Steel Alloy, A Holder Or A Holder Detail For A Plastic Moulding Tool, And Tough Hardened Blank For A Holder Or A Holder Detail, A Process For Producing A Stell Alloy


Updated about 2 years ago

Abstract

AbstractSTEEL ALLOY, A HOLDER OR A HOLDER DETAIL FOR A PLASTICMOULDING TOOL, AND TOVGH HARDENED BLANK FOR AHOLDER OR A HOLDER DETAIL, A PROCESS FORPRODUCING A STEEL ALLOYA steel alloy suitable for holder and holder details for plastic moulding tools contains in weight-%: 0.08 - 0.19C, 0.05 - 0.20 N, wherein the total amount of C + N shall satisfy the condition, 0.16 < C + N < 0.28. 0.1 - 1.5 Si, 0.1 -2.0 Mn, 13.0 - 15.4 Cr. 0.01 - i.8 Ni. 0.01 - 1,3 Mo, optionally vanadium up to max. 0.7 V, optionally sculpture in amounts up to max. 0.25 S and optionally also calcium and oxygen in amounts up to max. 0.01 (100 ppm) Ca and max. 0.01 (100 ppm) O, in order to improve the mach inability of the steel, balance iron and unavoidable impurities. The steel alloy shall have a microstructure which in tough hardened condition comprises a martens tic matrix containing up to 30 vo!-% ferrite, and having a hardness in its tough hardened condition between 290 - 352 HB, The invention also relates to a process for manufacturing said holders or holder details for plastic molding fools as well as the holders or holder details themselves.

Information

Application ID 1442/CHENP/2009
Invention Field METALLURGY
Date of Application 2009-03-12
Publication Number 34/2009

Applicants

Name Address Country Nationality
UDDEHOLM TOOLING AKTIEBOLAG SE-683 85, HAGFORS Sweden Sweden

Inventors

Name Address Country Nationality
SANDBERG, ODD STRANDVAGEN 28, SE-683 40 UDDEHOLM Sweden Sweden
TIDESTEN, MAGNUS RAGVAGEN 3, SE-683 34 HAGFORS Sweden Sweden
HILLSKOG, THOMAS MOSSTORP 237, SE-655 93 KARLSTAD Sweden Sweden

Specification

A STEEL ALLOY, A HOLDER OR A HOLDER DETAIL FOR A PLASTIC MOULDING TOOL, A TOUGH HARDENED BLANK FOR A HOLDER OR HOLDER DETAIL, A PROCESS FOR PRODUCING A STEEL ALLOY.
TECHNICAL FIELD
The invention relates to a steel alloy and particularly to a steel alloy for the manu¬facturing of holder or holder details foT plastic molding tools, plastic and rubber moulds with moderate requirement on polish ability, dies for plastic extrusion and also for constructional parts. The invention also concerns holders and holder details manufactured of the steel, as well as blanks made of the steel alloy for the manufacturing of such holders and holder details. The invention also concerns a production method of said steel alloy where improved production economy may be provided.
BACKGROUND OF THE INVENTION
Holders and holder details for plastic molding tools are enjoyed as clamping and/or framing components for the plastic molding tool in tool sets, in which tool the plastic product shall be manufactured through some kind of molding method. Among conceivable holder details there can be mentioned bolster plates and other construction parts as well as heavy blocks with large recesses which can accommodate and hold the actual moulding tool. A steel which is manufactured and marketed by the ^pliant under the registered trade name RAMAX S® has the following nominal composition in weight-%: 0.33 C, 0.35 Si, 1.35 Mn, 16.6 Cr, 0.55 Ni, 0.12 N, 0.12 S, balance iron and impurities irom the Manu Turing of the steel. The closest comparable standardized steel is AISI420F. Steels of this type have an adequate corrosion resistance, and are hardened and tempered to have a martens tic microstructure.
In recent years several steels have been developed which seeks to inquiries the features of steels for this field of application. Particularly, the corrosion resistance, ductility, hardenabihty and machinabilily are properties which have gained extensive focus in order to improve the features of the steels. These steels contain lower amounts of carbon and chromium than the above steels. Furthermore, copper is added and the amount of silicon, manganese and nickel are modified. In order to obtain very low carbon contents, the melt has to be processed m an additional process step. This so called decarburization requires a converter which is equipped with means for blowing gas, nonnaliy oxygen or

