20MnCr5: Steel Technical Specifications

0120MnCr5 Steel: Introduction and General Characteristics

20MnCr5 steel (material number 1.7147) is a manganese-chromium case-hardening alloy steel defined by EN ISO 683-3:2022 (formerly EN 10084). It is supplied and machined in the annealed condition, receives carbon at the surface through carburising and, after hardening and tempering, carries a hard case over a core that stays tough: it is the combination a gear tooth needs, hard where it rubs and tough where it flexes.

What the standard guarantees on this steel is a closed list, and it is worth saying so at the outset because it explains the shape of this page: the requirements that can be demanded on delivery are three - chemical composition, hardness in the delivery condition and hardenability. Everything else, starting with the hardness of the carburised case, is the result of the treatment cycle agreed on the part. Where the standard is silent, we say so below rather than put in a number taken from somewhere else.

1.120MnCr5 vs Conventional Case-Hardening Steels: Differences

Compared with an unalloyed case-hardening steel, 20MnCr5 moves the problem from the case alone to the core beneath the case: manganese 1.10-1.40% and chromium 1.00-1.30% give it a hardenability that the standard measures and guarantees with the Jominy test, whereas a plain carbon steel leaves it to the section of the part. Manganese gives the family its name, and in the designation 16MnCr5 carries the same MnCr5: what changes in the name is the carbon figure alone. In the composition table, however, the two grades part company on three elements, and the larger step is not carbon but chromium: 1.00-1.30% against 0.80-1.10%, with manganese rising from 1.00-1.30 to 1.10-1.40%.

One operating difference that can only be read in the standard concerns cold cutting: 20MnCr5 is cold-shearable in the +S condition, not in the untreated condition, whereas 16MnCr5 is among the grades that the same standard gives as shearable while still untreated. Anyone cutting on a shear in the workshop cannot take the two grades as interchangeable on this point.

1.220MnCr5 Advantages for Industrial Applications

The first advantage is machinability before treatment: in the annealed +A condition the standard sets a maximum hardness of 217 HBW, and that is the figure that really describes the bar arriving in the workshop, because it applies to every execution and does not depend on the diameter. Turning, gear cutting and finishing to size are all done at that hardness, and only then is the part carburised.

The second is the predictability of the core. The +H hardenability band is a contractual requirement, not an indicative value: it can be called up in a specification and it can be disputed. The third is one of scope: a single grade standard covers bars and forgings, so 20MnCr5 stays the same steel from the small-diameter rolled round to the large-section forging, with the same demandable requirements.

1.320MnCr5 Standards and Certifications

The reference standard for 20MnCr5 is EN ISO 683-3:2022 (formerly EN 10084), case-hardening steels - technical delivery conditions. The EN 10084 in brackets is the previous edition, now superseded: it is still met on drawings and orders, but the grade, the material number and the demandable values are those of the standard in force. Its scope covers bars and forgings and sets no dimensional limit: dimensions and tolerances are referred to the dimensional standards or to agreement at the time of order.

DIN 17210 is the historical German standard of this family: it was superseded by EN 10084 and today the reference is EN ISO 683-3:2022. 20MnCr5 has kept its name and its material number, 1.7147, through every one of those steps, which is why a decades-old drawing and an order placed today name the same steel.

Every supply is accompanied by EN 10204 inspection documents: a type 2.1 declaration of compliance with the order as standard and, on request, a type 3.1 inspection certificate with the chemical analysis of the cast and traceability.

02Chemical Composition of 20MnCr5 Steel: Alloying Elements and Standard Specifications

The chemical composition of 20MnCr5 is set by EN ISO 683-3:2022 on the cast analysis. Carbon at 0.17-0.22% is low by design: it is the content that keeps the core tough and that carburising raises at the surface. Manganese at 1.10-1.40% and chromium at 1.00-1.30% are the characterising alloying elements and carry the hardenability; silicon is a process deoxidiser, while phosphorus and sulphur are residual elements with a ceiling. Copper has had a limit of its own since the 2022 edition.

