Aisisae 4340 alloy steel 4340 steel properties all. Fatigue cracking initiated at the site of the weld toe undercut. Cracked 4340 after quench metal and metallurgy engineering. An investigation into the mechanisms of tempered martensite embrittlement tme, also know as 500 or 350 or onestep temper embrittlement, has been made in commercial, ultrahigh strength 4340 and simodified 4340 300m alloy steels. Quenchandtempering or heat treating requirements for 1045, 4140, and 4340 plate usually call out a hardness range, but it is not uncommon for an application to require certain mechanical properties beyond hardness. Quench cracking promoted by nonmetallic inclusions in aisi 4140 steel heat treatment defects quench cracks heat treatment defects quenched from an excessively high temperature tool steels fractography heat treatment defects.
In the quenching action, the steel is subject to nonuniform cooling, thermal deformation, and a phased grain transformation that can literally pull the. Conditions producing cracks in a particular oilhardening steel were determined. Except for plain carbon steels that are micro alloyed with just vanadium, niobium, andor titanium, most lowalloy steels are suitable as engineering quenched and tempered steels and are generally heat treated for. Aisi 4340 alloy steel aisi 4340 steel stockholders and suppliers, delivering to the whole of the uk. And it is used for making important quality controlling parts with good toughness, high strength, and large size, such as heavy machinery and high load shafts, dia of turbine shafts is larger than 250mm, helicopter rotor shafts, turbojet turbine shafts, blades, highload. It is ideal for achieving the required strength and hardness properties on many alloys. Cooling in ash or lime after forging is recommended. This location was a highly stressed area and the location of a large mechanical stressconcentration factor because ofthe weld toe undercut.
This is due to the very high hardenability which causes a severe volume change gradient going from austenite to martensite through the thickness. Fourquenchingbathsofabout18 galloncapacityeachnamely,water,60percentglycerininwater. Welding is not recommended because of the danger of quench cracking. Evaluation of toughness in aisi 4340 alloy steel austenitized at low. This type of 4340 is also known for its elongation and. Aisi 4340 is a nickel chromium molybdenum alloy steel specification widely used in the oil and gas sectors. A common misconception is that quench cracks can occur only while the piece is being quenched. The objective is to quench sufficiently fast to avoid undesirable concentration of the alloying elements in the defect and grain boundary structure while at the same time not quenching faster than necessary to minimize residual stresses, which may lead to excessive distortion or cracking. An aisi 4340 threaded steel connecting rod that was part of a connecting linkage used between a parachute and an instrumented drop test assembly frac.
Chemical composition has been found to influence the propensity to quench crack with a high purity low iron and silicon version alloys demonstrating the greatest susceptibility. Asquenched martensite is hard and brittle it has virtually no ductility. Oct 14, 20 heres a clip of an aggressive heat treatquenching process designed to allow maximum strength and hardness from this 4340 nickel alloy. Temper as soon as the steel reaches room temperature.
Nitriding should be followed by slow cooling no quench reducing the problem of distortion. The martensitic transformation starts at the outermost surfaces of the part being quenched. There is some evidence to suggest that high purity i. Mar 28, 2012 certain highhardenability materials, such as 4340, are particularly prone to quench cracking and must be tempered immediately usually within 15 minutes of quenching to avoid problems. Mechanisms of tempered martensite embrittlement in low. Aisi 4340 steel is a medium carbon, low alloy steel. If the use of water as quenching medium, 4140 steel cooling speed is faster at high temperature range, but the cooling speed is slow at low temperature range lower than the ms temperature. Commercial and military aircraft, automotive systems, forged hydraulic and other machine tool applications, forged steel crankshafts.