a mixture of oxygen and argon through the melt. This extra process step results in higher production costs.
An example of a steel alloy for use in the manufacture of plastic injection mold base components is disclosed in US 6,358,334. The steel alloy comprises 0,03-0.06 % C, 1.0-1.6 % Mn, 0.01-0.03 % P, 0.06-0.3 % S, 0.25-1.0 % Si, 12.0-14.0 % Cr, 0.5-1.3 % Cu, 0.01-0.1 % V, 0.02-0.08 % N, the rest Fe wilh trace amounts of ordinarily present elements. Compared to an AISI420F type of steel, fte steel is said to have a beneficial combination of features due to reduced hardness and hardenability, improved ductility, corrosion resistance, hot strength and weldability as well as improved surfece quality in hot worked condition,
US 2002/0162614 discloses a maraging steel alloy suitable for the manufacture of a frame construction for plastic moulds, a mould part and a process for production of the steel alloy which is said to obtain an improved machinability, good weldability and high corrosion resistance. The alloy comprises 0.02-0.075 % C, 0.1-0.6 % Si, 0.5-0.25 % S, up to max. 0.04 % P, 12.4-15.2 % Cr, 0,05-1.0 % Mo, 0.2-1.8 % Ni, up to max. 0.15 % V, 0.1 -0.4S % Cu, up to max. 0.03 % AI, 0.02-0.08 % N and residual Fe and impurities Jrom the manufacturing.
WO 2006/016043 discloses a martensilic stainless steel for a mould or a mould part for plastic injection moulding. The steel alloy comprises 0.02-0.09 % C, 0.025-0.12 % N, max. 0.34 % Si, max. 0.080 % Al, 0.55-1.8 % Mn, 11,5-16 % Cr, and possibly up to 0.4g % Cu, up to 0.90 % (Mo+Wy2), up to 0.90 % Ni, up to 0.090 % V, up to 0.090 % Nb, up to 0.025 % Ti, possibly up to 0.25 % S, the rest Fe and impurities from the manufecturtng. The steel is said to obtain an improved weldability, good corrosion resistance, good thermal conductivity and small problems during forging and recycling when compared for example to the steel disclosed in US 6,358,334.
A steel which is manufactured and marketed by the applicant under the registered trade name RAMAX 2® belongs to the recently developed steels. The steel alloy has the following nominal composition: 0.12 % C, 0.20 Si, 0.30 Mn, 0.10 S, 13.4 Cr, 1.60 Ni, 0,50 Mo, 0.20 V, and 0.105 N, the rest Fe and iitqiurities ftom the manufecturing. The manufacturing of the steel csn be performed without any need of a subsequent decarburization step. The steel has excellent machinability, good corrosion resistance and hardenability, uniform hardness in all dimensions and good indentation resistance

which result in lower mould production and maintenance costs and is a successfiil product on the market.
The above mentioned steels have become significantly more expensive to manufacture because the cost of certain alloying elements has increased lately. Furthermore, the low carbon content in some of these steels makes it necessary to perform a decarburization of the melt which results in increased production costs. Therefore it exists a demand for a steel which may be produced at lower alloying costs without any significant reduction in respect of the most important features of a steel for this application, e.g. corrosion resistance, bardenabJJity, machinability and hardness and which can be manufactured without any need of a subsequent decarburization step,
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide a steel alloy and particularly a steel alloy for the manufacturing of holders and holder details for plastic moulding tools, plastic and rubber moulds with moderate requirement on polishability, dies for plastic extrusion and also for coDStnjctional parts which can be manufactured at lower alloying cosis. This can be achieved with a steel alloy which is characterized in that it has a chemical composition which contains in weight-%:
0.08-0.19 C
0.16ds were heated to 740°C, cooled at a cooling rate of 15°C/h to 550°C, there from free cooling in air to room temperature.
The compositions of the steels manufactured at production scale are shown in table VIII below. Commercial steels (steels No 1, 2 and 3) for comparison of the features of the inventive steels No. 4 and 5 were obtained from the commercial market and no heat treatment or other treatment was performed to them.
The inventive steel No. 4 was manufactured as a 6 tons ftjll scale test heat and ingots were cast which were manufactured to test pieces by either hot rolling or forging at a temperature of 1240°C. The test pieces were cooled to an isothermal annealing temperature of 650°C and were subjected to an isothermal annealing at the isothermal annealing temperature during 10 h, thereafter cooled in free air to room temperature. The test pieces were then hardened by austenitizing at a temperature of 1000° C, 30 min, and tempered twice during two hours at a temperature of 550 - 620° C.
The inventive steel No 5 was manufactured as a 60 tons full scale test heat was produced in a conventional metallurgical process using an electric arc frimace, processed in a secondary ladle step and cast into ingots. The ingots were forged at a temperature of 1240°C to the shape of bars of size 610x254 mm, 600x100 mm and

