Korean
A precision machining and heavy equipment component manufacturer based in Santiago, Chile, selected us as its long-term supply partner for ASTM A193 Grade AISI 4140 / 42CrMo4 quenched and tempered precision ground steel round bar in 31.75mm diameter with an h7 tolerance band. The material is now used in the client's production of high-load fasteners, hydraulic shafting, and forged mechanical components destined for the Chilean mining and energy sectors.
The buyer operates a machining plant serving mining equipment OEMs and power generation contractors across northern Chile — one of the world's most demanding operating environments. Components supplied into these industries must withstand abrasive conditions, high static and dynamic loads, and long service intervals. The client's engineering team therefore specifies alloy steel bar stock with certified mechanical properties, tight dimensional control, and full traceability for every heat number.
- Local availability gap: Chilean distributors rarely stock 31.75mm (1-1/4") 4140 bar in the h7 ground condition, forcing costly imports with long lead times.
- Tolerance consistency: The client's CNC turning and grinding lines require a guaranteed h7 tolerance band — out-of-round or oversized bar caused scrap and rework with previous suppliers.
- Property verification: Quenched and tempered hardness and mechanical properties had to be verified per heat, with mill test certificates referencing ASTM A193 requirements.
- Surface quality: Precision ground and polished finish was mandatory to eliminate decarburization and surface defects before hard chrome plating.
We supplied AISI 4140 (42CrMo4) quenched and tempered precision ground round bar in 31.75mm diameter, produced to the client's h7 tolerance specification and supplied with a full EN 10204 3.1 mill test certificate for each heat number. The material was turned, heat treated, straightened, and centreless ground in a controlled sequence to guarantee dimensional stability and a defect-free surface.
Key features delivered to the Chilean client:
- Certified Chemistry: Chromium-molybdenum alloy steel (AISI 4140 / 42CrMo4 / 1.7225) with tightly controlled carbon, chromium, and molybdenum ranges for consistent hardenability.
- Quenched & Tempered: Through-hardened and tempered to the specified strength range, delivering high tensile strength with good toughness for dynamic loading.
- h7 Precision Tolerance: Ground to a 31.75mm h7 band, ensuring predictable fits and eliminating rework on the client's machining lines.
- Precision Ground Finish: Centreless ground and polished surface free from decarburization, seams, and scale — ready for hard chrome plating.
- Full Traceability: Heat number stamped and recorded on the mill test certificate for every bundle shipped.
| Parameter | Specification |
|---|---|
| Grade | ASTM A193 / AISI 4140 / 42CrMo4 / 1.7225 |
| Diameter | 31.75 mm (1-1/4 inch) |
| Tolerance | h7 precision ground |
| Condition | Quenched & Tempered |
| Surface | Precision ground / peeled, bright polished |
| Hardness | As specified by application (typical 28–32 HRC) |
| Length | 3–6 m random or fixed cut to order |
| Straightness | ≤ 0.5 mm/m after straightening |
| Certification | EN 10204 3.1 Mill Test Certificate per heat |
| Packing | Wooden crate / woven bag with anti-rust oil |
| Element | C | Si | Mn | Cr | Mo | P | S |
|---|---|---|---|---|---|---|---|
| Range | 0.38–0.45 | 0.17–0.37 | 0.60–0.90 | 0.90–1.20 | 0.15–0.30 | ≤0.035 | ≤0.035 |
AISI 4140 is the workhorse chromium-molybdenum alloy steel for medium-to-high strength applications. Its molybdenum addition improves hardenability and resistance to temper embrittlement, while chromium contributes wear resistance and corrosion resistance. In the quenched and tempered condition, the grade offers an excellent balance of strength, toughness, and fatigue resistance — the exact combination required for mining equipment fasteners, hydraulic rods, and forged shafts operating under continuous load.
- Eliminated dimensional rework: h7 ground bar arrived in tolerance on every bundle received.
- Reduced lead time versus European and Brazilian sources, with consolidated shipments to Valparaíso.
- Full heat-number traceability supported the client's quality audit requirements for mining OEM customers.
- Consistent mechanical properties allowed the client to standardise machining parameters across production runs.
- Repeat orders placed on a quarterly basis, extending the partnership to additional diameters in the 4140 range.
This Chile project shows how specifying the right grade, condition, and tolerance together — rather than price alone — protects downstream machining yield. For buyers sourcing ASTM A193 AISI 4140 42CrMo4 quenched and tempered precision ground round bar, the combination of certified chemistry, h7 dimensional control, and documented traceability is what actually reduces total cost of ownership. We supply this grade in diameters from 16mm to 300mm, in peeled, turned, ground, or polished condition, with shipment to major Latin American ports.