{
    "slug": "heat-treatment-conditions",
    "title": "Heat Treatment and Temper Conditions for CNC Alloys",
    "description": "Temper conditions for CNC alloys: steel quench-and-temper hardness by temperature, 6061-O to T651, 7075-T73 and 17-4PH H900 to H1150 with NACE limits.",
    "lang": "en",
    "tables": [
        {
            "caption": "Carbon and alloy steel — heat-treatment processes and typical hardness",
            "columns": [
                "Process",
                "What it does",
                "Typical hardness",
                "Typical application",
                "Governing standard"
            ],
            "rows": [
                {
                    "Process": "Annealing",
                    "What it does": "Heat above or near the critical temperature, then cool very slowly in the furnace to soften and relieve stress",
                    "Typical hardness": "160–217 HB (grade-dependent)",
                    "Typical application": "Machining stock, cold forming, stress relief before re-hardening",
                    "Governing standard": "GB/T 16923; ASTM A29; SAE J412"
                },
                {
                    "Process": "Normalizing",
                    "What it does": "Heat 30–50 °C above Ac3/Acm, then cool in still air to refine grain and homogenize the structure",
                    "Typical hardness": "187–300 HB (grade-dependent)",
                    "Typical application": "Large forgings, structural parts where quenching risks distortion",
                    "Governing standard": "GB/T 16923; ASTM A29"
                },
                {
                    "Process": "Quenching + tempering",
                    "What it does": "Austenitize, quench to martensite in water or oil, then reheat below Ac1 to relieve stress and tune hardness",
                    "Typical hardness": "24–57 HRC (depends on tempering temperature)",
                    "Typical application": "Finished engineering parts: shafts, gears, fasteners",
                    "Governing standard": "GB/T 16924; ASTM A29"
                },
                {
                    "Process": "Quench and high temper (Q&T)",
                    "What it does": "Quench followed by high-temperature tempering at 500–650 °C, producing tempered sorbite with the best strength-toughness balance",
                    "Typical hardness": "28–34 HRC (common supply band)",
                    "Typical application": "Connecting rods, bolts, gears, shafts under alternating load",
                    "Governing standard": "GB/T 16924; GB/T 7232"
                }
            ]
        },
        {
            "caption": "What Hardness Should I Expect from Annealed Versus Normalized 1045 Steel?",
            "columns": [
                "Condition",
                "Tensile (MPa)",
                "Yield (MPa)",
                "Elongation (%)",
                "Hardness",
                "Source"
            ],
            "rows": [
                {
                    "Condition": "Hot-rolled / annealed",
                    "Tensile (MPa)": "565 (typical hot-rolled)",
                    "Yield (MPa)": "310",
                    "Elongation (%)": "16",
                    "Hardness": "163 HB; annealed band 160–200 HB",
                    "Source": "S21 / S22 / S5"
                },
                {
                    "Condition": "Normalized",
                    "Tensile (MPa)": "640",
                    "Yield (MPa)": "410",
                    "Elongation (%)": "22",
                    "Hardness": "187 HB",
                    "Source": "S6 / S5"
                },
                {
                    "Condition": "Quenched and tempered",
                    "Tensile (MPa)": "—",
                    "Yield (MPa)": "—",
                    "Elongation (%)": "—",
                    "Hardness": "220–290 HB",
                    "Source": "S5"
                },
                {
                    "Condition": "As-quenched (water, surface)",
                    "Tensile (MPa)": "—",
                    "Yield (MPa)": "—",
                    "Elongation (%)": "—",
                    "Hardness": "55–60 HRC",
                    "Source": "S5"
                },
                {
                    "Condition": "Flame / induction hardened (surface)",
                    "Tensile (MPa)": "—",
                    "Yield (MPa)": "—",
                    "Elongation (%)": "—",
                    "Hardness": "55–58 HRC, case depth 1.5–5 mm",
                    "Source": "S5"
                }
            ]
        },
        {
            "caption": "What Hardness Is 4140 Supplied at in the Pre-Hardened Condition?",
