JPH0443978B2 - - Google Patents

Description

[Detailed description of the invention]

``Purpose of the Invention'' The present invention relates to the creation of a high-carbon steel material for high-temperature pressure welding that has excellent weld joint performance. Magna flaw detection and ultrasonic flaw detection do not generate defects in high carbon steel materials used after shearing and removal.
It is also an attempt to obtain a welded joint with excellent bending test characteristics. (Industrial application field) High carbon steel material for welded joints that are welded under high temperature pressure. (Prior art) One of the welding methods for high carbon steel materials is high temperature pressure welding such as gas pressure welding and flash welding. At the same time, mechanical pressure is applied to weld steel of various shapes, such as long steel and steel plates. The burr (or bulge) generated by the metal flow due to pressure during such high-temperature welding may be used as is or removed.There are various methods for removing it, such as using a glider or gas scarf. An efficient method is hot punching and shearing immediately after pressure welding. That is, this removal method by punching and shearing has the great advantage of being highly efficient, and is used to confirm the joint performance by conducting Magna flaw detection and ultrasonic flaw detection of welded joints. (Problem to be solved by the invention) However, the above-mentioned burr punching and shearing process
Due to its processing characteristics, tearing stress acts on the press-welded part, deteriorating the joint performance, and the above-mentioned flaw detection test and bending test characteristics deteriorate, so the quality of performance must be confirmed by each test before use. No. "Structure of the invention" (Means for solving the problem) (1) C: 0.60 to 0.85wt%, Si: 0.01 to 1.00wt%, Mn: 0.50 to 1.50wt%, sol.Al: 0.012wt% or less , B: A high-carbon steel material for high-temperature pressure welding with excellent weld joint performance, characterized by containing 0.0002 wt% or less, with the remainder consisting of Fe and inevitable impurities. (2) Contains C: 0.60 to 0.85 wt%, Si: 0.01 to 1.00 wt%, Mn: 0.50 to 1.50 wt%, Sol.Al: 0.012 wt% or less, B: 0.0002 wt% or less, and Cr: 0.15 ~1.00wt%, Mo: 0.01~0.30wt%, V: 0.01~0.30wt%, and the remainder is
A high-carbon steel material for high-temperature pressure welding with excellent weld joint performance, characterized by containing Fe and unavoidable impurities. (Function) By containing C: 0.60wt% or more and Mn: 0.50wt% or more, strength, hardness, and wear resistance are obtained.
C: 0.85wt% or less, Mn: 1.50wt% or less, Si:
By setting the content to 1.00wt% or less, deterioration of ductility is avoided. Si: 0.01wt% or more, when deoxidizing with Si only
By setting the content to 0.15wt% or more, deoxidation is achieved and at the same time it acts as a reinforcing element. Sol.Al: improves the cleanliness of steel at 0.002wt% or more,
Also, by setting B to 0.012wt% or less and B: 0.0003wt% or less, embrittlement cracking and precipitation embrittlement are avoided. Cr: 0.15wt% or more, Mo: 0.01wt% or more, V:
The base metal is strengthened by adding 0.01wt% or more of one or more of these to strengthen the weld heat-affected zone and improve joint performance. Cr: 1.00wt% or less,
By setting Mo: and V to 0.30 wt% or less, the formation of island-like martensite in the segregated portion during manufacturing is not promoted, and deterioration of ductility toughness is avoided. ``Example'' To further explain the present invention as described above, the present inventors believe that the deterioration of joint performance caused by hot press-out shear removal during high-temperature pressure welding is due to the embrittlement that occurs on the pressure welding surfaces at high temperatures. It was thought that this phenomenon was caused by chemical reaction, and various elements were investigated. In other words, the specific direction for such an investigation is that the pressure contact surface is always contaminated by oxygen and nitrogen in the atmosphere, and elements that have a strong affinity or reactivity with these two elements are associated with embrittlement. After detailed investigation, it was discovered that Al and B in the steel form a reaction product on the welding surface, causing embrittlement. This paper proposes a high carbon steel material for pressure welding. That is, first, the reason for limiting the composition of each element in the present invention is explained below in terms of wt% (hereinafter simply referred to as %). C is required to be at least 0.60% from the viewpoint of strength, hardness, and wear resistance, and if it exceeds 0.85%, it promotes the formation of coarse cementite and deteriorates ductility.
