1.7220 (34CrMo4) & SCM435 Steel CNC Machining | High Tensile Fasteners & Shafts

1.7220 (34CrMo4) / SCM435 Alloy Steel Machining

When global engineering drawings call for DIN 1.7220 (34CrMo4) or JIS SCM435, they are specifying a premium Chromium-Molybdenum alloy steel designed for high tensile applications. Slightly lower in carbon than 4140, this grade offers an excellent balance of strength, toughness, and wear resistance, particularly after Quenching and Tempering (Q&T). At JUCHENG, we specialize in processing these specific international grades. Whether you need high-strength automotive fasteners, gas cylinder components, or power transmission shafts, we ensure the material properties meet the strict requirements of European and Japanese standards.

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1.7220 Alloy Steel

JUCHENG's 1.7220/SCM435 Fabrication Capabilities

We provide specialized processing for high-stress components:

Precision Threading: Since SCM435 is the standard for high-strength bolts (Grade 10.9/12.9), we offer thread rolling and CNC single-point threading to ensure Class 3A/6g thread fits.
Heat Treatment (Q&T): We perform precise quenching and tempering to achieve the desired mechanical properties (typically 900-1100 MPa tensile strength) while maintaining toughness.
Hard Turning: For parts hardened after rough machining, we utilize CBN tooling to finish critical diameters to H6 tolerances without grinding.

Oberflächenschutz: We provide Phosphate Coating (Parkerizing), Dacromet, or Zinc-Nickel plating, which are standard finishes for automotive fasteners made from this material.

Advantages of CNC Machining 1.7220/SCM435

Vorteil	Detaillierte Beschreibung	Hauptvorteil
High Static & Dynamic Strength	Excellent response to heat treatment.	Capable of withstanding heavy static loads and dynamic shocks (axles/bolts).
Superior Toughness	Slightly better ductility and impact resistance than 4140 due to lower carbon.	Reduces the risk of brittle failure in safety-critical parts like steering knuckles.
Consistent Hardenability	The Cr-Mo content ensures uniform hardness penetration.	Reliable mechanical properties throughout the cross-section of shafts and bolts.
Cold Formability	In the annealed state, it has good plasticity.	Suitable for parts requiring cold heading or upsetting before machining.
Wear Resistance	Can be surface hardened (Induction/Nitriding).	Extends the life of gears and splines.

Technische Parameter & Materialnormen

We stock materials compliant with both European and Asian standards:

Güteklasse	Spezifikation	Eigenschaften & Ideale Verwendungen
DIN 1.7220 / 34CrMo4	European Standard	Characteristics: Chromium-Molybdenum tempering steel. High toughness in the QT condition. Widely used in the German automotive industry. Uses: High-pressure gas cylinders, axle arms, connecting rods, pinions.
JIS SCM435	Japanese Standard	Characteristics: The equivalent Japanese grade. The gold standard for high-strength bolts and automotive suspension parts. Uses: Grade 10.9 / 12.9 Bolts, engine components, motorcycle frames.
Condition +QT	Quenched & Tempered	Characteristics: Heat treated to obtain high tensile strength (e.g., 900-1100 MPa) before or after machining. Uses: Final functional parts ready for load.

CNC Machining Guidelines for SCM435

Zerspanbarkeit: In the annealed condition, machinability is good (similar to 4140). In the Q&T condition (approx. 30 HRC), it requires rigid setups and coated carbide tools.
Schweißen: Requires pre-heating (200-300°C) and post-weld stress relief to prevent cracking in the HAZ (Heat Affected Zone).
Distortion: Long shafts made from SCM435 can distort during heat treatment. We leave grinding allowance or use stress-relieved stock to mitigate this.
Induction Hardening: This material is excellent for induction hardening specific areas (like bearing journals) to 50-55 HRC while keeping the core tough.

Anwendungsszenarien

Automobil: Cylinder head bolts, crankshafts, steering arms, stabilizers.
Fasteners: High-strength socket head cap screws (SHCS), studs, anchors.
Energy: Seamless gas cylinders (CNG tanks), pressure vessel necks.
Schwermaschinen: Drive shafts, conveyor pins, high-stress gears.

Tabelle der physikalischen Eigenschaften

Typical mechanical properties in Quenched & Tempered (+QT) condition:

Eigenschaft	1.7220 / SCM435 (+QT)	1045 Carbon Steel	Einheit
Dichte	7.85	7.87	g/cm³
Zugfestigkeit	900 - 1100	570 - 700	MPa
Streckgrenze	650 - 900	310 - 450	MPa
Dehnung	10 - 14	16	%
Hardness	28 - 34 HRC	170 - 210 HB	-
Impact Energy (KV)	> 35	Niedrig	Joules

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