US3890136A - Raw powders to be used for production of low alloys steels having an excellent hardenability by powder metallurgy - Google Patents

Raw powders to be used for production of low alloys steels having an excellent hardenability by powder metallurgy Download PDF

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Publication number
US3890136A
US3890136A US484945A US48494574A US3890136A US 3890136 A US3890136 A US 3890136A US 484945 A US484945 A US 484945A US 48494574 A US48494574 A US 48494574A US 3890136 A US3890136 A US 3890136A
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weight
powders
hardenability
content
powder
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US484945A
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Inventor
Shunji Ito
Yasuaki Morioka
Yoshihiro Kajinaga
Minoru Nitta
Ichio Sakurada
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JFE Steel Corp
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Kawasaki Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%

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  • ABSTRACT Raw powders to be used for production of low alloy steels having an excellent hardenability by powder metallurgy consist of 0.902.50% by weight of Mn, ().35l 50% by weight of Cr, 0.]-1 .00% by weight of Mo, not more than 0.10% by weight of Si and remainder substantially being Fe, provided that the sum of Mn and Cr is l.703.l0% by weight.
  • 0.l0-l.00% by weight of Ni is additionally added July Japan 48'75299 thereto the hardenability is further improved.
  • the present invention relates to the raw powders to be used for production of low alloy steels by powder metallurgy and particularly the raw powders to be used for production of automobile parts through the socalled sinter forging.
  • the inventors have investigated the reason why the raw powders having the above described properties cannot be obtained and found the following facts.
  • the raw materials are powder, the specific surface area is large. Namely, the raw powders have a larger specific surface area than the molded products having the same volume and consequently the amount of oxygen increases. For example, even in the case of pure iron powders fully reduced, about 0.3% by weight of oxygen is usually contained and this value is much larger than rimmed steel 0.020.03% ⁇ and killed steel (0 0.0l%).
  • Cr and Mn are elements easily oxidized and are apt to form oxides. Furthermore, when the oxides of these elements are once formed, these oxides are difficult in the reduction and consequently the amount of oxygen increases and the inherent activity for improving the hardenability of Cr, Mn and the like cannot be developed and rather the contained non-metal inclu sion increases, whereby the mechanical properties are deteriorated.
  • the conventional raw powders have various problems and the present invention aims at to solve these problems.
  • the present invention consists in the raw powders to be used for the production of low alloy steels having an excellent hardenability by powder metallurgy, which consist of 0.902.5% by weight of Mn, 0.35-1.50 nowadays by weight of Cr. (HO-1.00% by weight of Mo, not more than 0.10% by weight of Si and the remainder substantially being Fe, provided that the sum of Mn and Cr is 1.70-3. l0% by weight.
  • Mn Mn is an element for improving the hardenability and in the present invention, this element is added for such a purpose.
  • the effect for improving the hardenability is low, so that the lower limit of Mn is defined to be 0.90%.
  • lt is preferable in view of the hardenability that the Mn content is larger but the present invention is characterized in that the improvement of the hardenability is attained by the coexistence of the defined amounts of Mo and Cr. Therefore, the Mn content has the upper limit in view of the hardenability and when said content exceeds 2.50%, the hardenability is rather deteriorated.
  • the upper limit of the Cr content should be determined from this view but when the Cr content is large, the viscosity of the molten steel becomes high and unless the temperature is raised abnormally, the atomizing nozzle before granulation is clogged, the oxygen content increases and the cold compactibility of the powders becomes difficult, so that the upper limit of Cr is defined to be 1.50% by weight.
  • M0 is an element which is ef' fective for the improvement of the hardenability, the annealing resistance, the annealing brittleness and the like, but the present invention is characterized in that it is noticed that M0 is an element which improves and promotes the hardenability owing to Mn and Cr.
  • M0 is expensive and therefore it is necessary to define the range of M0 in economical and effective view. From this point, the Mo content must be 0. l0-l 00% by weight in relation to the amounts of Mn and Cr.
  • Mn-l-Cr l.703.l0% by weight of Mn-l-Cr
  • the lower limit of the sum amount of Mn and Cr must be l.70% in view of the hardenability within the range of 0.902.50% of Mn and 0.35l.50% of Cr.
  • the sum amount of Mn and Cr is larger, when said amount is too large, the oxygen content of the powder increases and rather the hardenability is deteriorated and further the mechanical properties are impaired, so that the upper limit of the sum amount of Mn and Cr is defined to be 3.10%. Moreover, when the sum amount of Mn and Cr exceeds 3. l0%, the hardness of the powder granules themselves increases and the cold compactibility of the powders becomes difficult. This is also the reason of the definition.
  • Mn, Cr and Mo are the elements which develop the effect by positively existing. While it is preferable that Si rather is not present.
  • Si is a negative element in the present invention.
  • Si is not particularly added different from the case of the usual molded steel and the amount of Si inevitably allyed is not more than 0.10% by weight.
  • Si is a negative element in view of the hardenability in the present invention and less Si contributes to the improvement of the hardenability together with the above mentioned positive elements of Mn, Cr and Mo. Particularly, in this case. only when Si is not more than 010%, if Cr, Mo and Mn are within the above described ranges, the effect of Si can be de veloped to the largest extent.
  • Remainder of Fe The remainder does not consist of only Fe but con sists substantially of Fe and contains impurities in such an extent as in usual steels (powder, molded steel). Accordingly, this is the same with respect to C and C is about 0.2% by weight when used as a case-hardening steel and C is about 0.4% when used as tempering steel.
  • the powders of the present invention consist of the composition as mentioned in detail hereinbefore, but in this composition, when a part of the remainder of Fe is substituted with Ni, the effect for improving the hardenability can be more improved.
  • Ni is an element which does not contribute to the hardenability.
  • Si Si content
  • Mn Mn
  • Cr Cr
  • Mo Mo
  • Ni can improve the hardenability noticeably.
  • Ni improves the reducibility and even if Mn and Cr are contained in a large amount, the presence of Ni can lower the oxygen content considerably.
