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EP0393137A1 - Article en acier cemente a faible teneur en silicium et procede. - Google Patents

Article en acier cemente a faible teneur en silicium et procede.

Info

Publication number
EP0393137A1
EP0393137A1 EP89901165A EP89901165A EP0393137A1 EP 0393137 A1 EP0393137 A1 EP 0393137A1 EP 89901165 A EP89901165 A EP 89901165A EP 89901165 A EP89901165 A EP 89901165A EP 0393137 A1 EP0393137 A1 EP 0393137A1
Authority
EP
European Patent Office
Prior art keywords
article
carburized
steel
carbides
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP89901165A
Other languages
German (de)
English (en)
Other versions
EP0393137B1 (fr
EP0393137A4 (en
Inventor
Sheryl A Tipton
Gary D Keil
Gregory S Holloway
Dave R Gromer
Gary L Biltgen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Inc
Original Assignee
Caterpillar Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Caterpillar Inc filed Critical Caterpillar Inc
Publication of EP0393137A1 publication Critical patent/EP0393137A1/fr
Publication of EP0393137A4 publication Critical patent/EP0393137A4/en
Application granted granted Critical
Publication of EP0393137B1 publication Critical patent/EP0393137B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/78—Combined heat-treatments not provided for above

Definitions

  • Thi.s i.nventi.on relates generally to metal heat treatment and more particularly to case hardening with a gas containing carbon and a resulting article.
  • Carburizing is an effective method of increasing the surface hardness of low carbon, unalloyed, or low carbon, low alloy steels.
  • steel articles are placed in an atmosphere containing carbon in an amount greater than the base carbon content of the steel and heated to a temperature above the austenite transformation temperature of the steel. After the desired amount of carbon has been diffused into the article, hardness is induced by quenching.
  • Gas carburizing is efficient, controllable, and one of the most widely used methods of generating a carbonaceous atmosphere for carburizing.
  • most commonly used gas mixtures typically contain small amounts of oxygen which tend to form surface oxides with one or more of the steel elements which have a strong affinity for oxygen, such as silicon, chromium and manganese. Oxides that form along grain boundaries, i.e., intergranularly, extend inwardly from the surface and have a harmful effect on the mechanical properties of the carburized article.
  • This reference limits the amount of chromium in the steel composition to intentionally avoid the formation of case carbides. Furthermore, this reference fails to link the influence of a low silicon composition with the formation of surface oxides and carbides during carburizing.
  • the Sanyo low silicon steel composition described in the above publication is no longer in commercial production.
  • Another low silicon carburizing steel intended for use in applications wherein the formation of case carbides is purposefully avoided, was developed by Kobe Steel, Ltd.
  • Kobe's composition is described in Japanese Patent Publication No. 61-253346 and, as described therein, was developed for use in a gear that is heat treated after carburizing to improve the hardness of the root areas of gear teeth.
  • a low silicon steel composition intended for carburized articles in which near surface carbides are formed is disclosed by Daido Special Steel Co. in Japanese Patent Publication No. 61-104065.
  • Daido like the above references, recognizes that restricting the amount of silicon in the steel composition is beneficial for reducing intergranular oxides.
  • this reference also teaches that more than 1.2% chromium is essential to form carbides at or near the surface.
  • This reference also fails to recognize that in addition to its effect on oxidation, silicon effects surface carbide formation and, by limiting the amount of silicon in a carburizing steel as taught by the present invention, surface carbides may be easily formed with significantly smaller amounts of chromium.
  • Conventional gas carburizing processes as discussed above, generally attempt to prevent the formation of case carbides.
  • the present invention is directed to overcoming the problems set forth above. It is desirable to have a carburized steel article which is essentially free of surface intergranular oxides and which has a high ratio of carbides on the surface. It is also desirable to provide a process which will form this article in a short treatment time, and is economical and controllable.
  • a process for forming a carburized steel article includes carburizing an article made of a steel having no more than 0.10% silicon and less than 1.1% chromium at a temperature sufficient to form, on a surface of the article, austenite having a high density of carbides dispersed therein. After carburizing, the article is quenched to transform the carburized surface microstructure to martensite, retained austenite and carbides, whereby the article has a carburized surface substantially free of intergranular oxides and has carbides comprising at least 20% of the carburized surface.
