DE2452486A1 - PROCESS FOR MANUFACTURING A WORKPIECE FROM HARDENED STEEL - Google Patents

Description

Patent application

Process for the production of a workpiece from hardened steel

The present invention relates to a method for producing a workpiece made of hardened steel with a small thickness and good dimensional accuracy.

In order to be able to produce hardened and possibly tempered, thin workpieces, for example from thin sheet metal, preferably less than 3 mm, with good dimensional accuracy , the workpiece was previously removed from the shaping device after it had been shaped in the conventional manner, then hardened and tempered and clamped in a jig. This is a complicated process that places high demands on the hardenability of the steel used.

The invention aims to eliminate these disadvantages. It is characterized in that a blank made of hardenable Steel is heated to hardening temperature and then heated to its desired final shape in a forming device is shaped in which the workpiece has an essential shape » is subjected to change and is rapidly cooled so that it acquires a martensitic and / or bainitic structure.

509819/0848

The blanks used according to the invention are preferably of uniform thickness.

A carbon steel or carbon-manganese steel alloyed with boron is used as the starting material. In order to obtain the desired combination of hardness and toughness, through which tempering can be omitted, a steel is used that contains 0.4% carbon, silicon in a content that depends on the steelmaking method, but is otherwise insignificant, 0.5- 2.0% manganese, no more than 0.05% phosphorus and no more than 0.05% sulfur, 0.1-0.5% chromium and / or 0.05-0.5% molybdenum, up to 0.1% titanium , 0.0005-0.01% boron, - contains up to a total of 0.1% aluminum and possibly low, insignificant contents of copper and nickel, possibly in contents of up to 0.2% each.

A preferred embodiment of the invention is made of steel uses the carbon in an amount less than or equal to 0.25%, preferably 0.15-0.25%, silicon in one of the steelmaking method dependent, but otherwise insignificant content, 0.5-1.5%, preferably 0.7-1.5% manganese, at most 0.03% phosphorus and at most 0.04% sulfur, 0.1-0.3% chromium and / or 0.05-0.5% molybdenum, 0.02-0.1%, preferably 0.02-0.05% titanium, 0.001-0.007%, preferably 0.001-0.005% boron, 0.03-0.1%, preferably 0.03-0.07% aluminum and possibly low, insignificant contents of copper and Nickel may contain up to 0.2% each. Steel is already known in and of itself.

The steel is heated to the hardening temperature, ie to a _{temperature above Ac 3} , where it is in the austenitic state. The steel is preferably heated to a temperature between 775 ° C and 1000 ° C.

Shaping is primarily a pressing process. The invention can but also with other shaping methods, e.g. die cutting,

509819/0848 _{mQ mmmL}

Extrusion and explosive molding can be used. The blank is formed during pressing between two tools or with the aid of a pressure medium against a tool. It is desirable to use a fast press designed to allow the position and speed of the tool (s) during the whole process can be controlled. It is thus desirable; shaping in less than five seconds, preferably in less than three seconds to complete the molding before the desired hardening structure is obtained.

Shaping and cooling must be carried out so quickly that a fine-grain martessitic and / or bainitic structure results. The speed required for this depends on the composition of the steel, i.e. on its Continuous Cooling Transformation diagram (CCT diagram). At the end of the rapid cooling the workpiece is continuously in the forming device. The pressed workpiece is either indirect, by cooling Share the forming device, or directly, by direct contact with the Workpiece with a coolant after the completion of the molding, cooled. Since the tool (s) are used as a Clamping device serves (serve), an end product with good dimensional accuracy is obtained.

Due to the use of the steel specially adapted to the invention thin load-bearing sheet metal or shell structures with high strength can be produced. The combination of high Strength and good toughness enable the production of energy-absorbing (= shock-absorbing) workpieces. The hardened ones (and not tempered) sheet metal structures are primarily intended for use in transport vehicles for parts that expected to absorb shocks in the event of a collision, in particular

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others for the bumpers, but also for other body parts. In general it can be said that the parts of the vehicle that v / earth exposed to strong jolts, or the parts of the vehicle that are at risk of strong jolts can, should advantageously be produced according to the invention using the special steel adapted to the invention.

In the possibility of the steel in the hardened state without subsequent Being able to use tempering is a no small advantage. It lets a heat treatment process come to an end and eliminates a source of dimensional inaccuracy. Also are the resulting workpieces harder.

To take full advantage of the low boron content of 0.0005-0.01% to let, the specified titanium and aluminum contents should be added to the steel before the boron, so that oxygen and nitrogen are bound when adding boron.

The boron steel is a weldable structural steel, which by a simple Heat treatment imparted extremely high strength combined with good toughness.

A yield point of> 120 kp / mm is with a longitudinal elongation of approx. 10% not unusual.

The steel gets paired with the relatively great hardness Ruter elongation after hardening has very good shock-absorbing properties.

The basic composition of boron steel is carbon-manganese steel, It has been given very good hardening properties thanks to a special metallurgical treatment and alloy. The addition of boron gives the steel a fine-grain structure after hardening in water or Hl, which consists of low-temperature bainite and tempered high-temperature martensite. It is this structure

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that gives the boron steel its combination of hardness and toughness, in contrast to a steel that is not alloyed with boron, which is after Hardening receives a brittle hardening structure.

Apart from the mentioned improvements in mechanical properties e ^ in steel treated with boron also has a significantly better one Hardening capacity than a steel not treated with boron same basic composition.

The very high strength properties and the good steaming properties result after curing. A suitable curing temperature is about 900 ⁰ C (between 775 ° C and 1000 ⁰ C). Quenching in oil or salt water is recommended for thicknesses less than 6 mm.

