AASHTO/AWS D1.5:2025 · Table 12.8 · Fracture-Critical

HPS690W Preheat — 1.6≤HI<2.0 kJ/mm, 20<t≤25 mm: 120–200°C

Q: What is the preheat range for HPS690W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in with 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in?

D1.5 Table 12.8 requires a preheat range of 250–400°F (120–200°C) for HPS690W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in with 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in heat input. Both minimum AND maximum must be controlled.

Q: Why does HPS690W have a maximum preheat limit?

HPS690W achieves its 690 MPa (100 ksi) strength through quenching and tempering. Excessive preheat can soften the tempered microstructure in the heat-affected zone, reducing the steel's strength below the design minimum. The maximum limit of 400°F (200°C) protects this Q&T condition.

Q: What temperature applies to M270M HPS690W / M270 HPS100W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in?

Table 12.8 requires the preheat/interpass range 250–400°F (120–200°C) for this combination. Control both limits throughout welding.

Fracture-critical preheat requirement for M270M HPS690W / M270 HPS100W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in thickness, per AASHTO/AWS D1.5:2025, the Bridge Welding Code.

Built on AWS D1.5:2025 — every value traced to the clause.

Fracture-Critical Preheat Range

250–400°F / 120–200°C

Table 12.8 — 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in heat input at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in thickness

AASHTO/AWS D1.5M/D1.5:2025 Table 12.8

Both minimum AND maximum preheat/interpass must be maintained. Exceeding 400°F risks degrading the Q&T microstructure.

Reference tool. Verify against project-applicable edition and Engineer-approved WPS.

AASHTO M270 High-Performance Grades

M270M HPS690W / M270 HPS100W

AASHTO M270M HPS690W (M270 HPS100W) is the highest-strength bridge steel grade, reserved for demanding long-span and cable-stayed bridge applications. It follows a completely different FC preheat table (Table 12.8) with min-max ranges and many prohibited thickness-heat input combinations marked with “—”. Table 12.8 requires H4 or H8 designated consumables; H16 is not permitted.

Bridge Applications

Where M270M HPS690W / M270 HPS100W Is Used

Reserved for the most demanding long-span and cable-stayed bridge applications where maximum weight reduction justifies the material cost premium and fabrication complexity. Table 12.8 imposes both minimum AND maximum preheat limits, and many thickness-heat input combinations are outright prohibited. Fabricators must plan weld procedures around the permitted combinations before cutting plate. Filler metals must carry the H4 or H8 supplemental designator — H16 is not permitted for HPS690W FC applications.

Thickness: 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in

Why Preheat Matters at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in

The selected thickness interval is 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in. Use its own fracture-critical table row; non-fracture-critical thickness bands do not select this result. Table 12.8 requires the preheat/interpass range 250–400°F (120–200°C) for this combination. Control both limits throughout welding.

Fabrication Detail

M270M HPS690W / M270 HPS100W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in

At 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in, HPS690W (HPS100W) appears in cable-stayed bridge edge girder flanges and heavily loaded truss members. The preheat range requirement (both min and max) becomes more restrictive — the permitted window depends on the selected thickness and heat input, so use the specific range printed for this combination. Fabricators must plan weld sequences to maintain temperature within the narrow permitted band throughout multi-pass welds.

Preheat Range Required

Min–Max Preheat Control for M270M HPS690W / M270 HPS100W

D1.5 Table 12.8 requires a preheat range of 250–400°F (120–200°C) for HPS690W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in with 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in heat input. Both minimum AND maximum must be controlled.

Interactive Calculator

Try Different Combinations

Use the D1.5 Bridge Preheat Calculator to look up any AASHTO M270 steel, hydrogen level, and heat input combination. Also see the D1.1 Preheat Calculator for structural steel.

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FAQ

What is the preheat range for HPS690W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in with 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in?

D1.5 Table 12.8 requires a preheat range of 250–400°F (120–200°C) for HPS690W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in with 1.6 ≤ HI < 2.0 kJ/mm; 40 ≤ HI < 50 kJ/in heat input. Both minimum AND maximum must be controlled.

Why does HPS690W have a maximum preheat limit?

HPS690W achieves its 690 MPa (100 ksi) strength through quenching and tempering. Excessive preheat can soften the tempered microstructure in the heat-affected zone, reducing the steel's strength below the design minimum. The maximum limit of 400°F (200°C) protects this Q&T condition.

What temperature applies to M270M HPS690W / M270 HPS100W at 20 < t ≤ 25 mm; 3/4 < t ≤ 1 in?

Table 12.8 requires the preheat/interpass range 250–400°F (120–200°C) for this combination. Control both limits throughout welding.

D1.5:2025 reference data. Not affiliated with AWS or AASHTO.