  • a carburized low silicon steel article characterized by having not more than 0.10% silicon and less than 1.1% chromium, by having an outer surface substantially free of intergranular oxides, and by having a high percentage of carbides on the outer surface.
  • the carbides on the outer surface comprise at least 20% thereof.
  • Other features of the carburized low silicon article include a composition, by weight, of 0.08% to 0.35% carbon, 0.3% to 1.7% manganese, 0.2% to 2.5% carbide forming elements including said chromium, less than 6% additional hardenability agents, less than 1% grain refining elements, not more than 0.10% silicon, not more than 0.15% copper, and iron and trace elements.
  • Fig. 1 is a photomicrograph, at 750X 7 showing an unetched section of a carburized low silicon steel article containing less than 0.10% silicon according to the present invention.
  • Fig. 2 is a photomicrograph, at 75OX, of an etched section of the article shown in Fig. 1.
  • Fig. 3 is a photomicrograph, at 75OX, showing an unetched section of an article carburized with the article in Fig. 1, but formed of a typical carburizing grade low alloy steel containing 0.26% silicon.
  • Fig. 4 is a photomicrograph, at 750X, of an etched section of the article shown Fig. 3.
  • Fig. 5 is a photomicrograph, at 50OX, showing an etched section of an article formed of a typical carburizing grade low alloy steel containing 0.26% silicon and carburized by a conventional carburizing process.
  • Fig. 6 is a graph showing the relationship between silicon content in the steel composition, and the amount of oxides and carbides formed on the surface of an article carburized according to the present invention.
  • Fig. 7 is a graph illustrating the time and temperature relationship of the carburizing process embodying the present invention.
  • a process for forming a steel article includes the steps of selecting a low silicon steel, shaping the steel, carburizing, controllably cooling to the hardening temperature, and quenching.
  • low silicon steel means a steel material containing from 0% silicon to no more than 0.10% silicon, and whose composition in all other respects is recognized as generally suitable for carburizing. Restricting, or eliminating, the amount of silicon in the steel not only represses the formation of silicon oxides but also inhibits the oxidation of chromium and manganese on the surface of the carburized article. Furthermore, when low silicon steel articles are processed in accordance with the present invention, the formation of a high ratio of carbides on the surface is assured. Accordingly, selection of an appropriate steel composition is an important step.
  • Carbide forming elements such as
  • Grain refining elements 0.0% - 1.0%
  • the above steel composition if silicon is deleted or restricted to 0.10% or less, is suitable for the formation of carburized articles according to the present invention.
  • the accepted steel industry standard allowable residual amount of copper is steel compositions is 0.35%. It has been found that low silicon steels having copper toward the upper limit of such amount are sometimes inconsistent in the formation of carbides on the carburized surface. It is theorized that copper may inhibit the formation of surface carbides. Accordingly it is desirable, though apparently not essential in all cases, to limit the amount of copper in the composition to not more than 0.15%.
  • a low alloy carburizing grade steel such as one of the SAE 4110 to 4130 series, all modified particularly to limit silicon to no more than 0.10%, are particularly suited for the formation of carburized articles such as gears, bearings and shafts. Therefore, commercial low alloy carburizing grade steels containing relatively small but essential amounts of carbide forming elements such as chromium, molybdenum or vanadium, may be modified to be a low silicon steel composition. Additional hardenability agents may be included but should be limited to amounts less than about 6%. Grain refining elements in amounts less than 1% are often added to promote fine grain size. As noted above, it is also desirable to limit residual or trace amounts of copper to no more than 0.15% to further enhance surface carbide formation. Deleterious elements such as phosphorus and sulfur, often present in trace amounts, are preferably limited to no more than 0.05% and 0.08% respectively.
  • Articles having any of the above described compositions are shaped to a predetermined form by machining from rolled steel, by casting or forging, by consolidating steel powder, or by a combination of forming operations.
  • the article After shaping, the article is placed into a carburizing furnace and heated to a temperature sufficient to diffuse carbon from the furnace atmosphere into the article and to form a high density of carbides on the surface of the article.