            "columns": [
                "Condition / tempering temperature",
                "Tensile (MPa)",
                "Yield (MPa)",
                "Elongation (%)",
                "Hardness",
                "Source"
            ],
            "rows": [
                {
                    "Condition / tempering temperature": "Annealed",
                    "Tensile (MPa)": "~655",
                    "Yield (MPa)": "~415",
                    "Elongation (%)": "25",
                    "Hardness": "197–217 HB",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Normalized",
                    "Tensile (MPa)": "~1,020",
                    "Yield (MPa)": "~650",
                    "Elongation (%)": "17",
                    "Hardness": "250–300 HB",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "As-quenched (oil)",
                    "Tensile (MPa)": "—",
                    "Yield (MPa)": "—",
                    "Elongation (%)": "—",
                    "Hardness": "55–60 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Q&T at 205 °C",
                    "Tensile (MPa)": "~2,000",
                    "Yield (MPa)": "~1,600",
                    "Elongation (%)": "8",
                    "Hardness": "52–57 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Q&T at 315 °C",
                    "Tensile (MPa)": "~1,700",
                    "Yield (MPa)": "~1,450",
                    "Elongation (%)": "10",
                    "Hardness": "45–50 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Q&T at 425 °C",
                    "Tensile (MPa)": "~1,400",
                    "Yield (MPa)": "~1,250",
                    "Elongation (%)": "12",
                    "Hardness": "38–42 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Q&T at 540 °C (standard HT)",
                    "Tensile (MPa)": "1,000–1,100",
                    "Yield (MPa)": "850–950",
                    "Elongation (%)": "18",
                    "Hardness": "28–32 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Q&T at 650 °C (high ductility)",
                    "Tensile (MPa)": "~850",
                    "Yield (MPa)": "~700",
                    "Elongation (%)": "22",
                    "Hardness": "24–28 HRC",
                    "Source": "S4"
                },
                {
                    "Condition / tempering temperature": "Pre-hardened as-supplied",
                    "Tensile (MPa)": "—",
                    "Yield (MPa)": "—",
                    "Elongation (%)": "—",
                    "Hardness": "28–34 HRC",
                    "Source": "S4"
                }
            ]
        },
        {
            "caption": "How Hard Is Steel Immediately After Quenching, Before Tempering?",
            "columns": [
                "Steel",
                "Quench medium",
                "As-quenched (HRC)",
                "Tempered service hardness",
                "Note"
            ],
            "rows": [
                {
                    "Steel": "1045",
                    "Quench medium": "Water",
                    "As-quenched (HRC)": "55–60",
                    "Tempered service hardness": "220–290 HB (Q&T)",
                    "Note": "Shallow-hardening carbon steel; the core softens in large sections"
                },
                {
                    "Steel": "4140",
                    "Quench medium": "Oil",
                    "As-quenched (HRC)": "55–60",
                    "Tempered service hardness": "28–32 HRC (tempered at 540 °C)",
                    "Note": "Cr-Mo alloy with deep hardening; pick it for bigger sections"
                }
            ]
        },
        {
            "caption": "What Does Quenching and Tempering Mean and Why Is It Specified?",
            "columns": [
                "Steel",
                "Q&T supply band",
                "After quench only",
                "Why temper"
            ],
            "rows": [
                {
                    "Steel": "1045",
                    "Q&T supply band": "220–290 HB",
                    "After quench only": "55–60 HRC (water)",
                    "Why temper": "Untempered martensite cracks in service; tempering buys toughness back at a controlled hardness cost"
                },
                {
                    "Steel": "4140",
                    "Q&T supply band": "28–34 HRC pre-hard",
                    "After quench only": "55–60 HRC (oil)",
                    "Why temper": "High tempering at 500–650 °C forms tempered sorbite — the condition shafts and gears are specified in"
                }
