductility and inclusion shape control. | | **Silicon (Si)** | 0.15 - 0.35% | Deoxidizer and strengthener. | | **Aluminum (Al)** | 0.02 - 0.05% | Grain refiner. | | **Nickel (Ni)** | 0.70 - 1.20% | High nickel content is critical for achieving high core toughness at this strength level and improving hardenability. | | **Chromium (Cr)** | 0.60 - 0.90% | Significant addition for hardenability, strength, and tempering resistance. | | **Molybdenum (Mo)** | 0.20 - 0.35% | Essential for deep hardenability and to suppress temper embrittlement. | | **Vanadium (V)** | 0.04 - 0.10% | For precipitation strengthening and grain refinement. | | **Boron (B)** | 0.002 - 0.004% | Maximizes hardenability efficiently. | | **Carbon Equivalent (C.E. IIW)** | Typically 0.58 - 0.68 | Reflects the high alloy content; demands expert welding procedure design. | **Physical & Mechanical Properties** | Property | RQC90 Minimum/Target Requirement | Typical Performance | | :--- | :--- | :--- | | **Yield Strength (Min)** | 90 ksi (620 MPa) | 95 - 105 ksi (655 - 724 MPa) | | **Tensile Strength** | 105 - 125 ksi (725 - 860 MPa) | 110 - 120 ksi (760 - 827 MPa) | | **Elongation in 2" (Min)** | 14% | 15 - 18% | | **Yield-to-Tensile Ratio** | -- | Typically 0.86 - 0.90 | | **Modulus of Elasticity** | ~29,000 ksi (200 GPa) | ~29,000 ksi (200 GPa) | | **Density** | 0.284 lb/in³ (7.85 g/cm³) | 0.284 lb/in³ (7.85 g/cm³) | | **Charpy V-Notch Toughness (Hallmark)** | **High for its Strength Class (e.g., 25-40 ft-lb @ -40°F / -40°C)** | Achieving these impact values at 90 ksi yield is a significant metallurgical accomplishment, providing crucial fracture resistance. | | **Key Feature** | **Ultimate Strength-Toughness Synergy:** Represents one of the highest commercially viable combinations of yield strength and guaranteed Charpy toughness in a structural steel plate, enabling radical weight reduction in the most critical components. | **Product Applications** Bethlehem Steel RQC90 was specified for the most extreme applications where minimizing structural mass was absolutely critical, and material failure was unacceptable. * **Advanced Mobile Crane & Lift Equipment:** Critical boom sections, pendants, and sheave pins for the largest lattice-boom and mobile cranes, where every pound saved increases lift capacity. * **Aerospace Ground Support & Launch Structures:** Gantries, strongbacks, and erection masts requiring extreme strength with certified reliability. * **High-Performance Defense Vehicles:** Structural hull components, roll cages, and weapon mounts for armored vehicles where ballistic protection depends on underlying structural integrity. * **Energy & Heavy Industrial:** Components for advanced reactor systems, high-pressure hydraulic accumulators, and specialized forging presses. * **Competitive Racing & High-Performance Transport:** Chassis and structural members in elite motorsports (e.g., land speed record cars) and specialized hauling equipment. **Advantages & Fabrication Notes** * **Expert-Level Fabrication Required:** Welding and thermal processing are highly specialized operations. * **Welding:** Requires ultra-low-hydrogen processes (e.g., TIG, specially formulated SMAW/FCAW). Strict and high preheat (350-450°F / 177-232°C) and interpass temperature control are mandatory. **Post-Weld Heat Treatment (PWHT) is almost always required.** * **Filler Metal:** Must be carefully selected (often high-nickel, high-toughness grades) and procedures rigorously qualified on representative material. * **Thermal Cutting:** Plasma or laser cutting is preferred; flame cutting requires extensive preheat and controlled cooling. * **Unmatched Strength-to-Weight Ratio:** Enables dramatic reductions in component weight, translating directly into performance gains in mobile and aerospace applications. * **Fatigue-Critical Design Enabler:** Its high strength and clean microstructure make it suitable for components designed under high-cycle fatigue regimes, though detailed analysis is essential. * **Legacy Product Note:** RQC90 was a niche, state-of-the-art product. Modern direct equivalents are rare and highly proprietary, such as **"HY-100"** or advanced **"Maraging Steel"** alternatives for defense, or custom-melted **"S890Q/QL"** or **"S960Q/QL"** grades per EN 10025-6 from select European mills, specified with toughness guarantees. **Disclaimer:** This datasheet describes the historical **Bethlehem Steel RQC90**, a product at the frontier of plate steel technology. Specifying a modern equivalent is a major engineering undertaking. Requirements must include: **90 ksi min YS, 105-125 ksi UTS, guaranteed Charpy values at service temperature, maximum CE, and likely fracture mechanics (CTOD) testing.** Engagement must begin with a mill capable of such production. Fabrication is not standard shop work; it requires a qualified team, extensive procedure qualification (PQR/WPS), and likely the involvement of the material producer's technical consultants throughout the manufacturing process. -:- For detailed product information, please contact sales. -: Bethlehem Steel RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, steel plate Specification Dimensions Size： Diameter 20-1000 mm Length <4677 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. -: Bethlehem Steel RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, steel plate Properties -:- For detailed product information, please contact sales. -:

Applications of Bethlehem Steel Sheet,Plate RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, Steel Sheet,Plate plate -:- For detailed product information, please contact sales. -: Chemical Identifiers Bethlehem Steel Sheet,Plate RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, Steel Sheet,Plate plate -:- For detailed product information, please contact sales. -:

Packing of Bethlehem Steel Sheet/Plate RQC ASTM A678 RQC90 3/16 to 1-1/2 in. thick, Steel Sheet/Plate plate -:- 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 Sheet/Plate 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 1148 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