Hardness and ferrite content after heat treatment
The hardness versus the austenitizing lernperature is shown m Fig. IK - 2D. It is evident Irom the charts of these drawings that the reference steels (Q9261, Q927! and Q9283) have the highest hardness. It is also evident that the hardness increases wifli increasing austenitizing temperature. However, some of the tested steels of the invention may obtain a hardness which is close to the hardness of the reference steels, but that require that a somewhat higher austenitizing temperature is chosen, i.e. about 1000 °C.
The hardness after tempering of some of the tested steels which have been hardened ftom lOOCC is shown in Fig, 3. The conclusion can be drawn from the tempering curves that these steels can be tempered down to 34 HRC through tempering in the temperature range 520-600 "C. As is evident from the figure, the inventive steels No. Q9272, Q9273, Q9274 and Q9284 can be tempered at higher temperatures than the other inventive steels and still obtain a high hardness, which is beneficial from a stress relief point of view.
An appropriate hardness of the steel after tough-hardening is about 31 - 38 HRC, (i.e. 290 - 352 HB). In Table VTI below, the heat treatment are stated which provide a hardness within the interval to the different steels. The ferrite content has been measured by manual pomt counting (swe. mtnatsmetoden) after hardening and tempering.

Machinabilitv tests perfoimed at laboratory scale
The machinability of the inventive steels which were manufactured at laboratory scale (Q-ingots) where examined and compared to the reference steels Q9261, Q9271 and Q9283. The results are shown in table DC below. It shall be considered that laboratory manufactured steels may contain defects which impair the results.
By face milling with uncoated carbide inserts the time required to wear the flank 0.5
mm were examined. The cutting data were as follows:
Machine type = SEKN 1203AFTN-M14 S25M
Milling cutter = Seco R220.13-0040-12 040 mm, 3 inserts
Cutting speed, vc = 250 m/min
Tooth feed, fe = 0.2 mm/tooth
Axial depth of cut, ap = 2 mm
Radial depth of cut, ae = 22.5 mm
Wear criteria = flank wear 0.5 mm
The result indicated that the inventive steels can obtain equal or better face milling properties as the commercial steels. Q9284 is best among the inventive steels and Q9294 and Q9295 are very good as well.
By drilling with high speed steel, the average number of drilled holes that could be made before the drill were damaged, were examined. The drilling data were as follows; Drill type: Wedevig 120 uncoated HSS 02 mm Cutting speed, vc: 26 mymin Feed rate, f: 0.04 mm/rev. Drill depth: 5 mm
The result indicated that the inventive steel can obtain better drilling properties than the reference steels.
By end milling with high speed steel the time required to wear the flank 0.15 mm were
examined. The drilling data were as follows:
Milling cutter = Sandvik Coromant R216.33-05050-AK13P 1630 05 mm.
Cutting speed, vc = 200 m/min
Tooth feed, fe = 0.05 mm/tooth
Axial depth of cut, ap = 2 mm
Radial depth of cut, ae = 5 mm

As is evident from Fig. 5A the inventive steel may obtain equal or better face milling properties than the commercial steels. Particularly the inventive steels with somewhat lower hardness than the commercial steels shows superior -fece milling properties.
Fig. 5B shows the results from cavity milling with coated caibide tools. The cutting data
were as follows:
Milling tool: Coromant R200-028A32-12M, 0 40 mm, 1 = 145 mm
Carbide grade: Coromant RCKT 1204 MO-PM 4030
Wear criteria: VBmax 0.5 mm
Cutting speed, vc = Varying
Tooth feed, fe = 0.25 mm/tooth
Axial depth of cut, ^ = 2 mm
Radial depth of cut, ae = 12 mm
Fig. 5B shows that the inventive steel may obtain equal or better cavity milling properties than the commercial steel No. 2 and 3, and that (he inventive steel is superior the commercial steel No, 1.
Fig, 5C shows the result from drilling with high speed steel. It is evident from these
tests that the inventive steel can obtain equal or better drilling properties than the
commercial steels. The drilling data were as follows:
Drill type: WedevSg 120 uncoated HSS 05 mm
Cutting speed, vc: 26 m/mm
Feed rate, f: 0.15 mm/rev.
Drill deptii: 12.5 mm
Fig. 5D shows flie result from end milling with high speed steel. It is evident from these
tests that the inventive steel No.5 can obtain much better end milling properties than the
commercial steels. The drilling data were as follows:
Milling cutter: C200 uncoated HSS 012 mm
Cutting speed, vc: 70 m/min
Radial depth of cut, ae = 1.2 mm
Axial depth of cut, ap = 18 mm
Tooth feed, fe: 0.14 mm/tooth
Wear criteria = flank wear 0.15 mm