            ]
        },
        {
            "caption": "How Much Stronger Is 6061-T6 Compared with 6061-O?",
            "columns": [
                "Alloy and temper",
                "Tensile, MPa (ksi)",
                "Yield, MPa (ksi)",
                "Elongation (%)",
                "Hardness (HB)",
                "Source"
            ],
            "rows": [
                {
                    "Alloy and temper": "6061-O",
                    "Tensile, MPa (ksi)": "125 (18)",
                    "Yield, MPa (ksi)": "55 (8)",
                    "Elongation (%)": "25–27",
                    "Hardness (HB)": "30",
                    "Source": "S7 / S8"
                },
                {
                    "Alloy and temper": "6061-T4 / T451",
                    "Tensile, MPa (ksi)": "240 (35)",
                    "Yield, MPa (ksi)": "145 (21)",
                    "Elongation (%)": "22",
                    "Hardness (HB)": "65",
                    "Source": "S7 / S8"
                },
                {
                    "Alloy and temper": "6061-T6 / T651",
                    "Tensile, MPa (ksi)": "310 (45)",
                    "Yield, MPa (ksi)": "276 (40)",
                    "Elongation (%)": "12–15",
                    "Hardness (HB)": "95",
                    "Source": "S7 / S8"
                }
            ]
        },
        {
            "caption": "Is 6061-T651 Stronger Than 6061-T6?",
            "columns": [
                "Temper",
                "Process",
                "Mechanical difference",
                "Governing standard",
                "Source"
            ],
            "rows": [
                {
                    "Temper": "O",
                    "Process": "Fully annealed — heated and slowly cooled to the softest state",
                    "Mechanical difference": "Lowest strength, highest formability",
                    "Governing standard": "ISO 2107; ASTM B209/B221",
                    "Source": "S14 / S19 / S7"
                },
                {
                    "Temper": "T4",
                    "Process": "Solution heat-treated, then naturally aged at room temperature",
                    "Mechanical difference": "Moderate strength, still formable",
                    "Governing standard": "ISO 2107; ASTM B209/B221",
                    "Source": "S14 / S15 / S7"
                },
                {
                    "Temper": "T6",
                    "Process": "Solution heat-treated, then artificially aged to peak strength",
                    "Mechanical difference": "Highest strength for the alloy",
                    "Governing standard": "ISO 2107; ASTM B209/B221",
                    "Source": "S14 / S15 / S7"
                },
                {
                    "Temper": "T651",
                    "Process": "T6 plus 1–3% stretching for stress relief before aging",
                    "Mechanical difference": "Strength equal to T6; better dimensional stability in machining",
                    "Governing standard": "ISO 2107; ASTM B209/B221",
                    "Source": "S14 / S7 / S24"
                },
                {
                    "Temper": "T73",
                    "Process": "Solution heat-treated, then overaged in a two-step aging treatment",
                    "Mechanical difference": "Lower strength than T6; much better stress-corrosion resistance; mainly 7xxx series",
                    "Governing standard": "AMS 4078; ASTM B209; GB/T 3880",
                    "Source": "S9 / S2"
                }
            ]
        },
        {
            "caption": "What Is the T73 Temper and When Should I Choose It?",
            "columns": [
                "Applicable basis",
                "Tensile (MPa)",
                "Yield (MPa)",
                "Elongation (%)",
                "Hardness",
                "Source"
            ],
            "rows": [
                {
                    "Applicable basis": "7075-T73 — ASM Handbook typical (bar / forging reference)",
                    "Tensile (MPa)": "505",
                    "Yield (MPa)": "435",
                    "Elongation (%)": "13",
                    "Hardness": "—",
                    "Source": "S1 / S2"
                },
                {
                    "Applicable basis": "7075-T73 — ASTM B209 / AMS 4078 plate, by thickness (spec)",
                    "Tensile (MPa)": "460–475",
                    "Yield (MPa)": "385–390",
                    "Elongation (%)": "5–8",
                    "Hardness": "126–140 HB",
                    "Source": "S9"
                },
                {