Limited to 0.60-0.85%. Si is important as a deoxidizing element and a strengthening element.
When deoxidizing with Al etc., 0.01% or more is used as a reinforcing element, and when deoxidizing with Si, 0.15% or more is required. Even when used as a reinforcing element, if the content exceeds 0.60%, deterioration of ductility becomes evident. Furthermore, if necessary for reinforcement, elongation toughness can be ensured in practice by adding up to 1.00%, but if it exceeds 1.00%, deterioration is significant. Mn is an essential element for ensuring strength and elongation toughness, and the reason why the lower limit was set at 0.50% was to prevent hot working cracking due to the formation of low melting point sulfides during manufacturing. This is the amount required to form MnS. In addition, the upper limit was limited to 1.50% because island-shaped martensite is generated during manufacturing due to Mn segregation, which significantly deteriorates ductility. Note that PS may be contained up to 0.030% as an unavoidable impurity. Acid-soluble Al (sol.Al) is the most important element in the present invention. In other words, when deoxidizing with Si, sol.Al < 0.002% is acceptable, but when Al is added as a deoxidizing element, it significantly improves the cleanliness of steel, and the addition of sol.Al of 0.002% or more increases its effect. shows. On the other hand, increasing the amount of sol.Al further increases the degree of deoxidation and improves the steel quality, but
If added in excess of 0.012%, it will react with contaminated oxygen on the pressure welding surface during high-temperature pressure welding, forming many fine oxides of 1 μm or less, and 3MnO・Al ₂ O ₃・3SiO ₂
It also forms low melting point oxides such as oxides, which prevent grain boundary movement on the welding surface and cause embrittlement cracking due to the tearing force received from the flash hot punching and shearing immediately after the welding. Furthermore, Al reacts with contaminated nitrogen to form AlN on the welded surface, causing precipitation embrittlement and deteriorating bending test characteristics. Such effects deteriorate welded joint performance and cause defects in Magna flaw detection and ultrasonic flaw detection, so it is essential to keep the content to 0.012% or less in order to obtain excellent joint properties in such high-temperature pressure welding. B, like SoL.Al, is an important element in the present invention. That is, by undergoing the flash hot extrusion shearing process that is a feature of the present invention, the diffusion of B in the welded area is accelerated, and a considerable amount of BN is generated by reacting with the contaminated nitrogen on the welded surface, causing embrittlement. do. Unlike embrittlement in normal base metals, the performance of welded joints deteriorates due to a small amount of B, and the amount of B at which such BN-induced embrittlement becomes noticeable is 0.0003
% or more, and in order to obtain good joint performance, B
It is necessary to keep it below 0.0002%. Among the above elements, Cr, Mo, and V are effective as reinforcing elements, and they contribute to improving the performance of the base metal and strengthening the weld heat affected zone, improving joint performance. To get the effect
It is necessary to add one or more of Cr: 0.15% or more, Mo: 0.01% or more, and V: 0.01% or more. However, if large amounts of these elements are added, the effect will be less than the increase in the amount added, promoting the formation of island-like martensite in the segregated areas during manufacturing and deteriorating ductility. % or less, and Mo and V each need to be 0.30% or less. When a high carbon steel material having the above composition is subjected to high-temperature pressure welding, it is reheated to a temperature higher than the austenite region, so it is not particularly limited by the manufacturing method, such as being as rolled or heat-treated material. , similarly independent of shape. A specific manufacturing example of the product according to the present invention will be described below. Table 1 below shows examples of the chemical composition of high carbon steel materials adopted by the present inventors, and the burr removal method used was a punching method and a grinder removal method for comparison. The high-carbon steel materials are as-rolled and then reheated and slack-quenched, and are strip-shaped steel materials with a cross-sectional area of 77.5 cm ² and a section modulus Z = 397 cm ³ . Gas pressure welding was carried out under the normal conditions of heating with a reducing flame and a pressure of 2.4 kg/mm ² and a compression amount of 26 mm.
Note that steels A and J were not heat treated and gas pressure welding was performed as rolled.