  • the carburizing operation is carried out in two stages.
  • the carbon potential of the gas atmosphere in the furnace is maintained at a level about equal to the saturation limit of carbon in austenite.
  • the saturation level of carbon in austenite generally designated as "A__” / is temperature dependent.
  • the shaped article is preferably placed directly into a continuous type furnace having a temperature within the carburizing chamber of from about 1550°F (843°C) to about 1850°F (1010°C) and an atmosphere about equal to the A corresponding the specific steel composition of the article.
  • the first stage of the carburizing process includes holding the article in the carburizing chamber for a period of time sufficient to develop about 75% to 95% of the desired final case depth.
  • "case depth” is the distance below the surface where the carbon content is at 0.40%.
  • the time required to achieve the desired case depth of the article is dependent on a number of parameters, such as the chemical composition of the article, and composition and temperature of the gas atmosphere. Hence the length of time that the article is held in the carburizing chamber in this first stage may vary from about 2 to about 25 hours.
  • the furnace atmosphere is maintained as close as possible to the A of the particular steel, and the carburizing temperature is maintained at about 1700 F (927°C) , an initial case depth of about 1.0 mm can be achieved by holding the article in the furnace for about 4 to 5 hours. After completion of the second stage carburizing operation, described below, the final case depth is about 1.1 mm.
  • the article is cooled, preferably by gas quenching, to a temperature below that at which bainite and pearlite begin to form.
  • This temperature is commonly designated as "A " and is represented by the dashed horizontal line on Fig. 7. It is desirable to cool the surface of the article rapidly in this operation to suppress network carbide formation. This results in the formation of a supersaturated, metastable, solid solution of iron and carbon. If excessively slow cooling rates are used, carbides will form at grain boundaries, and not provide effective intragranular nuclei for the formation of carbides. After cooling the article to a temperature sufficiently below A .
  • the article is quickly reheated by placing it into a preheated carburizing furnace. This causes a homogenous carbide precipitation from the metastable solid solution, and results in a dispersion of carbides in the case microstructure.
  • the carbon potential of the furnace atmosphere is maintained at a level above the A , i.e., the carbon potential of the atmosphere is above the saturation limit of carbon in austenite of the article.
  • an atmosphere having a carbon potential of about 1.5% to 2% can be provided by a gas having a composition of 0.055% CO,, 1% CH., 20% CO, 40% H, and the balance N-.
  • the temperature of the second stage carburizing chamber is maintained between about 1550°F (843°C) and 1850°F (1010°C) , and preferably at about 1700°F (927°C) .
  • the second stage it is only necessary to reaustenitize the case of the article in a supersaturated gas environment, and thereby increase the surface carbon to a level above 1.5%.
  • the article need be held for only about 15 to 60 minutes at 1700°F (927°C) to achieve the desired case carbon content.
  • lower temperatures may be used, it will require holding the article in the furnace for a corresponding longer time.
  • the size and volume fraction of the surface carbides present in the carburized article can be controlled by selection of the second stage carburizing temperature and the rate of cooling in the subsequent cooling step described below. For example, higher second stage carburizing temperatures tend to produce more carbides, i.e., a higher volume fraction of larger carbides, on the surface of the article.
  • an austenitic microstructure having a high density of well dispersed surface carbides has been formed.
  • the article preferably while still in the furnace, is then controllably cooled to the hardening temperature of the steel core.
  • the hardening temperature of SAE 4118 steel having a low silicon composition is about 1540°F (838°C) .
  • the previously formed carbides increase in size and volume fraction.
  • the cooling rate of the article from the carburizing to hardening temperature is carefully controlled.
  • the cooling rate is about 1 F° (0.6 C°) to 20 F° (11 C°) per minute.
  • equalizing After cooling the surface of the article to the hardening temperature, it is desirable to maintain the article at the hardening temperature for a length of time sufficient to permit the temperature in the core of the article to cool to the hardening temperature.
  • This process known as equalizing, is identified in the process diagram shown in Fig. 7. Although desirable to minimize distortion, equalizing is not essential to obtain the desired surface microstructure. Depending on the article's mass and geometry, equalizing typically takes about 5 to 60 minutes to complete.
