How 6061-T651 Aluminum Plate is Rolled: From Slab to Finished Sheet

Introduction: A Process Engineered for Precision

6061-T651 aluminum plate is one of the most widely used precision-grade aluminum materials in machining, mold-making, and aerospace applications. Its reputation for dimensional stability and machinability is not accidental—it is the result of a carefully controlled manufacturing process that transforms a cast aluminum slab into a flat, stress-relieved plate.

The journey from slab to finished sheet involves multiple stages: melting and casting, hot rolling, solution heat treatment, stretching (stress relief) , and artificial aging . Each step is critical to achieving the final T651 temper, which provides the same strength as T6 but with significantly lower internal stress for superior machining stability .

Step 1: Melting and Casting

The process begins with melting high-purity aluminum and alloying elements in a furnace. The 6061 alloy composition is strictly controlled: silicon (0.40–0.80%), magnesium (0.80–1.20%), copper (0.15–0.40%), and other elements within tight limits .

The molten aluminum is then cast into large rectangular slabs called ingots or slabs. These can weigh several tons and measure hundreds of millimeters in thickness. This is the starting point for all rolled aluminum products .

Step 2: Pre-Rolling Preparation – Face Milling

After casting, the slab undergoes face milling—a machining process that removes the surface layer from the slab. This step eliminates surface defects, oxides, and impurities that could be rolled into the plate and cause imperfections. It also ensures a clean, uniform surface for subsequent rolling operations .

Step 3: Homogenization and Solution Heat Treatment

Before rolling, the slab is heated to approximately 450–510°C for several hours . This step serves two purposes:

1. Homogenization: It dissolves any coarse intermetallic particles that formed during casting, creating a uniform distribution of alloying elements.

2. Solution treatment: It puts the alloying elements (particularly Mg₂Si) into solid solution, preparing the material for subsequent heat treatment.

Step 4: Hot Rolling – The First Deformation Stage

Hot rolling is where the slab begins its transformation from a thick block into a thin plate.

The hot rolling process:

The heated slab is passed through a reversing rolling mill (often a “1+1” type hot rolling mill) in multiple passes, gradually reducing its thickness. This is known as hot rough rolling. The process continues until the plate reaches an intermediate thickness, typically 6.0–10.0 mm .

Temperature control is critical:

●Final rolling temperature significantly affects the final grain structure and mechanical properties. Research has shown that reducing the final rolling temperature from 420°C to 280°C effectively refines the grain structure and improves the uniformity of mechanical properties in both the transverse and longitudinal directions .

This grain refinement is key to 6061-T651‘s machinability—finer grains produce more consistent cutting behavior and better surface finishes.

●Large deformation vs. small deformation rolling: Some advanced rolling processes use a combination of high-deformation passes (single-pass reduction ≥50mm) followed by controlled small-deformation passes, with emulsion spray cooling to manage plate temperature and achieve a final rolling temperature of 200–230°C .

●Direct hot rolling and online quenching: Modern production methods can combine hot rolling with online quenching, eliminating separate reheating steps and reducing energy consumption .

Step 5: Solution Heat Treatment and Quenching

After hot rolling, the plate is subjected to solution heat treatment at approximately 525–545°C, followed by rapid cooling (quenching) .

The purpose: to trap the alloying elements in a supersaturated solid solution state, which is essential for the subsequent aging process that creates the T651 temper.

Step 6: Pre-Stretching – The T651 Advantage

This step is the defining characteristic of T651. The plate is permanently stretched by 1% to 3% after quenching and before artificial aging .

Why this matters:

●Eliminates internal stresses – Stretching releases residual stresses introduced during quenching and rolling.

●Prevents warping during machining – The stress-relieved condition means the plate will stay flat even after significant material removal.

●The “51” in T651: This stretching step is what separates T651 from T6 . Without it, the material would be T6 and much more prone to distortion.

Step 7: Artificial Aging (T6/T651)

The plate is then artificially aged at 160–180°C for 8–18 hours to precipitate Mg₂Si particles, which provide the alloy’s strength and hardness.

Step 8: Sawing and Finishing

The final steps involve sawing the plate to specified dimensions, surface finishing, and packaging for shipment.

Rolling Process Summary

Why Choose Mingtai Aluminum for 6061-T651 Plate?

Mingtai Aluminum (Stock Code: 601677), with over 28 years of experience and an annual production capacity exceeding 1.7 million tonnes, supplies 6061-T651 plate that is fully certified and stress-relieved for precision applications .

●Advanced rolling equipment – “1+4” hot continuous rolling lines and German SMS six-high cold rolling mills ensure consistent quality .

●Stress-relieved T651 temper – Guaranteed 1–3% stretching for superior machining stability .

●Full traceability – Each plate is marked with heat number and accompanied by a complete Mill Test Certificate.

●Wide thickness range – 0.3 mm to 500 mm .

●IATF 16949, ISO 9001, ISO 14001 certified – Automotive-grade quality management .

Conclusion

The rolling process for 6061-T651 aluminum plate is a sophisticated sequence of operations designed to achieve a precise balance of strength, flatness, and internal stress control. From the initial casting and homogenization to the critical pre-stretching step, each stage contributes to the material’s exceptional performance in precision machining applications. Understanding this process helps engineers and procurement professionals appreciate the value of certified T651 material and recognize the importance of proper handling and heat treatment.

Contact Mingtai Aluminum today for free samples, technical data sheets, or a factory-direct quotation.

FAQ – 6061-T651 Rolling Process
Q1: What is the difference between hot rolling and cold rolling for 6061 aluminum?
A: Hot rolling is performed at high temperatures (above the recrystallization temperature) to reduce the slab to intermediate thickness. Cold rolling is performed at room temperature to achieve final gauge and improve surface finish and dimensional accuracy.

Q2: Why is pre-stretching important for T651?
A: The 1–3% stretching step relieves internal residual stresses from quenching and rolling. This prevents the plate from warping during CNC machining, which is the key advantage of T651 over T6 .

Q3: What is the final rolling temperature for 6061-T651 plate?
A: Research shows that reducing the final rolling temperature from 420°C to 280°C improves grain refinement and mechanical property uniformity . Other processes target final rolling temperatures as low as 200–230°C for specific applications.

Q4: How long does the artificial aging process take?
A: Artificial aging for 6061-T651 typically takes 8–18 hours at 160–180°C .

Q5: What thickness range is available for 6061-T651 plate?
A: Mingtai supplies 6061-T651 plate from 0.3 mm to 500 mm in thickness .

Mingtai Aluminum – Precision Materials Division

Phone: +86-17760728273

Email: sales@mingtai-al.com

Website: https://m.mingtai-al.com/

Factory Address: Gongyi City Industrial Agglomeration Area, Henan, China