                    "Applicable basis": "7075-T6 — typical, for comparison",
                    "Tensile (MPa)": "572 (83 ksi)",
                    "Yield (MPa)": "503 (73 ksi)",
                    "Elongation (%)": "—",
                    "Hardness": "—",
                    "Source": "S7"
                }
            ]
        },
        {
            "caption": "What Is the Strongest Standard Aging Condition for 17-4PH?",
            "columns": [
                "Condition",
                "Aging temperature / time",
                "Tensile min, MPa (ksi)",
                "Yield min, MPa (ksi)",
                "Elongation min (%)",
                "Hardness",
                "Charpy V-notch (ft-lb)",
                "Source"
            ],
            "rows": [
                {
                    "Condition": "H900",
                    "Aging temperature / time": "482 °C (900 °F) / 1 h",
                    "Tensile min, MPa (ksi)": "1,310 (190)",
                    "Yield min, MPa (ksi)": "1,170 (170)",
                    "Elongation min (%)": "10",
                    "Hardness": "≥40 HRC (typical 44)",
                    "Charpy V-notch (ft-lb)": "10–15 (low)",
                    "Source": "S3 / S23"
                },
                {
                    "Condition": "H1025",
                    "Aging temperature / time": "552 °C (1,025 °F) / 4 h",
                    "Tensile min, MPa (ksi)": "1,070 (155)",
                    "Yield min, MPa (ksi)": "1,000 (145)",
                    "Elongation min (%)": "12",
                    "Hardness": "≥35 HRC (typical 38)",
                    "Charpy V-notch (ft-lb)": "35–45 (moderate)",
                    "Source": "S3 / S23"
                },
                {
                    "Condition": "H1150",
                    "Aging temperature / time": "621 °C (1,150 °F) / 4 h",
                    "Tensile min, MPa (ksi)": "930 (135)",
                    "Yield min, MPa (ksi)": "725 (105)",
                    "Elongation min (%)": "16",
                    "Hardness": "28–33 HRC (typical 33)",
                    "Charpy V-notch (ft-lb)": "60–80 (high)",
                    "Source": "S3 / S23"
                }
            ]
        },
        {
            "caption": "Which 17-4PH Condition Offers the Highest Toughness?",
            "columns": [
                "Condition",
                "Charpy V-notch (ft-lb)",
                "Elongation (%)",
                "Hardness",
                "Best for"
            ],
            "rows": [
                {
                    "Condition": "H900",
                    "Charpy V-notch (ft-lb)": "10–15 (low)",
                    "Elongation (%)": "10",
                    "Hardness": "≥40 HRC",
                    "Best for": "Highest-strength parts with no impact or cryogenic exposure"
                },
                {
                    "Condition": "H1025",
                    "Charpy V-notch (ft-lb)": "35–45 (moderate)",
                    "Elongation (%)": "12",
                    "Hardness": "≥35 HRC",
                    "Best for": "The general-purpose balance condition"
                },
                {
                    "Condition": "H1150",
                    "Charpy V-notch (ft-lb)": "60–80 (high)",
                    "Elongation (%)": "16",
                    "Hardness": "28–33 HRC",
                    "Best for": "Impact- and cryogenic-facing parts; also the NACE-compliant choice"
                }
            ]
        },
        {
            "caption": "Can 17-4PH Be Used in NACE Sour-Gas Service?",
            "columns": [
                "Condition",
                "Spec hardness",
                "NACE MR0175 status",
                "Note"
            ],
            "rows": [
                {
                    "Condition": "H900",
                    "Spec hardness": "≥40 HRC (typical 44)",
                    "NACE MR0175 status": "Not qualified",
                    "Note": "Exceeds the 33 HRC sour-service cap by a wide margin"
                },
                {
                    "Condition": "H1025",
                    "Spec hardness": "≥35 HRC (typical 38)",
                    "NACE MR0175 status": "Conditional",
                    "Note": "Only with per-heat verification that actual hardness stays at or below 33 HRC"
                },
                {
                    "Condition": "H1150",
                    "Spec hardness": "28–33 HRC (typical 33)",
                    "NACE MR0175 status": "Compliant",
                    "Note": "The standard pick for sour service"
                }
            ]
        }
    ]
}