moulding tool base is manufactured from a steel alloy with a chemical composition according to the invention.
The steel of the invention is manufactured by producing a melt, preferably in an electrical arc furnace, an induction ftmiace or any other fiimace which uses scrqj as the main raw material. Possibly, the melt is processed in a secondary ladle step to ensure appropriate conditioning of the steel before the casting process, i.e. alloying of the steel to target analysis, removal of deoxidation products etc. The steel does not need to be treated in a converter to lower the carbon content further. The melt, having a chemical composition according to the invention, is cast into large ingots. The melt may also be cast by continuous casting. It is also possible to cast electrodes of the molten metal and then remeltmg the electrodes through Eiectro-Slag-Remelting (ESR). It is also possible to manufacture ingots powder-metallurgically through gas-atomization of the melt to produce a powder, which then is compacted through a technique which may comprise hot isostatic pressing, so called HIPing, or, as an alternative, manufecture ingots through sprayforming.
Said process fiirther comprises the steps of hot working an ingol of said steel alloy at a temperature range of 1100- 1300°C, preferably 1240 - 1270°C, cooling said steel alloy, preferably in air, from the hot working temperature to a temperature of 50 - 200°C, preferably 50 - 100°C, thereby obtaining a hardening of said steel alloy, followed by tempering twice during 2 hours at a temperature of 510 - 650° C, preferably 540 - 620° C, thereby obtaining a tough hardened blank, and forming the holder base, the holder detail base or moulding tool base by machining operation to a holder, a holder detail for a plastic moulding tool or a moulding tool.
In an alternative process for producing a steel alloy for the manufacturing of a holder, a holder detail for a plastic moulding too! or a moulding tool, a holder base or a holder detail base or a moulding tool base is manufactured from a ingot containing a steel alloy according to the above, said process comprising the steps of hot working an ingot of said steel alloy at a temperature range of! 100 -1300°C, preferably 1240 -1270°C. The hot working is followed by a cooling of said steel alloy to an isothermal annealing temperature of 550 - 700°C, preferably 600 - 700'=C, where said alloy is subjected to an isothermal annealing at said isothermal annealmg temperature during 5 - 10 h. Normally, the isothermal annealing is followed by a cooling of said alloy to room temperature before the steel alloy is subjected to a hardening and tempering operation. The hardening is performed by austenitizing the steel alloy at a temperature of 900 -

1100° C, preferably 950 -1025° C, and even more preferred at 1000° C, 30 min, and teinperingtwiceduring2hoiirsatatemperatureof 510-650° C, preferably 540-620° C, tbereby obtaining a tough hardened blank, thereafter forming the holder base, the holder detail base or the moulding tool base by machining operation to a holder, a holder detail for a plastic moulding tool or a moulding tool. It is possible that the cooling from the isothermal annealing temperature to room temperature can be excluded, and that the heating to austenitizing temperature may follow directly after the isothermal annealing, but that has yet to be investigated.

PATENT CLAIMS
1. A steel alloy, characterized in that it has a chemical composition which
contains in weight-%:
0.08-0.19 C
0.16

Documents

Name Date
Wipo Publication Page_As Filed_12-03-2009.pdf 2009-03-12
Form5_As Filed_12-03-2009.pdf 2009-03-12
Form3_As Filed_12-03-2009.pdf 2009-03-12
Form2 Title Page_Complete_12-03-2009.pdf 2009-03-12
Form1_As Filed_12-03-2009.pdf 2009-03-12
Drawing_As Filed_12-03-2009.pdf 2009-03-12
Correspondence By Agent_As Filed_12-03-2009.pdf 2009-03-12
Description Complete_As Filed_12-03-2009.pdf 2009-03-12
Claims_As Filed_12-03-2009.pdf 2009-03-12
Abstract_As Filed_12-03-2009.pdf 2009-03-12
Correspondence By Agent_Annexure Form3_09-09-2009.pdf 2009-09-09
Form1_After Filing_10-09-2009.pdf 2009-09-10
Correspondence By Agent_Form1_10-09-2009.pdf 2009-09-10
Annexure Form3_After Filing_11-09-2009.pdf 2009-09-11
Form18_Normal Request_13-07-2010.pdf 2010-07-13
Form13_Complete Specification_13-07-2010.pdf 2010-07-13
Correspondence By Agent_Form18_13-07-2010.pdf 2010-07-13
Other Document_Change of Name_05-05-2011.pdf 2011-05-05
Claims_Amended_13-07-2010.pdf 2010-07-13
Form13_Name of Applicant Change_05-05-2011.pdf 2011-05-05
Correspondence By Agent_Form13_05-05-2011.pdf 2011-05-05
Form26_General Power of Attorney_06-06-2011.pdf 2011-06-06
Correspondence By Agent_Power of Attorney_06-06-2011.pdf 2011-06-06
1442-CHENP-2009-AbandonedLetter.pdf 2017-07-19
Correspondence By Office_FER_18-08-2016.pdf 2016-08-18

Orders

Applicant Section Controller Decision Date URL