Two cells of that table need reading with care, because they changed with the edition in force. Silicon has no minimum: the lower limit has been deleted, so the data sheets that print 0.15-0.40% are reading an earlier edition. Copper, the other way round, is new: the sheets that do not carry 0.40% max are not omitting a requirement, they are reading a table that did not have that column. To be kept apart from those two cells is an order option, which the table does not contain: 20MnCr5 can be ordered with a minimum silicon content of 0.15%, to be agreed. The reason is machinability, which a low silicon content worsens; on internal oxidation during carburising a low silicon content works the other way round, reducing it.

The standard prescribes neither molybdenum nor nickel for this steel: the hardenability of 20MnCr5 comes from manganese and chromium. It is a design choice of the family, not a gap in the table, and it explains why, set against the nickel-chromium-molybdenum grades, the difference shows on large sections and not on the tooth.

The third column of the table carries the permissible deviations of the product analysis, which are not a second specification but the tolerance within which the finished product is verified. They have to be read with the rule the standard attaches to them: the deviation may occur above the upper limit or below the lower limit, not on both in the same cast. The product analysis is carried out only if requested at the time of order, one per cast.

By agreement at the time of order the standard admits improved-machinability variants, with higher sulphur or with lead; in that case the upper limit of manganese may rise by 0.15%. These are options to be agreed, not the current delivery condition.

2.120MnCr5 International Equivalents

The international equivalents of 20MnCr5 are few, and for a reason worth knowing before looking for them in a commercial table: this steel has a European designation and a material number, and outside Europe it has almost no counterpart. The material number is 1.7147, the Italian and German designation is 20MnCr5 - the grade never had a national name of its own in Italy - and the French AFNOR designation is 20MC5.

20MnCr5 has no AISI/SAE, British or Japanese equivalent. BS 970-3 contains no manganese-chromium case-hardening steel; and the Japanese grades in this carbon range, including those of the manganese-chromium class, carry chromium contents roughly halved, so the hardenability is not the same and the comparison does not hold. The same goes for the AISI 5120 of the commercial tables: manganese and chromium are about a third lower there, and the hardenability with them.

In the Chinese GB/T 5216 system the corresponding grade is 20CrMnH, which EN ISO 683-3 declares identical to 20MnCr5. The word identical is the standard’s, and the standard adds no qualification to it.

Alongside the base grade there is the sulphur variant. 20MnCrS5 (1.7149) is the same steel with the sulphur specified as a range, 0.020-0.040%, that is with a guaranteed minimum and not only a maximum, to improve machinability: the other elements, the hardenability bands, the delivery hardnesses and the treatment temperatures are identical to those of 20MnCr5. Sulphur forms sulphides that break the chip: machinability is gained and transverse toughness is given up. The standard quantifies neither the gain nor the loss.

03Mechanical Characteristics of 20MnCr5 Steel: Properties and Structural Performance

The mechanical characteristics of 20MnCr5 have to be approached by saying first what the standard prescribes, because on a case-hardening steel the answer comes as a surprise: nothing. The demandable requirements are composition, hardness in the delivery condition and hardenability; mechanical properties appear at a single point of the document, Annex C, which is declared informative.

The reference standard prescribes neither elongation, nor reduction of area, nor impact energy: the only mechanical datum it contains is the minimum tensile strength of Annex C, declared informative. The values that circulate across four different and mutually incompatible sets come from a withdrawn Italian standard or from producers' data sheets, and we do not publish them. The same holds for yield: the standard prescribes no yield strength for this steel.