  • FIG. 1 relates to the powders of the present invention and when the powders of A. B and C are compared with the powders of A, B and C, in the former powders of A. B and C, Ni is particularly added and it can be seen that the oxygen contents in these powders are more reduced and the harden-abilities in these powders are more improved than those in the powders ofA', B and C.
  • Ni makes fine grain structure and consequently even if the cementation or the heat treatment are effected after the sinter forging, the structure does not become coarse and this contributes to the improvement of the mechanical properties.
  • Ni it is preferable in the present invention to add Ni and it is necessary to add at least 0.10% by ⁇ veight of Ni in order to attain the effect of the addition of Ni.
  • the upper limit of Ni is l.00% by weight.
  • the powders of the present invention can be obtained.
  • These powders can be produced. for example, by granulating the raw powders by atomizing process and other conventional processes and then, for example, subjecting to a reduction annealing under hydrogen atmosphere.
  • FIG. 1 is a diagram showing .lominy curves of the powders according to the present invention.
  • FIGS. 2 and 3 are diagrams showing Jominy curves of the comparative powders.
  • FlGS. 4 and 5 are diagrams showing Jominy curves of the well known powders.
  • the powders of the composition as shown in the following Table l were produced by water atomizing process and after granulation, the granules were subjected to a reduction annealing under hydrogen atmosphere at l,()50C for 3 hours.
  • A-C' are within the scope of the present invention and E-K are the comparative powders.
  • the powders A-K were almost composed of about l7% of lOO-lSO mesh powder about 28% of [50-200 mesh powder about l5% of 200250 mesh powder about [5% of 250325 mesh powder and about 25% of minus 325 mesh powder and there is no great difference in the particle size distribution of each powder.
  • the powders A-K were prepared as mentioned above and these powders and the powders having the composition as shown in the following Table 2 were compacted under a pressure of 5 t/cm to obtain the green compacts having a density of 6.5 g/cm, which were sintered under the endothermic gas (propane-air cracking gas) at l,()5()C for l hour and then the sintered bodies were heated at l,200C for 5 minutes under hydrogen atmosphere and was forged in a die under a pressure of IO tlcm By such a sinter forging, steel blocks having a density of more than 99.5% were obtained. These steel blocks were normalized at 870C following to MS G056l and then worked into Jominy test samples.
  • endothermic gas propane-air cracking gas
  • AISI 8600 Q 0.47 0.010 0.28 1.01 0.02 0.45 0.25 low MnNi M0.
  • AISI 4600 The powders of A, B and C do not substantially contain Ni. In A. B and C. the hardenability is more improved than those of FIGS. 2 and 3 but is more or less inferior to that in A. B and C. which contain Ni.
  • the hardening depth of the quenching hardness curve becomes more or less shallow but the curve takes such a form that the hardness decreases gradually from the quenching end towards the interior.
  • the materials having such a property are most suitable for parts in which the fatigue strength is important.
  • the quenching hardness curves takes such a form that the hardness lowers rapidly at a certain distance from the quenched end.
  • the materials having such a property are most suitable for parts which need an enough impact toughness.
  • the composition of A can be compared with the composition ot'G and the composition of A can be compared with the composition of F. From this comparison, it can be seen that the compositions of G and F are higher in the Si content than the defined Si content in the present invention and when Si is more than 0.10%, the oxygen content increases as shown in Table 1 and the hardenability is deteriorated.
  • the composition of A when the composition of A is compared with the composition of E, the composition of E is within the scope of the present invention in the amount of Mn. Cr and Si but the Mo content is lower than the defined content of Mo in the present invention and the hardenability in E is inferior to that of A. From this fact, it is apparent that the improvement of the hardenability of the powder does not coincide with the prior metallurgical common sense and relies upon the coexistence of Cr. Mn and Mo under such a condition that the amount of Si is not more than 0.10%.
  • composition of H When the composition of H is compared with the compositions of A(" according to the present invention. the former is very low Cr content. From the comparison with the data in FIG. 1 and those in FIG. 2, it can be seen that the defined content of Cr is essential as one of the coexisting elements.
  • the composition of K is too large in the Ni content and in this composition, the retained austenite amount increases, so that the hardness at the quenched end decreases as shown in FIG. 3 and the oxygen content is comparatively high as shown in Table I. This shows that although Ni has the above described effect but there is an optimum range.
  • any of the powders of LN contain 0.20-0.3570 of Si, the powder ofO does not contain Si nor contain Ni and Cr.
  • the powder of P is low in the Mn content and the powder ofQ is low in the Mn content and is too high in the Ni content and too low in the Cr content.
  • All the powders of L, M and N contains more than 0.10% of Si and the effect of coexistence of Mn, Cr and Mo and the effect of additionally adding Ni thereto are not developed and therefore the hardenability is not improved.
  • the effect of the powders of the present invention will be understood through the explanation in the above Example. If an explanation is made with respect to the carbon content and the hardening depth in the powders of the present invention, it can be considered that the powders are utilized for tempering steel and casehardening steel, In the case of using the powder for tempering steel, the carbon content is about 0.4% and it is characterized that the hardness of mm and mm from the quenched end is more than 50 in Rockwell C scale and more than 40 in said scale respectively and particularly the hardness is not rapidly varied at the zone of 10-15 mm from the quenched end.
  • Raw powders to be used for production of low alloy steels having an excellent hardenability by powder metallurgy which consisting mainly of 0.90-2.50% by weight of Mn, 0.351.50% by weight of Cr, 0. ⁇ 04.00% by weight of Mo, not more than 0.10% by weight of Si and remainder substantially being Fe, provided that the sum of Mn and Cr is l.703.l0% by weight.
  • Raw powders to be used for production of low alloy steels having an excellent hardenability by powder metallurgy which consisting mainly of 0.902.50% by weight of Mn, 0.35] 50% by weight of Cr, 0.l01.00"/Z by weight of Mo, O.l0l.00% by weight of Ni, not more than 0.10% by weight of Si and remainder substantially being Fe, provided that the sum of Mn and Cr is l.703.10% by weight.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
US484945A 1973-07-05 1974-07-01 Raw powders to be used for production of low alloys steels having an excellent hardenability by powder metallurgy Expired - Lifetime US3890136A (en)

