Tempering Furnace Temperature Range for Steel, Alloy and Tool Steel

Accurate temperature range control is the core of qualified tempering processing, directly determining the hardness, toughness, elasticity and fatigue resistance of quenched steel workpieces. Different steel grades including ordinary carbon steel, alloy structural steel and high-precision tool steel have distinct metallurgical characteristics, requiring exclusive tempering furnace temperature parameters and soaking time standards. Improper temperature setting will lead to insufficient stress relief, excessive hardness attenuation or material brittleness failure, resulting in mass defective products. This article sorts out the most authoritative industrial tempering temperature ranges for mainstream steel materials.

1. Ordinary Carbon Steel Tempering Temperature Range

Low-carbon steel (Q235, 10#, 20#) after quenching is mostly used for ordinary structural parts, with a standard tempering furnace temperature of 500°C–650°C, belonging to high-temperature tempering. This temperature range completely eliminates quenching residual stress, significantly improves material toughness and plasticity, and obtains excellent comprehensive mechanical properties. The soaking time is controlled at 1.5–2 hours per 100mm workpiece thickness, suitable for high-strength bolts, mechanical supports and ordinary structural accessories.

Medium carbon steel (45#, 50#) is the most widely used structural steel, with a conventional tempering temperature of 480°C–620°C. Proper tempering can balance strength and toughness, avoiding the brittleness problem of single quenching treatment. For parts requiring high impact resistance, the temperature can be appropriately increased to 600°C–650°C; for parts requiring medium hardness and wear resistance, the temperature is controlled at 480°C–550°C.

2. Alloy Steel Tempering Temperature Range

Alloy structural steel (40Cr, 35CrMo, 42CrMo) is widely used for high-load automotive and mechanical parts, with a standard tempering temperature of 500°C–600°C. Alloy elements improve steel hardenability, requiring slightly higher tempering temperature than ordinary carbon steel to fully release internal stress. Workpieces after tempering have high strength, strong impact resistance and stable dimensional accuracy, suitable for shafts, gears and heavy-load mechanical parts.

Spring alloy steel (65Mn, 60Si2Mn) focuses on elastic performance, adopting medium-temperature tempering at 380°C–450°C. This temperature range ensures the steel obtains excellent elastic limit and fatigue resistance, maintaining stable elasticity under long-term alternating load, which is the standard tempering parameter for industrial springs and vibration damping parts.

3. Tool Steel & Mold Steel Tempering Temperature Range

High-carbon tool steel (T8, T10, T12) is used for cutting tools and measuring tools, adopting low-temperature tempering at 160°C–220°C. The core purpose is to retain ultra-high hardness and wear resistance while removing tiny quenching stress, preventing tool cracking and dimensional deformation during use.

Cold work mold steel (Cr12, Cr12MoV) requires high hardness and wear resistance, with a tempering temperature of 180°C–250°C. Low-temperature tempering stabilizes the mold microstructure and size, avoiding deformation during stamping and cutting processing.

Hot work mold steel (H13, 4Cr5MoSiV1) bears high-temperature and alternating impact load, adopting medium-temperature tempering at 500°C–580°C to improve thermal fatigue resistance and toughness, ensuring long-term stable operation of hot forging and casting molds.

It is worth noting that tempering furnace temperature parameters need to be adjusted according to workpiece thickness and quenching state. Thick workpieces require appropriately extended soaking time to ensure uniform internal and external tempering effect; over-quenched workpieces need slightly increased tempering temperature to avoid residual stress concentration. Modern intelligent tempering furnaces can store exclusive parameter curves for various steel materials, realizing one-click accurate processing and effectively improving product qualification rate.