3.120MnCr5 Hardness in the Delivery Conditions

The hardness of 20MnCr5 in the delivery condition is the requirement that describes the bar being bought, and it is the only hardness figure the standard guarantees on the product as delivered. It is measured in Brinell HBW and - a point worth underlining - it does not depend on the diameter: the table in the standard has no dimensional bands, so a 25 mm round and a 400 mm forging answer to the same limit. The other hardness the standard guarantees is that of the Jominy band, but it holds on the hardenability test piece and not on the product: the two do not overlap.

Two practical warnings on this table. The first: neither the normalised condition nor the shearable condition +S is provided for on forgings, the latter being reserved by the standard to semi-finished products and bars; they are the two conditions that the large forged diameter loses. The second concerns disputes, which almost always arise over the point of measurement: on round bars the hardness is taken at a distance from the end equal to the diameter.

For peeled bar the requirements of the grade standard apply: the hardness of the annealed condition is the same, 217 HBW max. The higher hardnesses that can be read for cold-drawn bar belong to a product-form standard that we do not cite here.

3.2Core Tensile Strength: The Informative Classification of the Standard

The only mechanical datum of the standard document is a classification by minimum tensile strength as a function of the diameter, referred to the condition after quenching and tempering at 200 °C - not the delivery condition and not the carburised condition. It is guidance on the core, not a requirement that can be demanded on delivery. The values are expressed in MPa; the PDF datasheet prints the same quantity in N/mm², which is the same unit.

Above 100 mm the standard does not classify: no value at all, not even an informative one. This bears directly on the large-diameter forged round, which sits outside that table, and the correct way to handle it is not to extrapolate the bottom row: it is to size on the core that the treatment cycle actually produces on that section. The distinction between two things also has to be held firm: the scope of the standard has no dimensional limit, and it is only this informative table that stops at 100 mm.

3.3Surface Hardness After Carburising

The steel standard fixes neither the hardness of the carburised case nor the effective case depth, and it is not an oversight: neither of them is among the three demandable requirements listed at the top of this page. The case is the result of the carburising cycle agreed on the part: surface hardness and effective case depth (CHD) are defined in the heat-treatment specification, not in the steel standard.

The surface hardness obtained depends on the carbon content reached in the case and on the hardening and tempering cycle, and it is agreed in the specification of the part: the steel standard does not prescribe it and we do not publish a figure that no standard guarantees. What can be said without inventing numbers is the mechanism: the carbon-enriched layer transforms to martensite and stays in compression, and it is precisely the residual compressive stresses that make a carburised tooth perform well in fatigue.

3.4Jominy Hardenability: The +H, +HH and +HL Bands

The hardenability of 20MnCr5 is the demandable requirement that describes the core, and it is expressed as a hardness band on the Jominy test: a test piece is quenched from one end and the hardness is measured at increasing distances from the quenched end. The +H band is the requirement that applies unless otherwise agreed; the restricted +HH and +HL bands are agreed at the time of order.

The test piece is austenitised at 900 ±5 °C for at least 30 minutes, and it is the only temperature of the whole treatment table that is not for guidance, because it is the parameter of the test and not a recommendation on the cycle. The data sheets that give 870 °C are not wrong: they are reading the previous edition of the standard. The Jominy test is carried out to ISO 642, which defines the apparatus: the steel standard fixes the austenitising temperature alone.

A recurring question is whether the certificate carries the curve. Often it does not, and it is the standard itself that allows this: for alloy steels the manufacturer may verify hardenability by calculation; the Jominy test to ISO 642 is carried out if the calculation is not available or in the event of a dispute.

04Physical Characteristics of 20MnCr5 Steel: Density and Elastic Constants

The physical characteristics of this steel are those of the ferrous matrix and do not depend on the treatment, but they have to be published for what they are: five of them are settled design values and the table publishes them with the standard they come from; the other three are database figures on which published manufacturer data do not agree, and they stay out of the table. For weight calculation the conventional value for steels is used, 7.85 kg/dm³: it is the same one our bar weight calculator adopts, so the weight the site estimates and the weight that ends up on the quotation come from the same number.