[Table] Namely, steels A to H and J to L are made by hot pressing and shearing the burrs after gas pressure welding, and steels I and M are the same steels as steels H and L, but the burrs are released by shearing after welding by gas pressure. It was cooled and removed by a grinder at room temperature. However, the three-point bending test results for A to M steels are shown in Figure 1 for deflection, and Figure 2 for maximum load, but both the deflection and the maximum load are sol.Al. , B shows a transition phenomenon in the range of 0.013 to 0.016% sol.Al, showing good joint performance at sol.Al of 0.012% or less, and rapid performance deterioration at 0.013% or more. show. At the same time, it was confirmed that Magna flaw detection defects also occur when this sol.Al is 0.013% or more. Regarding B, the above-mentioned sol.Al0.013-0.016%
and above, the influence of sol.Al is strong, and the influence of B is only slight. But this sol.Al
Below 0.012%, the influence of B is clearly separated;
B: At 0.0003% or more, the deterioration is significant, and it is combined with sol.Al and has an adverse effect. As shown in I and M steels, when burrs are removed with a grinder, sol.Al: 0.013%,
B: 0.0003% and sol.Al: 0.025%, B: 0.0001
%, it shows excellent welded joint performance. Even when hot punching and shearing processing, which can efficiently remove burrs, is performed, the present invention is still effective.
It was confirmed that steel with sol.Al: 0.012% or less and B: 0.0002% or less exhibits excellent welded joint performance. However, although the above manufacturing example is for gas pressure welding, it is clear that the welding conditions are similar in the case of flash welding or other high temperature pressure welding, and the burr can be removed by hot pressing and shearing. It has been confirmed that the same results as those described above are obtained when removing the particles. "Effects of the Invention" According to the present invention as explained above, even under conditions where burrs formed by pressure during high-temperature pressure welding are mechanically pushed out and removed by shearing immediately after pressure welding, it is possible to efficiently process the burrs. It maintains good characteristics without deteriorating the joint performance, and shows excellent performance in Magna flaw detection, ultrasonic flaw detection, and bending tests, and is an industrially highly effective invention.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and Fig. 1 shows the results of a three-point bending test and is a chart summarizing the effects of sol.Al and B on the amount of deflection, and Fig. 2 shows the same results. It is a chart summarizing the influence of sol.Al and B on the maximum load in the three-point bending test results.

Claims (1)

[Claims] 1 Contains C: 0.60 to 0.85 wt%, Si: 0.01 to 1.00 wt%, Mn: 0.50 to 1.50 wt%, sol.Al: 0.012 wt% or less, B: 0.0002 wt% or less, A high-carbon steel material for high-temperature pressure welding with excellent weld joint performance, characterized in that the remainder consists of Fe and unavoidable impurities. 2 Contains C: 0.60 to 0.85 wt%, Si: 0.01 to 1.00 wt%, Mn: 0.50 to 1.50 wt%, Sol.Al: 0.012 wt% or less, B: 0.0002 wt% or less, and Cr: 0.15 to 1.00. wt%, Mo: 0.01 to 0.30 wt%, V: 0.01 to 0.30 wt%, and the remainder is
A high-carbon steel material for high-temperature pressure welding with excellent weld joint performance, characterized by containing Fe and unavoidable impurities.