Aisi 4340 has a favorable response to heat treatment usually oil quenching followed by tempering and exhibits a good combination of ductility and strength when treated thusly. When you oil quench steel forgings, theres also less risk of cracking compared to water quenching or polymer quenching. Overviewofthemechanismsoffailure in heat treated steel components. Quench cracks 3 ways to recognize quench cracks result from stresses produced during the transition from austenite to martensite, which involves an increase in volume. It is an alloy structural grade which used by the sae. However, as in motor shaft applications, under quenching and tempering conditions, 4340 steel typically use high preheating in low hydrogen processes.
Hence, thegeneralruleofquenchingfromjustabovethecriticalrange. Normal ranges of mechanical properties corresponding to a specific hardness are listed below. Sae aisi 4340 steel properties, heat treatment, equivalent. Overviewofthemechanismsoffailure in heat treated steel. For example, highcarbon and alloy steels with high hardenability often. Quench cracks 3 ways to recognize speaking of precision blog. This includes sharp changes of section, lack of radii, holes, sharp keyways, unbalanced sectional mass and other stress risers. I have some shafts to machine from 4340 512 dia stock, to an average size of 5. Throughhardening low alloy steel bar 4340 colour code.
Us20170002447a1 us15235,226 us201615235226a us2017002447a1 us 20170002447 a1 us20170002447 a1 us 20170002447a1 us 201615235226 a us201615235226 a us 201615235226a us 2017002447 a1 us2017002447 a1 us 2017002447a1 authority us united states prior art keywords alloy set forth contains steel up prior art date 20121024 legal status the legal status is an. Pdf analysis of quenching parameters in aisi 4340 steel by. Analysis of quenching parameters in aisi 4340 steel by. The objective is to quench sufficiently fast to avoid undesirable concentration of the alloying elements in the defect and grain boundary structure while at the same time not quenching faster than necessary to minimize residual stresses, which. Here are 7 ways that steel can fail as a result of quench cracking from heat treatment. Quench cracks do not have decarburization apparent, since the. It has high toughness and strength in the heat treated condition. Jade band marigold introduction atlas 4340 is a nominally 1. Preheat the steel 4340 first, heat up to 1150c 1200c maximum for forging, hold until temperature is uniform throughout the section. Polymer quenching is useful for a wide range of steels. A quench and temper steel alloy is disclosed having the following composition in weight percent.
Aisi 4340 is also one kind of nickel chromium molybdenum steels. Quenched and tempered saeaisi 4140 is saeaisi 4140 steel in the quenched and tempered condition. From aisi 1045 to aisi 4340 the polymer quenching hardening heat treatment can be the solution for complex jobs. Polymer quenching is particularly useful for quenching high integrity alloy steel forgings that require impact testing.
External corners need to at least be broken before heat treat, as they too are a stress concentration area. Inservice d2 toolsteel component failure due to quench cracking photograph. The coarse austenite grain size may promote quenching cracks and increase. Aisi 4340 steel, oil quenched 855c 1570f, 230c 450f. How to quenching and tempering of 4140 alloy steel. It has been reported for asquenched aisi 4340 steel that high temperature austenitizing. The quench andtemper process induces enormous stresses, which can lead to part cracking during the process if good part design guidelines and proper heat treating practices are not followed. Investigating the mechanisms that cause quench cracking in. Heat to 500c 530c and hold for sufficient time from 10 to 60 hours to develop the depth of the case. Quench cracking occurs when the material is unable to accommodate the plastic strains that result from the differential thermal contraction during quenching. Aisisae 4340 alloy steel 4340 steel properties all metals. Us20170002447a1 quench and temper corrosion resistant. Any condition that concentrates the stresses encountered in quenching will promote the formation of quench cracks e.
If the work is not tempered right away, quench cracks can and will occur. Six pieces of bar stock for each of the four grades of oil hardening steel 01 tool steel, 4140, 4150, and 4340 alloy steels were used for this test. Us20170002447a1 quench and temper corrosion resistant steel. Aisisae 4340 alloy steel, 4340, is a nickelchromiummolybdenum alloy steel known for its toughness and its ability to attain high strengths in the heattreated condition.
