Titanium bar rolling is the core plastic processing technology for transforming titanium billets into titanium bars of specific diameter and length. The process involves using rollers to compress and plastically deform the titanium billet, offering advantages such as high precision and uniform microstructure. The complete process is divided into three main stages: pre-rolling preparation, the core rolling process, and post-rolling finishing, with each stage further broken down into key steps.
I. Pre-rolling Preparation (Crucial for Rolling Quality, All Steps Are Essential)
Titanium is highly chemically reactive, easily oxidizes at high temperatures, and its plasticity is sensitive to temperature. Precise control of pre-rolling preparation is essential; otherwise, problems such as cracking and excessive oxidation will occur.
Billet Preparation and Inspection
The billets for rolling titanium rods are mainly square/round billets obtained after blooming titanium ingots. A small number of extruded billets are also used. The specifications are determined according to the size of the finished titanium rod (for example, for a finished φ20mm titanium rod, φ45-50mm round billets are commonly used).
First, billet inspection is performed: checking the grade (pure titanium Gr1/Gr2, titanium alloy Gr5, etc.) and chemical composition, and inspecting the surface for cracks, inclusions, and pores. Unqualified billets are directly rejected; then, the end faces of the billets are smoothed to avoid uneven stress during rolling.
Billet Heating (Core Key Step)
There are two heating methods:
Heating temperature: The heating temperature for pure titanium billets is 850-950℃, and for titanium alloy billets (such as Gr5) is 900-1050℃. Overheating is strictly prohibited (overheating will lead to coarse grains, affecting the strength of the titanium rod), and low temperatures are also unacceptable (insufficient plasticity at low temperatures, prone to cracking).
Heating equipment: Vacuum heating furnaces or protective atmosphere heating furnaces (using argon or nitrogen) are preferred to prevent titanium from contacting air at high temperatures and forming a brittle oxide layer; if a regular resistance furnace is used, an anti-oxidation coating (glass coating, borax coating) needs to be applied to the billet surface.
II. Core Rolling Process (Staged Deformation, Gradual Shaping)
Titanium bar rolling is not a single-step process, but rather involves multiple passes and stages. Based on rolling temperature and equipment type, the main process is divided into two steps: hot rolling (the main process) and cold rolling (for finishing and improving precision). Some high-precision products may also include warm rolling.
Phase 1: Hot Rolling (Core forming, primarily diameter reduction)
The purpose is to rapidly reduce the diameter of the rough billet to a size close to the finished product, while simultaneously refining the grain structure and improving the plasticity of the titanium rod. The entire process maintains the billet within the "rolling temperature range" to prevent embrittlement after cooling.
Phase 2: Cold Rolling (Precision finishing, primarily for quality improvement)
The purpose is to remove the excess material from the hot-rolled bars, achieving precise finished dimensions while improving surface finish (to Ra0.8μm or less), and increasing the strength and dimensional accuracy of the titanium bars. During cold rolling, the titanium bars are at room temperature, eliminating oxidation problems.
Stage 3: Warm Rolling (Optional, for high-precision products only)
This process is performed between hot rolling and cold rolling, with temperature controlled at 200-400℃. It combines the precision of cold rolling with the plasticity of hot rolling, making it suitable for difficult-to-deform titanium alloys or ultra-high-precision titanium rods. The process is similar to cold rolling, only requiring the addition of a low-temperature heating step.
Baoji Reliab Metal Materials Co.,Ltd
Mobile: 0086 13092900605
Sales Department 1: WhatsApp +8613092900605 (Mr.Gary)
Sales Department 2: +8613092913521(Ms. Sophia)
Address: No.35 Baoti Rd, Weibin District, Baoji, China
