D2 tool steel

Identity and purchasing basis

Uddeholm's Sverker 21 gives a 0.15% recommended machining allowance with an 80 × 80 × 80 mm dimensional-change specimen. It was austenitized at 1020°C for 30 minutes, vacuum cooled at 2 bar overpressure and tempered twice for two hours. Establish the allowance for the actual tool geometry and cycle. Uddeholm dimensional-change specimen

D2 is a high-carbon, high-chromium, air-hardening tool steel identified by Carpenter as UNS T30402. Carpenter describes mild corrosion resistance in the hardened condition; that statement does not establish suitability for an arbitrary corrosive service. Carpenter D2 product description

Uddeholm Sverker 21 and BÖHLER K110 are named producer products associated with AISI D2 and 1.2379. They are useful technical references, but their processing instructions and test results belong to those products. BÖHLER explicitly restricts its presented K110 data to long products, although it also lists plates as a product variant. Uddeholm Sverker 21 bulletin, BÖHLER K110 bulletin

Match the steel to the failure mechanism

Uddeholm positions Sverker 21 for tooling where abrasive wear dominates and the risk of chipping or cracking is not high. Its property balance combines high wear resistance with moderate toughness. Uddeholm selection guidance

Before selecting D2, identify whether the current tool abrades, chips, cracks, galls or plastically deforms. Record workpiece material, thickness, clearance, lubrication, impact and accepted wear limit. A harder replacement may not solve a chipping problem. Compare the complete manufacturing and maintenance route, including grinding effort, repair feasibility and the cost of accepted parts.

Supplied condition and property evidence

BÖHLER lists K110 delivery in the annealed condition, hardness ≤250 HB. That is distinct from the hardness required of a finished hardened tool. BÖHLER delivery condition

Uddeholm gives these approximate compressive 0.2% yield-strength values for Sverker 21:

These are producer reference values, not tensile properties, fatigue limits or guaranteed design allowables. Uddeholm compressive-strength table

Specify finished hardness range, test locations, surface condition and any toughness or microstructure requirements. A hardness result alone cannot establish core uniformity, retained-austenite control, decarburization depth or rolling/sliding contact life. Keep specification limits, typical data and actual lot-test results distinct.

Heat treatment belongs to the product and geometry

For K110, BÖHLER gives 1030–1070°C hardening, with 15–30 minutes holding after temperature equalization. Its tempering chart uses a 20 mm square specimen. The bulletin recommends at least three tempers above the secondary-hardness maximum, with cooling to room temperature between steps. BÖHLER treatment and chart basis

Uddeholm's Sverker 21 guidance instead specifies two tempers, with intermediate cooling to room temperature; its tempering curves use 15 × 15 × 40 mm samples cooled in forced air. It warns that actual tools and dies can attain lower hardness because of size and processing differences. Uddeholm tempering guidance

Agree on preheat, hardening, cooling and tempering for the actual section.

“Air hardening” does not guarantee that an arbitrary large die left in still air will meet its required through-section properties. Qualification must represent the purchased material and actual geometry.

Dimensional stability and finishing

Uddeholm's dimensional-change example uses an 80 × 80 × 80 mm sample, austenitized at 1020°C for 30 minutes, cooled in vacuum equipment with 2 bar overpressure, then tempered twice for two hours. Its 0.15% recommended machining allowance accompanies that example. Uddeholm dimensional-change basis

For illustration, 0.15% of a 200 mm dimension is 0.30 mm. This arithmetic does not determine total stock allowance, its distribution between faces, distortion direction or final grinding stock for a different part. Establish those choices from the drawing and qualified route.

Plan rough machining, stress relief where needed, heat treatment and final grinding as a sequence. Inspect dimensions after operations that can change them. Define edge and surface acceptance independently of bulk hardness. For coatings, resolve compatibility with the existing tempering condition and dimensional requirements before processing.

Uddeholm recommends an additional temper approximately 25°C below the previous tempering temperature after EDM on hardened-and-tempered Sverker 21. Uddeholm EDM guidance

Treat EDM and repair welding as changes to the local surface or thermal history. Obtain the applicable producer-supported procedure and inspect the affected region before release. A successful repair appearance does not demonstrate restored edge performance.

Release record and source versions

Retain producer, heat/lot, grade, specification edition, form, supplied/final condition, treatment record, drawing and final inspections. State environmental, dimensional, hardness and service-performance acceptance explicitly. Record approved substitutions against the complete requirement.

The inspected Sverker 21 bulletin prints Edition 13, 04.2019. BÖHLER's inspected bulletin prints K110 EN_GB – 10.2025. No technical revision date was verified for Carpenter's live product page. Confirm current order-specific requirements separately from these reference editions.

See grades, tempers and conditions.