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JP7529973A JPS5441968B2 (en(2012)) 1973-07-05 1973-07-05

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1068384C (zh) * 1994-11-25 2001-07-11 赫加奈斯公司 具有高拉伸强度的含锰材料
WO2003106079A1 (en) * 2002-06-14 2003-12-24 Höganäs Ab Prealloyed iron-based powder, a method of producing sintered components and a component
US20070048169A1 (en) * 2005-08-25 2007-03-01 Borgwarner Inc. Method of making powder metal parts by surface densification

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5616587Y2 (en(2012)) * 1975-05-24 1981-04-17
JPS5614505Y2 (en(2012)) * 1975-05-24 1981-04-06
JPS5365249A (en) * 1976-11-25 1978-06-10 Hoeganaes Ab Improved mixture and said manufacturing process for low alloy steel powder

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2284638A (en) * 1938-08-20 1942-06-02 Frances H Clark Metallurgy of ferrous metals
US3687654A (en) * 1971-03-10 1972-08-29 Smith Inland A O Method of making alloy steel powder
US3798022A (en) * 1971-02-17 1974-03-19 Federal Mogul Corp Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder
US3837845A (en) * 1972-03-27 1974-09-24 Int Nickel Co Oxide coated ferrous metal powder

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3725142A (en) * 1971-08-23 1973-04-03 Smith A Inland Inc Atomized steel powder having improved hardenability

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2284638A (en) * 1938-08-20 1942-06-02 Frances H Clark Metallurgy of ferrous metals
US3798022A (en) * 1971-02-17 1974-03-19 Federal Mogul Corp Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder
US3687654A (en) * 1971-03-10 1972-08-29 Smith Inland A O Method of making alloy steel powder
US3837845A (en) * 1972-03-27 1974-09-24 Int Nickel Co Oxide coated ferrous metal powder

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1068384C (zh) * 1994-11-25 2001-07-11 赫加奈斯公司 具有高拉伸强度的含锰材料
WO2003106079A1 (en) * 2002-06-14 2003-12-24 Höganäs Ab Prealloyed iron-based powder, a method of producing sintered components and a component
US20070048169A1 (en) * 2005-08-25 2007-03-01 Borgwarner Inc. Method of making powder metal parts by surface densification

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SE412256B (sv) 1980-02-25
SE7408807L (en(2012)) 1975-01-07
SE412257C (sv) 1987-05-18
JPS5441968B2 (en(2012)) 1979-12-11
GB1472331A (en) 1977-05-04
DE2432338A1 (de) 1975-01-16
JPS5023303A (en(2012)) 1975-03-13
SE7706654L (sv) 1977-06-08
SE412257B (sv) 1980-02-25
DE2432338B2 (de) 1977-01-27

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