Steel ZG340-640 Q&T-HH
Hardness band
GB GB/T 11352
Q&T-HH = quenched and low-tempered for wear
Choose for abrasion-dominated castings (crusher parts, wear plates) where hardness outranks impact toughness.
Values for the Q&T-HH condition
Other ZG340-640 tempers and conditions
ZG340-640 is listed in 6 conditions; see the grade overview at ZG340-640.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal (~840–870 °C, furnace cool) | Pick when maximum machinability and stress relief matter more than strength, e.g. before heavy rough machining. | 320 | 600 | 14 | 180 HB | — |
As fabricated | Lowest-cost condition for non-critical wear parts where cast-in stresses and coarse structure are acceptable. | 330 | 630 | 8 | 14 HRC | 8.6 % IACS |
NormalizedDefault 850–880 °C, air cool (standard GB/T 11352 delivery) | Default stocked condition: meets the 340/640 MPa spec with uniform fine pearlitic structure and good wear resistance. | 360 | 660 | 11 | 210 HB | — |
Normalized and tempered | Use when residual stresses from normalizing must be relieved while keeping spec strength and slightly better toughness. | 370 | 670 | 13 | 17 HRC | 8.6 % IACS |
Quenched and tempered | Highest strength/toughness combination for heavily loaded gears and rolls; section size limited by hardenability and quench-crack risk at 0.55%C. | 550 | 800 | 12 | 26 HRC | — |
Q&T-HHThis page Quenched and low-tempered for wear | Choose for abrasion-dominated castings (crusher parts, wear plates) where hardness outranks impact toughness. | 750 | 1,000 | 6 | 34 HRC | — |
What is ZG340-640 Q&T-HH?
ZG340-640 Q&T-HH is ZG340-640 heat treated to Q&T-HH — choose for abrasion-dominated castings (crusher parts, wear plates) where hardness outranks impact toughness. ZG340-640 Q&T-HH has a yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Elongation at break is 6% and the elastic modulus is 205 GPa (29.7 Msi). ZG340-640 Q&T-HH has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F). Normalized is the default condition FabDigit quotes; Q&T-HH is available on request or by drawing note.
Advantages
- High strength — 750 MPa (109 ksi), better than 84% of steel grades
Limitations
- Limited ductility — 6%, worse than 97% of steel grades
- Difficult to machine — 28/100, worse than 91% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
ZG340-640 Q&T-HH properties
Typical room-temperature values for ZG340-640 Q&T-HH; 11 are specific to this condition. Other listed values are ZG340-640 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
ZG340-640 Q&T-HH has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
ZG340-640 Q&T-HH has a yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Elongation at break is 6% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
ZG340-640 Q&T-HH is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
ZG340-640 Q&T-HH conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of ZG340-640 Q&T-HH takes about 24 MJ of energy and emits 2 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 80%.
Manufacturability8
ZG340-640 Q&T-HH's machinability is poor (28/100, worse than 91% of steel grades); weldability poor (20/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZG340-640 Q&T-HH
Is ZG340-640 easy to machine?
As a 0.5 % C pearlitic cast steel it cuts normally in the normalized condition with coated carbide at vc ≈ 100–150 m/min. Hard spots and residual sand in the as-cast skin chip cutting edges, so remove the skin layer first; in the Q&T condition reduce speed and increase feed.
Can ZG340-640 be welded?
Carbon equivalent is high (about 0.6–0.75), so weldability is poor: preheat to 150–250 °C, use low-hydrogen electrodes (E7015/E7016 or E5015), control interpass temperature and stress relieve at 600–650 °C after welding, otherwise cold cracking is likely.
Can ZG340-640 be formed, bent or molded?
Mainly sand cast at a pouring temperature of about 1540–1580 °C with roughly 2 % linear shrinkage; provide enough risers and chills to avoid shrinkage cavities. Abrupt thick-to-thin transitions hot tear, so keep wall thickness uniform and use generous fillet radii.
What surface finishes work on ZG340-640?
Not anodizable; after shot blasting apply phosphate plus primer or epoxy paint, zinc plating or black oxide for rust protection. Sliding wear faces can be flame or induction hardened, or nitrided, to raise surface hardness.
ZG340-640 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CGB/T 11352 caps C ≤0.60; held near 0.5 % for strength | 0.45 – 0.6 | 0.55 |
| Si | 0.2 – 0.6 | 0.45 |
| Mn | 0.5 – 0.9 | 0.8 |
| Pmaximum, general use | ≤ 0.04 | 0.02 |
| Smaximum, general use | ≤ 0.04 | 0.02 |
| Niresidual element | ≤ 0.3 | — |
| Crresidual element | ≤ 0.35 | — |
| Curesidual element | ≤ 0.3 | — |
| Moresidual element | ≤ 0.2 | — |
| Vresidual element; total residuals ≤1.00 % | ≤ 0.05 | — |
| Fe | balance | — |
ZG340-640 Q&T-HH — frequently asked
What is ZG340-640 Q&T-HH used for?
ZG340-640 Q&T-HH is typically used for crusher hammers, large gears, heavy-duty machine bases and mining equipment parts. In short: strongest common GB/T 11352 tier; wear-resistant cast steel; poor weldability, high CE.
What is the yield strength of ZG340-640 Q&T-HH?
ZG340-640 Q&T-HH has a typical yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is ZG340-640 Q&T-HH easy to machine?
Not especially — machinability is rated poor (28/100, worse than 91% of steel grades). As a 0.5 % C pearlitic cast steel it cuts normally in the normalized condition with coated carbide at vc ≈ 100–150 m/min. Hard spots and residual sand in the as-cast skin chip cutting edges, so remove the skin layer first; in the Q&T condition reduce speed and increase feed.
Can ZG340-640 Q&T-HH be welded?
Not readily — weldability is rated poor (20/100). Carbon equivalent is high (about 0.6–0.75), so weldability is poor: preheat to 150–250 °C, use low-hydrogen electrodes (E7015/E7016 or E5015), control interpass temperature and stress relieve at 600–650 °C after welding, otherwise cold cracking is likely.
What surface finishes work on ZG340-640 Q&T-HH?
Not anodizable; after shot blasting apply phosphate plus primer or epoxy paint, zinc plating or black oxide for rust protection. Sliding wear faces can be flame or induction hardened, or nitrided, to raise surface hardness.
Can ZG340-640 Q&T-HH be formed, bent or molded?
Mainly sand cast at a pouring temperature of about 1540–1580 °C with roughly 2 % linear shrinkage; provide enough risers and chills to avoid shrinkage cavities. Abrupt thick-to-thin transitions hot tear, so keep wall thickness uniform and use generous fillet radii.
What is the maximum service temperature of ZG340-640 Q&T-HH?
ZG340-640 Q&T-HH is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ZG340-640 Normalized and ZG340-640-F?
Normalized is the default condition — default stocked condition: meets the 340/640 MPa spec with uniform fine pearlitic structure and good wear resistance. F: lowest-cost condition for non-critical wear parts where cast-in stresses and coarse structure are acceptable. Yield strength is 360 MPa in Normalized versus 330 MPa in F.
Sources
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Cast Steels) — ASM International (1990)
- ASM Handbook Vol. 15 — Casting — ASM International (2008)
- ASTM A27/A148 (comparable cast carbon steel grades) — ASTM International (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.