Tool and Alloy Steels (42CrMo4, 1.2379)
Machining, heat treatment and grade selection for shafts, dies, gears and wear parts in Egypt, the UAE and Saudi Arabia
Tool and alloy steels are used where mild steel is not strong or hard enough: shafts under torque, gears, punches, dies, moulds, wear plates and hydraulic components. The most ordered grades in the region are 42CrMo4 (4140) for shafts and high-strength parts, C45 (1045) as a low-cost medium-carbon option, 1.2379 (D2) for cutting and forming dies, 1.2344 (H13) for hot-work tooling and die casting, and 1.2311 (P20) for plastic injection moulds. CutLinq machines these grades by CNC milling and turning, and arranges hardening, tempering and grinding through partner heat-treatment shops.
This page covers grade selection by application, delivery condition and achievable hardness, machining allowances before and after heat treatment, and what to specify so the part arrives at the right hardness and finish.
Grade selection
The choice depends on three questions: does the part need through-hardness or only a hard surface, does it work hot or cold, and does it need to be welded. 42CrMo4 answers most shaft and bracket requirements; die steels are chosen by the abrasion and impact they must survive.
Prices relative to S235JR: C45 costs about 20-30% more, 42CrMo4 about 60-80% more, 1.2379 roughly 3-4 times, and 1.2344 about 4-5 times, before heat treatment. Stock in Cairo, Dubai and Riyadh is usually round bar and flat bar; large plates in 1.2379 may need 1-2 weeks import time.
| EN / DIN grade | AISI equivalent | Delivery condition | Hardness after treatment | Typical use |
|---|---|---|---|---|
| C45 (1.0503) | 1045 | Normalised, 170-210 HB | Induction 50-55 HRC surface | Pins, low-load shafts, keys |
| 42CrMo4 (1.7225) | 4140 | QT, 28-34 HRC | Through 40-45 HRC, nitrided 58-62 HRC surface | Shafts, gears, bolts, hydraulic parts |
| 16MnCr5 (1.7131) | 5115 | Annealed, 150-200 HB | Case hardened 58-62 HRC | Gears, cams, splines |
| 1.2379 (X153CrMoV12) | D2 | Annealed, max 255 HB | 58-62 HRC | Blanking dies, shear blades, wear plates |
| 1.2344 (X40CrMoV5-1) | H13 | Annealed, max 235 HB | 44-52 HRC | Die-casting dies, extrusion tooling, hot punches |
| 1.2311 (40CrMnMo7) | P20 | Pre-hardened 28-32 HRC | Used as delivered | Injection mould plates, holders |
Machining allowances and tolerances
Most alloy steel parts are machined in two stages: rough machining in the soft or pre-hardened condition, heat treatment, then finish machining or grinding. Hardening distorts the part, typically 0.05-0.15 mm on a 100 mm feature for oil-quenched grades and up to 0.3 mm for water-quenched C45, so a grinding allowance must be left.
Pre-hardened 42CrMo4 at 28-34 HRC and 1.2311 at 28-32 HRC can be finish machined directly with carbide tooling at about 60-70% of the speed of mild steel; this avoids distortion and is the standard route for shafts and mould plates that do not need more than 34 HRC.
| Stage | Tolerance achievable | Surface Ra | Allowance to leave |
|---|---|---|---|
| Rough milling / turning, soft | ±0.1 mm | 3.2-6.3 µm | 0.3-0.5 mm per side for grinding |
| Finish milling, pre-hardened 28-34 HRC | ±0.02 to ±0.05 mm | 0.8-1.6 µm | none |
| Hard milling 50-60 HRC | ±0.01 to ±0.02 mm | 0.4-0.8 µm | 0.1-0.2 mm per side |
| Cylindrical / surface grinding | ±0.005 mm, IT5-IT6 | 0.2-0.4 µm | final |
| Wire EDM on hardened die | ±0.005 to ±0.01 mm | 0.8-1.6 µm | final |
Heat treatment options
Through hardening (quench and temper) changes the whole section; case hardening and nitriding harden only the surface and keep a tough core. Nitriding at 500-550 °C causes almost no distortion, which makes it the preferred finish for 42CrMo4 shafts and guide rails that are already ground to size. Case hardening of 16MnCr5 adds a 0.6-1.2 mm hard layer and requires grinding afterwards.
