Tabela De Dureza Aço

Hardness conversion charts are more useful than you think

Most people treating tabela de dureza aço as just a reference sheet end up getting burned. The chart is a starting point, not the whole job. I've spent years measuring steel hardness on the shop floor, and the real work happens in the gaps between the values on the page.

Why you can't trust a single scale

There are three main scales you'll actually use: Rockwell C (HRC) for hardened steels, Rockwell B (HRB) for softer conditions, and Brinell (HBW) for castings and forgings. Vickers (HV) shows up when you need precision or thin sections. The problem is each scale measures differently, and the relationship between them isn't linear. A conversion chart exists for a reason. I ran into this back in 2019 when we received a batch of 4140 bar stock that tested 28 HRC on the left edge and 34 HRC on the right edge of the same piece. The supplier's cert said 30 HRC average. That twenty percent variance across one meter of round stock would have destroyed a tooling insert we were hardening from it. We had to map every incoming piece across three points before approving it. The conversion tables didn't help with that, but knowing what numbers to expect for annealed versus normalized 4140 did.

The actual conversion table you need

Here's the approximate correlation most people are looking for. These values are rounded because nobody works to that precision anyway.

HBW	HV	HRC	HRB	MPa (approx Tensile)
120	125	—	68	400
150	157	—	85	500
180	188	—	96	600
200	210	—	103	670
225	236	4	111	750
250	262	9	119	830
275	288	14	127	915
300	314	18	134	1000
325	340	22	—	1080
350	367	25	—	1160
375	393	28	—	1240
400	420	31	—	1320
425	446	33	—	1400
450	472	36	—	1480
475	499	38	—	1560
500	525	40	—	1640
550	578	44	—	1800
600	630	47	—	1970
650	682	50	—	2140
700	734	53	—	2300

Those MPa column numbers are tensile strength estimates, not measurements. They work for steels in the quenched and tempered range. If your material is austempered or air-hardened, the correlation drifts by fifteen to twenty percent.

How to actually use this in practice

Start with the right test. Rockwell C is standard for anything over 20 HRC, which covers most heat-treated tool steels, case-hardened parts, and high-strength structural steels. Use Rockwell B if the material is under 20 HRC, because the C scale becomes unreliable below that threshold. Brinell is better for coarse-grained materials where a Rockwell indentation might sit partly on a graphite flake or inclusion and give a false reading. The common mistake is assuming one hardness number tells the whole story. Hardness correlates with strength, yes, but it doesn't tell you about toughness, fatigue life, or residual stress. A shaft at 55 HRC could be perfectly serviceable or one quench cycle away from cracking, depending on what the tempering curve looked like and how deep the case went. I learned that the hard way with a set of splined shafts in 2021. They tested 56 HRC everywhere we measured, but they fractured in the first run. The issue was carbide segregation at the spline roots, not the bulk hardness. A macroetch test would have caught it before shipment.

Surface preparation matters more than people admit

You need a flat surface within 0.003 inches of the indenter plane. That means grinding or milling the test area, not just wiping it clean. A machined surface finish around 63 microinches Ra is adequate. Anything rougher introduces variability that swamps the actual material response. I've seen technicians report readings that jumped five HRC points between two spots three millimeters apart, only to find the part had mill scale left from the rolling process. Test distance rules are also more important than most shops follow. Keep the indent at least two and a half times the diagonal length away from the edge, and at least that far from the previous indent. For HRC testing, that usually means 2mm minimum from the edge and 1.5mm between indents. Skip that and the support structure deforms instead of the material, and your reading goes up because the indentation can't develop properly. I once wasted half a day debugging a hardness problem only to realize the gauge operator was placing indents too close to a machined edge on a thin plate.

Calibration is non-negotiable

Master blocks wear out. A block rated at 45 HRC will drift lower with repeated use, especially if someone drops the indenter onto it hard. Check your machine weekly against a fresh calibration block. If your readings are consistently off by more than one point, the indenter or the load mechanism needs service. I've seen machines running six months without calibration on auto-hardening lines, and the parts shipped within spec until someone tried to weld them. Weld heat affected zones on improperly hardened steel will crack every time because the base metal wasn't where the drawing called for it.

When the table fails you

Conversion tables break down for unusual materials. Duplex stainless steels, maraging steels, and precipitation-hardening grades don't follow the standard correlations. Austenitic stainless steels like 304 and 316 are essentially unmeasurable on the Rockwell C scale because they're too soft for it and too work-hardening for Brinell to give consistent results. You need Vickers or a specialized Shore scleroscope for those. The table above is accurate for carbon and low-alloy steels in common heat treatment conditions. Everything else is a guess. Case-hardened parts present another problem. The surface might read 62 HRC while the core is 30 HRC. What hardness number goes on the inspection report? The drawing should specify, but when it doesn't, you need to measure at a defined depth below the case. Grinding a cross-section and testing at 0.5mm, 1.0mm, and 2.0mm below the surface tells you more than any surface reading ever will.

If you need a downloadable reference, search for the ASTM E140 standard. It's the official hardness conversion table for steel. The industry charts you find floating around are usually derived from it, but they vary enough between sources that going to the standard is worth the effort if you're doing formal inspection work.

Quick reference for common steels

1045 in the as-rolled condition sits around 130 HB, which converts to roughly 13 HRC. Normalize it and you might pick up ten points. Quench and temper at 400 degrees Celsius and you're looking at 30 to 35 HRC. Machine it at 28 HRC and you'll regret it on any carbide tool. That's the practical takeaway from the whole table. 4140 annealed is 170 to 200 HB. Hardened and tempered at 425 degrees Celsius, 38 to 42 HRC. That's the sweet spot for most general-purpose shafts and gears. Go higher than 45 HRC on 4140 without checking fracture toughness and you're gambling.

O1 tool steel comes annealed at about 200 HB and can go to 62 to 65 HRC after proper heat treatment. H13 dies steel typically runs 45 to 50 HRC in the service condition. If someone sends you H13 at 55 HRC as a "standard" delivery, ask about their tempering cycle. That number suggests either under-tempering or a misread, both of which will cause early failures in a die. 17-4 PH stainless in the H900 condition is 38 to 43 HRC. In the solution annealed condition it's under 25 HRC and essentially unmeasurable on Rockwell C. Again, the table doesn't help here because the alloy system is different. Use Vickers or switch to a B scale if the hardness drops low enough.

Reading accuracy limits

A properly calibrated Rockwell C tester has a repeatability of about plus or minus one point under ideal conditions. In a production environment with temperature swings, operator variation, and parts that aren't perfectly flat, expect two to three points of scatter. That means a reported 40 HRC is really somewhere between 37 and 43. If your application requires tighter tolerance, specify Vickers testing with a defined load and dwelling time, and require multiple indents averaged together. The conversion tables themselves carry their own error bands. The gap between HBW 300 and HRC 18 is an approximation based on regression data from hundreds of tests on specific steel grades. Your material might deviate by five percent or more. Use the table for screening and comparison, not for absolute verification on critical dimensions.

That's the honest version of how tabela de dureza aço actually works in a real environment. It's a tool for communication between suppliers and buyers, a quick check during heat treatment, and a starting point for troubleshooting. It's not a substitute for understanding what the number means about the material's actual behavior under load.