Example. As an example of the invention, reference is made to Table 1, in which the results are summarized in the form of strength values and hardnesses for five different steel compositions and some different thicknesses.

As guide values · for the mechanical properties can be summarized specify the following:

Hot-rolled he od £ r_ka _> ltg £ W £ lz ^ ter_un_d_geg] .ühter_Zijst ^ andj_

(Tq kp / mm Cj kp / mm CL%

36-42 50-60 25-35

Hardened_Zustandj_ Depending on the dimensions and The following standard values are obtained for hardening agents:

¹ To kp / mm 6t kp / mm ² U % hardness ₉ .

^{B ö} HRC KVU 0 ⁰ C kp / cin

120-150 '150-170 8-12 45-50 5-1 /

The weldability of the boron alloy steels is according to the basic analysis to be assessed, thus according to the carbon and manganese content, since the structure obtained in the heat-affected zone for hydrogen

509819/0848

embrittlement is not sensitive. The boron steels in the table can thus be easily welded like ordinary high-strength structural steels

will.

When the boron steel is to be welded before the P'ormung and curing, the properties of the base material can also be obtained after curing in the SchweiÄnaht characterized in that the boron steel

adapted special electrodes are used «

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TABLE 1
Examples according to H ^ rtunp: obtained strength

Batch thickness C.
rf
P. Si Vm analysis S. ·, ° f
Io Ti B. Λ1 strength 174
179 Vt Hardness' Hardening agent mm 0.2 4 0.37 0.94 P. 0.019 0.197 0.040 0.0050 0.060 * 0.2 * f
kp / mrn ^ 164
167 10
11 HB 47O • B 6959 6th 0.23
It 0.31
ti 0.95
dd 0.030 0.018
IT 0.154
It 0.036
11 0.0031
dd 0.123
It I.
118
132; 155
156 10 HVlO 486
HB 455 10 % saline solution B 7000
B 7000 6th 0.19 0.31 0.77 0.022
ti 0.016 0.207 0.032 0.0029 0.046 120
145 ¹ 153
158 11
11 dd
dd B 8307 6th 0.19 0.23 0.77 0.016 0.024 0.195 0.030 0.0031 0.040 112
114 143
134 10
12th * 11 A 2197 0.23 0.39 0.87 0.024 0.023. 0.196 0.043 0.0034 0.069 119
119 96
110 8th
8th HRC 42 B 6938 4th 0.19 0.31 0.77 0.020 0.016 0.207 0.032 0.0029 0.046
i 102
96 165
136 9
9 B 8307 6th 0.24 0.27 0.79 0.016 t
; 0.016 j 0.019
> 1
. t 0.18 .0.040. 0.0050 j 0.139 85 10 11V5 550
HV5 "435
HV 400-450
UV 420-490 dd B 8500 '1.75
1.75
1.75
"1.5 123
: '92
I.
I '
I. 107. Saline solution
«1"; _ 'Zl
tool
tool

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Claims (11)

Claims 1. Process for the production of a workpiece from hardened steel with low thickness and good dimensional accuracy, characterized in that a blank made of hardenable steel is heated to hardening temperature and thereafter is formed into the desired final shape in a molding machine in which the workpiece undergoes a substantial change in shape and is cooled quickly so that it has a martensitic and / or Baihitic structure. 2. The method according to claim 1, characterized in that the blank to a temperature above Ac _3, and preferably to a temperature zwisehen 775 ° C and 1000 ⁰ C is heated. 3. The method according to claim 1 or 2, characterized in that the Forming and cooling are carried out so quickly that a fine-grain martensitic and / or bainitic structure is obtained, and the required speed depends on the composition of the steel, i.e. on its Continuous Cooling Transformation diagram (CCT diagram). H. The method according to any one of the preceding claims, characterized in that the molding is carried out between two tools which are quickly pressed together. 5. The method according to any one of claims 1-3, characterized in, that the molding is carried out with the aid of a pressure medium against a tool. 6. The method according to any one of the preceding claims, characterized in, that the rapid cooling carried out after the molding has been completed with "the pressed continuously located in the molding device Blank takes place. 509819/0848 7. The method according to any one of the preceding claims, characterized in that the cooling of the pressed workpiece by cooling
Dividing the molding device is effected. 8. The method according to any one of the preceding claims, characterized in that the cooling of the pressed workpiece by direct contact
is effected with a coolant. 9. The method according to any one of the preceding claims, characterized in that the starting material from a blank is more uniform
Thickness consists, the thickness of which differs from that of the finished workpiece deviates by a maximum of 25%. 10. The method according to any one of the preceding claims, characterized in that the starting material is a steel which has less than 0.4% carbon, silicon in a content that is dependent on the steelmaking process but is otherwise insignificant, 0.5-2.0% Manganese, not more than 0.05% phosphorus and not more than 0.05% sulfur / 0.1-0.5% chromium and / or
0.05-0.5% molybdenum, up to 0.1% titanium, 0.0005-0.01% boron, up to a total of 0.1% aluminum and possibly low, insignificant contents of copper and nickel, possibly in Contains up to 0.2% each. 11. The method according to claim 10, characterized in that the steel, carbon in a content of less than or equal to 0.25%, preferably
0.15-0.25%, silicon in a content that depends on the steelmaking process, but is otherwise insignificant, 0.5-1.5%, preferably
0.7-1.5% manganese, 0.03% maximum phosphorus and 0.04% sulfur maximum, 0.1-0.3% chromium and / or 0.05-0.5% molybdenum, 0.02% 0.1%, preferably
0.02-0.05% titanium, 0.0005-0.007%, preferably 0.0005-0.005% boron, 0.03-
-0.1%, preferably 0.03-0.07% aluminum as well as possibly “small insignificant contents of copper and nickel possibly in contents of up to 0.2% each. 509 819/08