The modulus of elasticity at room temperature is 210 GPa and the shear modulus 81 GPa, consistent with a Poisson's ratio of 0.30: these are the design values we use across the whole datasheet series, and they are the ones to put into a calculation of elastic deflection or of torsional stiffness.

The coefficient of thermal expansion comes from the same clause of EN 1993-1-1 as the elastic moduli, and the table publishes it: 12 × 10⁻⁶/K, valid for temperatures up to 100 °C. On thermal conductivity, specific heat and electrical resistivity the available data sheets diverge substantially, in one case by a factor of two: they are database values, not requirements of a standard, and we do not publish them. If they are needed for a thermal calculation they should be asked of the producer of the cast, not read off a catalogue table.

05Heat Treatments of 20MnCr5 Steel: Carburising, Hardening and Optimal Parameters

The heat treatments of 20MnCr5 are the reason this steel exists: carburising, hardening and tempering build the gradient between a hard case and a tough core. Before the numbers, though, the label the standard puts on itself has to be reported, because it changes how they are used: the carburising, hardening and tempering temperatures are given by the standard for guidance; the actual ones are those that give the required properties.

5.120MnCr5 Carburising: Temperatures and Process Variants

The carburising of 20MnCr5 falls in the 880-980 °C range. It is a wide range, and the width is itself informative: the actual temperature is chosen on the part, between the control of distortion and the rate of carbon diffusion. The narrower ranges that circulate are the practice of individual producers, not prescriptions of the standard.

Two variants have a row of their own. If quenching is carried out directly from the carburising temperature, that temperature normally does not exceed 950 °C. With special processes, for example vacuum carburising, temperatures of 1,020-1,050 °C are not unusual, and the standard explicitly provides for it.

5.220MnCr5 Hardening: Core, Case and Quenching Medium

After carburising, hardening can follow two routes. In direct or single hardening the part is austenitised at 820-860 °C; in double hardening a core hardening at 860-900 °C is carried out first and then a case hardening at 780-820 °C, which refines the martensite of the carbon-enriched zone. It is the standard itself that warns that, in direct hardening, where there is a risk of distortion the parts should be quenched from a temperature intermediate between the core-hardening one and the case-hardening one.

The standard does not prescribe the quenching medium: it depends on the shape of the product, on the cooling conditions and on the furnace charge. That is why we do not list “oil hardening” as though it were a characteristic of the steel: it is a choice of cycle, agreed with the heat treater.

5.3Tempering and Stress Relieving After Carburising

Tempering is carried out at 150-200 °C for at least one hour. It is a stress relief, not a quench and temper: it serves to remove stresses and to stabilise the martensite of the case, not to lower the strength the way the high tempering of a quenched and tempered steel would. For this steel the standard publishes no tempering curve.

5.4Annealing, Normalising and Cycles the Standard Does Not Prescribe

The standard provides for the annealed condition and fixes its maximum hardness, 217 HBW, but does not prescribe the cycle by which it is reached. The annealing temperatures that circulate for this steel have no basis in the standard: we do not publish them. The same goes for normalising: the +N condition exists, with a hardness of 140-201 HBW, but the standard does not fix its temperature. And the standard prescribes no hot-working range.

For the cycles the standard does not prescribe - isothermal annealing, treatment to a ferrite-pearlite structure, spheroidise annealing, carbonitriding, welding preheat - the parameters are agreed with the heat treater on the part, they are not read off a steel table.

The critical points AC1 and AC3 and the martensite start temperature Ms are not published by the standard. The figures that circulate come from databases and from producers' data sheets that do not agree with each other: we prefer to report none of them.

5.5Effective Case Depth: What the Standard Fixes and What It Does Not

The effective case depth is the first thing a designer looks for on a case-hardening steel, and it is the first thing they will not find in the steel standard: neither the CHD nor the hardness of the case is a requirement of that document. They are defined in the heat-treatment specification of the component, together with the method by which they are measured, and they are verified on the treated part. What the choice of 20MnCr5 determines is not the depth of the case, which depends on the cycle, but the hardenability of the core beneath the case: and that the standard does fix, with the Jominy band.