  • a carbonaceous gas atmosphere is advantageously maintained about the article during the preceding cooling and equalizing operations to prevent carbon depletion at the surface of the article.
  • Both cooling and equalizing may be carried out in the second stage carburizing furnace, or in an interconnecting chamber, so that the same gas atmosphere used in carburizing may be simply cooled and circulated about the article.
  • the article is preferably directly quenched from the hardening temperature at a rate sufficiently rapid to transform the surface microstructure to martensite, retained austenite and carbides.
  • an oil medium is used with a quench rate high enough to assure the desired surface transformation.
  • the article may be cooled and then reheated to the hardening temperature of the steel, equalized and quenched.
  • the mass and geometry of the article are sufficiently small, and the controlled cooling rate sufficiently slow, equalizing may not be required. If these conditions are present, the article may be quenched directly after the controlled slow cooling step.
  • Shafts and gears are exemplary of articles subjected to high bending loads, surface wear and contact fatigue. Samples of these articles have been successfully formed in accordance with the above described process. The total time required to complete the carburizing process, including the final quench, was typically only about 7 hrs.
  • FIG. 1 and 2 Photomicrographs of a representative sample of an article embodying the present invention are shown in Figs. 1 and 2. Advantages of the present invention are emphasized by contrasting it with Figs. 3 to 5 which are photomicrographs of representative samples of articles formed differently as described below.
  • Figs. 1 and 3 are photomicrographs of polished and unetched samples in which intergranular oxides are identified.
  • Figs. 2 and 4 are the same samples as Figs. 1 and 3, but etched with a conventional 1% nital solution to better define the carbides in the microstructure.
  • Fig. 1 and 3 Photomicrographs of representative samples of articles formed differently as described below.
  • Figs. 1 and 3 are photomicrographs of representative samples of articles formed differently as described below.
  • Figs. 1 and 3 are photomicrographs of polished and unetched samples in which intergranular oxides are identified.
  • Figs. 2 and 4 are the same samples as Figs. 1 and 3, but etched with a conventional 1%
  • FIG. 5 is a sample of an article given a conventional heat treat, and polished and etched with 1% nital solution.
  • intergranular oxides appear as elongated black areas in the unetched samples.
  • Typical intergranular oxide formations are identified by the reference numeral 10.
  • Carbide structures appear in the photomicrographs of the etched samples as white areas, typical ones of which are identified by the reference numeral 12.
  • a representative sample of an article formed according to one embodiment of the present invention has a microstructure as shown in section, at 75OX, in Figs, l and 2.
  • the sample was cut from a modified wrought SAE 4118 steel having the following specific composition: Iron and residual elements Balance
  • the sample was placed in a carburizing furnace having a conventional endothermic gas carburizing atmosphere comprising about 0.07% C0 2 , 0.6% CH 4 , 20% CO, 40% H, and the balance N 2>
  • the furnace was preheated to a temperature of about 1700°F (927°C) .
  • the carbon potential of the atmosphere was maintained as close as the furnace control system permitted to the A , the carbon in austenite solubility limit of the above described steel composition.
  • the article was held in the furnace, at the same temperature and atmosphere for 4 1/2 hrs, and then gas quenched to 200°F (93°C) .
  • the article After cooling subsequent to the first carburizing operation, the article was placed in a carburizing furnace, preheated to about 1700°F (927°C) , and the gas atmosphere controlled so that the carbon potential of the gas was greater than the saturation limit of carbon in the steel material's austenite phase.
  • the article was held in the carbon rich atmosphere, at the same temperature, for about 30 minutes, and then slowly cooled over a period of about 60 minutes, i.e., at a rate of about 2.7 F°/minute (1.5 C°/minute) to 1540°F (838°C) , the hardening temperature of the steel.
  • the article was held at 1540°F (838°C) for about 40 minutes to allow the temperature of interior portions of the article to equalize to the hardening temperature.
  • the article was directly quenched in an oil medium.
  • the article has a high volume ratio of carbides 12 formed on the surface.
  • Direct measurement of the carbides on the surface immediately adjacent the band of black bedding material observable along the very top of the photomicrograph shows that carbides comprise about 50% of the article's surface area " .