What happens to the physical size of 4340 during heat treating. Quenched and tempered lowalloy steel total materia article. And it has good toughness, fatigue resistance, impact toughness and etc. Here are seven ways that steel can fail as a result of quench cracking from heat treatment. Material and process selection can contribute to cracking as well.
This material at my shop is quenched in 250f agitated oil without any issues. Overheating during the austenitizing portion of the heat treatment cycle can coarsen normally fine grained steels. Avoid over heating and overly long dwell times while austenitizing. Its selection depends on the hardenability of the alloy and the. The quenchandtemper process induces enormous stresses, which can lead to part cracking during the process if good part design guidelines and proper heat treating practices are not followed.
In order to better understand the mechanisms that give rise to quench cracking three different 7010 variants, whose. Quench cracking in steel as a case of hydrogen embrittlement. I even made a larger hand hammer out of 4140 since this has happened and did a full quench on it and it didnt crack. Magnetic particle inspection is useful for ferrous alloys. There has been no reported instance of quench cracking in the tooling grade 7010 grade z which has less restrictions on the combined fesi content. The following table shows the chemical composition of aisi 4340 alloy steel. Following forging operation the work piece should be cooled as slowly as. Aisi 4340 steel stockholders and suppliers, delivering to the whole of the uk. The physical properties of aisi 4340 alloy steel are. This is to reduce likelihood of cracking during quench. While large 4140 rounds can be waterquenched, squares are a different story. The high hardness of 4340 alloy steel requires that the material be welded in the annealed or tempered state and then heat treated to resist martensite formation and cold cracking.
If quench uniformity is required, such as in complying with the caterpillar 1e0106a or 1e0106b specification, polymer quenching. Quench cracks result from stresses produced during the transition from austenite to martensite, which involves an increase in volume. The 800 600 400 200 30 oil 60 90 time, s 120 150 o fig. Alloy description timkensteels 4140hw grade is a finegrained, lowalloy steel that offers optimum heattreat response in heavier crosssections. Quench cracks run from the surface towards the center of mass in a fairly straight line.
Overload failure of a quenchcracked aisi 4340 steel. Atlas 4340 lowalloy steel bar complies with grade as1444, grade 4340 andor. Coarsely grained steels increase hardening depth and are more prone to quench cracking than fine grain steels. Oil and gas completion equipment such as packers and liner hanger components and wellhead components. Parts can therefore be machined to near final size, leaving a grinding allowance only. Quench cracks 3 ways to recognize speaking of precision. Analysis of quenching parameters in aisi 4340 steel by using. Quench cracking of steel cracking resulting from stresses produced during the austenite to martensite transformation during heat treating quenching and tempering. Oil quenching is a common method for hardening alloy steel forgings. It has been reported for asquenched aisi 4340 steel that high temperature austenitizing treatments at 1200 instead of conventional heattreatment at 870 result in a two fold increase in fracture toughness, ktc, but a decease in charpy impact energy. The crack is seen to travel along the prior austenite grain boundaries. The quenched and tempered of 4140 alloy steel production process. According to the actual production situation, we believe that the main reason of quenching crack of 4140 steel plate is. Defects and distortion in heattreated parts asm international.
Heres a clip of an aggressive heat treatquenching process designed to allow maximum strength and hardness from this 4340 nickel alloy. Heat treating and brine quench of prepost machined 4340. If the use of water as quenching medium, 4140 steel cooling speed is faster at high temperature range, but the cooling speed is slow at low temperature range lower than the. C, followed by slow cooling no quench reducing the problem of distortion.
Aisi 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. Throughhardening low alloy steel bar 4340 atlas steels. Pre hardened and tempered 4340 can be further surface hardened by flame or. Certain highhardenability materials, such as 4340, are particularly prone to quench cracking and must be tempered immediately usually within 15 minutes of quenching to avoid problems.
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