Two neighbouring requirements have to be told apart, because the standard treats them differently. Fine grain is not an option: it is a base requirement, which applies unless otherwise agreed; what is agreed at the time of order is, if anything, its verification. And on large-diameter forgings the soundness of the core is not automatic: the standard governs it with a minimum reduction ratio, agreed at the time of order.

06Industrial Applications of 20MnCr5 Steel: Sectors and Strategic Uses

The applications of 20MnCr5 nearly all sit inside a single mechanical problem: a surface that rubs or meshes over a core that has to take bending and impact. It is the case-hardening steel in routine use for gears and for transmission components of small and medium section, and it remains the reference choice for as long as the section does not force a move to a nickel-chromium-molybdenum grade.

6.1Gears and Transmission Components

Gears and pinions are the main use: the teeth are cut in the annealed condition, the part is carburised and hardened, and the finished tooth has a hard surface over a tough core. Alongside gears, the same logic applies to splined shafts and camshafts, pins, bushings, planet gears and components of reduction units and gearboxes, where contact fatigue is the failure mode that governs the sizing.

6.2Agricultural Machinery, Earth-Moving and Machine Tools

Outside pure transmission work, 20MnCr5 is found in components for agricultural and earth-moving machinery, in machine tools and in automotive applications: shafts, pins, bushings, fastener parts with high wear resistance. These are uses in which the repeatability of the treatment and the machinability before carburising count for more than core strength in large sections.

6.3Performance Comparison vs Other Case-Hardening Steels

The comparison between case-hardening steels turns on the hardenability of the core, that is, on the section beyond which the core no longer hardens through, and on the alloying elements that produce it. The table below is deliberately qualitative: the values of each grade are in its own datasheet, and setting them side by side outside their reference condition is the quickest way to compare different things.

The operating criterion is simple to state and has to be checked case by case: for as long as the core hardens through on the required section, 20MnCr5 does the job without nickel or molybdenum; when it does not, the move is to a nickel or nickel-molybdenum grade. The check is made on the Jominy band for the section in question, not on a generic ranking; and on that band the minima run to 25 mm from the quenched end, no further.

07Frequently Asked Questions about 20MnCr5 Steel: Technical Answers for Professionals

The questions that follow are the ones that come in most often on this grade, from designers and purchasing departments. The answers stay inside what the standard says, and where the standard says nothing they declare it: that is information too, and it is usually the piece that prevents a dispute.

7.1What is the difference between 20MnCr5 and 16MnCr5?

They are two grades of the same manganese-chromium family and of the same standard: the difference lies in the nominal carbon content, which the designation itself declares, and in the alloy contents, which are higher on 20MnCr5. In practice 20MnCr5 offers higher core hardenability. Then there is the cold-cutting difference: 20MnCr5 is shearable in the +S condition, 16MnCr5 is among the grades shearable while still untreated. For a numerical comparison on a precise section the Jominy bands of the two grades are what to look at, not a general rule.

7.2What are the international equivalents of 20MnCr5?

Few. The material number is 1.7147, the French AFNOR designation is 20MC5, and in Italy and Germany the grade is called 20MnCr5, with no national name of its own. Outside Europe the only match is the Chinese 20CrMnH of GB/T 5216, which EN ISO 683-3 declares identical to 20MnCr5. AISI/SAE, British and Japanese counterparts do not exist, and the comparison with AISI 5120 found in commercial tables does not hold: that grade has about a third less manganese and a third less chromium.

7.3What surface hardness does 20MnCr5 reach after carburising?

No standard guarantees it, so we publish no figure: the hardness of the case is set by the heat-treatment specification of the part, as a function of the carbon reached in the case and of the hardening and tempering cycle. The hardness that can be demanded on delivery is a different one, and it is the hardness in the as-delivered condition: 217 HBW max on the annealed bar.