  • the carbide rich area formed on the surface of the article is essentially free of intergranular oxides.
  • A- second article a micrographic sample of which is shown in Figs. 3 and 4, was formed from modified wrought SAE 4118 steel having a silicon content within the typical range of silicon for commercially produced heats of similar material.
  • the article in this example has the following composition:
  • the material in this example has a silicon content of 0.26%, representative of silicon amounts normally present in conventional carburizing grade steels having a similar composition.
  • the article formed of the above material was heat treated simultaneously with the article described in Example 1, i.e., according to the process of the present invention.
  • Fig. 4 illustrates the influence of increased amounts of silicon on surface carbide formation. There are virtually no carbides 12 on the surface of this sample. Furthermore, the carbide free surface layer is commensurate with the depth of the intergranular oxides 10. Therefore, even when employing a case carbide forming, nonconventional carburizing process, it is necessary to limit the amount of silicon in the base steel to assure the formation of significant carbide structures on the surface of the carburized article.
  • intergranular oxides 10 are present in significantly greater quantity than in the low silicon material of Fig. 1.
  • the ratio of intergranular oxides to length of article surface shown in the field of view is about .50:1. That is, when measured along their major axes, the length of the intergranular oxides visible in Fig. 3 total about 50% of the length of the surface in the same field of view.
  • FIG. 5 A sample of an article having a modified SAE 4118H composition with 0.26% silicon, and given a conventional single stage carburizing treatment, is shown in Fig. 5.
  • the article has the following composition:
  • This example illustrates the metallurgical surface characteristics of conventionally treated standard carburizing grade steel in which case carbides were formed.
  • carbides were formed.
  • there is a- typical carbide depleted zone extending about .02 mm below the surface of the article.
  • this zone there are a significant number of oxide formations, both intergranular and intragranular.
  • intergranular oxides 10 have a deleterious affect on bending fatigue properties.
  • about .02 mm of the article's outer surface must be worn away before the benefit of the carbide structures can be used advantageously.
  • the steel material from which an article is formed must contain no more than 0.10% silicon. Limiting the silicon content to this amount not only inhibits the formation of intergranular oxides, but also promotes and enhances the formation of desirable carbide structures on the surface.
  • a high ratio of carbides are formed on the outer surface of the article, and not at some finite depth, e.g. 0.1 mm or more, below the surface.
  • the article is carburized in the manner described to assure the formation of a high density of carbides well dispersed in austenite on the article surface prior to growth by controlled cooling. As seen from Examples 2 and 3, if either of these two features are missing, the carburized article will not have an outer surface which is essentially free of intergranular oxides and on which a high volume ratio of carbides are formed.
  • the results of the above measurements are shown in a graphical form in Fig. 6.
  • the % ratio of oxides for each of the above samples is represented on the graph by a small circular symbol.
  • the scale for % silicon is shown along the base of the graph, and the scale for % ratio of oxides is shown along the right vertical side.
  • the amount of intergranular oxides increases with increasing silicon content in the samples.
  • the data indicates that for these particular samples, the silicon content may be as high as .11% or .12% and still yield less than about a 15% ratio of intergranular oxides with respect to a representative surface length.
  • the % ratio of carbides for each of the above samples is represented on the graph by a small triangular-shaped symbol, and plotted according to the scale shown along the left vertical side of the graph.
  • a line representing a reasonable fit of the individual data points, readily shows that the % ratio of carbides with the respect to the surface generally decreases with increases in silicon in the samples.
  • Sample e appears to have a lower carbide ratio than either sample d or f, respectively representing lower and higher silicon amounts on each side of sample e.
  • Articles formed according to the above are particularly useful as gears, couplings, shafts, bearings, and similar articles subjected to a combination of high bending loads, surface wear and contact fatigue.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Silicon Compounds (AREA)

