AISI 1074/1075 Carbon Steel Springs

AISI 1074/1075 Carbon Steel Springs

AISI 1074/1075 are tempered spring steels that look and act much like blue tempered steels. The difference being that scaleless tempered is of medium-high carbon, have been tempered and have better forming qualities.

AISI 1074/1075 Springs FAQs

What is AISI 1074/1075 steel and how does it differ from other tempered spring steels?

AISI 1074 and 1075 are high-carbon plain steels with carbon content of approximately 0.70%–0.80%, produced most commonly as scaleless tempered strip for flat spring applications. Unlike blue-tempered steel—which may carry surface scale from the tempering process—scaleless tempered 1074/1075 undergoes a controlled, scale-free tempering process that produces a consistently clean surface and better dimensional control. This makes it easier to stamp or bend into precise flat spring geometries than traditional blue-tempered alternatives while producing equivalent mechanical properties. The two grades are nearly identical in composition and frequently used interchangeably, with selection typically driven by material availability.

What types of springs are most commonly manufactured from AISI 1074/1075?

AISI 1074 and 1075 are primarily used for flat spring applications—the geometry for which their scaleless tempered strip form is most well suited. Common examples include clock and power springs, stamped flat springs, retaining clips, snap rings, brush springs, trigger springs, and light-duty leaf springs. These materials are less commonly used for round-wire compression or extension springs, where music wire or hard drawn wire are standard specifications, because their principal advantage—scaleless tempered strip with good forming characteristics—is most valuable in flat or strip spring geometries.

What heat treatment process is used for AISI 1074/1075 springs?

For springs manufactured from annealed strip, the process involves: (1) forming by stamping, rolling, or bending in the annealed condition; (2) austenitizing at approximately 1,475°F–1,525°F (802°C–829°C); (3) quenching in oil or a controlled atmosphere to produce a martensitic structure; and (4) tempering at 400°F–700°F (204°C–371°C) to achieve the desired hardness and reduce brittleness. Processing is typically performed in a controlled atmosphere furnace to minimize surface decarburization. For scaleless tempered strip supplied in the pre-tempered condition, further heat treatment after forming is not required—the strip arrives ready for precision forming operations.

What is the typical hardness range for heat-treated AISI 1074/1075 springs?

After hardening and tempering from the annealed condition, AISI 1074/1075 springs typically achieve 44–52 HRC depending on temper temperature. Higher temper temperatures (500°F–700°F) yield 44–50 HRC with better ductility; lower temper temperatures (350°F–400°F) yield 50–56 HRC with maximum strength but reduced toughness. The specific target is selected based on the spring's load requirements, deflection range, and service conditions. Scaleless tempered strip is typically supplied in the 44–52 HRC range ready for direct forming operations.

What is the maximum operating temperature for AISI 1074/1075 springs?

AISI 1074/1075 springs are limited to continuous service at approximately 250°F (121°C)—the same upper limit as music wire. Above this temperature, the tempered microstructure begins to soften and the spring will experience accelerated stress relaxation, resulting in loss of the intended spring load over time. Applications near heat sources should specify chrome silicon, stainless steel, or other alloys with higher temperature ratings.

Does AISI 1074/1075 offer corrosion resistance for outdoor or wet environments?

No. Like all plain carbon steels, AISI 1074 and 1075 have no meaningful corrosion resistance and will rust when exposed to moisture, salt, or corrosive media. Springs intended for outdoor or humid environments require protective surface treatment. Common options include zinc electroplating (provides galvanic protection), phosphate-and-oil treatment (minimal protection, useful as a primer base), powder coating (good coverage and aesthetics for visible components), and epoxy or polyurethane paint systems for more aggressive exposures. For inherent corrosion resistance, stainless steel or copper alloy grades should be specified.

What is the smallest material thickness or wire diameter available for AISI 1074/1075 springs?

For flat spring applications, Coiling Technologies can work with AISI 1074/1075 strip material down to approximately 0.003 inches (0.080 mm) in thickness, enabling very thin precision flat springs. This fine-gauge capability supports precision instruments, clock mechanisms, miniature device springs, and other applications requiring extremely thin, high-strength spring strip.

What are common applications for AISI 1074/1075 springs?

Applications include power tool brush springs, automotive interior trim retaining clips and latching mechanisms, clock and instrument mainsprings, agricultural equipment light-duty retaining springs, snap rings and retaining clips, trigger and mechanism springs in firearms and hand tools, and general stamped spring components in industrial machinery. These grades are most cost-effective where a flat spring geometry is required at moderate performance levels, corrosion protection can be applied externally, and the maximum service temperature does not exceed approximately 250°F.