7.4What case depth can be obtained, and up to what section?

The steel standard does not fix the effective case depth, neither a floor nor a ceiling: the CHD is a parameter of the heat-treatment specification, it depends on the time and the temperature of the cycle and it is verified on the part. The grade does not decide it: what 20MnCr5 does fix, through the Jominy band, is the hardenability of the core beneath the case. So there is no case thickness that this steel allows or forbids: there is a cycle that produces it, to be agreed on the part. The section limit, on the other hand, is read off that band, where the standard specifies a minimum up to 25 mm from the quenched end and no further.

7.5Is 20MnCr5 weldable?

20MnCr5 is not a steel for welded construction: with 0.17-0.22% carbon, 1.10-1.40% manganese and 1.00-1.30% chromium - and after carbon it is chromium, not manganese, that weighs most - welding is possible but has to be done in the annealed condition and before carburising, with preheat and stress relief defined by the welding procedure. The steel standard prescribes neither preheat nor carbon equivalent: we do not publish figures that it does not have.

7.6Which standard does 20MnCr5 comply with?

EN ISO 683-3:2022, case-hardening steels - technical delivery conditions. It superseded EN 10084, which in turn had taken the place of the German DIN 17210; the designation never changed, and the name and the material number 1.7147 are the same as they were then.

7.7In which delivery conditions is 20MnCr5 available?

The standard provides for delivery in the untreated condition +U, shearable +S, annealed +A, treated to a hardness range +TH, ferrite-pearlite structure +FP and normalised +N, plus other conditions by agreement; for surfaces it provides for the as-rolled condition +HW, pickled +PI, shot-blasted +BC and rough-machined +RM. Unless otherwise agreed at the time of order the products are delivered in the untreated condition, that is, as hot worked: the annealed +A condition is an option that has to be ordered. Our four 20MnCr5 formats are all in the annealed condition.

The ordering syntax is that of the standard itself, which uses this very grade as its example: ISO 683-3 - 20MnCr5+A+BC to EN ISO 683-3:2022 gives the grade, the treatment condition and the surface condition, in that order.

7.8When should 20MnCr5 be chosen over 18NiCrMo5 or 18CrNiMo7-6?

The discriminator is the section, that is, the hardenability required of the core. 20MnCr5 covers gears and transmission components of small and medium section with an alloy free of nickel and molybdenum; when the section grows and the core no longer hardens through, or when the dynamic load calls for more core toughness, the move is to 18NiCrMo5 or to 18CrNiMo7-6. The informative classification of the standard stops at 100 mm of diameter: beyond that, no data, not even indicative, so the comparison on substantial sections has to be made on the cycle and on the hardenability band, not on a table - bearing in mind that, as far as specified minima go, that band too stops at 25 mm from the quenched end.

7.9What is the density of 20MnCr5?

7.85 kg/dm³, which is not a measured property of this grade but the conventional value for steels: it is the design convention with which weight and price are calculated. The same number sits behind our bar weight calculator, where the profile and the dimensions are enough to obtain the weight per metre and the total weight.

08The Siderticino Offer for 20MnCr5 Steel: Solutions for Case-Hardening Applications

Siderticino supplies 20MnCr5 steel (1.7147) in compliance with EN ISO 683-3:2022 (formerly EN 10084), in round bars in the hot-rolled, cold-drawn, peeled and forged executions, all in the annealed condition - the condition the material is machined in before carburising. Cutting is carried out to size on the lengths required and the EN 10204 inspection documentation accompanies the supply, with a 3.1 inspection certificate on request.

For diameters, executions and a quote request see the product page: 20MnCr5 steel products. For the related grades see the technical datasheet of 18NiCrMo5 and the category page for case-hardening steels; to estimate the weight of semi-finished products the steel bar weight calculator is available.

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