Tempering temperature sets the final hardness: 42CrMo4 tempered at 550 °C gives about 32 HRC, at 450 °C about 40 HRC. Specify the hardness range on the drawing, for example 40-45 HRC, not just the word hardened.
- Quench and temper (42CrMo4, C45): 28-45 HRC through, distortion 0.1-0.3 mm
- Induction hardening (C45, 42CrMo4): 50-58 HRC to 2-4 mm depth on selected surfaces
- Case hardening (16MnCr5): 58-62 HRC, 0.6-1.2 mm case, grinding required
- Gas or plasma nitriding (42CrMo4, 1.2344): 55-65 HRC, 0.2-0.5 mm, negligible distortion
- Vacuum hardening (1.2379, 1.2344): 44-62 HRC, clean surface, low distortion, 2-3 tempers
Corrosion and handling in MENA conditions
None of these grades is stainless. A ground 42CrMo4 shaft left unprotected in a Dammam workshop shows flash rust within a day. Ground parts are delivered oiled and wrapped in VCI paper; for storage over two weeks, or for parts in washdown areas, add black oxide, phosphating, or a hard chrome or nitrided surface. Dies for the humid coast are often chrome plated 10-20 µm on the working faces.
High summer temperatures do not affect hardened parts in service, but 1.2379 dies should not be shipped or stored at over 60 °C in a closed container together with wet parts; condensation on a hardened D2 surface pits within hours.
Welding limits
42CrMo4 and C45 can be welded with preheat of 200-300 °C and post-weld tempering, but welded assemblies lose local hardness and are prone to cracking; design shafts as single machined pieces where possible. 1.2379 and 1.2344 are repair-welded only with matching electrodes and full preheat, normally by a die shop rather than a fabricator. 1.2311 is weldable for mould repairs with preheat of 250 °C.
Design tips
- Specify hardness as a range (for example 40-45 HRC) and the test location, not just the grade.
- Leave 0.3-0.5 mm per side for grinding on any feature tighter than ±0.05 mm that is hardened after machining.
- Keep internal corners in hardened dies at R0.5 mm minimum; sharp corners are crack initiation points during quenching.
- For shafts under 34 HRC, order 42CrMo4 QT pre-hardened and finish machine directly; skip the heat-treatment step.
- Place keyways and cross holes away from shaft shoulders by at least 1.5x shaft diameter to reduce stress concentration.
- Use nitriding instead of case hardening when the part is already ground to size and distortion must stay under 0.02 mm.
- Add a thread or centre hole for lifting on any part over 25 kg; hardened surfaces are easily chipped by chain slings.
Applications
| Industry | Example parts | Typical material |
|---|---|---|
| Machinery and OEM | Drive shafts, gears, couplings | 42CrMo4 QT, 16MnCr5 |
| Packaging and conveyors | Cutting blades, cam followers, rollers | 1.2379, 42CrMo4 induction |
| Plastics and moulding | Mould plates, cores, ejector plates | 1.2311, 1.2344 |
| Aluminium die casting | Die inserts, cores, sprue bushes | 1.2344 at 46-50 HRC |
| Oil and gas | Valve stems, wellhead components, wrench parts | 42CrMo4, 34CrNiMo6 |
| Construction equipment | Pins, bushes, bucket teeth adapters | C45 induction, 42CrMo4 |
| Sheet-metal tooling | Punches, dies, press-brake tools | 1.2379, 1.2842 |
Pricing and lead time
Price of a tool steel part is driven by the raw material grade and stock size (a 1.2379 plate blank can cost more than the machining itself), by the machining volume and tolerance (removing 70% of a block to reach a pocket, or holding ±0.01 mm by grinding, multiplies machine hours), and by the heat-treatment route (a vacuum harden plus three tempers plus grinding adds 3-5 working days and a fixed batch charge). Machined-only parts in pre-hardened 42CrMo4 or 1.2311 ship in 5-8 working days; parts that are hardened and ground need 10-15 working days; imported special plate sizes add 7-10 working days.
Frequently asked questions
Not usually. Machining, quench and temper, and finish grinding take 10-12 working days in Egypt or the UAE. If 30-34 HRC is acceptable, we machine pre-hardened QT bar and deliver in 5-7 working days.
Upload your STEP file with grade, hardness range and surface finish, and receive a binding quote within 12 hours.