Abstract

Le procédé décrit, qui permet d'obtenir un article en acier cémenté, consiste à effectuer la cémentation d'un matériau à base d'acier ne contenant pas plus de 0,10% de silicium et contenant moins de 1,1% de chrome, de façon à former une matrice de surface austénitique dans laquelle est dispersée une densité élevée de carbures. Après trempe, l'article en acier cémenté se caractérise par une surface extérieure ayant une proportion élevée de carbures et exempte d'oxydes inter-granulaires. Ceci a pour effet d'empêcher toute formation d'oxydes de surface non désirables et em même temps de former une structure de carbures de surface avantageuse; une telle invention permet d'améliorer considérablement la résistance à la rupture par pliage, les propriétés de résistance à l'usure et de résistance à la rupture par contact d'articles tels qu'engrenages, arbres de transmission, paliers et accouplements.
EP89901165A 1987-12-21 1988-12-14 Article en acier cemente a faible teneur en silicium et procede Expired - Lifetime EP0393137B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US13577587A 1987-12-21 1987-12-21
WOPCT/US87/03450 1987-12-21
US135775 1987-12-21
US8703450 1987-12-21
PCT/US1988/004470 WO1989005865A1 (fr) 1987-12-21 1988-12-14 Article en acier cemente a faible teneur en silicium et procede

Publications (3)

Publication Number Publication Date
EP0393137A1 true EP0393137A1 (fr) 1990-10-24
EP0393137A4 EP0393137A4 (en) 1991-03-20
EP0393137B1 EP0393137B1 (fr) 1996-09-11

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EP89901165A Expired - Lifetime EP0393137B1 (fr) 1987-12-21 1988-12-14 Article en acier cemente a faible teneur en silicium et procede

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EP (1) EP0393137B1 (fr)
KR (1) KR960005595B1 (fr)
AU (1) AU631528B2 (fr)
CA (1) CA1300472C (fr)
WO (1) WO1989005865A1 (fr)

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US7169238B2 (en) 2003-12-22 2007-01-30 Caterpillar Inc Carbide method and article for hard finishing resulting in improved wear resistance
DE102005023952B9 (de) * 2005-05-20 2007-07-26 Carl Aug. Picard Gmbh & Co. Kg Sicherheitspanzerung zum Schutz gegen Beschuss sowie Verfahren zu ihrer Herstellung
US11624106B2 (en) * 2020-03-18 2023-04-11 Caterpillar Inc. Carburized steel component and carburization process
CN113564515B (zh) * 2021-08-05 2023-04-14 常州天山重工机械有限公司 一种提高渗碳钢耐磨性的表面改性工艺

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DE3707003A1 (de) * 1987-03-05 1988-09-15 Ewald Schwing Verfahren zum aufkohlen eines werkstueckes aus stahl

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EP0393137B1 (fr) 1996-09-11
KR900700630A (ko) 1990-08-16
EP0393137A4 (en) 1991-03-20
AU631528B2 (en) 1992-12-03
KR960005595B1 (ko) 1996-04-26
AU2913489A (en) 1989-07-19
CA1300472C (fr) 1992-05-12
WO1989005865A1 (fr) 1989-06-29

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